JoaMat

I tie cathode direct to -HV, -400 V in my case. Works with EL34, 300B, 2A3, EML 20B-V4 and EL156. The datasheet for my Electro-Harmonix 2A3EH Gold says 450 V maximum plate voltage.

Happy Birthday!

Higher gain and in my opinion better frequency response. I haven’t tried other than the 100uF electrolytics. With the capacitors the amplifier is an absolute favorite.

Happy Birthday!

I put 100uF/16V electrolytics in those positions in my Megatron with solid state CCS. I think it made a big difference.

Happy belated Birthday!

Thank you everyone. Had a nice one with my wife in our summer(winter)cottage. Now I’m preparing for Boxing Day +6. Birthday of both our children and one grandchild. Happy New Year everyone!

Happy Birthday!

A frendly Head-Caser has kindly lent me four EL156, So, I made myself some EL156 to EL34 adaptors. Here a Megatron SS CCD something with the four EL156. Same friendly fellow has built himself a couple of filament supply for DHT similar to the one in above post.

Perhaps you are right, but that’s nothing I can verify. It’s correct that pos input is dancing. Now I think that the neg input is a perfect dancing partner which results in a working servo. With the servo the amplifier behaves similar to the ones without servo except that the bias doesn’t drift. And cross talk? Not a problem - I’m married and used to cross talk.

I’ve a smd version of CFA3. Only output transistors on heat sink. Bias is servo controlled. Works all right. Output stage with servo looks like this…

Only in fantasy world... Filament supply for DHT. 9VAC in and 2.5/5.0VDC out. Size 2.07in x 0.7in. All you need is to connect a transformer and a tube to heat.

A small 120 V supply for above grid voltage control. 6.3VAC Hammond 229A transformer and LT8365 DC/DC converter. Out 120V . Size 2.3in x 2.3in.

Seems simmconn reads shematics. Regarding Q12, schematics and gerbers don't match, I think.

Completed servo controlled grid voltage. Works with EL34, 2A3, 300B and EML 20B-V4.