The Reference 6SN7 Thread

[sam6550a]

So what you're telling me: I can watch one of those restoration youtube videos for 10min and handle this myself, no problem?

Sure, just see that your significant other has 911 on speed dial.

 

[triod750]

So what you're telling me: I can watch one of those restoration youtube videos for 10min and handle this myself, no problem?

If you don't want to make the adapter yourself our fellow member @Deyan can make it for you. @mordy usually gives instructions on the external PSU needed and how to DIY it.

 

[WildPhydeaux]

If you don't want to make the adapter yourself our fellow member @Deyan can make it for you. @mordy usually gives instructions on the external PSU needed and how to DIY it.

I was just thinking the same thing. If a guy could stand a slightly taller adaptor it would be possible to put a female barrel connector in adaptor, wired to the heater pins. If having it made you would probably want the connector at the back, so provide alignment information.

Putting a flat back connector on a round adaptor might sound a little bush league, but I've seen small plastic backers which are flat on one side and saddle shaped on the other. Just checked - apparently they're called saddle washers.

Just a thought, but then you could have as long a feed cable as you need to get to your outboard power supply. And make it truly audiophile by choosing silver conductors and fancy coloured tecflex.

Cheers,
Robert

 

[Isaacc7]

Random question for fellow tubeheads...

Anyone know how one might run 12SN7s in a circuit designed for 6SN7s? It seems relatively trivial to step down a 12v signal to 6v but I can't find a readily available adapter without terminating in 9pin and having to re-adapt back to octal...

@Deyan makes them. It looks like a socket saver with a cable attached to it. That gets plugged into an external power supply. I would take a picture of the your amp from the top without tubes and see if he can orient the cable in a convenient way. It is a bit more expensive than a regular adapter but well worth it to get access to 12v and possibly other voltages. I now use a different power supply than the one he supplies that can go up to 30v. That has allowed me to use c3m, 407a, and the 13d1.

 

[mordy]

@Deyan makes them. It looks like a socket saver with a cable attached to it. That gets plugged into an external power supply. I would take a picture of the your amp from the top without tubes and see if he can orient the cable in a convenient way. It is a bit more expensive than a regular adapter but well worth it to get access to 12v and possibly other voltages. I now use a different power supply than the one he supplies that can go up to 30v. That has allowed me to use c3m, 407a, and the 13d1.

Random question for fellow tubeheads...

Anyone know how one might run 12SN7s in a circuit designed for 6SN7s? It seems relatively trivial to step down a 12v signal to 6v but I can't find a readily available adapter without terminating in 9pin and having to re-adapt back to octal...

I have some experience with external power to use tubes of different voltages than your amp was designed for.
You need a few things to make things work but it is not difficult to put it together; the main difficulty is to make it aesthetically pleasing. There will be ugly wires and boxes sitting around your amp unless you find a way to hide them.
Here are the ingredients:
Octal socket with leads for external power.
A voltmeter (an inexpensive one will do)
Voltage regulator.
Power supply.
You can find voltage regulators with a readout of the voltage for just a few dollars.
You can buy a fancy power supply or just use an old power supply from an old PC or laptop. Or, in your case, a regulated wall wart power supply of 12V which cuts out the voltage regulator.
Here is a picture of my current setup with the socket for external power mounted in a 6V socket and using a 12V tube. The wall wart puts out 12.6V at 0.5A:

 

[Isaacc7]

I have some experience with external power to use tubes of different voltages than your amp was designed for.
You need a few things to make things work but it is not difficult to put it together; the main difficulty is to make it aesthetically pleasing. There will be ugly wires and boxes sitting around your amp unless you find a way to hide them.
Here are the ingredients:
Octal socket with leads for external power.
A voltmeter (an inexpensive one will do)
Voltage regulator.
Power supply.
You can find voltage regulators with a readout of the voltage for just a few dollars.
You can buy a fancy power supply or just use an old power supply from an old PC or laptop. Or, in your case, a regulated wall wart power supply of 12V which cuts out the voltage regulator.
Here is a picture of my current setup with the socket for external power mounted in a 6V socket and using a 12V tube. The wall wart puts out 12.6V at 0.5A:

Here’s the one @Deyan made for me.

