EL34 PP Layout Proposal

[tubekiddo]

Hi,

I found Guiseppe Amato’s DIY Tube page and this project inspired me to look into a layout editor for myself. Here are my results…

A) Guiseppe’s page: https://www.vtadiy.com/
B) The amp I am specifically interested in (Il Primo Bis): https://www.vtadiy.com/home/tube-amplifiers/il-primo-bis/
C) Guiseppe used an open source layout designer app which amazed me, DiyLC by bancika (who also builds his own guitars): http://diy-fever.com/blog/, http://diy-fever.com/software/diylc/

Guiseppe provided a picture of his build’s layout which I took and re-engineered for learning purpose. I herewith share my result with the community. Any feedback welcome…

You can find the schematics on Guiseppe’s home page…

 

[xsaboi]

Can you please explain what are these leads (in purple circles)? I can't find this in schematics, why is it connected to that dots? What is purposte of that?

 

[Steve Morley]

The PT has lots of current so you could likely run KT88s or 6550s. Even for fixed bias EL34s the opt primary impedance is kind of high. I'm not keen on a 12AX7 for phase splitter duty with EL34s. The bias adjust and bias balancing is kind of awkward, why not just bias each tube individually?

The AC input neutral shouldn't be switched. It should go directly to the PT primary. Also with with line voltages we typically see wire the PT primary for 120 volts.

 

[baudouin0]

Placing the left and right channels on opposite sides of the layout looks lovely, but its encouraging a differential ground loop. Left and Right inputs and first stage tubes are bested placed next to each other. or use the same tube for both inputs.

 

[jcalvarez]

Have a look at the Eico HF-89 (EL34 PP) user manual. Includes layout, wiring, schematics, troubleshooting, you name it.