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I am looking for complete instructions on all of the steps needed to convert from 6v6 to el34-can't seem to find it in the tramp build instruction pdf
M

I'm working on this at the moment, and as I understand it goes like this:

wire one side of an extra DPDT switch to switch between the normal 6L6 (not the 6v6) output transformer lead (brown & yellow 5k) and the typically unused brown & white 2.5K lead. The output of the switch then goes to pin 3 on the tube socket.

If you need to adjust the stock cathode resistor value, you can wire that up on the other side of the switch. I have read here that is assumed to be fairly safe on the 6L6 setting, so long as you have the correct OT lead connected.

sounds good
I will get working on it
m

If you just want to run it with EL34s rather than 6V6s, you can dispense with the need for switches. Just change the cathode resistor value as for a 6L6 and use the OT's 2.5k primary connections. In my own amp I have installed separate switches for the cathode resistor and OT connections.

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Great tones come in small glass jars!

how would the layout look exactly for the extra switch.

The way I did it was I soldered one leg of the extra 5W resistor to the eyelet one the top side (if the controls are closest to you) of the 1st bias resistor, then the other leg went to one lug of the switch. The center lug connects to ground via a jumper wire. The other lug of the switch is unconnected.

When the switch connects the resistor to ground the resistance of the pair changes. When it is switched away, the ground connection is lifted and you get the value of the single resistor.

I set this up on the same switch as the transformer lead, one set of contacts for each part: one side switches transformer leads, the other switches the additional resistor in & out.

It's a little cluttered - my wiring isn't as picturesque as Stephen's - but here's a photo:



We're looking at the lower switch here. The leads are covered in black shrinkwrap - you can see the one to the right going to the board, and the one to the left going to the to the top right lug of the switch. The green wire in the center goes to a chassis ground connection, in this case on the other side of the board. The transformer tap for the EL34 is connected to the top left lug of the same switch, so that the xformer & resistor are switched in at the same time. (The other xformer tap is on the other lug, of course, and the switch output is connected via a jumper wire.)

You can get really smart if you set the impedance switch to six positions and use the 'second set' of 4/8/16 to connect the 2.5K impedance tap. kurtlives did this.

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Stephen
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So he has 4/8/16 with two different taps (3 each)?