Heater connection

Heater connection

Hello.
For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as 12AX7,
etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.

I am wondering, is there a preferred way of doing it? Which connection
results in a lower hum?

If there is no difference hum-wise, perhaps grounding of pin 9 is more
convenient in case one wants to plug in a 6.3V only tube, e.g. ECC85 or
Russian 6N2P -- less rewiring will be needed.

What do you think?

Regardss,
Alex

Re: Heater connection

Phil Allison wrote:
> "Alex"
>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
>> 12AX7,
>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
>>
>> I am wondering, is there a preferred way of doing it? Which connection
>> results in a lower hum?
>
>
> ** Neither.
>
> The correct ways with AC heaters are:
>
> 1. Use a centre tapped 6.3 volt heater supply or
>
> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
>
> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
> grounded & adjusted for least hum.
>
>
> If you want to avoid all such tedious hum issues - use 6.3 volt regulated
> DC.
>
>

And even easier, with the tube the OP mentioned, use a 12V regulated dc
supply.

Cheers

Ian

Re: Heater connection


"Ian Thompson-Bell"
> Phil Allison wrote:
>> "Alex"
>>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
>>> 12AX7,
>>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5,
>>> or
>>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
>>>
>>> I am wondering, is there a preferred way of doing it? Which connection
>>> results in a lower hum?
>>
>>
>> ** Neither.
>>
>> The correct ways with AC heaters are:
>>
>> 1. Use a centre tapped 6.3 volt heater supply or
>>
>> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
>>
>> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with
>> wiper grounded & adjusted for least hum.
>>
>>
>> If you want to avoid all such tedious hum issues - use 6.3 volt
>> regulated DC.
>>
>>
>
> And even easier, with the tube the OP mentioned, use a 12V regulated dc
> supply.


** The Ian T-B autistic mental defective has selective eyesight - it only
sees what it wants to see.

So it is totally wrong - again ....




..... Phil

Re: Heater connection



Ian Thompson-Bell wrote:
>
> Phil Allison wrote:
> > "Alex"
> >> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
> >> 12AX7,
> >> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
> >> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
> >>
> >> I am wondering, is there a preferred way of doing it? Which connection
> >> results in a lower hum?
> >
> >
> > ** Neither.
> >
> > The correct ways with AC heaters are:
> >
> > 1. Use a centre tapped 6.3 volt heater supply or
> >
> > 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
> >
> > 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
> > grounded & adjusted for least hum.
> >
> >
> > If you want to avoid all such tedious hum issues - use 6.3 volt regulated
> > DC.
> >
> >
>
> And even easier, with the tube the OP mentioned, use a 12V regulated dc
> supply.
>
> Cheers
>
> Ian 12V isn't the right voltage for heaters where 2 x 6.3V heaters are connected in series.

It should be 12.6V

This is easily gained by using 3 leg 12V regulator chip but with a
series diode in the adjust
with cathode to -V rail.

Patrick Turner.

Re: Heater connection

Patrick Turner wrote:
>
> Ian Thompson-Bell wrote:
>> Phil Allison wrote:
>>> "Alex"
>>>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
>>>> 12AX7,
>>>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
>>>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
>>>>
>>>> I am wondering, is there a preferred way of doing it? Which connection
>>>> results in a lower hum?
>>>
>>> ** Neither.
>>>
>>> The correct ways with AC heaters are:
>>>
>>> 1. Use a centre tapped 6.3 volt heater supply or
>>>
>>> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
>>>
>>> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
>>> grounded & adjusted for least hum.
>>>
>>>
>>> If you want to avoid all such tedious hum issues - use 6.3 volt regulated
>>> DC.
>>>
>>>
>> And even easier, with the tube the OP mentioned, use a 12V regulated dc
>> supply.
>>
>> Cheers
>>
>> Ian 12V isn't the right voltage for heaters where 2 x 6.3V heaters are connected in series.
>
> It should be 12.6V
>
> This is easily gained by using 3 leg 12V regulator chip but with a
> series diode in the adjust
> with cathode to -V rail.
>
> Patrick Turner.

Strictly speaking, yes it should be 12.6V, but that is only a nominal
value and tubes were designed to expect at least a +- 5% variation in
mains supply and hence heater supply. Emission is hardly affected at all
when running from 12V dc and heater life is likely to be extended.

