Discussion:
Triode Naming Convention
(too old to reply)
Xtrchessreal
2020-08-29 08:50:27 UTC
Permalink
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
Big Bad Bob
2020-09-30 17:41:18 UTC
Permalink
Post by Xtrchessreal
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?
Xtrchessreal
2020-10-01 05:35:23 UTC
Permalink
Post by Big Bad Bob
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?
Xtrchessreal
2020-10-01 06:09:57 UTC
Permalink
Post by Big Bad Bob
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.
Big Bad Bob
2020-10-01 18:22:31 UTC
Permalink
Post by Xtrchessreal
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.
Post by Xtrchessreal
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.
Phil Allison
2020-10-02 02:57:05 UTC
Permalink
Xtrchessreal wrote:

===================
Post by Xtrchessreal
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
Xtrchessreal
2020-10-02 08:50:41 UTC
Permalink
Post by Phil Allison
===================
Post by Xtrchessreal
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.
Xtrchessreal
2020-10-02 09:16:38 UTC
Permalink
Post by Phil Allison
===================
Post by Xtrchessreal
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
Phil Allison
2020-10-02 23:34:12 UTC
Permalink
Xtrchessreal wrote:

=======================
Post by Xtrchessreal
Post by Phil Allison
Post by Xtrchessreal
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.
=====================================================
Post by Xtrchessreal
Post by Phil Allison
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.
Post by Xtrchessreal
I don't understand the perpetual misinformation.
** There is a great deal more to your not understanding.
Post by Xtrchessreal
But hey, thanks for making my point more clear.
** You never made any clear point - sunshine.

.... Phil
Big Bad Bob
2020-10-04 21:47:14 UTC
Permalink
Post by Phil Allison
=======================
Post by Xtrchessreal
Post by Phil Allison
Post by Xtrchessreal
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.
=====================================================
Post by Xtrchessreal
Post by Phil Allison
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.
Phil Allison
2020-10-05 03:30:02 UTC
Permalink
Big Bad Bob wrote:

==================
Post by Big Bad Bob
Post by Phil Allison
Post by Xtrchessreal
Post by Phil Allison
** The 2 triodes of a 12AX7 / ECC83 are identical,
one doe not "hum" more than the other.
=====================================================
Post by Xtrchessreal
Post by Phil Allison
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,
** The source impedance is what matters, and is as I stated.

Guitar PUs and phono PUs are both low value resistors at 50/60 Hz.
Post by Big Bad Bob
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 frequency spectrum as compare to the high end.
** The RIAA curve boost gain by 16 dB or 6.3 times 50/60Hz compared to mid frequencies. It also boost tube noise by the same amount.

There is NO audible supply frequency hum caused by stray C *inside* a 12AX7.

The OP has misconstrued the comment on the data sheet.


.... Phil
Big Bad Bob
2020-10-09 18:10:22 UTC
Permalink
Post by Phil Allison
Post by Big Bad Bob
Post by Phil Allison
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,
** The source impedance is what matters, and is as I stated.
Guitar PUs and phono PUs are both low value resistors at 50/60 Hz.
yeah, but a typical amplifier is going to have a 100k-220k in series
with the preamp input for dual jacks. And the volume control on the
guitar is 50k-100k. So you're right in saying that it has low impedence
at the guitar pickup [which has its own issues with inductive coupling
of hum, but that's a different issue] but the amplifier itself typically
has those series resistors so that you can have multiple guitars on the
same amp.

Given that, even if there's only a slight "barely detectable"
difference, if it's known, I'd just make the design leverage the one
with lower hum (alleged or otherwise) be the 1st stage amplifier.
Phil Allison
2020-10-09 22:20:25 UTC
Permalink
Big Bad Bob wrote:

==================
Post by Big Bad Bob
Post by Phil Allison
Post by Big Bad Bob
Post by Phil Allison
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,
** The source impedance is what matters, and is as I stated.
Guitar PUs and phono PUs are both low value resistors at 50/60 Hz.
yeah, but a typical amplifier is going to have a 100k-220k in series
with the preamp input for dual jacks.
** 68k is most common value on guitar amps with dual jacks.

Has no effect on hum or noise coming from the tube.
Post by Big Bad Bob
So you're right in saying that it has low impedence
at the guitar pickup [which has its own issues with inductive coupling
of hum, but that's a different issue]
** No it isn't - cos it totally swamps the issue here.

FFS give up posting wild guesses as fact.


.... Phil
Big Bad Bob
2020-10-14 19:36:47 UTC
Permalink
Post by Phil Allison
FFS give up posting wild guesses as fact.
which ones?

It's not like I haven't built a bunch of guitar amps since I was a
teenager, both tubes AND transistors, nor seen a number of schematics,
nor reverse engineered a Fender amp to build a custom amp based on
Fender's circuits because someone wanted me to, nor having played guitar
since the 1960's, nor having re-worked the electronics on guitars a few
times [including putting a 5 pos switch on a Hondo strat copy that had a
3 pos switch for a friend], yotta yotta.

