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Driving "Miss" 300B
Driving "Miss" 300B
Hi:
I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
these amps, I liked the 300B ones the least. With that in mind, I just
recently came across a website for a foreign amplifier manufacturer that has
some interesting thoughts about driving the 300B.
I would appreciate your comments about their ideas. Here's the exact text
from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
in the translation):
What points we are interested in?
Perhaps there are so many 300B single ended amps that we could
not discern good ones from bad.
For its natural and mellow mid-range, 300B single ended amp
is loved so much but its anemic bass and weak high frequency
response drive out many tube amp enthusiast from entering in the
Single Ended World.
What are the problems?
Basically there has been no good driving force for 300B.
First, Western Electric's 91B circuit was improvised for
easy manufacturing (for delayed production of 86B) and higher gain for
a theater system.
It's driving tube 310B ( or 6SJ7 or 6SH7 ) is pentode, notorious for
its distortion (too sensitive of its screen grid condition ) and cotton
sugar bass response and too high internal impedance (about 100K?!!
bad frequency response in low and high spectrums).
Second, there are two stage driver circuit. Some use 6SN7 twin triodes
one triode for 1st stage and 2nd stage for driving stage. Alas! 6SN7
is not so powerful for 300B and it's high gain of two stage is not
suitable
for 300B power amps, so they sell them as integrated amps.
Its major defect come from capacitor coupling, which can transfer a few
percent of driving wattage to 300B grid, almost of its energy is
converted
into useless heat of 6SN7's plate resister.
There are also a power drive circuit using EL34 or 6V6 or we349A (triode
connection).
They are not really 'power' drive, why? They use big plate resistor for
EL34 about
10k? 20w, but it generates big heat only and could not drive 300B
sufficiently due
to the next coupling capacitor, in theory it transfers only few
percentage of its
power.
There are only two methods to consider.
First, there is interstage transformer coupling and then plate choke
drive method
(which will be discussed in our 300B integrated amplifier). A interstage
coupling
method is a ideal one for transferring driving power to 300B grid for
its full
operation.
Its driving wattage could be transferred about 93% (less some coil and
core loss of
interstage transformer). We need sufficient power to make 300B work of
its full
capacity.
You will be surprised to the difference between under driven operation
of 300B and
full driven one. But it is really difficult to get a good interstage
transformer.
There three points to check for interstage transformer.
1. Must be wide range. Minimum 20Hz - 20KHz FLAT at designated source
impedance.
2. Good response to 10KHz square wave for flexibility and musicality.
3. Low distortion at low frequencies.
What do you think? Thanks!
Gerry
Hi:
I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
these amps, I liked the 300B ones the least. With that in mind, I just
recently came across a website for a foreign amplifier manufacturer that has
some interesting thoughts about driving the 300B.
I would appreciate your comments about their ideas. Here's the exact text
from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
in the translation):
What points we are interested in?
Perhaps there are so many 300B single ended amps that we could
not discern good ones from bad.
For its natural and mellow mid-range, 300B single ended amp
is loved so much but its anemic bass and weak high frequency
response drive out many tube amp enthusiast from entering in the
Single Ended World.
What are the problems?
Basically there has been no good driving force for 300B.
First, Western Electric's 91B circuit was improvised for
easy manufacturing (for delayed production of 86B) and higher gain for
a theater system.
It's driving tube 310B ( or 6SJ7 or 6SH7 ) is pentode, notorious for
its distortion (too sensitive of its screen grid condition ) and cotton
sugar bass response and too high internal impedance (about 100K?!!
bad frequency response in low and high spectrums).
Second, there are two stage driver circuit. Some use 6SN7 twin triodes
one triode for 1st stage and 2nd stage for driving stage. Alas! 6SN7
is not so powerful for 300B and it's high gain of two stage is not
suitable
for 300B power amps, so they sell them as integrated amps.
Its major defect come from capacitor coupling, which can transfer a few
percent of driving wattage to 300B grid, almost of its energy is
converted
into useless heat of 6SN7's plate resister.
There are also a power drive circuit using EL34 or 6V6 or we349A (triode
connection).
They are not really 'power' drive, why? They use big plate resistor for
EL34 about
10k? 20w, but it generates big heat only and could not drive 300B
sufficiently due
to the next coupling capacitor, in theory it transfers only few
percentage of its
power.
There are only two methods to consider.
First, there is interstage transformer coupling and then plate choke
drive method
(which will be discussed in our 300B integrated amplifier). A interstage
coupling
method is a ideal one for transferring driving power to 300B grid for
its full
operation.
