Anyone have a simple circuit for . .

gehumph · 25th October 2009, 05:36 AM

. . a single channel using a 12AY7 and an EL84?
Any suggestions & advice will be mucho appreciated.

If that combo doesn't sound right for a very clean ~5W, then I'd listen to reason if there's a good alternative>
All the best
Gerry

Eli Duttman · 25th October 2009, 05:52 PM

Gerry,

A 5 W. O/P means full pentode mode for the EL84. You said a single channel using a 12AV7 for small signal handling. OK, how about a LED biased, CCS loaded, 12AV7 section DC coupled to the 2nd 'V7 section setup as a cathode follower. That's plenty of open loop gain to drive the EL84 and the requisite NFB circuitry. Whether you go GNFB or short loop is a matter of personal preference. NFB of some kind around the power pentode is essential to obtaining a satisfactory damping factor.

BTW, don't forget to regulate EL84 g2 B+.

25th October 2009, 05:36 AM	#1
gehumph diyAudio Member Join Date: Oct 2009	Anyone have a simple circuit for . . . . a single channel using a 12AY7 and an EL84? Any suggestions & advice will be mucho appreciated. If that combo doesn't sound right for a very clean ~5W, then I'd listen to reason if there's a good alternative> All the best Gerry

25th October 2009, 05:52 PM	#2
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Gerry, A 5 W. O/P means full pentode mode for the EL84. You said a single channel using a 12AV7 for small signal handling. OK, how about a LED biased, CCS loaded, 12AV7 section DC coupled to the 2nd 'V7 section setup as a cathode follower. That's plenty of open loop gain to drive the EL84 and the requisite NFB circuitry. Whether you go GNFB or short loop is a matter of personal preference. NFB of some kind around the power pentode is essential to obtaining a satisfactory damping factor. BTW, don't forget to regulate EL84 g2 B+. __________________ Eli D.

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