Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Re: Who has built Gary Kaufman's 6EM7 DC triode amp?

Well, I've built it > grin <.

I continue to use it as my office system, and remain pleased. Original tubes still test fine 2+ years later, and the NiMH AA's are still going strong. It's so simple that you can clip-lead it together in a few minutes.

Most DC coupled designs operate the second section at an elevated voltage to "line up" with the first section. Unfortunately this does translate to higher voltages and quite a bit of heat in the cathode resistor. The plus is that there's no coupling cap.

There's always a danger in a DC coupled design - if the first triode is removed the circuit can damage the second triode as the bias is also removed. With the 6EM7 they are both in the same bottle - so you can't remove the driver triode accidentally.

6EM7's are dirt cheap, but you can try the higher voltage 10EM7, 13EM7/15EM7 versions or 6EA7/6GL7. Also the 6FD7 (9 pin minature base), 6FM7 (12 pin compactron) or 6GF7 (novar) types. They may require some fiddling with resistor values, but are fairly similar tubes.

Lastly, the voltage divider in the cathode resistor had a few purposes - it made use of resistors I had on hand, and gave a positive voltage of around 70v to bias the filament tap positive. This makes the circuit very quiet - but may not be critical.

Enjoy,

- Gary



This post is made possible by the generous support of people like you and our sponsors:
  Kimber Kable  


Follow Ups Full Thread
Follow Ups
  • Re: Who has built Gary Kaufman's 6EM7 DC triode amp? - Gary Kaufman 11/1/0419:33:44 11/1/04 (1)


You can not post to an archived thread.