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300B push pull amplifier
300B push pull amplifier
I'm working on a 300B PP amplifier that using 8 x 300B for the output.
How much power can kick out when operating each at 405V @ 55ma?
Thanks!
I'm working on a 300B PP amplifier that using 8 x 300B for the output.
How much power can kick out when operating each at 405V @ 55ma?
Thanks!
Re: 300B push pull amplifier
Tube747 wrote:
>
> I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> How much power can kick out when operating each at 405V @ 55ma?
>
> Thanks!
The Pda in each at idle is 22.2 watts, so 44.4 watts total.
Max efficiency in pure class A is around 30%, so expect a maximum
of pure class A of 13.3 Watts.
If the tubes were operated at 32 watts, Pda total = 64W,
so class A PO max = 19 watts approx.
Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
So for a 300B at 55mA, Ra = approx 1,000 ohms.
So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
where you have a PP amp in class A the load a-a becomes twice that of
one triode,
or 10,727 ohms in this case.
Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
where approximately 28 watts max is reasonable to expect.
Never try to operate most 300B at more than 32 watts at idle.
KR Audio 300B can be operated at 40 watts at idle though.
Class AB2 does allow more PO to be had.
See my page at
* w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
Patrick Turner.
Tube747 wrote:
>
> I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> How much power can kick out when operating each at 405V @ 55ma?
>
> Thanks!
The Pda in each at idle is 22.2 watts, so 44.4 watts total.
Max efficiency in pure class A is around 30%, so expect a maximum
of pure class A of 13.3 Watts.
If the tubes were operated at 32 watts, Pda total = 64W,
so class A PO max = 19 watts approx.
Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
So for a 300B at 55mA, Ra = approx 1,000 ohms.
So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
where you have a PP amp in class A the load a-a becomes twice that of
one triode,
or 10,727 ohms in this case.
Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
where approximately 28 watts max is reasonable to expect.
Never try to operate most 300B at more than 32 watts at idle.
KR Audio 300B can be operated at 40 watts at idle though.
Class AB2 does allow more PO to be had.
See my page at
* w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
Patrick Turner.
Re: 300B push pull amplifier
Dear Patrick Turner,
Therefore, what is the PO from 4 pairs of 300B in push pull pure class
A configuration while the primary impedance of the output transformer
is 1.5K ohm?
Thanks!
On Apr 6, 10:11 pm, Patrick Turner <i...@turneraudio . com .au> wrote:
> Tube747 wrote:
>
> > I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> > How much power can kick out when operating each at 405V @ 55ma?
>
> > Thanks!
>
> The Pda in each at idle is 22.2 watts, so 44.4 watts total.
>
> Max efficiency in pure class A is around 30%, so expect a maximum
> of pure class A of 13.3 Watts.
>
> If the tubes were operated at 32 watts, Pda total = 64W,
> so class A PO max = 19 watts approx.
>
> Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
> So for a 300B at 55mA, Ra = approx 1,000 ohms.
>
> So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
> where you have a PP amp in class A the load a-a becomes twice that of
> one triode,
> or 10,727 ohms in this case.
>
> Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
> where approximately 28 watts max is reasonable to expect.
>
> Never try to operate most 300B at more than 32 watts at idle.
> KR Audio 300B can be operated at 40 watts at idle though.
>
> Class AB2 does allow more PO to be had.
>
> See my page at
>
> * w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
>
> Patrick Turner.
Dear Patrick Turner,
Therefore, what is the PO from 4 pairs of 300B in push pull pure class
A configuration while the primary impedance of the output transformer
is 1.5K ohm?
Thanks!
On Apr 6, 10:11 pm, Patrick Turner <i...@turneraudio . com .au> wrote:
> Tube747 wrote:
>
> > I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> > How much power can kick out when operating each at 405V @ 55ma?
>
> > Thanks!
>
> The Pda in each at idle is 22.2 watts, so 44.4 watts total.
>
> Max efficiency in pure class A is around 30%, so expect a maximum
> of pure class A of 13.3 Watts.
>
> If the tubes were operated at 32 watts, Pda total = 64W,
> so class A PO max = 19 watts approx.
>
> Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
> So for a 300B at 55mA, Ra = approx 1,000 ohms.
>
> So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
> where you have a PP amp in class A the load a-a becomes twice that of
> one triode,
> or 10,727 ohms in this case.
>
> Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
> where approximately 28 watts max is reasonable to expect.
>
> Never try to operate most 300B at more than 32 watts at idle.
> KR Audio 300B can be operated at 40 watts at idle though.
>
> Class AB2 does allow more PO to be had.
>
> See my page at
>
> * w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
>
> Patrick Turner.
Re: 300B push pull amplifier
Tube747 wrote:
>
> Dear Patrick Turner,
> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> A configuration while the primary impedance of the output transformer
> is 1.5K ohm?
The load EACH pair would "see" is 4 x 1.5k = 6k.
You will get a higher maximum class AB1 PO than for pure class A,
so proably you'd get a comfortable 100 watts, depending on the
transformer
winding losses.
If the OPT you have is a 1k5 primary to whatever speaker output Z is
nominated,
the winding RwP should be < 5% of 1k5, and RwS < 5% of the S winding.
Measuring the RwS isn't easy because its usually less than 1 ohm and
some DVM
can't tell you the truth below 2 ohms.
So, dear Tube747, you have a lot of things to consider.
Patrick Turner.
>
> Thanks!
>
> On Apr 6, 10:11 pm, Patrick Turner <i...@turneraudio . com .au> wrote:
> > Tube747 wrote:
> >
> > > I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> > > How much power can kick out when operating each at 405V @ 55ma?
> >
> > > Thanks!
> >
> > The Pda in each at idle is 22.2 watts, so 44.4 watts total.
> >
> > Max efficiency in pure class A is around 30%, so expect a maximum
> > of pure class A of 13.3 Watts.
> >
> > If the tubes were operated at 32 watts, Pda total = 64W,
> > so class A PO max = 19 watts approx.
> >
> > Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
> > So for a 300B at 55mA, Ra = approx 1,000 ohms.
> >
> > So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
> > where you have a PP amp in class A the load a-a becomes twice that of
> > one triode,
> > or 10,727 ohms in this case.
> >
> > Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
> > where approximately 28 watts max is reasonable to expect.
> >
> > Never try to operate most 300B at more than 32 watts at idle.
> > KR Audio 300B can be operated at 40 watts at idle though.
> >
> > Class AB2 does allow more PO to be had.
> >
> > See my page at
> >
> > * w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
> >
> > Patrick Turner.
Tube747 wrote:
>
> Dear Patrick Turner,
> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> A configuration while the primary impedance of the output transformer
> is 1.5K ohm?
The load EACH pair would "see" is 4 x 1.5k = 6k.
You will get a higher maximum class AB1 PO than for pure class A,
so proably you'd get a comfortable 100 watts, depending on the
transformer
winding losses.
If the OPT you have is a 1k5 primary to whatever speaker output Z is
nominated,
the winding RwP should be < 5% of 1k5, and RwS < 5% of the S winding.
Measuring the RwS isn't easy because its usually less than 1 ohm and
some DVM
can't tell you the truth below 2 ohms.
So, dear Tube747, you have a lot of things to consider.
Patrick Turner.
>
> Thanks!
>
> On Apr 6, 10:11 pm, Patrick Turner <i...@turneraudio . com .au> wrote:
> > Tube747 wrote:
> >
> > > I'm working on a 300B PP amplifier that using 8 x 300B for the output.
> > > How much power can kick out when operating each at 405V @ 55ma?
> >
> > > Thanks!
> >
> > The Pda in each at idle is 22.2 watts, so 44.4 watts total.
> >
> > Max efficiency in pure class A is around 30%, so expect a maximum
> > of pure class A of 13.3 Watts.