Its driving wattage could be transferred about 93% (less some coil and
core loss of
interstage transformer). We need sufficient power to make 300B work of
its full
capacity.
You will be surprised to the difference between under driven operation
of 300B and
full driven one. But it is really difficult to get a good interstage
transformer.
There three points to check for interstage transformer.
1. Must be wide range. Minimum 20Hz - 20KHz FLAT at designated source
impedance.
2. Good response to 10KHz square wave for flexibility and musicality.
3. Low distortion at low frequencies.
What do you think? Thanks!
Gerry
Re: Driving "Miss" 300B
GerryE123 wrote:
>
> Hi:
>
> I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
> these amps, I liked the 300B ones the least. With that in mind, I just
> recently came across a website for a foreign amplifier manufacturer that has
> some interesting thoughts about driving the 300B.
>
> I would appreciate your comments about their ideas. Here's the exact text
> from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
> in the translation):
>
> What points we are interested in?
>
> Perhaps there are so many 300B single ended amps that we could
> not discern good ones from bad.
>
> For its natural and mellow mid-range, 300B single ended amp
> is loved so much but its anemic bass and weak high frequency
> response drive out many tube amp enthusiast from entering in the
> Single Ended World.
The bad ones lack a decent full range response, usually because of
a poor OPT, such as many used in ancient cinema amps.
Combined with a poor load and op conditions, sound wasn't wonderful.
But with decent OPT, the 300B or any other triode in SE mode is just
fine
and the the idea 300B amps and other triodes just cannot do bass,
midrange and treble
all simultaneously and as well as each other; ie, do any type of music,
is a complete myth,
ie, a pile of ideolgical bullshit.
However, the performance from a single 300B is limited to what around 7
watts max can do.
It was designed and produced originally for theatre amps which powered
horns with
typical 100dB sensitivity, and without a full F range.
But most ordinary dynamic speakers in normal boxes are 90dB/W/M,
and you cannot expect the same dynamics as you would get if you had a
horn speaker.
With today's low sensitivity, you'd need multiple parallel tubes.
THEN there is never going to be a problem with dynamics and people
bashing
huge drums and so on.
Try a 7 watt transistor amp. They will flounder just like a lone 300B
if you drive it beyond its capability, which so many people do
when making a silly comparison.
I just auditioned a pair of 845 in parallel for 60W max.
Utterly no clipping, oddles of bass and treble, and the OPT
allows 8Hz to 50kHz, -3dB points, even without NFB.
300B will do just the same!!!
>
> What are the problems?
>
> Basically there has been no good driving force for 300B.
> First, Western Electric's 91B circuit was improvised for
> easy manufacturing (for delayed production of 86B) and higher gain for
> a theater system.
>
> It's driving tube 310B ( or 6SJ7 or 6SH7 ) is pentode, notorious for
> its distortion (too sensitive of its screen grid condition ) and cotton
> sugar bass response and too high internal impedance (about 100K?!!
> bad frequency response in low and high spectrums).
Forget the old ancient ways of driving 300B, 845, 2A3, et all.
Use a 6SN7 with both triodes paralleled.
Have Ea = 250V at least, and Iadc for the two triodes totalling 8mA at
least.
Have a dc carrying resistance of 20k and a 70H choke in series to the B+
of 520V approx.
As F rises, the L ensures the 6SN7 does not have to work hard
putting AC power into the anode feed resistance.
The reactive properties of the choke are isolated from the anodes
because of the 20k.
The 300B being driven should be cap coupled to the driver anodes and
should be cathode biased in the normal way
with R&C, with C > 330uF. Bias R should be around 220k, which will be
the
lowest load the 'SN7 has to drive when ZL is high in the mid F.
Since the load is so high compared to the low Ra of the 'SN7 = about 5k,
you'll get a wide Vswing,
at very low THD.
>
> Second, there are two stage driver circuit. Some use 6SN7 twin triodes
> one triode for 1st stage and 2nd stage for driving stage. Alas! 6SN7
> is not so powerful for 300B and it's high gain of two stage is not
> suitable
> for 300B power amps, so they sell them as integrated amps.
> Its major defect come from capacitor coupling, which can transfer a few
> percent of driving wattage to 300B grid, almost of its energy is
> converted
> into useless heat of 6SN7's plate resister.
Use a second paralleled 6SN7 for an input tube if you want sensitivity
and to be able to apply some loop FB, usually 10dB is plenty.
>
> There are also a power drive circuit using EL34 or 6V6 or we349A (triode
> connection).
>
> They are not really 'power' drive, why? They use big plate resistor for
> EL34 about
> 10k? 20w, but it generates big heat only and could not drive 300B
> sufficiently due
> to the next coupling capacitor, in theory it transfers only few
> percentage of its
> power.
