compactron power amp project

[Lavane]

I built a single ended compactron amp last year. 6JC5, beefier version of the 6JB5, in pentode mode with regulated screen voltage. The driver is a 6BN11, double pentode, triode strapped in a mu-follwer configuration. I threw in a 6CG3 diode for delayed B+. All compactron tubes except for the voltage regulator tubes, 0D3. About 1% THD at 1W, almost all second order. Very fun amp to listen to.View attachment 3202335

Very cool! Nice tube glow too.

 

[StepheK]

I built a single ended compactron amp last year. 6JC5, beefier version of the 6JB5, in pentode mode with regulated screen voltage. The driver is a 6BN11, double pentode, triode strapped in a mu-follwer configuration. I threw in a 6CG3 diode for delayed B+. All compactron tubes except for the voltage regulator tubes, 0D3. About 1% THD at 1W, almost all second order. Very fun amp to listen to.View attachment 3202335

You you mind sharing the schematic? Very cool amp BTW

 

[drteming]

Happy to oblige. GNFB!!! Kill it with fire!!!

 

[nerdorama]

@drteming , what are the output transformers you chose?

edit: You posted your schem while I was writing. Those MPS are nice outputs.

 

[nerdorama]

Sorry all, I never followed up with this. The amp was finished about Dec last year. It sounds very nice. I like it. I’m writing from my phone so don’t have the final schematic here but will try to remember when on the laptop.

 

[vinylkid58]

The amp was finished about Dec last year. It sounds very nice.

Looks great too! Congrats.

jeff

 

[knockbill]

I was thinking of building a PP amp at one point using FU-32's.
They're cheap, way cheaper than the western version. But being able to get two of them matched would be mor difficult since each tube has two pentodes inside. Like some sweep tubes, some transmitter tubes can be used to build an audio amp.

Just saw this,, These are a smaller version of the 829B I just used in a build, IIRC...

 

[Lavane]

Just saw this,, These are a smaller version of the 829B I just used in a build, IIRC...

Ya, the Chinese FU32 is cheaper than the western 832A. You might find the 832A's at a hamfest fir a couple bucks though.

 

[knockbill]

I see em (if 832 are the same as the china FU32) all the time, but the 829Bs are more powerful,,, I'm goin to a hamfest tomorrow,,, how many do ya want??? Its the sockets that are expensive, tho!!!

 

[nerdorama]

This is my final schematic. The 5HA7 is a handy sort of tube as it is very similar to, and maybe identical to, the 12DW7/7247. The only snag is that it is a 5.6V heater. I added a couple of 0.68 ohm resistors in front of it and the voltage hit the target.


And here are some test results. Not bad for what to me were unknown output transformers. They are a bit small but seem to do well enough. The HF is starting to roll off at 20kHz but not badly and the roll is fairly slow at first with -3dB around 60kHz.

 

[Lavane]

I see em (if 832 are the same as the china FU32) all the time, but the 829Bs are more powerful,,, I'm goin to a hamfest tomorrow,,, how many do ya want??? Its the sockets that are expensive, tho!!!

Don't tempt me John! The last thing I need right now is a other project.

 

[knockbill]

HA,
How many times have we built from the same schems!!!! I have the guitar plugged into that Super Champ 5881 amp in the L/R as we speak!!!! This 829B sounds way better than folks gave it credit for,,, May just stay in the shop for a while!!!
This will be a good day to gather some 829Bs,, 811s,, 6AS7s !!!
take care...