Triode Naming Convention

The question is simple: When it comes to schematics e.g. I see V1A and V1B How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most data sheets indicate pins 123 to triode two and pins 678 to triode 1

In the Philips data sheet for a 12AX7 they even have a remark stating pins 678 or triode 1 is a better triode with regard to hum.

Some schematics actually show the pins for the specific triode but most only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp stage unless there is a reason by the designer to have something a little different.

Can anyone explain this convention or lack there of?

Thank you
X

On 2020-08-29 01:50, Xtrchessreal wrote:
> The question is simple: When it comes to schematics e.g. I see V1A and V1B How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most data sheets indicate pins 123 to triode two and pins 678 to triode 1
>
> In the Philips data sheet for a 12AX7 they even have a remark stating pins 678 or triode 1 is a better triode with regard to hum.
>
> Some schematics actually show the pins for the specific triode but most only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp stage unless there is a reason by the designer to have something a little different.
>
> Can anyone explain this convention or lack there of?
>

yeah it's a little disturbing they're not being precise.

Only other thing I would do is look at the GE tube manual for how they
draw it, and maybe infer pin numbers and "which triode" from that.

which tube is it, 12AX7 or ?

The GE manual I'm looking at shows "section one" on pins 6,7,8 and
"section two" on pins 1,2,3. So I'm guessing 'V1A' would be section
one, and 'V1B' would be section two. If you look at the actual
equpment, maybe you can trace a pin to a component to verify?

assembly was often "by hand" back then with point-point wiring. The
schematic could be "the other way" and it still got built right. I
would expect they're all consistent within themselves, but when compared
to other gear... who knows?

On Wednesday, September 30, 2020 at 11:41:25 AM UTC-6, Big Bad Bob wrote:
> On 2020-08-29 01:50, Xtrchessreal wrote:
> > The question is simple: When it comes to schematics e.g. I see V1A and V1B How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most data sheets indicate pins 123 to triode two and pins 678 to triode 1
> >
> > In the Philips data sheet for a 12AX7 they even have a remark stating pins 678 or triode 1 is a better triode with regard to hum.
> >
> > Some schematics actually show the pins for the specific triode but most only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp stage unless there is a reason by the designer to have something a little different.
> >
> > Can anyone explain this convention or lack there of?
> >
> yeah it's a little disturbing they're not being precise.
>
> Only other thing I would do is look at the GE tube manual for how they
> draw it, and maybe infer pin numbers and "which triode" from that.
>
> which tube is it, 12AX7 or ?
>
> The GE manual I'm looking at shows "section one" on pins 6,7,8 and
> "section two" on pins 1,2,3. So I'm guessing 'V1A' would be section
> one, and 'V1B' would be section two. If you look at the actual
> equpment, maybe you can trace a pin to a component to verify?
>
> assembly was often "by hand" back then with point-point wiring. The
> schematic could be "the other way" and it still got built right. I
> would expect they're all consistent within themselves, but when compared
> to other gear... who knows?

On Wednesday, September 30, 2020 at 11:41:25 AM UTC-6, Big Bad Bob wrote:
> On 2020-08-29 01:50, Xtrchessreal wrote:
> > The question is simple: When it comes to schematics e.g. I see V1A and V1B How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most data sheets indicate pins 123 to triode two and pins 678 to triode 1
> >
> > In the Philips data sheet for a 12AX7 they even have a remark stating pins 678 or triode 1 is a better triode with regard to hum.
> >
> > Some schematics actually show the pins for the specific triode but most only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp stage unless there is a reason by the designer to have something a little different.
> >
> > Can anyone explain this convention or lack there of?
> >
> yeah it's a little disturbing they're not being precise.
>
> Only other thing I would do is look at the GE tube manual for how they
> draw it, and maybe infer pin numbers and "which triode" from that.
>
> which tube is it, 12AX7 or ?
>
> The GE manual I'm looking at shows "section one" on pins 6,7,8 and
> "section two" on pins 1,2,3. So I'm guessing 'V1A' would be section
> one, and 'V1B' would be section two. If you look at the actual
> equpment, maybe you can trace a pin to a component to verify?
>
> assembly was often "by hand" back then with point-point wiring. The
> schematic could be "the other way" and it still got built right. I
> would expect they're all consistent within themselves, but when compared
> to other gear... who knows?

I found some good source information by a guy named Rob Robinette.
Its is pretty simple. V1A is pins 123 and V1B is pins 678. The Logic is sequential in nature "A" refers to the lower numbers "123" and "B" refers to higher numbers "678" B comes after A alphabetically and 678 comes after 123.

Many data books refer to triode 1 section 1 as pins 678 and triode 2 section 2 as pins 123. Section 1 is so called due to lower hum compared to section 2. It is suggested to use V1B for a first stage preamp to keep the SNR lower in reference to hum providing a cleaner preamp with more head room less chance of early distortion. Typically you find on most schematics for Fender, Marshall, and many others V1B is the first preamp stage and V1A the distortion stage.

There are a few schematics that show the pin numbers for each triode added to the design of the circuit.

I find information on google groups forums to be mostly intentionally wrong, opposite, and generally terrible. Bogged down with misinformation designed to be provocative and misleading. Its a troll mentality I despise. It is especially despicable since the forums were developed with intention to help people discuss the finer points of the subject matter. Now it is only spiteful with intent to harm by misleading people. As such it is no longer functional as a helpful apparatus. If I had the power to do so I would shut it down as a waste of money, time, and thought.

On 2020-09-30 23:09, Xtrchessreal wrote:
> There are a few schematics that show the pin numbers for each triode added to the design of the circuit.

looks like that's the only reliable way to know for sure. thanks,
though. Your analysis of A/B vs section 1/2 is interesting.

