6SN7 Tube Addicts

[jamato8]

I just ordered some adapters for my 6J5 and 76 to 6SN7. I looked and realized I have a lot of each in round plate and the charcoal black type of plate. I have some 6J5 round plate with clear mica spacers and metal bases. These are from the early 1940's. I have 76 RCA in round plate, that are also excellent and then Tungsol, Sylvania and on and on. Should be interesting as I haven't used either tube types in a long time but I have all these NOS so why not. 

 

[gibosi]

I, for one, look forward to learning how you think these tubes, especially the 76, perform in circuits designed for the 6SN7.
 
I have only one pair, RCA 76, round plate, dated 1943, and find them to be similar to a 1943 RCA VT-231/6SN7GT, but with better highs.

 

[jamato8]

  I, for one, look forward to learning how you think these tubes, especially the 76, perform in circuits designed for the 6SN7.
 
I have only one pair, RCA 76, round plate, dated 1943, and find them to be similar to a 1943 RCA VT-231/6SN7GT, but with better highs.

The operating points are the same for the 6SN7 and the 76 and 6J5. The difference will be in the longer signal path and different plate design etc but on electrical properties they are pretty much the same, which is a good thing. 

 

[MP1968]

I have an Icon Audio HP8 mk ii and am always interested in rolling a few tubes.  For those unfamiliar with the amp it has an ECC83 for the first stage, and 2 6SN7s for the output.
 
So would four of these 76 or 6J5 tubes be suitable replacements for the two 6SN7s, or am I taking a risk?
 
I've found the relevant adaptors on eBay:
 
http://www.ebay.co.uk/itm/1pc-Dual-RCA-76-TO-6SN7GT-B65-CV1988-tube-converter-adapter-/201398487020?hash=item2ee44907ec:g:XOcAAOSwyQtVvETC
 
http://www.ebay.co.uk/itm/1pc-Dual-6J5G-6C5G-VT-94-L63-CV1932-VR67-VT154-TO-6SN7GT-CV181-B65-tube-adapter-/201359298646?hash=item2ee1f31056:g:kckAAOSwN81WEJ7U
 
Unfortunately the seller doesn't give total width of these.  I have around a 4 cm gap on the top plate of the Icon, between the two tube sockets.  For those who have these adaptors is that wide enough?

 

[jamato8]

  I have an Icon Audio HP8 mk ii and am always interested in rolling a few tubes.  For those unfamiliar with the amp it has an ECC83 for the first stage, and 2 6SN7s for the output.
 
So would four of these 76 or 6J5 tubes be suitable replacements for the two 6SN7s, or am I taking a risk?
 
I've found the relevant adaptors on eBay:
 
http://www.ebay.co.uk/itm/1pc-Dual-RCA-76-TO-6SN7GT-B65-CV1988-tube-converter-adapter-/201398487020?hash=item2ee44907ec:g:XOcAAOSwyQtVvETC
 
http://www.ebay.co.uk/itm/1pc-Dual-6J5G-6C5G-VT-94-L63-CV1932-VR67-VT154-TO-6SN7GT-CV181-B65-tube-adapter-/201359298646?hash=item2ee1f31056:g:kckAAOSwN81WEJ7U
 
Unfortunately the seller doesn't give total width of these.  I have around a 4 cm gap on the top plate of the Icon, between the two tube sockets.  For those who have these adaptors is that wide enough?

The adapters can be rotated some so if you can use them offset to make more room you are good. The heater current of the 76 and 6J5 are half that of a 6SN7 and the operating points for the cathode and plate and current draw are the same so 2X76 or 6J5 are the same as the 6SN7. I have some killer 6J5 and 76 I am looking forward to using. I have around 40 NOS RCA 76 alone. Most were made by RCA but mine I tested years ago as are the 6J5 so they are already matched and ready to go. 

 

[gibosi]

  I have an Icon Audio HP8 mk ii and am always interested in rolling a few tubes...
 