> >
> > If the tubes were operated at 32 watts, Pda total = 64W,
> > so class A PO max = 19 watts approx.
> >
> > Maximum Class A1 PO for 1 triode in SE = ( Ea / Ia ) - ( 2 x Ra ) .
> > So for a 300B at 55mA, Ra = approx 1,000 ohms.
> >
> > So its A1 load = 405/0.055 - 2,000 = 5,363 ohms, so
> > where you have a PP amp in class A the load a-a becomes twice that of
> > one triode,
> > or 10,727 ohms in this case.
> >
> > Loads down to 5k a-a are OK if you wish slightly more PO in class AB1,
> > where approximately 28 watts max is reasonable to expect.
> >
> > Never try to operate most 300B at more than 32 watts at idle.
> > KR Audio 300B can be operated at 40 watts at idle though.
> >
> > Class AB2 does allow more PO to be had.
> >
> > See my page at
> >
> > * w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
> >
> > Patrick Turner.
Re: 300B push pull amplifier
"Patrick Turner"
> Tube747 wrote:
>
>> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
>> A configuration while the primary impedance of the output transformer
>> is 1.5K ohm?
>
> The load EACH pair would "see" is 4 x 1.5k = 6k.
>
> You will get a higher maximum class AB1 PO than for pure class A,
** But he only asked about pure class A.
> so proably you'd get a comfortable 100 watts, depending on the
> transformer winding losses.
** Bollocks.
300Bs will not provide enough voltage swing with only a 405 volt supply.
They ain't pentodes or beam tubes.
..... Phil
"Patrick Turner"
> Tube747 wrote:
>
>> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
>> A configuration while the primary impedance of the output transformer
>> is 1.5K ohm?
>
> The load EACH pair would "see" is 4 x 1.5k = 6k.
>
> You will get a higher maximum class AB1 PO than for pure class A,
** But he only asked about pure class A.
> so proably you'd get a comfortable 100 watts, depending on the
> transformer winding losses.
** Bollocks.
300Bs will not provide enough voltage swing with only a 405 volt supply.
They ain't pentodes or beam tubes.
..... Phil
Re: 300B push pull amplifier
Phil Allison wrote:
>
> "Patrick Turner"
> > Tube747 wrote:
> >
> >> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> >> A configuration while the primary impedance of the output transformer
> >> is 1.5K ohm?
> >
> > The load EACH pair would "see" is 4 x 1.5k = 6k.
> >
> > You will get a higher maximum class AB1 PO than for pure class A,
>
> ** But he only asked about pure class A.
>
> > so proably you'd get a comfortable 100 watts, depending on the
> > transformer winding losses.
>
> ** Bollocks.
>
> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>
> They ain't pentodes or beam tubes.
>
> ..... Phil
Mr Boolocks, you don't appear to have understood me.
I gave the OP an extensive answer on what PO he would get with 300B
which would stand up to load lime analysis if anyone were capable and
willing to do it.
If a 300B can make 8 watts as an SE tube in class A, depending on Ia,
and depending on load value
and with Ea = 405V, then FOUR PAIRS, ie, and octet would make 64 watts
in SE class A1, or PP class A1.
In PP and with a load of 1k5, for the 4 pairs, he'd get about 100Watts
in class AB1,
with a substantial but lesser amount of class A before the action became
AB.
He would not get 64 watts of pure class A, but perhaps 40 watts.
The OP I think would have understood what I meant as what I said
followed on from a previous post
where the means by which the class A could be calculated was given.
Do I have to spoon feed everyone, including you?
A 1k5 load a-a is 6k per pair.
Each tube while in class A only sees 3k as its class A load.
And 1k5 as its class B load beyond the class A region.
As the action continues into AB which is possible with the 1k5 a-a for 4
pairs,
the class A load for 4 tubes each side of the PP circuit is 750 ohms,
and
375 ohms for the quad as it moves into AB. Its not a simple switch of
loads and in fact the change of tube loading from A to AB is gradual,
so the load line each 1/2 of the triode PP circuit sees is NOT a
straight line, but a curved line.
Even while in pure class A the load seen by each tube isn't a straight
line unless the tubes
are in SE.
3k per tube is NOT the load one would use for maximum PO for symetrical
clipping in a triode
for pure class A because you'd get cut off at Ea max occurring well
before Ia max at grid current at Ea min.
This is plain to see with load line analysis.
See my pages at
* w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
I am not a doormat for ppl to clean their lazy boots on the way in.
diyers and manufacturers are lazy if they ask questions here without
reading pages to which they are directed, and doing some experiments in
their own workshops
to find their own answers!!!!
So if any of you have been slothful today, get busy, and a life, OK!
Patrick Turner.
Phil Allison wrote:
>
> "Patrick Turner"
> > Tube747 wrote:
> >
> >> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> >> A configuration while the primary impedance of the output transformer
> >> is 1.5K ohm?
> >
> > The load EACH pair would "see" is 4 x 1.5k = 6k.
> >
> > You will get a higher maximum class AB1 PO than for pure class A,
>
> ** But he only asked about pure class A.
>
> > so proably you'd get a comfortable 100 watts, depending on the
> > transformer winding losses.
>
> ** Bollocks.
>
> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>
> They ain't pentodes or beam tubes.
>
> ..... Phil
Mr Boolocks, you don't appear to have understood me.
I gave the OP an extensive answer on what PO he would get with 300B
which would stand up to load lime analysis if anyone were capable and
willing to do it.
If a 300B can make 8 watts as an SE tube in class A, depending on Ia,
and depending on load value
and with Ea = 405V, then FOUR PAIRS, ie, and octet would make 64 watts
in SE class A1, or PP class A1.
In PP and with a load of 1k5, for the 4 pairs, he'd get about 100Watts
in class AB1,
with a substantial but lesser amount of class A before the action became
AB.
He would not get 64 watts of pure class A, but perhaps 40 watts.
The OP I think would have understood what I meant as what I said
followed on from a previous post
where the means by which the class A could be calculated was given.
Do I have to spoon feed everyone, including you?
A 1k5 load a-a is 6k per pair.
Each tube while in class A only sees 3k as its class A load.
And 1k5 as its class B load beyond the class A region.
As the action continues into AB which is possible with the 1k5 a-a for 4
pairs,
the class A load for 4 tubes each side of the PP circuit is 750 ohms,
and
375 ohms for the quad as it moves into AB. Its not a simple switch of
loads and in fact the change of tube loading from A to AB is gradual,
so the load line each 1/2 of the triode PP circuit sees is NOT a
straight line, but a curved line.
Even while in pure class A the load seen by each tube isn't a straight
line unless the tubes
are in SE.
3k per tube is NOT the load one would use for maximum PO for symetrical
clipping in a triode
for pure class A because you'd get cut off at Ea max occurring well
before Ia max at grid current at Ea min.
This is plain to see with load line analysis.
See my pages at
* w w w .turneraudio . com .au/loadmatch3-pp-triodes.html
I am not a doormat for ppl to clean their lazy boots on the way in.
diyers and manufacturers are lazy if they ask questions here without
reading pages to which they are directed, and doing some experiments in
their own workshops
to find their own answers!!!!
So if any of you have been slothful today, get busy, and a life, OK!
Patrick Turner.
Re: 300B push pull amplifier
"Patrick Turner"
>
>> You will get a higher maximum class AB1 PO than for pure class A,
>> so proably you'd get a comfortable 100 watts, depending on the
>> transformer winding losses.
>
>>
>> ** Bollocks.
>>
>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>>
>> They ain't pentodes or beam tubes.
>>
>> ..... Phil
>
> Mr Boolocks, you don't appear to have understood me.
