12SN7 vs. 6SN7
Vince Rhea
the filament voltage. Also understand the same is true for SL7's. Is this
true? If so, are there any major sonic differences that anyone is aware of?
I am thinking particularly of use in a phono preamp. Thanks!
Vince
--
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Vince Rhea
the best. May have to use the 6sn7 article in VTV # 11 as a starting point
and see if it holds true for the 12's also.
Vince
--
Vintage Audio http://www.users.mis.net/~vintage/
The Victorian Lady http://www.users.mis.net/~victoria/vl/index.htm
SpermBank http://www.users.mis.net/~victoria/sb/index.htm
SBench wrote in message <19990503213055...@ng-fb1.aol.com>...
>>It is my understanding that these tubes are basically the same except for
>>the filament voltage. Also understand the same is true for SL7's. Is this
>>true? If so, are there any major sonic differences that anyone is aware
of?
>>I am thinking particularly of use in a phono preamp. Thanks!
>>Vince
>>
>>--
>>Vintage Audio http://www.users.mis.net/~vintage/
>
>Hi Vince,
>If you plan on using AC on the heaters, the 12V versions
>can produce more induced hum, due to capacitive
>coupling. Unlike the 12A*7 series, there is no CT so
>there is no option of running "paralleled" heaters.
>
>Otherwise, you ought to be OK.
>
>
>Best Regards,
>Steve
>
>Check my web page .. <A
>HREF="http://members.aol.com/sbench101/">http://members.aol.com/sbench101</
A>
>Remove the .gov to EMail me
SBench
speeds...@my-dejanews.com
"Vince Rhea" <vin...@mis.net> wrote:
> It is my understanding that these tubes are basically the same except for
> the filament voltage. Also understand the same is true for SL7's. Is this
> true? If so, are there any major sonic differences that anyone is aware of?
> I am thinking particularly of use in a phono preamp. Thanks!
> Vince
>
> --
> Vintage Audio http://www.users.mis.net/~vintage/
> SpermBank http://www.users.mis.net/~victoria/sb/index.htm
>
amplification, d-c is needed on the heaters. With a higher heater supply the
diode drop is not as pronounced and a lower amount of capacitance is needed.
Be sure to use 25V condensers for a 12V heater supply. Running the heaters at
12V instead of 12,6V will give a constant gm over the life of the valve. The
same is true of 6,3V types at 6V. The amount of capacitance is determined
imperically. Use Sprague condensers, NOT foreign types. They are inferiour to
American types. The heater voltage may be lower IF the valves are run light
duty, e.g. half the maximum rated current. The lower the load resistance the
more frequency response you will get. This is why the video output in tvs
have a low load resistance to get the 4,5mc bandwidth to the cathode(s) of
the kine. A high load resistance will give more gain at the loss of frequency
response. This is found radios where voice is listened to freqently. The
amount of gain, number of valves and space will be the main factours in
determining the load resistance. I personally use the lowest load resistance
for maximum fidelity. Space, weight, number of valves, etc are of little
concern for my designs. Good luck on your design.
Mark
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David Crittle
just a 12SN7GT, so I dunno why they even called it a 12SX7. Anyone know
the difference? Only difference I can see is that my tube book includes
data for 12SX7 running with a plate voltage of 26.3 volts. Presumably a
battery supply. I have a few GE Canadian 12SX7GT, 1969 date code. I
haven't used them myself, but I have not no complaints from those who have
bought them from me. Their major factor in choosing to use 12v instead of
6v was because a 12SX7 is cheaper than a 6SN7.
In article <sSsX2.203$co2....@news2.randori.com>, "Vince Rhea"
<vin...@mis.net> wrote:
> Thanks to all who replied. Now all I have to do is figure out which 12sn7 is
> the best. May have to use the 6sn7 article in VTV # 11 as a starting point
> and see if it holds true for the 12's also.
--
david in wagga wagga
retr...@bigpond.com
retr...@bigpond.com
has very similar spec to type 6SN7. It is an older style tubes, G shape, with
one grid connection coming out on a top cap. Anyone tried these in place of a
6SN7?
John Byrns
sbe...@aol.com.gov (SBench) wrote:
> >It is my understanding that these tubes are basically the same except for
> >the filament voltage. Also understand the same is true for SL7's. Is this
> >true? If so, are there any major sonic differences that anyone is aware of?
> >I am thinking particularly of use in a phono preamp. Thanks!
> >Vince
> >
> >--
> >Vintage Audio http://www.users.mis.net/~vintage/
>
> Hi Vince,
> If you plan on using AC on the heaters, the 12V versions
> can produce more induced hum, due to capacitive
> coupling. Unlike the 12A*7 series, there is no CT so
> there is no option of running "paralleled" heaters.