Cheers

Ian

Re: Heater connection



Ian Thompson-Bell wrote:
>
> Patrick Turner wrote:
> >
> > Ian Thompson-Bell wrote:
> >> Phil Allison wrote:
> >>> "Alex"
> >>>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
> >>>> 12AX7,
> >>>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
> >>>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
> >>>>
> >>>> I am wondering, is there a preferred way of doing it? Which connection
> >>>> results in a lower hum?
> >>>
> >>> ** Neither.
> >>>
> >>> The correct ways with AC heaters are:
> >>>
> >>> 1. Use a centre tapped 6.3 volt heater supply or
> >>>
> >>> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
> >>>
> >>> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
> >>> grounded & adjusted for least hum.
> >>>
> >>>
> >>> If you want to avoid all such tedious hum issues - use 6.3 volt regulated
> >>> DC.
> >>>
> >>>
> >> And even easier, with the tube the OP mentioned, use a 12V regulated dc
> >> supply.
> >>
> >> Cheers
> >>
> >> Ian 12V isn't the right voltage for heaters where 2 x 6.3V heaters are connected in series.
> >
> > It should be 12.6V
> >
> > This is easily gained by using 3 leg 12V regulator chip but with a
> > series diode in the adjust
> > with cathode to -V rail.
> >
> > Patrick Turner.
>
> Strictly speaking, yes it should be 12.6V, but that is only a nominal
> value and tubes were designed to expect at least a +- 5% variation in
> mains supply and hence heater supply. Emission is hardly affected at all
> when running from 12V dc and heater life is likely to be extended.
>
> Cheers
>
> Ian
You are quite right of course, 12.0V is near enough for signal tubes at
least.
I still use the diode though and tube life is only threatened
when IH is extremely low, or over 10% too high.
I think RDH4 say +/- 10% VH is OK, so from 5.7V to 7V.

The Jolida 502 I am working on to improve had 7.15Vrms everywehere.
We get 252Vrms mains, supposed to be 240Vrms, and if that was so,
VH would be 6.8Vac, still wrong, but it would be right if mains =
220Vrms
where VH would then be 6.24V.

This indicates the Chinese mains tranny was originally designed for
220Vrms, and no
allowance has been made for Oz voltages at 252Vrms.
And and one reason why it is mechanically noisy.

Patrick Turner.

Re: Heater connection

Patrick Turner wrote:
>
> Ian Thompson-Bell wrote:
>> Patrick Turner wrote:
>>> Ian Thompson-Bell wrote:
>>>> Phil Allison wrote:
>>>>> "Alex"
>>>>>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
>>>>>> 12AX7,
>>>>>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
>>>>>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
>>>>>>
>>>>>> I am wondering, is there a preferred way of doing it? Which connection
>>>>>> results in a lower hum?
>>>>> ** Neither.
>>>>>
>>>>> The correct ways with AC heaters are:
>>>>>
>>>>> 1. Use a centre tapped 6.3 volt heater supply or
>>>>>
>>>>> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
>>>>>
>>>>> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
>>>>> grounded & adjusted for least hum.
>>>>>
>>>>>
>>>>> If you want to avoid all such tedious hum issues - use 6.3 volt regulated
>>>>> DC.
>>>>>
>>>>>
>>>> And even easier, with the tube the OP mentioned, use a 12V regulated dc
>>>> supply.
>>>>
>>>> Cheers
>>>>
>>>> Ian 12V isn't the right voltage for heaters where 2 x 6.3V heaters are connected in series.
>>> It should be 12.6V
>>>
>>> This is easily gained by using 3 leg 12V regulator chip but with a
>>> series diode in the adjust
>>> with cathode to -V rail.
>>>
>>> Patrick Turner.
>> Strictly speaking, yes it should be 12.6V, but that is only a nominal
>> value and tubes were designed to expect at least a +- 5% variation in
>> mains supply and hence heater supply. Emission is hardly affected at all
>> when running from 12V dc and heater life is likely to be extended.
>>
>> Cheers
>>
>> Ian
> You are quite right of course, 12.0V is near enough for signal tubes at
> least.
> I still use the diode though and tube life is only threatened
> when IH is extremely low, or over 10% too high.
> I think RDH4 say +/- 10% VH is OK, so from 5.7V to 7V.
>
> The Jolida 502 I am working on to improve had 7.15Vrms everywehere.
> We get 252Vrms mains, supposed to be 240Vrms, and if that was so,
> VH would be 6.8Vac, still wrong, but it would be right if mains =
> 220Vrms
> where VH would then be 6.24V.
>
> This indicates the Chinese mains tranny was originally designed for
> 220Vrms, and no
> allowance has been made for Oz voltages at 252Vrms.
> And and one reason why it is mechanically noisy.
>
> Patrick Turner.

Th other facter is of course the load regulation of the heater winding
which depends on the transformer construction and how close the heater
current comes to the rated load .

Whatever happened to mains trannys with tapped primaries?

Cheers

Ian

Re: Heater connection

Ian Thompson-Bell wrote:

>
> Whatever happened to mains trannys with tapped primaries?
>
> Cheers
>
> Ian

They are there if you want to pay for them, Sowter have two standard
primary layouts

European type: 240, 220, 200, 0, -10 volts taps.

