6SN7, 6CG7/6FQ7, and 6SL7 in Elekit amps?

[Eric Brandon]

I have an Elekit TU-8200DX amp which takes 12AU7 driver tubes, and an Elekit TU-8600 amp which takes both 12AX7 and 12AU7 driver tubes.

I was hoping to try 6SN7 tubes instead of the 12AU7 using this adpater https://www.ebay.com/itm/1-6SN7-To-...Amp-Convert-Socket-Adapter-6-3V-/283133429197

I was also hoping to try 6CG7/6FQ7 tubes instead of 12AU7 using this adapter https://www.ebay.com/itm/1pc-gold-p...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649

Finally, I was planning to try using a 6SL7 tube instead of the 12AX7 using the same adapter I would use for 6SN7 in a 12AU7 socket.

Is any of this a bad idea? Don't want to damage my amp.

Thanks!

 

[thorpej]

6SN7 and 6FQ7/6CG7 are identical from a characteristics perspective. Neither have the same characteristics of the 12AU7, although they are similar. They are similar enough that nothing bad is likely to happen.

The 6SL7 has 30% lower amplification factor than the 12AX7, and depending on the topology of the circuit it's in, the effect on the operating point could in fact impact later stages in a bad way if the result affects their operating points.

In my experience, things tend to work better when you stick to the parts a circuit was designed to use.

 

[kward]

Also two more conditions must exist for those noval to octal adapter sockets to work. 1) pin 9 on the noval socket must be energized, so that you measure 6.3V between pin 4,5 and pin 9. 2) the amp must be able to support the extra filament current draw from the 6SN7 tubes. The current draw is double—a 12AU7 will require 0.3 A while a 6SN7 will require 0.6 A. (per tube).

If all those conditions are met, it’s likely the substitutions will “work” but as pointed out above the subs may not make the amp perform or sound optimally because of their different electrical characteristics in the triode itself as compared to their noval counterparts.

Musicians do make similar substitutions in guitar amps but that is a different environment where distortions are wanted.

 

[gadget73]

A 12BH7 is a little closer to a 6SN7, but is pin-compatible with a 12AU7. It does want more heater current though. Off the top of my head I think 0.45a ? Not looking at the datasheet currently.

but yeah, I'm somewhat inclined to leave things as they were designed. There are other 12AU7 alternatives that are more of a drop-in too. The number escapes me right now, but there are at least two 4 digit industrial tubes that are often suggested.

 

[eickmewg]

I have an Elekit TU-8200 DX and I recall in my reading about this amp, if you want to use 12BH7 drivers instead of the 12AU7, the appropriate voltage regulators need to be changed to account for a greater heater current draw. The same would apply with 6SN7 tubes with adapters. In a somewhat related way, I have a Latino VTA ST-120 amp designed for 12AU7/12BH7 drivers. I experimented with using 6SN7 tubes with adapters and an octal driver board. I found no difference relative to the original 12AU7/12BH7 drivers and noval board.