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previous: Rebel420 Davis 106 Pa Head -- 3/7/2000 8:47 PM

Self-inverting EL84's, etc.

3/10/2000 6:44 PM
MBSetzer	Self-inverting EL84's, etc. Hi Folks: Well, I did get this amp drawn and it is interesting with the self-inverting EL84's. Also a pretty cool Low Impedance Input and minimalist tone stack. Didn't try it yet but as soon as I find that 6CA4 I'll variac it up and add some voltages to the drawing if all is well. As a reminder, the 6EU7 is supposed to be identical in electrical properties to a 12AX7 except for the heaters and pinout. The 6CA4 functions similarly to a 5volt rectifier except that the cathode (source of HV DC) is isolated from the heaters, so it can use the same heater supply as the rest of the tubes, and does not need a separate 5volt winding. http://members.aol.com/mbsetzer Anyone who wants to post it to the ampage schems, or if SteveA is interested in putting at blueguitar, be my guest, I won't be able to keep it at AOL forever. there is a GIF and a PDF version, I ususally have better luck printing the PDF's by clicking the print option to fit it to the page. If it operates, something tells me that the Booster Out could be an input instead, depending on what you hook up to it I might not change anything until I try it as is and see how it sounds, just have to dig in to the CB radio surplus and get a screw-on microphone connector to make an adapter for a guitar cable. Two gain stages and a pair of 6BQ5's shouldn't be too bad. If I did decide to change it, I would probably go clean-slate, and just think of it as transformers & tube sockets with three 1Meg Audio pots that could be changed in value & function too. Maybe wire silicon diodes underneath and use the 6CA4 socket for a different tube as a driver or trem. Or go single-end using only one 6BQ5, replacing the other one with a 12AX7 for more serious gain. Or both. Maybe even reassigning the 6BQ5 to the former 6CA4 position. If I was real ambitious I would even consider rewiring only the power tube sockets to be 6BM8 triode-pentodes for more gain after converting the second preamp triode to a split-load to drive the 6BM8 triodes separately. Anyway, if it comes to life as is, I'll try to get some sound clips posted. Good Luck, Mike

3/10/2000 6:44 PM

MBSetzer

Self-inverting EL84's, etc.

Hi Folks:

Well, I did get this amp drawn and it is interesting with the self-inverting EL84's. Also a pretty cool Low Impedance Input and minimalist tone *stack*.

Didn't try it yet but as soon as I find that 6CA4 I'll variac it up and add some voltages to the drawing if all is well.

As a reminder, the 6EU7 is supposed to be identical in electrical properties to a 12AX7 except for the heaters and pinout.

The 6CA4 functions similarly to a 5volt rectifier except that the cathode (source of HV DC) is isolated from the heaters, so it can use the same heater supply as the rest of the tubes, and does not need a separate 5volt winding.

http://members.aol.com/mbsetzer

Anyone who wants to post it to the ampage schems, or if SteveA is interested in putting at blueguitar, be my guest, I won't be able to keep it at AOL forever.

there is a GIF and a PDF version, I ususally have better luck printing the PDF's by clicking the print option to fit it to the page.

If it operates, something tells me that the Booster Out could be an input instead, depending on what you hook up to it ;-)

I might not change anything until I try it as is and see how it sounds, just have to dig in to the CB radio surplus and get a screw-on microphone connector to make an adapter for a guitar cable. Two gain stages and a pair of 6BQ5's shouldn't be too bad.

If I did decide to change it, I would probably go clean-slate, and just think of it as transformers & tube sockets with three 1Meg Audio pots that could be changed in value & function too. Maybe wire silicon diodes underneath and use the 6CA4 socket for a different tube as a driver or trem. Or go single-end using only one 6BQ5, replacing the other one with a 12AX7 for more serious gain. Or both. Maybe even reassigning the 6BQ5 to the former 6CA4 position. If I was real ambitious I would even consider rewiring only the power tube sockets to be 6BM8 triode-pentodes for more gain after converting the second preamp triode to a split-load to drive the 6BM8 triodes separately.

Anyway, if it comes to life as is, I'll try to get some sound clips posted.

Good Luck,
Mike

Replies:

Rebel420 I owe you a proverbial beer man!! ... -- 3/10/2000 7:10 PM
Rebel420 another intersting thing I noticed,... -- 3/10/2000 8:05 PM
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Marc how do you draw the schematics? -- 3/14/2000 3:56 AM