** Mr Turneroid
You have avoided, evaded and completely side stepped the question.
SOP for posturing gurus.
..... Phil
"Patrick Turner"
>
>> You will get a higher maximum class AB1 PO than for pure class A,
>> so proably you'd get a comfortable 100 watts, depending on the
>> transformer winding losses.
>
>>
>> ** Bollocks.
>>
>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>>
>> They ain't pentodes or beam tubes.
>>
>> ..... Phil
>
> Mr Boolocks, you don't appear to have understood me.
** Mr Turneroid
You have avoided, evaded and completely side stepped the question.
SOP for posturing gurus.
..... Phil
Re: 300B push pull amplifier
Phil Allison wrote:
>
> "Patrick Turner"
> >
> >> You will get a higher maximum class AB1 PO than for pure class A,
> >> so proably you'd get a comfortable 100 watts, depending on the
> >> transformer winding losses.
> >
> >>
> >> ** Bollocks.
> >>
> >> 300Bs will not provide enough voltage swing with only a 405 volt supply.
> >>
> >> They ain't pentodes or beam tubes.
> >>
> >> ..... Phil
> >
> > Mr Boolocks, you don't appear to have understood me.
>
> ** Mr Turneroid
>
> You have avoided, evaded and completely side stepped the question.
>
> SOP for posturing gurus.
>
> ..... Phil
The original question was......
""Dear Patrick Turner,
Therefore, what is the PO from 4 pairs of 300B in push pull pure class
A configuration while the primary impedance of the output transformer
is 1.5K ohm?
Thanks! ""
I gave a good answer considering the previous post before this last
question.
Please go back and read the whole thread from the beggining.
However, this last question isn't composed as carefully as it should
have been
and if I was impolite, I'd put it into the catergory of what is a "dumb
question".
The questioner does not say what Ea and Ia he wants to run the 8 PP
tubes with.
All he says is I have 1k5 for the load, so how much class A?
1k5 translates to 6k per pair, and I gave a whole lot of figures for
what you might get in class A, and AB.
At my website I have provided all the means by which diyers and
manufacturers can
calculate all their own answers about the most basic elementary simple
electronic behaviour known to man, ie, a coupla triodes in an audio amp.
ALL THE INFORMATION ANYONE WOULD EVER NEED
is at my website pages but Tube 747 must use his brains in his time,
rather than my brains in my time.
If people fail to take the time to read the many sources of information,
and fail demonstrate they understand the basics, I refuse to
always spoonfeed them, unless there is a benefit to many others present,
and if it helps my understanding.
Now Phil, perhaps you feel you'd prefer to answer the question better
than I have the time for.
The question should have been posed as...
What amount of pure class A1 ( and not A2 ) is possible with 8 x 300B in
PP
with 1k5 a-a load, and with Pda at idle for each tube = 32 watts,
and with whatever Ea and Ia best suits the tubes?
Please supply full biasing and Ea/Ia set up details.
Feel free to wade through all the boring details regarding load line
analysis
at my website.
Patrick Turner.
Phil Allison wrote:
>
> "Patrick Turner"
> >
> >> You will get a higher maximum class AB1 PO than for pure class A,
> >> so proably you'd get a comfortable 100 watts, depending on the
> >> transformer winding losses.
> >
> >>
> >> ** Bollocks.
> >>
> >> 300Bs will not provide enough voltage swing with only a 405 volt supply.
> >>
> >> They ain't pentodes or beam tubes.
> >>
> >> ..... Phil
> >
> > Mr Boolocks, you don't appear to have understood me.
>
> ** Mr Turneroid
>
> You have avoided, evaded and completely side stepped the question.
>
> SOP for posturing gurus.
>
> ..... Phil
The original question was......
""Dear Patrick Turner,
Therefore, what is the PO from 4 pairs of 300B in push pull pure class
A configuration while the primary impedance of the output transformer
is 1.5K ohm?
Thanks! ""
I gave a good answer considering the previous post before this last
question.
Please go back and read the whole thread from the beggining.
However, this last question isn't composed as carefully as it should
have been
and if I was impolite, I'd put it into the catergory of what is a "dumb
question".
The questioner does not say what Ea and Ia he wants to run the 8 PP
tubes with.
All he says is I have 1k5 for the load, so how much class A?
1k5 translates to 6k per pair, and I gave a whole lot of figures for
what you might get in class A, and AB.
At my website I have provided all the means by which diyers and
manufacturers can
calculate all their own answers about the most basic elementary simple
electronic behaviour known to man, ie, a coupla triodes in an audio amp.
ALL THE INFORMATION ANYONE WOULD EVER NEED
is at my website pages but Tube 747 must use his brains in his time,
rather than my brains in my time.
If people fail to take the time to read the many sources of information,
and fail demonstrate they understand the basics, I refuse to
always spoonfeed them, unless there is a benefit to many others present,
and if it helps my understanding.
Now Phil, perhaps you feel you'd prefer to answer the question better
than I have the time for.
The question should have been posed as...
What amount of pure class A1 ( and not A2 ) is possible with 8 x 300B in
PP
with 1k5 a-a load, and with Pda at idle for each tube = 32 watts,
and with whatever Ea and Ia best suits the tubes?
Please supply full biasing and Ea/Ia set up details.
Feel free to wade through all the boring details regarding load line
analysis
at my website.
Patrick Turner.
Re: 300B push pull amplifier
"Patrick Turner"
> >
>> >> You will get a higher maximum class AB1 PO than for pure class A,
>> >> so proably you'd get a comfortable 100 watts, depending on the
>> >> transformer winding losses.
>> >
>> >>
>> >> ** Bollocks.
>> >>
>> >> 300Bs will not provide enough voltage swing with only a 405 volt
>> >> supply.
>> >>
>> >> They ain't pentodes or beam tubes.
>> >>
>> >> ..... Phil
>> >
>> > Mr Boolocks, you don't appear to have understood me.
>>
>> ** Mr Turneroid
>>
>> You have avoided, evaded and completely side stepped the question.
>>
>> SOP for posturing gurus.
>>
>>
>
> The original question was......
** Snip whole school of red herrings.
WRONG QUESTION !!
You have not got the faintest clue about following context.
...... Phil
"Patrick Turner"
> >
>> >> You will get a higher maximum class AB1 PO than for pure class A,
>> >> so proably you'd get a comfortable 100 watts, depending on the
>> >> transformer winding losses.
>> >
>> >>
>> >> ** Bollocks.
>> >>
>> >> 300Bs will not provide enough voltage swing with only a 405 volt
>> >> supply.
>> >>
>> >> They ain't pentodes or beam tubes.
>> >>
>> >> ..... Phil
>> >
>> > Mr Boolocks, you don't appear to have understood me.
>>
>> ** Mr Turneroid
>>
>> You have avoided, evaded and completely side stepped the question.
>>
>> SOP for posturing gurus.
>>
>>
>
> The original question was......
** Snip whole school of red herrings.
WRONG QUESTION !!
You have not got the faintest clue about following context.
...... Phil
Re: 300B push pull amplifier
Phil Allison wrote:
>
> "Patrick Turner"
> > >
> >> >> You will get a higher maximum class AB1 PO than for pure class A,
> >> >> so proably you'd get a comfortable 100 watts, depending on the
> >> >> transformer winding losses.
> >> >
> >> >>
> >> >> ** Bollocks.
> >> >>
> >> >> 300Bs will not provide enough voltage swing with only a 405 volt
> >> >> supply.
> >> >>
> >> >> They ain't pentodes or beam tubes.
> >> >>
> >> >> ..... Phil
> >> >
> >> > Mr Boolocks, you don't appear to have understood me.
> >>
> >> ** Mr Turneroid
> >>
> >> You have avoided, evaded and completely side stepped the question.