>
> There are only two methods to consider.
>
> First, there is interstage transformer coupling and then plate choke
> drive method
> (which will be discussed in our 300B integrated amplifier). A interstage
> coupling
> method is a ideal one for transferring driving power to 300B grid for
> its full
> operation.
The driving "power" is negligible, because there isn't any grid current
in 300B operation.
You just need a linear voltage source with low Ra to overcome Miller C.
Se above about combined L&R to get dc supply.
Interstage trannies are very difficult to make with 8Hz to 60kHz BW.
The usually don't allow loop NFB because of te phase shift of the Cshunt
and Lp.
>
> Its driving wattage could be transferred about 93% (less some coil and
> core loss of
> interstage transformer). We need sufficient power to make 300B work of
> its full
> capacity.
>
> You will be surprised to the difference between under driven operation
> of 300B and
> full driven one. But it is really difficult to get a good interstage
> transformer.
We all know that....
>
> There three points to check for interstage transformer.
>
> 1. Must be wide range. Minimum 20Hz - 20KHz FLAT at designated source
> impedance.
> 2. Good response to 10KHz square wave for flexibility and musicality.
> 3. Low distortion at low frequencies.
>
> What do you think? Thanks!
The whole business of an IST is difficult.
The parafeed I mentioned above is the best I have used,
wide BW, with slight shelving of response at LF and HF,
and no added iron cause distortions at any F.
One can also use a µ-follower which also works well,
or use a pentode for the dc anode supply with extremely high AC
impedance.
I like the parafeed choke plus R method because it works, and sounds
well,
and has electronic simplicity of elements, even though
you would need a choke with 25mm square core section and have
7,000 turns of fine wire, and just the right gap size.
There is one other way, just make a B+ suply at say +750V, and have the
anode
dc supply resistance for 8mA to be about 70k, well rated for power, made
up of
3 x series R of about 22k each, so the R won't suffer over voltage.
The higher R load will be more easily driven then 20k.
I have used EL84 in triode which is the best IMHO, because
it has gain = 18 when loaded with choke + RL, and with Ia = 15mA,
Ea = 300V, with supply voltage about 500. R would be approx 12k,
and choke = 50H.
Ra will be about 2k2, or equal to about 5 x 1/2 6SN7 triodes paralelled.
An input tube is still needed, so use a 6CG7.
I have 3 x EL84 in parallel to drive the 845, which needs 127vrms max.
The 3 x '84 can produce 160Vrms at 2% THD with parafeed, and at 127Vrms
THD is about 1.4%
At normal listening levels they make about 20Vrms, with THD less than
0.4%,
all of which naturally cancels output tube THD because its all mainly
2H,
so all listening can be done with THD < 0.05%, even with only 8dB loop
FB.
There are several very good ways to build triode amps.
Use the brains and the soldering to find out.
Buy as much good iron from Sowter or Lundahl or someone else as you can
afford.
Don't be afraid of global NFB. Its not a monster, but a technique
to allow the beauty of the music pass without the added artifacts to
spoil anything,
and mainly to ensure the output resistance of the amp gives good control
over speakers because they all have been designed to be driven by a
voltage source < 1 ohm.
My experience with NFB is positive, but many dislike global NFB around
triode amps
and its often because they have no clue how to make sure the amp remains
stable
under any load condition.
I have heard audiophiles say after I have demonstrated my SE amps that
"This proves NFB is OK around SE amps".
Patrick Turner.
>
> Gerry
GerryE123 wrote:
>
> Hi:
>
> I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
> these amps, I liked the 300B ones the least. With that in mind, I just
> recently came across a website for a foreign amplifier manufacturer that has
> some interesting thoughts about driving the 300B.
>
> I would appreciate your comments about their ideas. Here's the exact text
> from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
> in the translation):
>
> What points we are interested in?
>
> Perhaps there are so many 300B single ended amps that we could
> not discern good ones from bad.
>
> For its natural and mellow mid-range, 300B single ended amp
> is loved so much but its anemic bass and weak high frequency
> response drive out many tube amp enthusiast from entering in the
> Single Ended World.
The bad ones lack a decent full range response, usually because of
a poor OPT, such as many used in ancient cinema amps.
Combined with a poor load and op conditions, sound wasn't wonderful.
But with decent OPT, the 300B or any other triode in SE mode is just
fine
and the the idea 300B amps and other triodes just cannot do bass,
midrange and treble
all simultaneously and as well as each other; ie, do any type of music,
is a complete myth,
ie, a pile of ideolgical bullshit.