That is one of my beloved 14n7 tubes being used. He made a 12sn7 to 6sn7 adapter for me and then I used the 7n7 adapter I already had. Having it come off the front isn’t ideal IMO, it’s why I suggested to talk with him about routing beforehand.

 

[mordy]

Here is the next 12V tube to try in the Ultimate: A GE 12SL7GT with round silver plates from 1954:

In the past I used silver plate 6AK5 family tubes in another amp but they sounded terrible. However, this GE tube sounds very good - similar to the gray plate same tube but a little more mellow which I like. Unsung heroes?
Everybody knows that black plates sound better, and round plates are the best...No? Ever heard of bronze plates?
IMHO I know that I don't know, and each tube has to be judged on its individual merit.
And what happened to the GE white dots - ain't there?

 

[triod750]

And what happened to the GE white dots - ain't there?

Did GE source them elsewhere?

 

[Edward Ng]

In case there’s still anybody in here interested in new production tubes rather than NOS, I have a matched quad set of Psvane CV181-T MkII tubes available with about 350 hours in them (genuine, originally purchased from Viva Tubes). They were on my Freya+ until I decided I personally preferred Linlai’s E-6SN7 tubes. I have them up on eBay as two matched pairs right now, but nobody’s bid yet, so I can still cancel the auctions if anybody here is interested. Great tube, my feedback is in this thread a few months back.

-Ed

 

[JKDJedi]

Just fast forward to the part where the gear catches on fire and you can reduce the watch time to about 30 seconds…

 

[bcowen]

I have some experience with external power to use tubes of different voltages than your amp was designed for.
You need a few things to make things work but it is not difficult to put it together; the main difficulty is to make it aesthetically pleasing. There will be ugly wires and boxes sitting around your amp unless you find a way to hide them.
Here are the ingredients:
Octal socket with leads for external power.
A voltmeter (an inexpensive one will do)
Voltage regulator.
Power supply.
You can find voltage regulators with a readout of the voltage for just a few dollars.
You can buy a fancy power supply or just use an old power supply from an old PC or laptop. Or, in your case, a regulated wall wart power supply of 12V which cuts out the voltage regulator.
Here is a picture of my current setup with the socket for external power mounted in a 6V socket and using a 12V tube. The wall wart puts out 12.6V at 0.5A:

Does it matter if the voltage sent to the heaters from the external supply is AC or DC? Or is it tube dependent?

 

[WildPhydeaux]

Call back to several posts back re: 7N7 variations.

My original impressions between the "common" 7N7 and the oddball with smoked glass/chrome top found the latter to be superior. This was several years ago and several gears ago in a Cary preamp. My use of them now is in the output stage of a Lampizator DAC and having spent a couple days with the smoked and a good part of today with the common one I have to say I can't tell the difference in this application which, to my ear, is far more revealing than when in the preamp. So I became curious and looked closely at my small supply of 7N7 and now see more variation than I had initially noted. Poor pictures as a result of my general uselessness, sorry.

1. Grey glass, chrome top, black parallel plates, rounded corner rectangle bottom mica, oval top mica, extra support rods and copper rods in the plates, too hard to see getter holder almost flat top.
   
   
   
   
   
   
   
2. Heavy Chrome top, black parallel plates with rough finish, oval bottom and top mica, copper rods in the plates, too hard see getter holder, round top.
   
   
   
   
   
   
   
3. Thinner chrome top with less "drip" down the sides, more refined looking black angled plates, dimpled square foil getter holder, round upper and lower mica, copper rods in plates, round top.
   
   
   
   
   
   
   
4. Chrome only on the very top of glass, refined black angled plates, round "spiked" upper mica and round lower mica, halo getter holder, copper rods in plates, round top.
   