> >>
> >> SOP for posturing gurus.
> >>
> >>
> >
> > The original question was......
>
> ** Snip whole school of red herrings.
>
> WRONG QUESTION !!
>
> You have not got the faintest clue about following context.
>
> ...... Phil
Well if you are sure you're right, then OK, it doesn't bother me.
It shouldn't bother you when I disagree, or because nobody else thinks I
have avoided
answering the question.
The OP has been somewhat quiet on the matter.
So, how about you answer the question re-300B working conditions et all?
Its only reasonable you should step in to help us since you are so
displeased
about my attempt.
No need to become hysterical now. But then again, Betty Davis did like a
good row. Oh yeah.
Nothing like a beauty she said. She reckoned a really good shouting
match
with lots of angst and a few things being chucked around
was like having a big orgasm, so it had to be good for you....
But someone else being orgasmic can very easily be ignored.....
Patrick Turner.
Phil Allison wrote:
>
> "Patrick Turner"
> > >
> >> >> You will get a higher maximum class AB1 PO than for pure class A,
> >> >> so proably you'd get a comfortable 100 watts, depending on the
> >> >> transformer winding losses.
> >> >
> >> >>
> >> >> ** Bollocks.
> >> >>
> >> >> 300Bs will not provide enough voltage swing with only a 405 volt
> >> >> supply.
> >> >>
> >> >> They ain't pentodes or beam tubes.
> >> >>
> >> >> ..... Phil
> >> >
> >> > Mr Boolocks, you don't appear to have understood me.
> >>
> >> ** Mr Turneroid
> >>
> >> You have avoided, evaded and completely side stepped the question.
> >>
> >> SOP for posturing gurus.
> >>
> >>
> >
> > The original question was......
>
> ** Snip whole school of red herrings.
>
> WRONG QUESTION !!
>
> You have not got the faintest clue about following context.
>
> ...... Phil
Well if you are sure you're right, then OK, it doesn't bother me.
It shouldn't bother you when I disagree, or because nobody else thinks I
have avoided
answering the question.
The OP has been somewhat quiet on the matter.
So, how about you answer the question re-300B working conditions et all?
Its only reasonable you should step in to help us since you are so
displeased
about my attempt.
No need to become hysterical now. But then again, Betty Davis did like a
good row. Oh yeah.
Nothing like a beauty she said. She reckoned a really good shouting
match
with lots of angst and a few things being chucked around
was like having a big orgasm, so it had to be good for you....
But someone else being orgasmic can very easily be ignored.....
Patrick Turner.
Re: 300B push pull amplifier
"Phil Allison" <philallison@tpg . com .au> wrote in message
news:65vtmiF2hm5soU1@mid.individual . net ...
>
> "Patrick Turner"
>>
>>> You will get a higher maximum class AB1 PO than for pure class A,
>>> so proably you'd get a comfortable 100 watts, depending on the
>>> transformer winding losses.
>>
>>>
>>> ** Bollocks.
>>>
>>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>>>
>>> They ain't pentodes or beam tubes.
>>>
>>> ..... Phil
>>
>> Mr Boolocks, you don't appear to have understood me.
>
>
> ** Mr Turneroid
>
> You have avoided, evaded and completely side stepped the question.
>
> SOP for posturing gurus.
>
>
>
> ..... Phil
>
>
Patrick. If you are wondering why people like Per Lundahl,
Brian Sowter, Morgan Jones etc etc avoid this group, and
others like it, then the above friendly and informative post
from Phill will provide the answer.
Iain
"Phil Allison" <philallison@tpg . com .au> wrote in message
news:65vtmiF2hm5soU1@mid.individual . net ...
>
> "Patrick Turner"
>>
>>> You will get a higher maximum class AB1 PO than for pure class A,
>>> so proably you'd get a comfortable 100 watts, depending on the
>>> transformer winding losses.
>>
>>>
>>> ** Bollocks.
>>>
>>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
>>>
>>> They ain't pentodes or beam tubes.
>>>
>>> ..... Phil
>>
>> Mr Boolocks, you don't appear to have understood me.
>
>
> ** Mr Turneroid
>
> You have avoided, evaded and completely side stepped the question.
>
> SOP for posturing gurus.
>
>
>
> ..... Phil
>
>
Patrick. If you are wondering why people like Per Lundahl,
Brian Sowter, Morgan Jones etc etc avoid this group, and
others like it, then the above friendly and informative post
from Phill will provide the answer.
Iain
Re: 300B push pull amplifier
Iain Churches wrote:
>
> "Phil Allison" <philallison@tpg . com .au> wrote in message
> news:65vtmiF2hm5soU1@mid.individual . net ...
> >
> > "Patrick Turner"
> >>
> >>> You will get a higher maximum class AB1 PO than for pure class A,
> >>> so proably you'd get a comfortable 100 watts, depending on the
> >>> transformer winding losses.
> >>
> >>>
> >>> ** Bollocks.
> >>>
> >>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
> >>>
> >>> They ain't pentodes or beam tubes.
> >>>
> >>> ..... Phil
> >>
> >> Mr Boolocks, you don't appear to have understood me.
> >
> >
> > ** Mr Turneroid
> >
> > You have avoided, evaded and completely side stepped the question.
> >
> > SOP for posturing gurus.
> >
> >
> >
> > ..... Phil
> >
> >
>
> Patrick. If you are wondering why people like Per Lundahl,
> Brian Sowter, Morgan Jones etc etc avoid this group, and
> others like it, then the above friendly and informative post
> from Phill will provide the answer.
The Usernet discussion groups attract a wide range of people
who have a wide range of communication skills and styles.
Some are more painful to put up with than others, and because
Usernet isn't moderated, and then "difficult" people
find a home where otherwise they would be quite lost.
Usernet is a bit of a rabble because its like a university
where anyone off the street can walk in and hold forth on any subject
anytine,
and you don't need to pass entrance exams, or have to behave, or sit for
final exams.
Whether anyone becomes better qualified to build electronics is a moot
point, but then we ain't
a group dealing with life and death issues like heart surgery
techniques.
I have grown quite used to the difficulties sustained by posting here
and elsewhere,
and its sad that the guys you mention may not share my serenity in the
presence of bollickful commentary, or the flood of spam now hitting the
group
which begs we buy a pile of junk none of us want.
Lundahl, Sowter & Jones ( sounds like a company of lawyers :-) have
said all they wanted
to by shutting up and just getting on with making product that pleases
their customers or
else in the case of Jones, by writing a book.
Like me all 3 are probably time starved and wish there was 240 hours in
a day.
Patrick Turner.
>
> Iain
Iain Churches wrote:
>
> "Phil Allison" <philallison@tpg . com .au> wrote in message
> news:65vtmiF2hm5soU1@mid.individual . net ...
> >
> > "Patrick Turner"
> >>
> >>> You will get a higher maximum class AB1 PO than for pure class A,
> >>> so proably you'd get a comfortable 100 watts, depending on the
> >>> transformer winding losses.
> >>
> >>>
> >>> ** Bollocks.
> >>>
> >>> 300Bs will not provide enough voltage swing with only a 405 volt supply.
> >>>
> >>> They ain't pentodes or beam tubes.
> >>>
> >>> ..... Phil
> >>
> >> Mr Boolocks, you don't appear to have understood me.
> >
> >
> > ** Mr Turneroid
> >
> > You have avoided, evaded and completely side stepped the question.
> >
> > SOP for posturing gurus.
> >
> >
> >
> > ..... Phil
> >
> >
>
> Patrick. If you are wondering why people like Per Lundahl,
> Brian Sowter, Morgan Jones etc etc avoid this group, and
> others like it, then the above friendly and informative post
> from Phill will provide the answer.
