I have a bunch of these. The 6J6 does have a u-Factor that falls nicely between that if the 6SN7-oids and the 6SL7/12AX7. On the downside, it's primarily an RF type intended for use as a VHF oscillator/power amp/mixer and so isn't so swell for audio. The u-Characteristic is curved, though not so bad as some RF types. You'll probably have to work at finding a good audio loadline.
The same idea is the 6SC7 that is also a dual triode with a common cathode for easy LTP implementation. This type is intended for audio, and so has a much flatter u-Characteristic. The gain is about the same as a 6SL7, and it's a metal Octal type.
6SC7 is a pretty nice tube, actually-
VinylSavor: Tube of the Month: The 6SC7
The available datasheets are pretty sparse as far as details, but the actual real world curves are very nice. Sort of like a common-cathode 6SL7.
6N7 is another common cathode type that's actually pretty good for audio, and can do a nice little rig simply-
https://frank.pocnet.net/sheets/093/6/6N7.pdf
VinylSavor: Tube of the Month: The 6SC7
The available datasheets are pretty sparse as far as details, but the actual real world curves are very nice. Sort of like a common-cathode 6SL7.
6N7 is another common cathode type that's actually pretty good for audio, and can do a nice little rig simply-
https://frank.pocnet.net/sheets/093/6/6N7.pdf
Morgan Jones used a 6J6 for an LTP with an LM134 in the tail, for the input stage of a HiFi amp in one of the earlier versions of his book. I don't remember which book it was in, because they are all stuffed in a box somewhere since I moved.
The LM134 will work with only a volt across it, but can handle only 10 mA max. The 6J6 will work within those constraints without a negative voltage source.
I saved some of those for a metal (literally) guitar amp. I have 8 X metal 6V6's and a pair of metal 6L6's along with several other metal tubes including some 6SJ7's, 6SF5's and 6C5's. I'm thinking those metal 6V6's would look cool with some round finned heat sinks on them, if I could find any. I still need a 5Z4 or 5T4 for the rectifier depending on whether I use the 6V6's or 6L6's.
The LM134 will work with only a volt across it, but can handle only 10 mA max. The 6J6 will work within those constraints without a negative voltage source.
I saved some of those for a metal (literally) guitar amp. I have 8 X metal 6V6's and a pair of metal 6L6's along with several other metal tubes including some 6SJ7's, 6SF5's and 6C5's. I'm thinking those metal 6V6's would look cool with some round finned heat sinks on them, if I could find any. I still need a 5Z4 or 5T4 for the rectifier depending on whether I use the 6V6's or 6L6's.
No, not really. There's a distinct lack of 7-pin mini singleton triodes, one of the few is another RF type that's not very useful for audio, except for cathodyne splitters: the 6C4. Most of the small signal singletons are metal envelope, Octal types.
Other singleton triodes are primarily VHF types in the 9-pin mini format to allow for multiple connections to G1 so's this can be grounded with minimum impedance. The types operate at such extreme frequencies that they only work as grounded grid gain stages.
If you want singleton triodes, the 6AU6 as a pseudotriode works nicely: more linear than a 6J6, but with similar u-Factor. As for a more linear 6J6 type of dual, I don't know of any.
I got some 8532 (6J4) 7 pin tubes off Ebay recently, and most do not meet the data sheet Mu factor of 55. Most of them are Mu 40 to 45, with rolled over triode curves. I'm thinking of sending them back.
I did get two good ones with Mu 55 and with nice constant Mu curve traces, which are going to be used in Pete Millett's universal driver board. But I've found 6JC6 ($1 frame grid pentodes) work better for high Mu, hi gm triodes.
I found some tube adapter thingies on Ebay to convert any tube to any socket, so no more 7 pin tubes for me. (except maybe 6EW6 and 9002) [ Use two adapters, with a socket on one, and pins on the other, wire the adapters together for whatever pin-out you want.]
Hmmm, I could put two matched 5744 sub-mini triodes onto a 7 pin plug.
Or two 5639 and two 5902 sub-mini's onto a 12 pin plug, for the 1st two stage P-P SPUD amp. A clear pill bottle glued over them (with ventilation holes). Although I think I would prefer to find something like a giant IC case, with a glass window on top, and bent header pins on the sides. An IC with sub-mini tubes glowing inside!
I did get two good ones with Mu 55 and with nice constant Mu curve traces, which are going to be used in Pete Millett's universal driver board. But I've found 6JC6 ($1 frame grid pentodes) work better for high Mu, hi gm triodes.
I found some tube adapter thingies on Ebay to convert any tube to any socket, so no more 7 pin tubes for me. (except maybe 6EW6 and 9002) [ Use two adapters, with a socket on one, and pins on the other, wire the adapters together for whatever pin-out you want.]
Hmmm, I could put two matched 5744 sub-mini triodes onto a 7 pin plug.
Or two 5639 and two 5902 sub-mini's onto a 12 pin plug, for the 1st two stage P-P SPUD amp. A clear pill bottle glued over them (with ventilation holes). Although I think I would prefer to find something like a giant IC case, with a glass window on top, and bent header pins on the sides. An IC with sub-mini tubes glowing inside!
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the 832 and the 829b are two distinct tubes with a common cathode connection, so tube matching is a hit or miss thing..
the 5894 otoh used just a single cathode....now this is to me ideal...
there are other miniature tube that have a single cathode construction as well...
i almost forgot about this tube...thanks for reminding me,
perhaps the metal shell has put me off, not anymore, will deploy those in my upcoming builds..
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