> I find information on google groups forums to be mostly intentionally wrong, opposite, and generally terrible.

is that how you posted here, through google? I've been using USENET
since before Google existed (the mid 90's to be precise). No need to
involve google for a newsgroup post, or for reading them. I also think
they filter...

"I sit in Siberia and all I have is telnet" - you can post to USENET
that way! (the page is still around on the www archive). Or I just use
thunderbird.

Xtrchessreal wrote:

===================

> Section 1 is so called due to lower hum compared to section 2.
>

** The 2 triodes of a 12AX7 / ECC83 are identical, one doe not "hum" more than the other.

Internal connection arrangements for grids and heaters vary between versions and brands, maybe having a small effect on capacitive coupling if high impedances feed he grids.

It is very common to use DC voltage for the heaters to eliminate any issues whether grid or cathode related.



..... Phil

On Thursday, October 1, 2020 at 8:57:07 PM UTC-6, wrote:
> Xtrchessreal wrote:
>
> ===================
> > Section 1 is so called due to lower hum compared to section 2.
> >
> ** The 2 triodes of a 12AX7 / ECC83 are identical, one doe not "hum" more than the other.
>
> Internal connection arrangements for grids and heaters vary between versions and brands, maybe having a small effect on capacitive coupling if high impedances feed he grids.
>
> It is very common to use DC voltage for the heaters to eliminate any issues whether grid or cathode related.
>
>
>
> .... Phil
Just read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf
I don't understand the perpetual misinformation. V1B is triode with pins 6,7,8.
But hey, thanks for making my point more clear.

On Friday, October 2, 2020 at 2:50:43 AM UTC-6, Xtrchessreal wrote:
> On Thursday, October 1, 2020 at 8:57:07 PM UTC-6, wrote:
> > Xtrchessreal wrote:
> >
> > ===================
> > > Section 1 is so called due to lower hum compared to section 2.
> > >
> > ** The 2 triodes of a 12AX7 / ECC83 are identical, one doe not "hum" more than the other.
> >
> > Internal connection arrangements for grids and heaters vary between versions and brands, maybe having a small effect on capacitive coupling if high impedances feed he grids.
> >
> > It is very common to use DC voltage for the heaters to eliminate any issues whether grid or cathode related.
> >
> >
> >
> > .... Phil
Just read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf
I don't understand the perpetual misinformation. V1B is triode with pins 6,7,8.
But hey, thanks for making my point more clear.

http://www.eierc.com/rc/ECC83.htm NOTE: under the pinout
Similar remarks and notes can be found on many 12ax7,12au7,...etc data sheets

Xtrchessreal wrote:

=======================
> > > Section 1 is so called due to lower hum compared to section 2.
> > >
>
> > ** The 2 triodes of a 12AX7 / ECC83 are identical,
> > one doe not "hum" more than the other.
================================================== ===
> >
> > Internal connection arrangements for grids and heaters vary
> > between versions and brands, maybe having a small effect
> > on capacitive coupling if high impedances feed he grids.
> >
> > It is very common to use DC voltage for the heaters to
> > eliminate any issues whether grid or cathode related.
> >
>
> Just read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf


** My post is *about that exact remark* - explaining it.

An *earthed* internal link from pin 9 travels past grid pin 7 in the scenario described. A link carrying 3.13VAC travels past grid pin 2.

This might inject up to 1mV into pin 2 if the grid source impedance were *10Mohms*. However, for a MM phono cartridge, the impedance is 1kohm at 50/60Hz and for a guitar PU about 10kokms.

So hum injection falls to under 1 microvolt in the above examples and is buried in tube noise - so completely inaudible.

> I don't understand the perpetual misinformation.

** There is a great deal more to your not understanding.

> But hey, thanks for making my point more clear.

** You never made any clear point - sunshine.

..... Phil

On 2020-10-02 16:34, Phil Allison wrote:
> Xtrchessreal wrote:
>
> =======================
>>>> Section 1 is so called due to lower hum compared to section 2.
>>>>
>>
>>> ** The 2 triodes of a 12AX7 / ECC83 are identical,
>>> one doe not "hum" more than the other.
> ================================================== ===
>>>
>>> Internal connection arrangements for grids and heaters vary
>>> between versions and brands, maybe having a small effect
>>> on capacitive coupling if high impedances feed he grids.
>>>
>>> It is very common to use DC voltage for the heaters to
>>> eliminate any issues whether grid or cathode related.
>>>
>>
>> Just read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf
>
>
> ** My post is *about that exact remark* - explaining it.
>
> An *earthed* internal link from pin 9 travels past grid pin 7 in the scenario described. A link carrying 3.13VAC travels past grid pin 2.
>
> This might inject up to 1mV into pin 2 if the grid source impedance were *10Mohms*. However, for a MM phono cartridge, the impedance is 1kohm at 50/60Hz and for a guitar PU about 10kokms.

Actually it's more like 100k for a typical guitar amp pre-amp input, but
your point is still worth it because a low impedence path on the grid
helps to mitigate the problem. The thing about the phono cartridge amp
is the RIAA curve which I believe is around 40db higher gain at the low
end of the frequencvy spectrum as compare to the high end. I believe
the curve is ~2db per octave (with some flatter and steeper spots at
transition points), which closely matches a ceramic pickup. So yeah,
low freq noise is going to be worse in this case, because it's about
20db higher than the mid-range for the phono input.

https://en.wikipedia.org/wiki/RIAA_equalization

In any case, I'd be concerned about injecting ANY low frequencies into a
phono pre-amp.