The Usernet discussion groups attract a wide range of people
who have a wide range of communication skills and styles.
Some are more painful to put up with than others, and because
Usernet isn't moderated, and then "difficult" people
find a home where otherwise they would be quite lost.
Usernet is a bit of a rabble because its like a university
where anyone off the street can walk in and hold forth on any subject
anytine,
and you don't need to pass entrance exams, or have to behave, or sit for
final exams.
Whether anyone becomes better qualified to build electronics is a moot
point, but then we ain't
a group dealing with life and death issues like heart surgery
techniques.
I have grown quite used to the difficulties sustained by posting here
and elsewhere,
and its sad that the guys you mention may not share my serenity in the
presence of bollickful commentary, or the flood of spam now hitting the
group
which begs we buy a pile of junk none of us want.
Lundahl, Sowter & Jones ( sounds like a company of lawyers :-) have
said all they wanted
to by shutting up and just getting on with making product that pleases
their customers or
else in the case of Jones, by writing a book.
Like me all 3 are probably time starved and wish there was 240 hours in
a day.
Patrick Turner.
>
> Iain
Re: 300B push pull amplifier
On Apr 6, 5:14 pm, Tube747 <Tube...@lycos . com > wrote:
> Dear Patrick Turner,
> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> A configuration while the primary impedance of the output transformer
> is 1.5K ohm?
>
> Thanks!
First of all, Tube747, I have a lot of experience with 300B at all
kinds of operating conditions, and in particular my favourite output
transformers have a primary impedance of 5K6 which is very close to
the effective 6K you're talking about per pair. Secondly, it is not
bright to keep stacking 300B; you soon lose what it is that actually
makes them 300B, which is clarity and delicacy; it would be smarter to
go to 845 which have an even nicer tone and are much more powerful.
Thirdly, despite Patrick's attempts to help you, you really haven't
given us enough information. For instance, is your 405V at the plate
or on the plate -- i.e. does it include the drop over the cathode
resistor for autobias, or is it all operating voltage with fixed bias
being supplied from somewhere else? Fourthly, the 55mA you mention in
another post is ludicrously low for a modern application. I know, I
know, the GE tables and the WE tables all give operating points even
lower. But 55mA is an invitation to distortion every time you turn the
wick up. You'd do better to remember that a 300B is only a 450V tube,
and to look at 65mA operating at a more reasonable operating voltage.
About 380/385/390 volts at the plate and 60-65-70V negative bias and
60-65-70mA current with autobias (a very attractive option with 300B
because fixed bias bloats the bass -- YMMV, you may want bloated bass)
will give you both a cleaner sound and tubes that will last better.
Fifth: In Class A1 that will give you a minimum of 30W of the cleanest
power you ever heard. If you want or need more power, go to a steeper
loadline i.e. a *lower* impedance, even down to 1K actual or 4K
effective. Sixth: There is in my mind very little point in running
300B in any configuration outside Class A1; that's the sound that you
pay for; running 300B in A/B is a waste, because you can get the same
sound with KT88 or something. The same in fact applies to 845; running
in class A1, 845 always sound better than 211 which reach for the same
power by driving the signal across the 0V bias line into the positive
area.
Finally, still on the subject of the fewer 300B the better, and the
simpler the better, the best amp I ever built, and one which sounds
better in blind tests to classical musicians playing their own disks,
is PP EL34 Class A. I respect your ambition but I fear the outcome of
4x pairs of 300B will fall short of 4x the pleasure of one pair
properly implemented -- with the rest of the money spent on sensitive
speakers better suited to what is best about 300B.
One final note. I am always vastly irritated when I hear manufacturers
talk about 10W from 300B. It is bullshit. Even Patrick's casual talk
of 8W per single 300B is still an overstatement. 7.6W is the best I
ever got out of a single 300B not on shortterm test (I've run WE 300B
briefly at 450V with no ill effects but I wouldn't advise you try that
with Chinese tubes -- nor 405V, for that matter). In the scheme I've
laid out for you above, at the low end the tubes won't even be
averaging 4W each or 8W per pair -- they will last forever; I have a
pair of 300B that lasted 14K hours. And of course the sound will be
totally linear, with a hugely advantageous distribution of harmonic
distortion.
So, in summary, if you really need that much power, 300B are not the
right tube, and if you decided you want to marry 300B, the answer is
to use them right and get more sensitive speakers instead of stacking
up 300B so far that you will lose all their special benefits.
Sorry to be a drag on a bright dream.
Andre Jute
Visit Jute on Amps at * members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
On Apr 6, 5:14 pm, Tube747 <Tube...@lycos . com > wrote:
> Dear Patrick Turner,
> Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> A configuration while the primary impedance of the output transformer
> is 1.5K ohm?
>
> Thanks!
First of all, Tube747, I have a lot of experience with 300B at all
kinds of operating conditions, and in particular my favourite output
transformers have a primary impedance of 5K6 which is very close to
the effective 6K you're talking about per pair. Secondly, it is not
bright to keep stacking 300B; you soon lose what it is that actually
makes them 300B, which is clarity and delicacy; it would be smarter to
go to 845 which have an even nicer tone and are much more powerful.
Thirdly, despite Patrick's attempts to help you, you really haven't
given us enough information. For instance, is your 405V at the plate
or on the plate -- i.e. does it include the drop over the cathode
resistor for autobias, or is it all operating voltage with fixed bias
being supplied from somewhere else? Fourthly, the 55mA you mention in
another post is ludicrously low for a modern application. I know, I
know, the GE tables and the WE tables all give operating points even
lower. But 55mA is an invitation to distortion every time you turn the
wick up. You'd do better to remember that a 300B is only a 450V tube,
and to look at 65mA operating at a more reasonable operating voltage.
About 380/385/390 volts at the plate and 60-65-70V negative bias and
60-65-70mA current with autobias (a very attractive option with 300B
because fixed bias bloats the bass -- YMMV, you may want bloated bass)
will give you both a cleaner sound and tubes that will last better.
Fifth: In Class A1 that will give you a minimum of 30W of the cleanest
power you ever heard. If you want or need more power, go to a steeper
loadline i.e. a *lower* impedance, even down to 1K actual or 4K
effective. Sixth: There is in my mind very little point in running
300B in any configuration outside Class A1; that's the sound that you
pay for; running 300B in A/B is a waste, because you can get the same
sound with KT88 or something. The same in fact applies to 845; running
in class A1, 845 always sound better than 211 which reach for the same
power by driving the signal across the 0V bias line into the positive
area.
Finally, still on the subject of the fewer 300B the better, and the
simpler the better, the best amp I ever built, and one which sounds
better in blind tests to classical musicians playing their own disks,
is PP EL34 Class A. I respect your ambition but I fear the outcome of
4x pairs of 300B will fall short of 4x the pleasure of one pair
properly implemented -- with the rest of the money spent on sensitive
speakers better suited to what is best about 300B.
One final note. I am always vastly irritated when I hear manufacturers
talk about 10W from 300B. It is bullshit. Even Patrick's casual talk
of 8W per single 300B is still an overstatement. 7.6W is the best I
ever got out of a single 300B not on shortterm test (I've run WE 300B
briefly at 450V with no ill effects but I wouldn't advise you try that
with Chinese tubes -- nor 405V, for that matter). In the scheme I've
laid out for you above, at the low end the tubes won't even be
averaging 4W each or 8W per pair -- they will last forever; I have a
pair of 300B that lasted 14K hours. And of course the sound will be
totally linear, with a hugely advantageous distribution of harmonic
distortion.
So, in summary, if you really need that much power, 300B are not the
right tube, and if you decided you want to marry 300B, the answer is
to use them right and get more sensitive speakers instead of stacking
up 300B so far that you will lose all their special benefits.
