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In Reply to: RE: Tube Adapters posted by jcmusic on January 05, 2017 at 08:31:32
Having an octal based adapter to take a 9 pin is not a great idea for tube rolling-
putting a 6BQ5 in place of a KT88 would result in some damage to the tube and most likely the amp-
Similarly substituting a 12A_7 for a 6SN7 would not yieds listenable results-
This mostly has to do with pin-outs, bias (B+) voltages and filament voltages-
perhaps if you give us a better idea of what you are interested in achieving we could offer encouraging help
Happy Listening
Follow Ups:
OK I want to try the 6j5g in place of the 6sn7.
ok-
a single triode versus a twin triode-
well, make sure that the heater pins are changed - 2&7 for 6J5 versus 7&8 for 6SN7-
and the plate voltage should be reduced to 300 ...
It can be done, but are you sure that you are replacing functionally similar tubes?
is the 6SN7 being used as a Single Triode?
Happy Listening
Yes in my amp the 6sn7 tubes are only using one half, the other half is going to ground.i spoke with the amp builder yesterday and he told me that.
6SN7s with only one half of each tube actually used? I take it this was built in someone's garage?
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Buy Chinese. Bury freedom.
Actually the builder is well known and his amps are highly sought after. I don't why he builds them that but I can ask.
"Actually the builder is well known and his amps are highly sought after."
??
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Buy Chinese. Bury freedom.
Since the 6J5 is half of a 6SN7 you will need two 6J5s to duplicate the function of the one 6SN7 tube. There are adapters on epay that will do this; just remember that the adapters take up a lot of space and may interfere with other components already mounted on the amp.
Exactly that's why I want to try and build adapters for a single tube and run them in my amp, which only uses one half of the 6sn7 tubes.
OK, then the smart approach is to rewire the socket for a 6J5. You can then use a 6P5 or 6C5 as well.
OK the other two tubes you mentioned, are they on par with the 6j5g?
The 6C5 is electrically equivalent to the 6J5. The 6P5 is an octal 76. The 76 is a predecessor of the 6J5. You will have to determine for yourself about par, but the 6P5 is available with cylindrical plates which some who revere the TS 6SN7 and 6F8 attribute to their good sound.
Don't forget 6L5, and 7193, 7A4 or 76 with a completely different type of adapter (plus there are others).
I am not aware of an adapter that will take one 6J5 in place of a 6SN7, but there are adapters for 2 6J5 and you could probably leave one off.
While I am not an expert, I have heard of people using 1/2 of a 12AX7 or 6DJ8 in an attempt to reduce noise floor.
While I am sure that the builder is quite good, there does not seem to be any reason to use 1/2 of a 6SN7 when 6J5 (and other similar single triodes) are readily available and dirt cheap.
By the way, here is a decent write up on the 6J5:
http://vinylsavor.blogspot.com/2013/03/tube-of-month-6j5.html
P.S.: I love adapters just because they give me more tubes to play with without having to rewire (which I am not good at).
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