A Single Ended presentation

[Electroshocked]

This is the schematic.


This is the board.


Some wiring information.




The board with parts.


The complete construction.


Inside...


Get the story in pdf.

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PCB FOR TUBE AMPLIFIER EL34 6L6 SINGLE ENDED (PAIR) - eBay (item 320467295208 end time Jan-25-10 10:20:02 PST)

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[Evenharmonics]

Originally Posted by Electroshocked

Inside...

I wouldn't have put power lines so close to the board and (especially) the input signal wires.

[Electroshocked]

Evenharmonics, thank you for your comment.

Mains input at the back and power switch in front is taken for granted for me.

In distant future power on switch will drive a relay with a soft start circuit.
It is "distant" because nothing really happens as long the mains wire are twisted and close to chassis.

[Arnulf]

Originally Posted by Electroshocked

This is the schematic.

Just a tip: Eagle's library "supply" (and numbers after "supply") contains supply symbols which allow you to make your schematics less cluttered (it can be broken into smaller subunits rather than ending up with just one gigantic schematic). All copies of same supply symbol are connected to same signal, so you can use them anywhere you need to connect something to a supply rail (GND, V+, etc.).

[Electroshocked]

Originally Posted by Arnulf

Just a tip: .

Thanks Arnulf.

This is the updated pdf with my amplifier's part list.

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[regal]

Never understood how a push pull input stage could be called SE

[Arnulf]

Well, the output is obviously SE. For nice elaboration on SE vs. PP nature of "SRPP" check out John Broskie's Tubecad webpage (you'll have to google it up but it's easy to locate, just search for SRPP).

[Electroshocked]

Originally Posted by regal

Never understood how a push pull input stage could be called SE

Never understood how a se output stage could be called push pull

[tomchr]

I think you might be able to get better performance in terms of stability at sub-sonic frequencies by swapping R104 and the R105||C101||C102 combo.

In the current implementation, the global feedback is roughly R104/(R104+R106) at DC. If you swap the two impedances, you'll get (R104+R105)/(R104+R105+R106) at DC. Above the lower -3dB frequency, the feedback factor will be the same for the two implementations as C101||C102 "short out" R105 (i.e. Z = R105||1/wC101||1/wC102 approaches 1/wC101||1/wC102 for high values of w -- w = 2*pi*frequency).

~Tom

[Palustris]

I never understood why such a low gm tube like the 12AX7 would be used to drive an output tube, even if it is SRPP. I know there are famous designs that use the 6SL7 in SRPP to drive a 2A3 or 300B. I found that removing the 6SL7 SRPP and replacing it with a normal 6J5 plate follower made a huge difference in dynamics, frequency response, and transparency. I am no fan of SRPP. YMMV...