Sorry to be a drag on a bright dream.
Andre Jute
Visit Jute on Amps at * members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
Re: 300B push pull amplifier
Andre Jute wrote:
>
> On Apr 6, 5:14 pm, Tube747 <Tube...@lycos . com > wrote:
> > Dear Patrick Turner,
> > Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> > A configuration while the primary impedance of the output transformer
> > is 1.5K ohm?
> >
> > Thanks!
>
> First of all, Tube747, I have a lot of experience with 300B at all
> kinds of operating conditions, and in particular my favourite output
> transformers have a primary impedance of 5K6 which is very close to
> the effective 6K you're talking about per pair. Secondly, it is not
> bright to keep stacking 300B; you soon lose what it is that actually
> makes them 300B, which is clarity and delicacy; it would be smarter to
> go to 845 which have an even nicer tone and are much more powerful.
It depends a bit how much power is needed.
If you only need 5 watts most days and occasionally 10 watts max,
then a pair of 300B would be be fine, and the expense of using 8 x 300B
would not yield a vast improvement imho.
One NEEDS to know how much power one uses,
A peak and hold DVM can be left connected to a speaker running from an
amp
and after a few CDs the peak max voltage is recorded.
If the speaker Z is known power required = peak voltage squared / ( 2 x
speaker ohms ).
Nevertheless, Late last year I heard a VAC amp with a quad of 300B in PP
per channel.
There was no difference in the sound whether the 9dB of global NFB was
connected or not.
And frankly, the thing worked excellently for a class AB1 triode amp.
The guy was using VAF speakers, model I-66, rated at about 90dB/W/M,
and used maybe 2 watts average sometimes, but mainly less most days.
He'd never lisen to anything that wasn't being handled by the
class A region of the AB amp, good for over 55 watts AB.
This amp also blew a lotta smoke a couple of months back, and I have to
repair it.
I'll get the experience to improve it.
The 6k load per pair of 300B isn't all that bad a load, but it means
each tube sees
3k when in class A. To get a maximal amount of class A with the 6k load
the Ea must be lower and Ia higher than if you had a 10k load.
The lower the Ea, the lower tha amount of voltage swing at the anode
because of the
limitation of grid current; see the anode curve where Eg = 0V on the
tube data sheet,
and where a 3k load line cuts this curve.
The higher the load, and higher the Ea, the more swing is possible, so
efficiency
rises with Ea rise.
But the maximum Ea should NOT be much more than 430V.
Ia must be lower as Ea is increased, and if the tubes are run for pure
class A only,
then you can base the idle dissipation at 32 watts and NO MORE unless
you have special versions of 300B
such as those made by KRAudio in Prague. These special 300B are quite
happy with 40 watts at idle,
ie, 400V x 100mA.
> Thirdly, despite Patrick's attempts to help you, you really haven't
> given us enough information. For instance, is your 405V at the plate
> or on the plate --
"At" the plate, or "on" the plate would be confusing for many.
I prefer to say Ea for the tube's working voltage.
This means the Vdc at idle between anode and cathode regardless of
biasing method
or what the grid bias voltage is.
Ek is the cathode voltage where cathode bias with RC network is used.
B+ is the power supply voltage at the OPT, or wherever else on a voltage
rail
supplying any stage.
> i.e. does it include the drop over the cathode
> resistor for autobias, or is it all operating voltage with fixed bias
> being supplied from somewhere else? Fourthly, the 55mA you mention in
> another post is ludicrously low for a modern application. I know, I
> know, the GE tables and the WE tables all give operating points even
> lower. But 55mA is an invitation to distortion every time you turn the
> wick up. You'd do better to remember that a 300B is only a 450V tube,
> and to look at 65mA operating at a more reasonable operating voltage.
I agree, if you want huge PO levels then the more class A the better.
But where Ea = 400V, Ia of 55mA is OK for where PO wanted is low.
The difference to the sound when going from say 33mA to 80mA
is utterly negligible for most ppl because they only need few watts,
and the first few watts is class A even if Ia is only 33mA.
A pure class A1 triode amp using 300B, KT88, 6550, KT90, EL34 KT66 et
all
can be configured to make 1% THD at clipping with zero loop NFB.
This is with the highest safe bias, so 400V and 80mA would give 32 watts
absolute max.
Ratings are for 42W max, but its too risky, and 300B are expensive.
28 watts is often used, so 70mA is OK.
55mA or less will still give you a lot of class A where the first 5
watts
is little different in THD/IMD measurment or sound quality compared to
the higher Ia of say 70mA.
Suppose you have a load to give pure class A for say 400V x 70mA.
Then you re-bias to to 400V x 35mA.
The PO at clipping will slightly increase, and instead of 1% THD,
you may get 3%, because the PO has become class AB, not all pure class
A.
If the load RLa-a is raised say to twice the value then the amp reverts
back to being pure
class A with 1% THD at clipping but you get less total power.
The load can be tailored to the Ea and Ia and vice versa, hence it pays
to learn all about
load line analysis, because it may be needed to get the best using a
given PSU and available OPT
and speakers.
Tube amp building is about arrangeing tubes, PSU, OPT and speakers to
get the best sound and
enough of it.
But there will be little difference to sound for the first few watts of
"sweetzone"
as long as the amp has enough pure class A to cover the power needed
and tubes do not move into cut off.
> About 380/385/390 volts at the plate and 60-65-70V negative bias and
> 60-65-70mA current with autobias (a very attractive option with 300B
> because fixed bias bloats the bass -- YMMV, you may want bloated bass)
> will give you both a cleaner sound and tubes that will last better.
I cannot see why bass is bloated with fixed bias.
If anything, the reverse might be true; bass could become less
well controlled with low Ra because the Ck across the Rk goes to high Z
at LF.
What is bloat anyway? LF intermodulation?
The answer to good performance with cathode bias is to use a large C
value across Rk,
and not the values used 60 years ago. Use 470uF instead of 47uF.
Fixed bias is fine, but you need to fiddle with adjustments
and there isn't any self regulation.
For pure class A the cathode bias is the best because the tube is set to
work hard even at idle
and you don't want to tempt fate and have a tube thermally run away
because of
bias failure. Shite does happen.
A spontaneous increase in Ia causes the Rk to develop more Ek,
so grid is effectively more negative, so Ia increase is opposed.
In class AB the tubes never have the same high Ia levels so fixed bias
is less risky.
> Fifth: In Class A1 that will give you a minimum of 30W of the cleanest
> power you ever heard.
How many 300B tubes would be used for this? a quad?
30W from 8 x 300B means only 7.5W per pair....
> If you want or need more power, go to a steeper
> loadline i.e. a *lower* impedance, even down to 1K actual or 4K
> effective.
With a fixed Ea & Ia reducing octet 300B RLa-a from say 1k5 to 1k
would reduce class A and threshold of class A to AB, so you'd get more
AB.
> Sixth: There is in my mind very little point in running
> 300B in any configuration outside Class A1; that's the sound that you
> pay for; running 300B in A/B is a waste, because you can get the same
> sound with KT88 or something.
KT90 is probably the best "something."
I am never sure what makes the best triode. Is is a real one, like a
300B or 2A3, 45 etc,
or a multigrid?
The tests I have done with 6550 show they make just as good a triode as
a 300B.
> The same in fact applies to 845; running
> in class A1, 845 always sound better than 211 which reach for the same
> power by driving the signal across the 0V bias line into the positive
> area.
That perception would seem driven my the technicals.
845 have 1/2 the Ra of the 211, so 845 have twice the damping factor.
Ie, Rout of the amp is lower with 845.
The use of Class A2 for 211 poses the problem of driving the tube
without the added distortions of the driver. The driver circuit becomes
more complex
and hence after the threshold for A1 to A1 is passed, the 211 amp
can't give the low THD offered by the 845 amp.
