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6SN7 Equivelents
6SN7 Equivelents
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Old 7th November 2019, 06:46 PM   #31
cogsncogs is offline cogsncogs  United States
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Quote:
Originally Posted by Lingwendil View Post
I have used both tubes extensively, and find them indistinguishable from each other sonically. The 6CG7 is a fine tube, so long as you keep the power dissipation reasonable. I actually like them a bit better in some applications, as they have a sheild between the two triodes that is brought out to pin no. 9 that can be grounded to reduce crosstalk in applications where two channels of sound are going through a single tube.

The 6FQ7 and 6CG7 are both great substitutes for the 6SN7.
The 6FQ7 has a shield brought out to pin 9, whereas the 6CG7 does not, as per data sheet. Other than that, they are identical.
There may be some that are marked as a 6CG7 floating around that have a shield, but...they're really 6FQ7's.

So if you want the shield, be sure to get a 6FQ7.
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Old 7th November 2019, 06:50 PM   #32
6A3sUMMER is offline 6A3sUMMER  United States
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Want to know how different (or how similar) the 6SN7 and 6CG7 sound? Try these experiments:

1. For how the tubes sound in a preamp or a line amp, install them in a single stage line amp.
Use either fixed bias, or self bias with bypass cap.
Do not use any form of negative feedback around the tube (including cathode degeneration).

Insert the line stage between your line level music signal source, and your integrated amplifier.
Turn the integrated amplifier volume control to a comfortable or desired listening level.
Now do your tube rolling, and draw your own conclusions.

2. For how the tubes sound as drivers in a power amp, you need to use a much larger signal than just a line level music signal source.
Install the 6SN7/6CG7 in a single line stage amp, as above, but that has voltage, current, and resistances suitable for a driver stage.
Do not use any form of negative feedback around the tube (including cathode degeneration).

Start with a line level music signal source, and apply that to a line amp that is capable of a high enough signal output level to drive the 6SN7/6CG7 to the same output as it would need to drive the output tubes.

Install a series resistor between the 6SN7/6CG7 output and the integrated amplifier. With the same 6SN7/6CG7 single stage line amp between the high level signal, and the series resistor to the integrated amplifier. Turn the volume control to get to the comfortable or desired listening level.
Now do your tube rolling, and draw your own conclusions.

3. Install the 6SN7/6CG7 in an integrated amplifier that has lots of stages and lots of global negative feedback around all the stages, including the test 6SN7/6CG7.
Now do your tube rolling.

Listen really hard, and to the best of your ability. Then draw your own conclusions.
If in this setup, you hear much of a difference, one of the tubes is bad, or out of spec,
or the tubes are being used beyond their specified voltage, current, and dissipation levels.
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Old 7th November 2019, 07:47 PM   #33
Lingwendil is offline Lingwendil  United States
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Quote:
Originally Posted by cogsncogs View Post
The 6FQ7 has a shield brought out to pin 9, whereas the 6CG7 does not, as per data sheet. Other than that, they are identical.
There may be some that are marked as a 6CG7 floating around that have a shield, but...they're really 6FQ7's.

So if you want the shield, be sure to get a 6FQ7.
Most of mine are dual marked 6CG7/6FQ7, and some are marked 6CG7 with a shield, some have no shield. All of the 6FQ7 I have on hand have the shield. Loooks like the 6CG7 with a shield are all later production box codes too. Interesting

My favorites (for no particular reason) are the clear top 6FQ7 with the side-getter flash. They seem very consistent but all sound great.
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Old 7th November 2019, 08:51 PM   #34
cogsncogs is offline cogsncogs  United States
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Quote:
Originally Posted by Lingwendil View Post
My favorites (for no particular reason) are the clear top 6FQ7 with the side-getter flash. They seem very consistent but all sound great.
I believe those are RCA clear tops. Quite nice.
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Old 8th November 2019, 08:13 AM   #35
6A3sUMMER is offline 6A3sUMMER  United States
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In Vacuum Tube Valley Issue # 11, 6SN7 and 6CG7 were tested.
Both were tested at 250V.
6SN7 had 48k plate resistors
6CG7 had 25k plate resistors

The 2nd Harmonic of multiple 6SN7 were tested, ranging from 0.015% to 0.042%.
The 2nd Harmonic of multiple 6CG7 were tested, ranging from 0.005% to 0.037%.