   
   

The reigning champ had been number 1 and "common one" I mentioned listening to at the start of this post is number 3 - so one parallel plates and the other angled. To be honest I'm not sure which of 2, 3 & 4 I had compared with 1 back when I had that preamp. I plan on checking them all out this weekend.

Oh, I vaguely recall briefly listening to a pair of 7AF7 I had back then (still have) with round black plates and disliking them. I may dig them out of the bottom of my drawer and give them a second chance too...

Cheers,
Robert

 

[Isaacc7]

Call back to several posts back re: 7N7 variations.

My original impressions between the "common" 7N7 and the oddball with smoked glass/chrome top found the latter to be superior. This was several years ago and several gears ago in a Cary preamp. My use of them now is in the output stage of a Lampizator DAC and having spent a couple days with the smoked and a good part of today with the common one I have to say I can't tell the difference in this application which, to my ear, is far more revealing than when in the preamp. So I became curious and looked closely at my small supply of 7N7 and now see more variation than I had initially noted. Poor pictures as a result of my general uselessness, sorry.

1. Grey glass, chrome top, black parallel plates, rounded corner rectangle bottom mica, oval top mica, extra support rods and copper rods in the plates, too hard to see getter holder almost flat top.
   
   
   
   
   
2. Heavy Chrome top, black parallel plates with rough finish, oval bottom and top mica, copper rods in the plates, too hard see getter holder, round top.
   
   
   
   
   
3. Thinner chrome top with less "drip" down the sides, more refined looking black angled plates, dimpled square foil getter holder, round upper and lower mica, copper rods in plates, round top.
   
   
   
   
   
4. Chrome only on the very top of glass, refined black angled plates, round "spiked" upper mica and round lower mica, halo getter holder, copper rods in plates, round top.
   
   

The reigning champ had been number 1 and "common one" I mentioned listening to at the start of this post is number 3 - so one parallel plates and the other angled. To be honest I'm not sure which of 2, 3 & 4 I had compared with 1 back when I had that preamp. I plan on checking them all out this weekend.

Oh, I vaguely recall briefly listening to a pair of 7AF7 I had back then (still have) with round black plates and disliking them. I may dig them out of the bottom of my drawer and give them a second chance too...

Cheers,
Robert

I have a 7n7 that is similar to your #3 but has a support rod, not copper. Sylvania really made quite a variety of 7n7, I wonder why? Most of the parallel plates sound similar to me and I have a memory of not liking the one like your #1. But that could just be a bad tube that I got. The Frankie does sound different to me, it reminds me of the round plate NU 7n7 and 6f8g.

I also tried the 14af7 with round plates. I liked the grey plates quite a bit more than the black but again, that’s a sample of 1. As far as I can tell there were only two versions made of the 7/14af7, black and grey plates along with their matching different micas. The same holds true for the octal version the 6/12ah7. Pretty sure they are the only octal equivalent of the 12au7 made.

 

[Designsfx]

Does it matter if the voltage sent to the heaters from the external supply is AC or DC? Or is it tube dependent?

“I believe” that most tube filaments will require DC. I’ve seen some tube data sheets that state AC or DC operation but not certain if that applied to just heater/filaments.

 

[Isaacc7]

“I believe” that most tube filaments will require DC. I’ve seen some tube data sheets that state AC or DC operation but not certain if that applied to just heater/filaments.

I have a vague recollection of at least some tubes that need slightly different amounts of voltage depending on whether you run ac or dc. Something to do with reactance vs resistance. It really shouldn’t matter as long as the heater gets to the right temperature, it is just straight resistance/reactance creating heat.

There are some that claim that ac is the only way to get the best sound with directly heated tubes. That does run the risk of hum leaking into the signal if things aren’t balanced properly. I have also seen measurements of intermodulation distortion caused by ac on the filaments. Going to dc got rid of that. Of course maybe that IM distortion is why people like ac on the filaments. Shrug