I would have to say that for most ppl this is a negligible concern,
because
a PP amp using either 845 or 211 can be respectively a 60W A1 amp ot A2
amp.
There will be plenty of PO to cover 99% of music before A2 op begins in
the 211.
I'm using 2 x 845 in parallel SET, and get 60W with some slight A2
even though its id RC coupled.
I'm also using KR Audio 845, with oxide cathodes, which don't permit
Ea over 1,100Vdc.
So PP op does not allow a huge AB PO amount.
The Chinese 845 with tungsten cathodes would take maybe 1.5kV at the OPT
CT
and thus the tube does not have so much A2 operation.
Hi-fi is NOT an eternal chase for watts though, we need enough PO and no
more.
> Finally, still on the subject of the fewer 300B the better, and the
> simpler the better, the best amp I ever built, and one which sounds
> better in blind tests to classical musicians playing their own disks,
> is PP EL34 Class A. I respect your ambition but I fear the outcome of
> 4x pairs of 300B will fall short of 4x the pleasure of one pair
> properly implemented -- with the rest of the money spent on sensitive
> speakers better suited to what is best about 300B.
Unless someone is running ATC floor stander speakers rated at 80dB/W/M,
I doubt there is any need to have 8 x 300B per channel.
It does look very nice, it WILL atract a monumental carbon tax when they
make us pay in future.
Distortion at a watt will be slightly lower with 8 tubes instead of 2.
>
> One final note. I am always vastly irritated when I hear manufacturers
> talk about 10W from 300B. It is bullshit. Even Patrick's casual talk
> of 8W per single 300B is still an overstatement.
Most 300B set up for 32 watts of Pd at idle can easily make 8W
at some RL. Some make 10W at 3%. Depends how serious you consider THD.
> 7.6W is the best I
> ever got out of a single 300B not on shortterm test (I've run WE 300B
> briefly at 450V with no ill effects but I wouldn't advise you try that
> with Chinese tubes -- nor 405V, for that matter).
With Ea at 450V, the trouble is that the grid bias has to be very
negative to hold the
Ia down, and the tube is near the region where the grid is running out
of control.
> In the scheme I've
> laid out for you above, at the low end the tubes won't even be
> averaging 4W each or 8W per pair -- they will last forever; I have a
> pair of 300B that lasted 14K hours. And of course the sound will be
> totally linear, with a hugely advantageous distribution of harmonic
> distortion.
A customer of mine has EL34 in PP triode and with Ea = 270V and
maybe it makes 10W max. He's had the same tubes since 1962.
>
> So, in summary, if you really need that much power, 300B are not the
> right tube, and if you decided you want to marry 300B, the answer is
> to use them right and get more sensitive speakers instead of stacking
> up 300B so far that you will lose all their special benefits.
It depends what speakers the man already may have and wish to keep.
But its hard work building for a total of 16 output tubes.
I've tried using 12 x 6550 per channel for UL which sounded pretty well
at a watt.
I've yet to complete the change to CFB for these which I think is better
than triode or UL to my ears.
But its very difficult to make a terrible sounding triode amp
providing its not overdriven.
Patrick Turner.
>
> Sorry to be a drag on a bright dream.
>
> Andre Jute
> Visit Jute on Amps at * members.lycos.co.uk/fiultra/
> "wonderfully well written and reasoned information
> for the tube audio constructor"
> John Broskie TubeCAD & GlassWare
> "an unbelievably comprehensive web site
> containing vital gems of wisdom"
> Stuart Perry Hi-Fi News & Record Review
Andre Jute wrote:
>
> On Apr 6, 5:14 pm, Tube747 <Tube...@lycos . com > wrote:
> > Dear Patrick Turner,
> > Therefore, what is the PO from 4 pairs of 300B in push pull pure class
> > A configuration while the primary impedance of the output transformer
> > is 1.5K ohm?
> >
> > Thanks!
>
> First of all, Tube747, I have a lot of experience with 300B at all
> kinds of operating conditions, and in particular my favourite output
> transformers have a primary impedance of 5K6 which is very close to
> the effective 6K you're talking about per pair. Secondly, it is not
> bright to keep stacking 300B; you soon lose what it is that actually
> makes them 300B, which is clarity and delicacy; it would be smarter to
> go to 845 which have an even nicer tone and are much more powerful.
It depends a bit how much power is needed.
If you only need 5 watts most days and occasionally 10 watts max,
then a pair of 300B would be be fine, and the expense of using 8 x 300B
would not yield a vast improvement imho.
One NEEDS to know how much power one uses,
A peak and hold DVM can be left connected to a speaker running from an
amp
and after a few CDs the peak max voltage is recorded.
If the speaker Z is known power required = peak voltage squared / ( 2 x
speaker ohms ).
Nevertheless, Late last year I heard a VAC amp with a quad of 300B in PP
per channel.
There was no difference in the sound whether the 9dB of global NFB was
connected or not.
And frankly, the thing worked excellently for a class AB1 triode amp.
The guy was using VAF speakers, model I-66, rated at about 90dB/W/M,
and used maybe 2 watts average sometimes, but mainly less most days.
He'd never lisen to anything that wasn't being handled by the
class A region of the AB amp, good for over 55 watts AB.
This amp also blew a lotta smoke a couple of months back, and I have to
repair it.
I'll get the experience to improve it.
The 6k load per pair of 300B isn't all that bad a load, but it means
each tube sees
3k when in class A. To get a maximal amount of class A with the 6k load
the Ea must be lower and Ia higher than if you had a 10k load.
The lower the Ea, the lower tha amount of voltage swing at the anode
because of the
limitation of grid current; see the anode curve where Eg = 0V on the
tube data sheet,
and where a 3k load line cuts this curve.
The higher the load, and higher the Ea, the more swing is possible, so
efficiency
rises with Ea rise.
But the maximum Ea should NOT be much more than 430V.
Ia must be lower as Ea is increased, and if the tubes are run for pure
class A only,
then you can base the idle dissipation at 32 watts and NO MORE unless
you have special versions of 300B
such as those made by KRAudio in Prague. These special 300B are quite
happy with 40 watts at idle,
ie, 400V x 100mA.
> Thirdly, despite Patrick's attempts to help you, you really haven't
> given us enough information. For instance, is your 405V at the plate
> or on the plate --
"At" the plate, or "on" the plate would be confusing for many.
I prefer to say Ea for the tube's working voltage.
This means the Vdc at idle between anode and cathode regardless of
biasing method
or what the grid bias voltage is.
Ek is the cathode voltage where cathode bias with RC network is used.
B+ is the power supply voltage at the OPT, or wherever else on a voltage
rail
supplying any stage.
> i.e. does it include the drop over the cathode
> resistor for autobias, or is it all operating voltage with fixed bias
> being supplied from somewhere else? Fourthly, the 55mA you mention in
> another post is ludicrously low for a modern application. I know, I
> know, the GE tables and the WE tables all give operating points even
> lower. But 55mA is an invitation to distortion every time you turn the
> wick up. You'd do better to remember that a 300B is only a 450V tube,
> and to look at 65mA operating at a more reasonable operating voltage.
I agree, if you want huge PO levels then the more class A the better.
But where Ea = 400V, Ia of 55mA is OK for where PO wanted is low.
The difference to the sound when going from say 33mA to 80mA
is utterly negligible for most ppl because they only need few watts,
and the first few watts is class A even if Ia is only 33mA.
A pure class A1 triode amp using 300B, KT88, 6550, KT90, EL34 KT66 et
all
can be configured to make 1% THD at clipping with zero loop NFB.
This is with the highest safe bias, so 400V and 80mA would give 32 watts
absolute max.