However, the performance from a single 300B is limited to what around 7
watts max can do.
It was designed and produced originally for theatre amps which powered
horns with
typical 100dB sensitivity, and without a full F range.
But most ordinary dynamic speakers in normal boxes are 90dB/W/M,
and you cannot expect the same dynamics as you would get if you had a
horn speaker.
With today's low sensitivity, you'd need multiple parallel tubes.
THEN there is never going to be a problem with dynamics and people
bashing
huge drums and so on.
Try a 7 watt transistor amp. They will flounder just like a lone 300B
if you drive it beyond its capability, which so many people do
when making a silly comparison.
I just auditioned a pair of 845 in parallel for 60W max.
Utterly no clipping, oddles of bass and treble, and the OPT
allows 8Hz to 50kHz, -3dB points, even without NFB.
300B will do just the same!!!
>
> What are the problems?
>
> Basically there has been no good driving force for 300B.
> First, Western Electric's 91B circuit was improvised for
> easy manufacturing (for delayed production of 86B) and higher gain for
> a theater system.
>
> It's driving tube 310B ( or 6SJ7 or 6SH7 ) is pentode, notorious for
> its distortion (too sensitive of its screen grid condition ) and cotton
> sugar bass response and too high internal impedance (about 100K?!!
> bad frequency response in low and high spectrums).
Forget the old ancient ways of driving 300B, 845, 2A3, et all.
Use a 6SN7 with both triodes paralleled.
Have Ea = 250V at least, and Iadc for the two triodes totalling 8mA at
least.
Have a dc carrying resistance of 20k and a 70H choke in series to the B+
of 520V approx.
As F rises, the L ensures the 6SN7 does not have to work hard
putting AC power into the anode feed resistance.
The reactive properties of the choke are isolated from the anodes
because of the 20k.
The 300B being driven should be cap coupled to the driver anodes and
should be cathode biased in the normal way
with R&C, with C > 330uF. Bias R should be around 220k, which will be
the
lowest load the 'SN7 has to drive when ZL is high in the mid F.
Since the load is so high compared to the low Ra of the 'SN7 = about 5k,
you'll get a wide Vswing,
at very low THD.
>
> Second, there are two stage driver circuit. Some use 6SN7 twin triodes
> one triode for 1st stage and 2nd stage for driving stage. Alas! 6SN7
> is not so powerful for 300B and it's high gain of two stage is not
> suitable
> for 300B power amps, so they sell them as integrated amps.
> Its major defect come from capacitor coupling, which can transfer a few
> percent of driving wattage to 300B grid, almost of its energy is
> converted
> into useless heat of 6SN7's plate resister.
Use a second paralleled 6SN7 for an input tube if you want sensitivity
and to be able to apply some loop FB, usually 10dB is plenty.
>
> There are also a power drive circuit using EL34 or 6V6 or we349A (triode
> connection).
>
> They are not really 'power' drive, why? They use big plate resistor for
> EL34 about
> 10k? 20w, but it generates big heat only and could not drive 300B
> sufficiently due
> to the next coupling capacitor, in theory it transfers only few
> percentage of its
> power.
>
> There are only two methods to consider.
>
> First, there is interstage transformer coupling and then plate choke
> drive method
> (which will be discussed in our 300B integrated amplifier). A interstage
> coupling
> method is a ideal one for transferring driving power to 300B grid for
> its full
> operation.
The driving "power" is negligible, because there isn't any grid current
in 300B operation.
You just need a linear voltage source with low Ra to overcome Miller C.
Se above about combined L&R to get dc supply.
Interstage trannies are very difficult to make with 8Hz to 60kHz BW.
The usually don't allow loop NFB because of te phase shift of the Cshunt
and Lp.
>
> Its driving wattage could be transferred about 93% (less some coil and
> core loss of
> interstage transformer). We need sufficient power to make 300B work of
> its full
> capacity.
>
> You will be surprised to the difference between under driven operation
> of 300B and
> full driven one. But it is really difficult to get a good interstage
> transformer.
We all know that....
>
> There three points to check for interstage transformer.
>
> 1. Must be wide range. Minimum 20Hz - 20KHz FLAT at designated source
> impedance.
> 2. Good response to 10KHz square wave for flexibility and musicality.
> 3. Low distortion at low frequencies.
>
> What do you think? Thanks!
The whole business of an IST is difficult.
The parafeed I mentioned above is the best I have used,
wide BW, with slight shelving of response at LF and HF,
and no added iron cause distortions at any F.
One can also use a µ-follower which also works well,
or use a pentode for the dc anode supply with extremely high AC
impedance.