>
> Otherwise, you ought to be OK.
>
>
> Best Regards,
> Steve
Hi Steve,
Relative to the recent discussion of the sound of the 12SN7 vs. the 6SN7,
it is worth noting that the two tubes appear identical, except for the
internal wiring of the two heater sections. The 12SN7's that I purchased
for use in my "Power Amplifier Without Power Transformer" have the heaters
of the two triodes internally connected in series, while the 6SN7's I have
inspected, have the two heaters connected in parallel. This implies that
6SN7's and 12SN7's of the same manufacture would be identical in all
respects, even using the same heater assemblies, the only difference being
the internal wiring of the two heater sections. The sound of the two
types should be identical, except for differences in electrostatic
coupling of hum Voltages from the heater circuit.
Bottom line, it looks like the 12SN7 and 6SN7 are the same tube, with the
heaters internally prewired either in series (12SN7), or parallel (6SN7).
With the 9 pin miniatures, such as the 12BH7, the 9th pin made it possible
to have one tube which could be externally wired for either series (12
Volt), or parallel (6 Volt) heater operation.
Regards,
John Byrns
SBench
<snip>>Relative to the recent discussion of the sound of the 12SN7 vs. the
6SN7,
>it is worth noting that the two tubes appear identical, except for the
>internal wiring of the two heater sections. The 12SN7's that I purchased
>for use in my "Power Amplifier Without Power Transformer" have the heaters
>of the two triodes internally connected in series, while the 6SN7's I have
>inspected, have the two heaters connected in parallel. This implies that
>6SN7's and 12SN7's of the same manufacture would be identical in all
>respects, even using the same heater assemblies, the only difference being
>the internal wiring of the two heater sections. The sound of the two
>types should be identical, except for differences in electrostatic
>coupling of hum Voltages from the heater circuit.
>
>Bottom line, it looks like the 12SN7 and 6SN7 are the same tube, with the
>heaters internally prewired either in series (12SN7), or parallel (6SN7).
>With the 9 pin miniatures, such as the 12BH7, the 9th pin made it possible
>to have one tube which could be externally wired for either series (12
>Volt), or parallel (6 Volt) heater operation.
>
>
>
Hi John,
Yep. It's the additional capacitive coupling due to the higher heater
voltage. On those tube types that can be series or parallel wired,
like the 12a*7 series, you'll often find the note (I'll quote from the
Sylvania manual): "To realize the low hum capabilities, the heaters
should be operated in parallel at 6.3 volts".
John Harper
sbe...@aol.com.gov (SBench) wrote:
>
> Hi John,
> Yep. It's the additional capacitive coupling due to the higher heater
> voltage. On those tube types that can be series or parallel wired,
> like the 12a*7 series, you'll often find the note (I'll quote from the
> Sylvania manual): "To realize the low hum capabilities, the heaters
> should be operated in parallel at 6.3 volts".
>
in series or in parallel, then each of them will see 6.3 VAC across Chk,
regardless of the way they are wired. It's true that there is a difference
in the DC offset, but this is so small (6.3 VDC in fact) that I can't
imagine why it would make any difference. The phase is also inverted at one
triode in series connection, but again I can't imagine why it would make
any difference.
Clearly if you had a single heater with 12.6V across it versus 6.3V,
there is greater capacitive coupling of AC into the cathode, no doubt about
it. But this doesn't seem to apply in this case.
And frankly in any case, if you have a hum-sensitive application then these
days you should just use DC and not even think about it. (Regulated to
5.7V or 11.2V as the case may be, of course).
John
TubeGarden
>there is greater capacitive coupling of AC into the cathode, no doubt about
>it. But this doesn't seem to apply in this case.
>
>And frankly in any case, if you have a hum-sensitive application then these
>days you should just use DC and not even think about it. (Regulated to
>5.7V or 11.2V as the case may be, of course)
Hi John,
Good thinking :-)
Just wanted to add that if you are designing for production, an arbitrary
absolute voltage is appropriate. But, if building one each for sound,
designing in adjustable filament voltages can provide rewards for the ears. DHT
are most obviously affected.
Happy Ears!
Al B^}
Alan J. Marcy
Phoenix, AZ
PWC/mystic/Earhead
Bob Fitzgerald
John Harper wrote in message <7gp05l$16k$1...@nnrp1.dejanews.com>...
>And frankly in any case, if you have a hum-sensitive application then
>these days you should just use DC and not even think about it.
>(Regulated to 5.7V or 11.2V as the case may be, of course).
>
> John
It's not obvious to me where you got 5.7 V, 11.2V when using DC vs. 6.3,
12.6 with AC.
Are you suggesting reducing on both AC and DC, or just DC?
Bob