It seems that there may be almost as much variance in the sound of multiple 6SN7s; and there may be almost as much variance in the sound of multiple 6CG7s; as the range of sound of 6SN7s versus 6CG7s.

Don't try and find the one 6CG7 that had 0.005% 2nd.
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Old 8th November 2019, 02:00 PM   #36
Kay Pirinha is offline Kay Pirinha  Germany
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Which conclusion can seriously be drawn from an experiment in which more that one parameter was altered?
OTOH, why, by which reason, should two tubes that share the same characteristics (6SN7 vs. 6CG7/6FQ7) perform differently? Just by the different markings on the envelopes?
Best regards!
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Old 8th November 2019, 02:12 PM   #37
Lingwendil is offline Lingwendil  United States
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Quote:
Originally Posted by 6A3sUMMER View Post
In Vacuum Tube Valley Issue # 11, 6SN7 and 6CG7 were tested.
Both were tested at 250V.
6SN7 had 48k plate resistors
6CG7 had 25k plate resistors

The 2nd Harmonic of multiple 6SN7 were tested, ranging from 0.015% to 0.042%.
The 2nd Harmonic of multiple 6CG7 were tested, ranging from 0.005% to 0.037%.

It seems that there may be almost as much variance in the sound of multiple 6SN7s; and there may be almost as much variance in the sound of multiple 6CG7s; as the range of sound of 6SN7s versus 6CG7s.

Don't try and find the one 6CG7 that had 0.005% 2nd.
I'd bet with the same value resistors those numbers would be closer together, since running higher current through the 6CG7 will put it at an unfair advantage. I'd bet running a CCS plate load on both would yield similar results. Hmmm.

Anybody have a link to that issue archived, if possible?
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Old 8th November 2019, 07:29 PM   #38
Lingwendil is offline Lingwendil  United States
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Quote:
Originally Posted by cogsncogs View Post
I believe those are RCA clear tops. Quite nice.
Yup, RCA

I have maybe six of them left, holding on to them for a Williamson build of some sort eventually.
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Old 8th November 2019, 08:12 PM   #39
6A3sUMMER is offline 6A3sUMMER  United States
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The whole point of my post # 35 was:
Given a set of one labeled type number (Only 6SN7; or Only 6CG7) of many tubes from multiple manufacturers, you will find a range of results.

Or in simpler words:
1. A 6SN7 tube is Not created equal to all other 6SN7 tubes.
2. A 6CG7 tube is Not created equal to all other 6CG7 tubes.

For a forum that so often talks about the fun of tube rolling, I thought this was assumed.
My mistake!

Examples:
"Which KT88 is going to sound the way I want it to sound?" . . .
"What manufacturer's KT88 sounds the way I want it to sound in my amplifier?" . . .

Some posters on this forum are Much Much more knowledgeable than me.
And many of their posts are taken for Gospel.
Some New-bes are trying to learn.

Last edited by 6A3sUMMER; 8th November 2019 at 08:20 PM.
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Old 8th November 2019, 08:49 PM   #40
kodabmx is offline kodabmx  Canada
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6SN7 Equivelents
For me, the 6SN7 = 6N8S = 6CG7/6FQ7 with lower PD and voltage specs. Electrically they are supposed to be the same, so in a properly designed circuit, they should all do the job. Even 6N16B should sound the same if the voltage/current of the circuit is within specs.

I find the only time I notice a difference between one tube and another of the same electrical type is either in a poorly designed circuit, or the tube is simply worn out.

Right now, I'm listening to an amp with 12SN7 tubes in it. The only reason I haven't put 6N8S in it instead is I'm too lazy to wire the heaters in series.
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