I like the parafeed choke plus R method because it works, and sounds
well,
and has electronic simplicity of elements, even though
you would need a choke with 25mm square core section and have
7,000 turns of fine wire, and just the right gap size.
There is one other way, just make a B+ suply at say +750V, and have the
anode
dc supply resistance for 8mA to be about 70k, well rated for power, made
up of
3 x series R of about 22k each, so the R won't suffer over voltage.
The higher R load will be more easily driven then 20k.
I have used EL84 in triode which is the best IMHO, because
it has gain = 18 when loaded with choke + RL, and with Ia = 15mA,
Ea = 300V, with supply voltage about 500. R would be approx 12k,
and choke = 50H.
Ra will be about 2k2, or equal to about 5 x 1/2 6SN7 triodes paralelled.
An input tube is still needed, so use a 6CG7.
I have 3 x EL84 in parallel to drive the 845, which needs 127vrms max.
The 3 x '84 can produce 160Vrms at 2% THD with parafeed, and at 127Vrms
THD is about 1.4%
At normal listening levels they make about 20Vrms, with THD less than
0.4%,
all of which naturally cancels output tube THD because its all mainly
2H,
so all listening can be done with THD < 0.05%, even with only 8dB loop
FB.
There are several very good ways to build triode amps.
Use the brains and the soldering to find out.
Buy as much good iron from Sowter or Lundahl or someone else as you can
afford.
Don't be afraid of global NFB. Its not a monster, but a technique
to allow the beauty of the music pass without the added artifacts to
spoil anything,
and mainly to ensure the output resistance of the amp gives good control
over speakers because they all have been designed to be driven by a
voltage source < 1 ohm.
My experience with NFB is positive, but many dislike global NFB around
triode amps
and its often because they have no clue how to make sure the amp remains
stable
under any load condition.
I have heard audiophiles say after I have demonstrated my SE amps that
"This proves NFB is OK around SE amps".
Patrick Turner.
>
> Gerry
New Hagerman 2A3 Amp (was Driving "Miss" 300B)
"Patrick Turner" <info@turneraudio . com .au> wrote in message
news:481DED13.3F4D42A4@turneraudio . com .au...
> The whole business of an IST is difficult.
>
> The parafeed I mentioned above is the best I have used,
> wide BW, with slight shelving of response at LF and HF,
> and no added iron cause distortions at any F.
>
> One can also use a µ-follower which also works well,
> or use a pentode for the dc anode supply with extremely high AC
> impedance.
>
> I like the parafeed choke plus R method because it works, and sounds
> well,
> and has electronic simplicity of elements, even though
> you would need a choke with 25mm square core section and have
> 7,000 turns of fine wire, and just the right gap size.
A belated THANK YOU to Patrick (I was hoping you would respond) and everyone
else who replied! I know that interstage transformers are a well known
design option, I just thought it was interesting to read a manufacturers
deatiled explanation for using it as opposed to other specific choices.
Jim Hagerman is coming out with a new and unusual 2A3 amp. Here's a quote
from it's description:
"Distortion is exceedingly low, especially given the fact that no feedback
is used, thanks to the harmonic cancellation of the output stage, which
operates partially in both single-ended parallel and push-pull differential
modes. This balance results in SET-like musicality yet with PP control and
dynamics."
Here's the link to the manufacturers web page for the new amp:
* w w w .haglabs . com /pa10.html
What do you think? Thanks.
Gerry
"Patrick Turner" <info@turneraudio . com .au> wrote in message
news:481DED13.3F4D42A4@turneraudio . com .au...
> The whole business of an IST is difficult.
>
> The parafeed I mentioned above is the best I have used,
> wide BW, with slight shelving of response at LF and HF,
> and no added iron cause distortions at any F.
>
> One can also use a µ-follower which also works well,
> or use a pentode for the dc anode supply with extremely high AC
> impedance.
>
> I like the parafeed choke plus R method because it works, and sounds
> well,
> and has electronic simplicity of elements, even though
> you would need a choke with 25mm square core section and have
> 7,000 turns of fine wire, and just the right gap size.
A belated THANK YOU to Patrick (I was hoping you would respond) and everyone
else who replied! I know that interstage transformers are a well known
design option, I just thought it was interesting to read a manufacturers
deatiled explanation for using it as opposed to other specific choices.
Jim Hagerman is coming out with a new and unusual 2A3 amp. Here's a quote
from it's description:
"Distortion is exceedingly low, especially given the fact that no feedback
is used, thanks to the harmonic cancellation of the output stage, which
operates partially in both single-ended parallel and push-pull differential
modes. This balance results in SET-like musicality yet with PP control and
dynamics."