Ratings are for 42W max, but its too risky, and 300B are expensive.
28 watts is often used, so 70mA is OK.
55mA or less will still give you a lot of class A where the first 5
watts
is little different in THD/IMD measurment or sound quality compared to
the higher Ia of say 70mA.
Suppose you have a load to give pure class A for say 400V x 70mA.
Then you re-bias to to 400V x 35mA.
The PO at clipping will slightly increase, and instead of 1% THD,
you may get 3%, because the PO has become class AB, not all pure class
A.
If the load RLa-a is raised say to twice the value then the amp reverts
back to being pure
class A with 1% THD at clipping but you get less total power.
The load can be tailored to the Ea and Ia and vice versa, hence it pays
to learn all about
load line analysis, because it may be needed to get the best using a
given PSU and available OPT
and speakers.
Tube amp building is about arrangeing tubes, PSU, OPT and speakers to
get the best sound and
enough of it.
But there will be little difference to sound for the first few watts of
"sweetzone"
as long as the amp has enough pure class A to cover the power needed
and tubes do not move into cut off.
> About 380/385/390 volts at the plate and 60-65-70V negative bias and
> 60-65-70mA current with autobias (a very attractive option with 300B
> because fixed bias bloats the bass -- YMMV, you may want bloated bass)
> will give you both a cleaner sound and tubes that will last better.
I cannot see why bass is bloated with fixed bias.
If anything, the reverse might be true; bass could become less
well controlled with low Ra because the Ck across the Rk goes to high Z
at LF.
What is bloat anyway? LF intermodulation?
The answer to good performance with cathode bias is to use a large C
value across Rk,
and not the values used 60 years ago. Use 470uF instead of 47uF.
Fixed bias is fine, but you need to fiddle with adjustments
and there isn't any self regulation.
For pure class A the cathode bias is the best because the tube is set to
work hard even at idle
and you don't want to tempt fate and have a tube thermally run away
because of
bias failure. Shite does happen.
A spontaneous increase in Ia causes the Rk to develop more Ek,
so grid is effectively more negative, so Ia increase is opposed.
In class AB the tubes never have the same high Ia levels so fixed bias
is less risky.
> Fifth: In Class A1 that will give you a minimum of 30W of the cleanest
> power you ever heard.
How many 300B tubes would be used for this? a quad?
30W from 8 x 300B means only 7.5W per pair....
> If you want or need more power, go to a steeper
> loadline i.e. a *lower* impedance, even down to 1K actual or 4K
> effective.
With a fixed Ea & Ia reducing octet 300B RLa-a from say 1k5 to 1k
would reduce class A and threshold of class A to AB, so you'd get more
AB.
> Sixth: There is in my mind very little point in running
> 300B in any configuration outside Class A1; that's the sound that you
> pay for; running 300B in A/B is a waste, because you can get the same
> sound with KT88 or something.
KT90 is probably the best "something."
I am never sure what makes the best triode. Is is a real one, like a
300B or 2A3, 45 etc,
or a multigrid?
The tests I have done with 6550 show they make just as good a triode as
a 300B.
> The same in fact applies to 845; running
> in class A1, 845 always sound better than 211 which reach for the same
> power by driving the signal across the 0V bias line into the positive
> area.
That perception would seem driven my the technicals.
845 have 1/2 the Ra of the 211, so 845 have twice the damping factor.
Ie, Rout of the amp is lower with 845.
The use of Class A2 for 211 poses the problem of driving the tube
without the added distortions of the driver. The driver circuit becomes
more complex
and hence after the threshold for A1 to A1 is passed, the 211 amp
can't give the low THD offered by the 845 amp.
I would have to say that for most ppl this is a negligible concern,
because
a PP amp using either 845 or 211 can be respectively a 60W A1 amp ot A2
amp.
There will be plenty of PO to cover 99% of music before A2 op begins in
the 211.
I'm using 2 x 845 in parallel SET, and get 60W with some slight A2
even though its id RC coupled.
I'm also using KR Audio 845, with oxide cathodes, which don't permit
Ea over 1,100Vdc.
So PP op does not allow a huge AB PO amount.
The Chinese 845 with tungsten cathodes would take maybe 1.5kV at the OPT
CT
and thus the tube does not have so much A2 operation.
Hi-fi is NOT an eternal chase for watts though, we need enough PO and no
more.
> Finally, still on the subject of the fewer 300B the better, and the
> simpler the better, the best amp I ever built, and one which sounds
> better in blind tests to classical musicians playing their own disks,
> is PP EL34 Class A. I respect your ambition but I fear the outcome of
> 4x pairs of 300B will fall short of 4x the pleasure of one pair
> properly implemented -- with the rest of the money spent on sensitive
> speakers better suited to what is best about 300B.
Unless someone is running ATC floor stander speakers rated at 80dB/W/M,
I doubt there is any need to have 8 x 300B per channel.
It does look very nice, it WILL atract a monumental carbon tax when they
make us pay in future.
Distortion at a watt will be slightly lower with 8 tubes instead of 2.
>
> One final note. I am always vastly irritated when I hear manufacturers
> talk about 10W from 300B. It is bullshit. Even Patrick's casual talk
> of 8W per single 300B is still an overstatement.
Most 300B set up for 32 watts of Pd at idle can easily make 8W
at some RL. Some make 10W at 3%. Depends how serious you consider THD.
> 7.6W is the best I
> ever got out of a single 300B not on shortterm test (I've run WE 300B
> briefly at 450V with no ill effects but I wouldn't advise you try that
> with Chinese tubes -- nor 405V, for that matter).
With Ea at 450V, the trouble is that the grid bias has to be very
negative to hold the
Ia down, and the tube is near the region where the grid is running out
of control.
> In the scheme I've
> laid out for you above, at the low end the tubes won't even be
> averaging 4W each or 8W per pair -- they will last forever; I have a
> pair of 300B that lasted 14K hours. And of course the sound will be
> totally linear, with a hugely advantageous distribution of harmonic
> distortion.
A customer of mine has EL34 in PP triode and with Ea = 270V and
maybe it makes 10W max. He's had the same tubes since 1962.
>
> So, in summary, if you really need that much power, 300B are not the
> right tube, and if you decided you want to marry 300B, the answer is
> to use them right and get more sensitive speakers instead of stacking
> up 300B so far that you will lose all their special benefits.
It depends what speakers the man already may have and wish to keep.
But its hard work building for a total of 16 output tubes.
I've tried using 12 x 6550 per channel for UL which sounded pretty well
at a watt.
I've yet to complete the change to CFB for these which I think is better
than triode or UL to my ears.
But its very difficult to make a terrible sounding triode amp
providing its not overdriven.
Patrick Turner.
>
> Sorry to be a drag on a bright dream.
>
> Andre Jute
> Visit Jute on Amps at * members.lycos.co.uk/fiultra/
> "wonderfully well written and reasoned information
> for the tube audio constructor"
> John Broskie TubeCAD & GlassWare
> "an unbelievably comprehensive web site
> containing vital gems of wisdom"
> Stuart Perry Hi-Fi News & Record Review
Re: 300B push pull amplifier
Many thanks to you guys for the valuable comments! What about this
driver
circuit with 4 x 300B in push pull in class A2 operation?
* w w w .kandkaudio . com /images/PPAmpInput.pdf
Do you think 2 x 5AW4 good enough for 4 x 300B as far as rectification
goes?
Thanks!
Many thanks to you guys for the valuable comments! What about this
driver
circuit with 4 x 300B in push pull in class A2 operation?
* w w w .kandkaudio . com /images/PPAmpInput.pdf
Do you think 2 x 5AW4 good enough for 4 x 300B as far as rectification
goes?
Thanks!
