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?
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 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?
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.
Section 1 is so called due to lower hum compared to section 2.
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.
.... PhilJust read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf
On Thursday, October 1, 2020 at 8:57:07 PM UTC-6, palli...@gmail.com 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.... Phil
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
I don't understand the perpetual misinformation.
But hey, thanks for making my point more clear.
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.
Xtrchessreal wrote:
=====================================================
** 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,
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.
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.
Phil Allison wrote:
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.
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]
FFS give up posting wild guesses as fact.
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,
A typical old amplifier: 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)
shows volume and tone controls are 250k. I have seen as low as 50k, but typically 100k as I recall.
My guess ..
And I still accept what the tube spec sheet says
Big Bad Boob wrote:
=================
Phil Allison wrote:
FFS give up posting wild guesses as fact.
which ones?
** All of them.
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.
Phil Allison wrote:
FFS give up posting wild guesses as fact.
which ones?
** All of them.
** Fraid you have no learnt much.
whatever.
and now you're just
insisting on getting the last word in.
Big Bad Bob + TROLL wrote:
=======================
Phil Allison wrote:
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.
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.
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