Here's the link to the manufacturers web page for the new amp:
* w w w .haglabs . com /pa10.html
What do you think? Thanks.
Gerry
Re: New Hagerman 2A3 Amp (was Driving "Miss" 300B)
GerryE123 wrote:
>
> "Patrick Turner" <info@turneraudio . com .au> wrote in message
> news:481DED13.3F4D42A4@turneraudio . com .au...
> > The whole business of an IST is difficult.
> >
> > The parafeed I mentioned above is the best I have used,
> > wide BW, with slight shelving of response at LF and HF,
> > and no added iron cause distortions at any F.
> >
> > One can also use a µ-follower which also works well,
> > or use a pentode for the dc anode supply with extremely high AC
> > impedance.
> >
> > I like the parafeed choke plus R method because it works, and sounds
> > well,
> > and has electronic simplicity of elements, even though
> > you would need a choke with 25mm square core section and have
> > 7,000 turns of fine wire, and just the right gap size.
>
> A belated THANK YOU to Patrick (I was hoping you would respond) and everyone
> else who replied! I know that interstage transformers are a well known
> design option, I just thought it was interesting to read a manufacturers
> deatiled explanation for using it as opposed to other specific choices.
>
> Jim Hagerman is coming out with a new and unusual 2A3 amp. Here's a quote
> from it's description:
>
> "Distortion is exceedingly low, especially given the fact that no feedback
> is used, thanks to the harmonic cancellation of the output stage, which
> operates partially in both single-ended parallel and push-pull differential
> modes. This balance results in SET-like musicality yet with PP control and
> dynamics."
>
> Here's the link to the manufacturers web page for the new amp:
>
> * w w w .haglabs . com /pa10.html
>
> What do you think? Thanks.
>
> Gerry
Sun Corp made an almost identical amp many years ago.
I repaired a pair last year.
The IST had a gap for the DC through the primary of the IST.
The above amp uses a CCS and cap couples the IST primary, which means
that
an un-gapped IST can be used, and if the core material is good, THD
should be lower
and BW wider because of fewer turns needed to get sufficient primary
inductance.
One could do the same with any SE output stage, but the CCS must come
from a voltage source
equal to about twice the Ea of the tube to allow the swing upwards of
anode signal.
So you'd have say 400V at 60mA floe in a CCS at idle, which is 24 watts,
and the same as the Pd of the tube.
So you never see the CC done like this for any SE amp.
A choke is used instead.
And the magnetic stored energy allows the positive rise in signal
voltage as the tube
is turned off by a negative goingf grid.
Its a case of turning something off and getting something more,
yet another thing that defies ordinary human common sense.
Patrick Turner.
GerryE123 wrote:
>
> "Patrick Turner" <info@turneraudio . com .au> wrote in message
> news:481DED13.3F4D42A4@turneraudio . com .au...
> > The whole business of an IST is difficult.
> >
> > The parafeed I mentioned above is the best I have used,
> > wide BW, with slight shelving of response at LF and HF,
> > and no added iron cause distortions at any F.
> >
> > One can also use a µ-follower which also works well,
> > or use a pentode for the dc anode supply with extremely high AC
> > impedance.
> >
> > I like the parafeed choke plus R method because it works, and sounds
> > well,
> > and has electronic simplicity of elements, even though
> > you would need a choke with 25mm square core section and have
> > 7,000 turns of fine wire, and just the right gap size.
>
> A belated THANK YOU to Patrick (I was hoping you would respond) and everyone
> else who replied! I know that interstage transformers are a well known
> design option, I just thought it was interesting to read a manufacturers
> deatiled explanation for using it as opposed to other specific choices.
>
> Jim Hagerman is coming out with a new and unusual 2A3 amp. Here's a quote
> from it's description:
>
> "Distortion is exceedingly low, especially given the fact that no feedback
> is used, thanks to the harmonic cancellation of the output stage, which
> operates partially in both single-ended parallel and push-pull differential
> modes. This balance results in SET-like musicality yet with PP control and
> dynamics."
>
> Here's the link to the manufacturers web page for the new amp:
>
> * w w w .haglabs . com /pa10.html
>
> What do you think? Thanks.
>
> Gerry
Sun Corp made an almost identical amp many years ago.
I repaired a pair last year.
The IST had a gap for the DC through the primary of the IST.
The above amp uses a CCS and cap couples the IST primary, which means
that
an un-gapped IST can be used, and if the core material is good, THD
should be lower
and BW wider because of fewer turns needed to get sufficient primary
inductance.
One could do the same with any SE output stage, but the CCS must come
from a voltage source
equal to about twice the Ea of the tube to allow the swing upwards of
anode signal.