So would four of these 76 or 6J5 tubes be suitable replacements for the two 6SN7s, or am I taking a risk?
 
[.......]
 
Unfortunately the seller doesn't give total width of these.  I have around a 4 cm gap on the top plate of the Icon, between the two tube sockets.  For those who have these adaptors is that wide enough?

 
The major difference I see is that the 76 has a mu of about 13.8 while the 6SN7 has a mu of about 20. This may or may not require the volume control to be turned up higher. However, in my amp, this difference is very small. Otherwise, I can't see that there is any risk at all, other than they may not sound all that good in your amp...
 
The real challenge, as I see it, is that it might be difficult to find 4 fairly well-matched tubes, at least on eBay. (It would appear that Jamato has already purchased all the good ones? lol) By fairly well-matched, I mean, four tubes manufactured in the same factory at about the same time that measure reasonably close. And given that there is always the chance that one or more might be noisy and/or microphonic, you might want to try to purchase more than 4....
 
As you can see below, the tubes themselves are fairly narrow, extending just a smidge beyond the edges of the adapter when installed.
 
This adapter dimension (width?) is just under 3.5 cm.
 

 
And this dimension (length?) is just under 8.5 cm
 

 

[Jozurr]

Just placed orders for the Ken-Rad VT231 and RCA Grey Glass 6SNGT (Pre 1948) pairs. Looking forward to buying more 6SN7 or tubes which can be used instead on my liquid glass or with 6SN7 adapters.
 
The sound I'm after, hard hitting bass slam and smooth non sibilant highs. Anyone got recommendations for something better than what I have on order?

 

[jamato8]

   
The major difference I see is that the 76 has a mu of about 13.8 while the 6SN7 has a mu of about 20. This may or may not require the volume control to be turned up higher. However, in my amp, this difference is very small. Otherwise, I can't see that there is any risk at all, other than they may not sound all that good in your amp...
 
The real challenge, as I see it, is that it might be difficult to find 4 fairly well-matched tubes, at least on eBay. (It would appear that Jamato has already purchased all the good ones? lol) By fairly well-matched, I mean, four tubes manufactured in the same factory at about the same time that measure reasonably close. And given that there is always the chance that one or more might be noisy and/or microphonic, you might want to try to purchase more than 4....
 

True enough. But often two halves of the same tube aren't that well matched and unless the circuit requires that the two halves be matched, which often isn't the real need, 2 single triodes should work fine. Also as they are used they will drift anyway but I agree that getting them close never hurts. I can check them on my very modified 439C, with digital meters to get everything pretty close although I can't do a trace, obviously but for normal use it works fine using my Hickok. 
 
Yep, I have a crazy number of 76 and 6J5 but they, at the time, weren't too expensive and I like both tubes. I am glad I picked them up. I must have around 100 76 tubes and 50 6J5. Of the 6J5 I have some really nice European versions in ST but I am looking forward to trying the Sylvania tubes from the early 1940's. I don't find that mu always, within reason, will play that big a difference but for my own amps, I have always found that with the 76 and 6J5, getting them close to max dissipation, gets the best sound and I mean right on the edge but there is a transparency and realism that getting close to the max reveals. 

 

[gibosi]

  Just placed orders for the Ken-Rad VT231 and RCA Grey Glass 6SNGT (Pre 1948) pairs. Looking forward to buying more 6SN7 or tubes which can be used instead on my liquid glass or with 6SN7 adapters.
 
The sound I'm after, hard hitting bass slam and smooth non sibilant highs. Anyone got recommendations for something better than what I have on order?

 
Mullard ECC32 or Mullard ECC31. The ECC31 is identical to the ECC32, but with a different pinout (common cathode), so an adapter is necessary. As the ECC31 requires an adapter, it is typically less costly. But as always, my ears and my gear... YMMV.