OK - which of the things I said were "wild guesses" ?

keep in mind that the tech manuals said something I'm agreeing with.
YOU are disagreeing with the tech manuals, and after I provide several
examples based on what I've seen (particularly for older amplifiers,
where this would be more relevant), you say that I'm "posting wild
guesses as fact".

So, since I never actually DID that, then you're welcome.

A typical old amplifier:
Loading Image...

(in this case 75k - I've seen as high as 220k, but on average, input
resistors on the shared input are around 100k, which if you think about
it, isn't a whole lot different from 75k or even 68k when you average it
all out)

A typical guitar (strat):
Loading Image...

https://tinyurl.com/y6dew9vv

shows volume and tone controls are 250k. I have seen as low as 50k, but
typically 100k as I recall.

This one shows 1M volume controls on the guitar:

Loading Image...

I'm sure you'll see LOTS of variability. Some old guitars [I used to
have one] even had ceramic pickups. And you also have pedal output
impedence. So the variability is pretty wide here.

My guess is that a pre-amp would be designed such that any noise
generated by an audio tube's filament would be minimized based on a very
wide range of possible inputs, single guitar, two guitars, ceramic or
dynamic pickups, 50k or 250k or 1M volume controls, etc. etc..

So if I happen to "ballpark" the values, you should be able to see why.

And I still accept what the tube spec sheet says about hum on one of the
triodes being slightly higher.
Phil Allison
2020-10-16 02:26:10 UTC
Permalink
Big Bad Boob wrote:

=================
Post by Big Bad Bob
Post by Phil Allison
FFS give up posting wild guesses as fact.
which ones?
** All of them.
Post by Big Bad Bob
It's not like I haven't built a bunch of guitar amps since I was a
teenager, both tubes AND transistors, nor seen a number of schematics,
nor reverse engineered a Fender amp to build a custom amp based on
Fender's circuits because someone wanted me to, nor having played guitar
since the 1960's, nor having re-worked the electronics on guitars a few
times [including putting a 5 pos switch on a Hondo strat copy that had a
3 pos switch for a friend], yotta yotta.
** Fraid you have no learnt much.
Post by Big Bad Bob
OK - which of the things I said were "wild guesses" ?
** The whole lot.
Post by Big Bad Bob
keep in mind that the tech manuals said something I'm agreeing with.
YOU are disagreeing with the tech manuals,
** Never said any such thing.
Post by Big Bad Bob
http://www.thevintagesound.com/ffg/schem/deluxe_5c3_schem.gif
(in this case 75k - I've seen as high as 220k, but on average, input
resistors on the shared input are around 100k, which if you think about
it, isn't a whole lot different from 75k or even 68k when you average it
all out)
** Average of what? Not amps sold for sure.

Vox, Marshall, Fender, Peavey, Music Mann and countless others ...
Post by Big Bad Bob
shows volume and tone controls are 250k. I have seen as low as 50k, but
typically 100k as I recall.
** With a 10 kohm source (at 50/60 Hz) and turned to half value = what?
Post by Big Bad Bob
My guess ..
** Another wild guess ????
Post by Big Bad Bob
And I still accept what the tube spec sheet says
** You have no fucking idea what that 50s doc refers to or if it has any relevance to guitar amps or modern examples of 12AX7s.

FYI

I have 50 years experience designing and repairing guitar amps plus LOTS of other types of audio gear - including tube condenser mics.

You came here on a damn silly notion & got an expert who pointed that out.

You get to like or lump it.


..... Phil
Big Bad Bob
2020-10-17 20:25:43 UTC
Permalink
Post by Phil Allison
=================
Post by Big Bad Bob
Post by Phil Allison
FFS give up posting wild guesses as fact.
which ones?
** All of them.
Post by Big Bad Bob
It's not like I haven't built a bunch of guitar amps since I was a
teenager, both tubes AND transistors, nor seen a number of schematics,
nor reverse engineered a Fender amp to build a custom amp based on
Fender's circuits because someone wanted me to, nor having played guitar
since the 1960's, nor having re-worked the electronics on guitars a few
times [including putting a 5 pos switch on a Hondo strat copy that had a
3 pos switch for a friend], yotta yotta.
** Fraid you have no learnt much.
whatever. I'm done with you. It stopped being fun, and now you're just
insisting on getting the last word in.

/me thinking of Pee Wee Herman, "I know you are, but what am I?"
Phil Allison
2020-10-17 23:24:50 UTC
Permalink
Big Bad Bob + TROLL wrote:

=======================
Post by Big Bad Bob
Post by Phil Allison
Post by Big Bad Bob
Post by Phil Allison
FFS give up posting wild guesses as fact.
which ones?
** All of them.
** Fraid you have no learnt much.
whatever.
** Fuck you.

I'm done with you.

** Man, you are done like a dinner.

It stopped being fun,

** Never come her for fun - shihead.
Post by Big Bad Bob
and now you're just
insisting on getting the last word in.
** ROTFL - what the HELL do you think this post of yours is?

You need to take along look in a mirror pal.



..... Phil

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