So you'd have say 400V at 60mA floe in a CCS at idle, which is 24 watts,
and the same as the Pd of the tube.
So you never see the CC done like this for any SE amp.
A choke is used instead.
And the magnetic stored energy allows the positive rise in signal
voltage as the tube
is turned off by a negative goingf grid.
Its a case of turning something off and getting something more,
yet another thing that defies ordinary human common sense.
Patrick Turner.
300B SE amps and sanity
The WE 91 was designed by professional but not audiophilically anal
engineers at a particular time for a particular purpose under a particular
set of conditions. For that purpose under those terms at that time it was a
competent, hardly earth-shakingly good, piece of gear.
Those conditions had about as much to do with "high fidelity" as a Fender
Champ or a Bell & Howell projector amp speaker.
The Oriental buyers of them want them because they provide virtual penis
enhancement amongst their circle of friends. It's that very simple.
Evolution drives penis size development: the penis must be large enough to
provide visual sign of status-the literal peckering order-so the high
status males copulate more frequently and with the better women, whilst
being not too big to actually fit in most vaginas or scare off potential
mates for fear of damage. Certain tribes in equatorial Africa, where
nakedness is common, have evolutionary pressure for large penis
development whereas in Asian society genital size was utterly unimportant
for millennia. Only with greater constant awareness of big Occidental and
African penises has this caused feelings of losing face amongst these
Asians.
To get back to electronics, the WE 91 was designed for use as a
projection booth monitor amplifier, using at any time one of the several
used spares kept on hand from rotating stock in the main, push-pull
amplifiers used in the cinema service. It did this adequately. No more.
At that time it was technically a violation of the license under which
tubes were sold to use regular entertainment radio tubes in cinema
playback gear or to use WE ERPI vended tubes in consumer service. WE had
cross licensing of patents under an agreement which prohibited this. Third
party independent phone equipment which used off the shelf receiving tubes
violated this license, giving WE an effective monopoly in the telco
market. That was a lucrative monopoly. To maintain its pretense-and actual
litigability-WE ERPI had to honor it "the other way", that locked WE tubes
into ERPI gear and everyone else's out so long as ERPI gear was on lease
from and maintained by ERPI. Consequently, even though WE tubes lacked
cost effectiveness once reliable commodity 45s, 2A3s and 50s came out,
they stayed with them.
--
Message posted using * w w w .talkaboutaudio . com /group/rec.audio.tubes/
More information at * w w w .talkaboutaudio . com /faq.html
The WE 91 was designed by professional but not audiophilically anal
engineers at a particular time for a particular purpose under a particular
set of conditions. For that purpose under those terms at that time it was a
competent, hardly earth-shakingly good, piece of gear.
Those conditions had about as much to do with "high fidelity" as a Fender
Champ or a Bell & Howell projector amp speaker.
The Oriental buyers of them want them because they provide virtual penis
enhancement amongst their circle of friends. It's that very simple.
Evolution drives penis size development: the penis must be large enough to
provide visual sign of status-the literal peckering order-so the high
status males copulate more frequently and with the better women, whilst
being not too big to actually fit in most vaginas or scare off potential
mates for fear of damage. Certain tribes in equatorial Africa, where
nakedness is common, have evolutionary pressure for large penis
development whereas in Asian society genital size was utterly unimportant
for millennia. Only with greater constant awareness of big Occidental and
African penises has this caused feelings of losing face amongst these
Asians.
To get back to electronics, the WE 91 was designed for use as a
projection booth monitor amplifier, using at any time one of the several
used spares kept on hand from rotating stock in the main, push-pull
amplifiers used in the cinema service. It did this adequately. No more.
At that time it was technically a violation of the license under which
tubes were sold to use regular entertainment radio tubes in cinema
playback gear or to use WE ERPI vended tubes in consumer service. WE had
cross licensing of patents under an agreement which prohibited this. Third
party independent phone equipment which used off the shelf receiving tubes
violated this license, giving WE an effective monopoly in the telco
market. That was a lucrative monopoly. To maintain its pretense-and actual
litigability-WE ERPI had to honor it "the other way", that locked WE tubes
into ERPI gear and everyone else's out so long as ERPI gear was on lease
from and maintained by ERPI. Consequently, even though WE tubes lacked
cost effectiveness once reliable commodity 45s, 2A3s and 50s came out,
they stayed with them.