World-wide type: Two separate windings with 120, 110, 0 volts taps.

--
Nick

Re: Heater connection

Nick Gorham wrote:
> Ian Thompson-Bell wrote:
>
>>
>> Whatever happened to mains trannys with tapped primaries?
>>
>> Cheers
>>
>> Ian
>
> They are there if you want to pay for them, Sowter have two standard
> primary layouts
>
> European type: 240, 220, 200, 0, -10 volts taps.
>
> World-wide type: Two separate windings with 120, 110, 0 volts taps.
>

Ah, good old Brian.

Cheers

Ian

Re: Heater connection


>
> European type: 240, 220, 200, 0, -10 volts taps.
>
> World-wide type: Two separate windings with 120, 110, 0 volts taps.
>

Some cheaper transformers just did 110, 120, 220 and 240 as a single
winding. Which meant that half the winding didn't do any work if ran
off of 120V. I have a couple of radios from Europe that have this
set-up, and as I have avaliable 240V@15A outlets (a pair of 120V lines
180 degrees out of phase) I set the radio to 240V to make life easier on
teh primary winding (half the current than if I set it to 120V).

Re: Heater connection


"Robert Casey"
>
> Some cheaper transformers just did 110, 120, 220 and 240 as a single
> winding. Which meant that half the winding didn't do any work if ran off
> of 120V.


** The AC transformers used in Marshall and Fender valve guitar amps were
all like that - right through the 70s and most of the 80s.

These were 250 to 350 VA jobs too.



..... Phil

Re: Heater connection



Ian Thompson-Bell wrote:
>
> Patrick Turner wrote:
> >
> > Ian Thompson-Bell wrote:
> >> Patrick Turner wrote:
> >>> Ian Thompson-Bell wrote:
> >>>> Phil Allison wrote:
> >>>>> "Alex"
> >>>>>> For the 12.6/6.3V heater tubes, with a centre-tapped heater, such as
> >>>>>> 12AX7,
> >>>>>> etc., apparently one can ground pin 9 and supply 6.3V to pins 4 and 5, or
> >>>>>> alternatively, ground pins 4 and 5 and supply 6.3V to pin 9.
> >>>>>>
> >>>>>> I am wondering, is there a preferred way of doing it? Which connection
> >>>>>> results in a lower hum?
> >>>>> ** Neither.
> >>>>>
> >>>>> The correct ways with AC heaters are:
> >>>>>
> >>>>> 1. Use a centre tapped 6.3 volt heater supply or
> >>>>>
> >>>>> 2 Use a pair or 100 ohm resistors to provide a simulated centre tap or
> >>>>>
> >>>>> 3 Use a 100 ohm wire-wound pot wired across the 6.3 volt supply with wiper
> >>>>> grounded & adjusted for least hum.
> >>>>>
> >>>>>
> >>>>> If you want to avoid all such tedious hum issues - use 6.3 volt regulated
> >>>>> DC.
> >>>>>
> >>>>>
> >>>> And even easier, with the tube the OP mentioned, use a 12V regulated dc
> >>>> supply.
> >>>>
> >>>> Cheers
> >>>>
> >>>> Ian 12V isn't the right voltage for heaters where 2 x 6.3V heaters are connected in series.
> >>> It should be 12.6V
> >>>
> >>> This is easily gained by using 3 leg 12V regulator chip but with a
> >>> series diode in the adjust
> >>> with cathode to -V rail.
> >>>
> >>> Patrick Turner.
> >> Strictly speaking, yes it should be 12.6V, but that is only a nominal
> >> value and tubes were designed to expect at least a +- 5% variation in
> >> mains supply and hence heater supply. Emission is hardly affected at all
> >> when running from 12V dc and heater life is likely to be extended.
> >>
> >> Cheers
> >>
> >> Ian
> > You are quite right of course, 12.0V is near enough for signal tubes at
> > least.
> > I still use the diode though and tube life is only threatened
> > when IH is extremely low, or over 10% too high.
> > I think RDH4 say +/- 10% VH is OK, so from 5.7V to 7V.
> >
> > The Jolida 502 I am working on to improve had 7.15Vrms everywehere.
> > We get 252Vrms mains, supposed to be 240Vrms, and if that was so,
> > VH would be 6.8Vac, still wrong, but it would be right if mains =
> > 220Vrms
> > where VH would then be 6.24V.
> >
> > This indicates the Chinese mains tranny was originally designed for
> > 220Vrms, and no
> > allowance has been made for Oz voltages at 252Vrms.
> > And and one reason why it is mechanically noisy.
> >
> > Patrick Turner.
>
> Th other facter is of course the load regulation of the heater winding
> which depends on the transformer construction and how close the heater
> current comes to the rated load .
>
> Whatever happened to mains trannys with tapped primaries?