 

[Jozurr]

   
Mullard ECC32 or Mullard ECC31. The ECC31 is identical to the ECC32, but with a different pinout (common cathode), so an adapter is necessary. As the ECC31 requires an adapter, it is typically less costly. But as always, my ears and my gear... YMMV.

 
I did try the Mullard CV181 and it was very nice. I think better than the RCA 5692 brown base I currently have.
 
Some others on my very small list (hopefully) are the Tung-Sol round plates 6SN6GT and the Sylvania 6SN7W. I believe both are said to have a nice bass impact and open sound.
 
Edit: Missed the question. Are there any "equivalents" of these Sylvania and CV181? @jamato8 mentioned that the 6F8G version of the Tung-Sol are similar with 6SN7 adapters, so looking into those.

 

[Jim Hodgson]

 
Unfortunately the seller doesn't give total width of these.  I have around a 4 cm gap on the top plate of the Icon, between the two tube sockets.  For those who have these adaptors is that wide enough?

 
I've been searching online for a picture of the HP8 MKII with the 6SN7 sockets exposed.  No luck.  How are the keyway recesses oriented -- toward the front?  This will obviously have an impact on whether these adapters will fit.  I figure you've already considered this ... I guess I'm just curious.

 

[jamato8]

   
I've been searching online for a picture of the HP8 MKII with the 6SN7 sockets exposed.  No luck.  How are the keyway recesses oriented -- toward the front?  This will obviously have an impact on whether these adapters will fit.  I figure you've already considered this ... I guess I'm just curious.

Some of the adapters can be rotated some, the top plate in relation to the plug. 

 

[gibosi]

   
I did try the Mullard CV181 and it was very nice. I think better than the RCA 5692 brown base I currently have.
 
Some others on my very small list (hopefully) are the Tung-Sol round plates 6SN6GT and the Sylvania 6SN7W. I believe both are said to have a nice bass impact and open sound.
 
Edit: Missed the question. Are there any "equivalents" of these Sylvania and CV181? @jamato8 mentioned that the 6F8G version of the Tung-Sol are similar with 6SN7 adapters, so looking into those.

 
IMO the TS RPBG 6SN7GT and Syl 6SN7W have very good bass, but neither has the bass slam of say, the Ken Rad or the ECC32. Still, they are both very fine tubes.
 
In my experience, for most manufacturers, the 6F8G and the 6SN7 sound almost identical. For example, while some hear differences between the round-plate versions of the TS 6F8G and the 6SN7, given my ears and gear, these differences are too small for me to be able to reliably differentiate between them. The major exception is the National Union 6F8G. It sounds significantly different than either the gray-glass or the later black-glass NU 6SN7GT, Some prefer the NU 6F8G over either of the NU 6SN7, and in fact, some prefer it over the TS 6F8G/6SN7.
 
Therefore, given my ears, other than the NU, the only reason to purchase the 6F8G is that typically they can be had for a bit less than the 6SN7. That said, the NU 6F8G is different enough that it might be worth checking out.
 
One last thought....  In some amps, the 6C8G sounds about the same as the 6F8G, and they are even less expensive. The 6C8g uses the same adapter as the 6F8G. However, the 6C8G has an amplification factor of 36, so it is not a direct plug-in replacement for the 6F8G/6SN7, with an amplification factor of 20. But then, the ECC32, with an amplification factor of 32, plus a number of other differences, is also not a direct plug-in replacement. And yet, many love the sound of the ECC32 in a 6SN7 socket. So the 6C8G might also be worth a try...
 
Cheers

 

[ken6217]

I find the best for my amp are Tung Sol 6SL7 GT Round Plate Black Glass. Hard to find. Glad I stocked up.

 

[gibosi]

I find the best for my amp are Tung Sol 6SL7 GT Round Plate Black Glass. Hard to find. Glad I stocked up.

 
Just a note: The 6SL7 has an amplification factor of 70 while the 6SN7 has an amplification factor of 20, that is, 3.5 times higher. But again, many folks use these tubes in their 6SN7-based amps with very good results.