--
Message posted using * w w w .talkaboutaudio . com /group/rec.audio.tubes/
More information at * w w w .talkaboutaudio . com /faq.html
Reply from: -- messaggio eliminato --
Date: 05 May 2008, 13:28
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Date: 06 May 2008, 03:19
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Date: 06 May 2008, 04:50
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Date: 06 May 2008, 09:32
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Date: 07 May 2008, 15:35
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Date: 07 May 2008, 16:52
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Re: Driving "Miss" 300B
GerryE123 wrote:
> Hi:
>
> I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
> these amps, I liked the 300B ones the least. With that in mind, I just
> recently came across a website for a foreign amplifier manufacturer that has
> some interesting thoughts about driving the 300B.
>
> I would appreciate your comments about their ideas. Here's the exact text
> from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
> in the translation):
>
> What points we are interested in?
>
> Perhaps there are so many 300B single ended amps that we could
> not discern good ones from bad.
>
> For its natural and mellow mid-range, 300B single ended amp
> is loved so much but its anemic bass and weak high frequency
> response drive out many tube amp enthusiast from entering in the
> Single Ended World.
>
> What are the problems?
>
> Basically there has been no good driving force for 300B.
> First, Western Electric's 91B circuit was improvised for
> easy manufacturing (for delayed production of 86B) and higher gain for
> a theater system.
Two drivers I have found work well for 300b.
1. c3g, running as a pantode with a VR tube regulated screen supply
works very well. d3a is also good.
2. 6n6p Aikido also works well. Best combination I found was a ecc40 as
voltage amp, then 6n6p aikido cap coupled to 300b grid.
If you like the idea of a interstage, the AE interstages are very good,
and drive 300bs nicely driven by something like a 45 or 6em7.
* w w w .ae-europe.nl/uitgangstrafo_engels.htm
--
Nick
GerryE123 wrote:
> Hi:
>
> I have heard or owned a number of single-ended 45, 2A3 and 300B amps. Of
> these amps, I liked the 300B ones the least. With that in mind, I just
> recently came across a website for a foreign amplifier manufacturer that has
> some interesting thoughts about driving the 300B.
>
> I would appreciate your comments about their ideas. Here's the exact text
> from the manufacturers website (NOTE: I am copying it as-is, it loses a bit
> in the translation):
>
> What points we are interested in?
>
> Perhaps there are so many 300B single ended amps that we could
> not discern good ones from bad.
>
> For its natural and mellow mid-range, 300B single ended amp
> is loved so much but its anemic bass and weak high frequency
> response drive out many tube amp enthusiast from entering in the
> Single Ended World.
>
> What are the problems?
>
> Basically there has been no good driving force for 300B.
> First, Western Electric's 91B circuit was improvised for
> easy manufacturing (for delayed production of 86B) and higher gain for
> a theater system.
Two drivers I have found work well for 300b.
1. c3g, running as a pantode with a VR tube regulated screen supply
works very well. d3a is also good.
2. 6n6p Aikido also works well. Best combination I found was a ecc40 as
voltage amp, then 6n6p aikido cap coupled to 300b grid.
If you like the idea of a interstage, the AE interstages are very good,
and drive 300bs nicely driven by something like a 45 or 6em7.
* w w w .ae-europe.nl/uitgangstrafo_engels.htm
--
Nick
Re: Driving "Miss" 300B
Nice to see Nick mention ECC40 - lovely sounding tube.
Anyway - back to drivers for the 300b. We had a shootout at the London
Audiocircle and the clear winner was 10Y. Also good were 46 and 71A.
2a3 and 45 are possible - neutral sound but not quite as good as the
above.
As input tube the good ones were 26, 201A and again the 10Y.
In fact 10Y > 10Y > 300b is very, very good. All the above choices
sounded better than 6SN7 or any other indirectly heated tube.
We spent hours on these listening tests over several days. Speakers
were Jordan JX92S with ribbon tweeters. Front end was a valve DAC and/
or vinyl (Garrard 301 etc). Music was orchestral, jazz and female
vocals like Joni Mitchell.
Andy Evans
Nice to see Nick mention ECC40 - lovely sounding tube.
Anyway - back to drivers for the 300b. We had a shootout at the London
Audiocircle and the clear winner was 10Y. Also good were 46 and 71A.
2a3 and 45 are possible - neutral sound but not quite as good as the
above.
As input tube the good ones were 26, 201A and again the 10Y.
In fact 10Y > 10Y > 300b is very, very good. All the above choices
sounded better than 6SN7 or any other indirectly heated tube.
We spent hours on these listening tests over several days. Speakers
were Jordan JX92S with ribbon tweeters. Front end was a valve DAC and/
or vinyl (Garrard 301 etc). Music was orchestral, jazz and female
vocals like Joni Mitchell.
Andy Evans