Bean counters ate them up then vomited them down the toilet.

Having many taps on mains trannies can be a curse.
One sets the tap to suit the mains in your area, then forget all about
it and
after biasing the fixed bias, you move house, or sell the amp
and the next time the amp is used the HT is way too high and heaters,
and OP tubes glow red.

Then someone has to wake up what's happening.

Unwanted drama.

Better is to have a less critical set up of the amp.

Its not always possible.

In the Jolida I have here to fix, there
are two primaries for either 220V in series or presumably 110V in
parallel.
This will suit Europe with 230V, and US with 110V.

But in Oz we have 252V most days where I am.

The local importers of Jolida had to change caps in the PSU
and bias the tubes for lower current to get the amp past a month of use.

It is possible to simply place a series 35 ohm resistor in series with
the
mains input, but I figured out that to get a drop of 32V at 0.9 amps
input
current means the R will put out 28 watts, so should be rated for 100W.

Possibly there would be a certain value of inductance which would work
instead of the series R, but the wire size would need to be 1.0mm dia,
and maybe 100mH, which is a fair sized inductor to make and fit in.

I put 25ohms in series with 235uF resevoir cap and bridge rectifier to
allow the B+ to be lowered to where it should be, and also to
limit C charge currents and reduce PT noise. I put some series R
to reduce input tube heater voltages.



Patrick Turner.
>
> Cheers
>
> Ian

Re: Heater connection

In article <480337E3.AE5A668A@turneraudio . com .au>,
Patrick Turner <info@turneraudio . com .au> wrote:

> In the Jolida I have here to fix, there
> are two primaries for either 220V in series or presumably 110V in
> parallel.
> This will suit Europe with 230V, and US with 110V.

The US does not have 110V, the standard in the US is 120V, so two 110V
primaries in parallel would not suit the US.


Regards,

John Byrns

--
Surf my web pages at, * fmamradios . com /

Re: Heater connection



John Byrns wrote:
>
> In article <480337E3.AE5A668A@turneraudio . com .au>,
> Patrick Turner <info@turneraudio . com .au> wrote:
>
> > In the Jolida I have here to fix, there
> > are two primaries for either 220V in series or presumably 110V in
> > parallel.
> > This will suit Europe with 230V, and US with 110V.
>
> The US does not have 110V, the standard in the US is 120V, so two 110V
> primaries in parallel would not suit the US.
>
> Regards,
>
> John Byrns

I thought it was officially 117V for the US.

But we see 240:110V step down trannies for sale for US made gear.

Mains V does vary considerably though.

I provide 2 x 120V windings on my PT with each winding having
taps at 110V and 100V so there is considerable choice.

In my latest 845 amps there are a total of 48 connections
to multiple windings to suit a wide range of tubes
if 845 become unavailable.
Even the OPT can be re-configured to suit many other tubes besides the 2
x 845 in parallel.
There are a total of 12 windings and 24 connections.

Patrick Turner.


>
> --
> Surf my web pages at, * fmamradios . com /

Re: Heater connection

In article <480363BA.226B2D85@turneraudio . com .au>,
Patrick Turner <info@turneraudio . com .au> wrote:

> John Byrns wrote:
> >
> > In article <480337E3.AE5A668A@turneraudio . com .au>,
> > Patrick Turner <info@turneraudio . com .au> wrote:
> >
> > > In the Jolida I have here to fix, there
> > > are two primaries for either 220V in series or presumably 110V in
> > > parallel.
> > > This will suit Europe with 230V, and US with 110V.
> >
> > The US does not have 110V, the standard in the US is 120V, so two 110V
> > primaries in parallel would not suit the US.
>
> I thought it was officially 117V for the US.

As far as I know that is just an Urban Legend, the standard as I have
seen it is 120VAC with plus and minus tolerances that I forget. I'm not
sure where 117V came from, it seems to have been used by many old radio
manufacturers, and perhaps by manufacturers of other equipment, perhaps
as a sort of a design center value, but as near as I can tell it was not
an official standard, 120VAC has been the standard for a very long time.

> But we see 240:110V step down trannies for sale for US made gear.
>
> Mains V does vary considerably though.
>
> I provide 2 x 120V windings on my PT with each winding having
> taps at 110V and 100V so there is considerable choice.

Line voltages here in the US seem to run from 120VAC up, I have seen
them as high as 135VAC. I suspect lower voltages are seen mostly out in
the boonies at times of day when the load is heaviest.


Regards,

John Byrns

--
Surf my web pages at, * fmamradios . com /