Any sonic differences between 12SN7 and 6SN7 (in Preamp ap..

Archived from groups: rec.audio.tech (More info?)

simonleemd wrote:

> Hi, I am contemplating of getting a tube preamp for pairing with SS
> Amp. The preamp that I am interested offer 2 different tubes choice-
> 12SN7 or 6SN7 . I wonder which one of them would deliver fuller(more
> full-bodied)sound ? Any sonic advantages for one over the other ??
> Your explaination and suggestions is highly appreciated and thanks in
> advance
> Simon

I believe the only difference is the heater voltage. So as long
as you heat the 12.6V version with 12.6V and the 6.3V version with
6.3V, they should be the same (except for whatever possible VERY
small difference, e.g. in hum, might result from the different
potentials between heater and cathode).

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Archived from groups: rec.audio.tech (More info?)

"Richard Tomkins" <tomkinsr@istop.com> wrote in message news:<6c62ffc81fe5c72232a4ca75380df96d@news.teranews.com>...
> Ah, tubes, my past is back in vogue.
>
> The obvious difference between the two is the heater voltages.
>
> The RCA Tube Manual says they are the same but, the plate voltages are
> different, 90 vs. 250, plate resistance , 6700 vs. 7700 ohms,
> transconductance 300 vs. 2600 umhos, grid voltage for a plate current of 10
> uA 7 vs. 18 volts, these being some items for use as a Class A amplifier.
>
> The 12SN7 would appear to be a beefier tube in use in a Vertical Deflection
> Amplifier.
>
> The 12SN7 probably has a higher capability to generate electrons at the
> cathode than the 6SN7, so it can probably produce more voltage swing at the
> plate.
>
> rtt

<snip>

You missed the fine print in that RCA book.
The differences you cited aren't between the 6 and the 12, they are
between the two independent triodes inside the glass envelope. RCA
refers to them as "Unit No. 1" and "Unit No. 2". It's right above the
"Direct Interelectrode Capacitances" line.
It is a little confusingly laid out, due to RCA's attempts to get as
much info into the book as possible while remaining at a manageable
size.

Archived from groups: rec.audio.tech (More info?)

Richard Tomkins wrote:

> Darn, and I thought I was doing someone a good favour.
>
> In any event, then, the RCA manual did initially say they were the same and
> that is what I did recite up front.
>
> I'd still believe that the 12Volt tube can produce a greater number of
> electrons and thus would have better gain?

I doubt it. They probably have the same heaters in the two halves -- in
series in the 12V version and parallel in the 6V version.

>
> rtt
>
>
> "unitron" <unitron@coastalnet.com> wrote in message
> news:ae27d822.0406022333.75920b38@posting.google.com...
>
>>"Richard Tomkins" <tomkinsr@istop.com> wrote in message
>
> news:<6c62ffc81fe5c72232a4ca75380df96d@news.teranews.com>...
>
>>>Ah, tubes, my past is back in vogue.
>>>
>>>The obvious difference between the two is the heater voltages.
>>>
>>>The RCA Tube Manual says they are the same but, the plate voltages are
>>>different, 90 vs. 250, plate resistance , 6700 vs. 7700 ohms,
>>>transconductance 300 vs. 2600 umhos, grid voltage for a plate current of
>
> 10
>
>>>uA 7 vs. 18 volts, these being some items for use as a Class A
>
> amplifier.
>
>>>The 12SN7 would appear to be a beefier tube in use in a Vertical
>
> Deflection
>
>>>Amplifier.
>>>
>>>The 12SN7 probably has a higher capability to generate electrons at the
>>>cathode than the 6SN7, so it can probably produce more voltage swing at
>
> the
>
>>>plate.
>>>
>>>rtt
>>
>><snip>
>>
>>You missed the fine print in that RCA book.
>>The differences you cited aren't between the 6 and the 12, they are
>>between the two independent triodes inside the glass envelope. RCA
>>refers to them as "Unit No. 1" and "Unit No. 2". It's right above the
>>"Direct Interelectrode Capacitances" line.
>>It is a little confusingly laid out, due to RCA's attempts to get as
>>much info into the book as possible while remaining at a manageable
>>size.
>
>
>


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The e-mail address in our reply-to line is reversed in an attempt to
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Archived from groups: rec.audio.tech (More info?)

Isaac Wingfield <isw@witzend.com> wrote in message news:<isw-C9F33C.20534103062004@netnews.comcast.net>...
> In article <40BF8678.6090109@prodigy.net>, CJT <abujlehc@prodigy.net>
> wrote:
>
> > Richard Tomkins wrote:
> >
> > > Darn, and I thought I was doing someone a good favour.
> > >
> > > In any event, then, the RCA manual did initially say they were the same and
> > > that is what I did recite up front.
> > >
> > > I'd still believe that the 12Volt tube can produce a greater number of
> > > electrons and thus would have better gain?
> >
> > I doubt it. They probably have the same heaters in the two halves -- in
> > series in the 12V version and parallel in the 6V version.
>
> It's easy to do the numbers; emission is a function of temperature, and
> temperature is a function of heater *power*. Multiply heater volts times
> heater amps; if they are the same, the tubes behave identically.
>
> And, FWIW, the "number of electrons" has absolutely *nothing* to do with
> the gain of the tube -- unless the number is zero. Then the gain is
> likely to be zero too...
>
> Some tubes were 6/12 volt. The filament had a center tap which was
> brought out.You could hook 'em up either way.
>
> Isaac


This one ain't center-tapped. Not enough pins available. The 12 gives
0.3 Amps of heater current at 12.6 volt and the 6 gives 0.6 Amps at
6.3 volts, so 37.8 Watts of heater power either way. The two
independant triodes aren't exactly identical (according to the specs)
but maximum plate dissipation for either is 5 Watts and with both
operating the max is 7.5 Watts total (so if one is running at 5 you
can't ask the other one for more than 2.5).