Hi all.
I built a single channel push pull amp from the Dynaco 10W schematic found everywhere.
Also used some simple 15W output transformers designed for guitar amps without UL taps so had to run a SG resistor off B+. That OT claimed primary impedance 8k and output 4ohm. My speakers say 6ohm.
I fed B+ with 300V and the thing sounded fantastic as per that schematic.
I can't remember what the value was but I fed the EL84 screens with b+ across a resistor.
So now I am in a position where I want to build a stereo version of this amp and in a chassis rather than just bread boarding. I have a few questions.
The power transformer I want to use is the Hammond 260E.
260E 80VA 450V C.T. @ 115ma. 5V @ 2A 6.3V C.T. @ 3A
The 6.3vAC tap should be sufficient to run the EL84 heaters and I plan to rectify the 5VAC into DC which through the solid state rectifier should come out at 6.3VDC? Throw a cap across that and send it straight to the 12AX7 heaters?
Below a sketch of what I am thinking. Any comments in addition to what I have mentioned above also welcome.
I built a single channel push pull amp from the Dynaco 10W schematic found everywhere.

Also used some simple 15W output transformers designed for guitar amps without UL taps so had to run a SG resistor off B+. That OT claimed primary impedance 8k and output 4ohm. My speakers say 6ohm.
I fed B+ with 300V and the thing sounded fantastic as per that schematic.
I can't remember what the value was but I fed the EL84 screens with b+ across a resistor.
So now I am in a position where I want to build a stereo version of this amp and in a chassis rather than just bread boarding. I have a few questions.
- I want to feed the screens with B+ across a resistance, do you think the 100ohm is sufficient in this case?
- 1W in that position or should I be going 5W?
- I've dropped the resistor feeding the 12AX7s. This is of course because I will be feeding 2x 12AX7s so the increase in current meant I needed to decrease the resistance but I went further to increase the voltage going to them. Is this too much now? I was hoping it may increase my clean volume.
- Should I also drop the resistance of the 100ohm 10W resistor and use a 20W+ resistor in this position as it is now feed both amps? Unless I separated the feed from the rectifier into two power filter boards, one for each side of the amp?
The power transformer I want to use is the Hammond 260E.
260E 80VA 450V C.T. @ 115ma. 5V @ 2A 6.3V C.T. @ 3A
The 6.3vAC tap should be sufficient to run the EL84 heaters and I plan to rectify the 5VAC into DC which through the solid state rectifier should come out at 6.3VDC? Throw a cap across that and send it straight to the 12AX7 heaters?
Below a sketch of what I am thinking. Any comments in addition to what I have mentioned above also welcome.