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KT88 use 2.5K impedance, same as EL34,. Set bias to 6L6 side

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Cecelius2, I made this up to print out and stick to my chassis. I used the Hi/Low bias (6V6 being low) and the rotary switch as explained above.

Very helpful!

Here are two pictures of the two temporary labels I made for the rotary impedance switch and the bias switch [the first is the same picture from my build thread]. If I decide to keep this then I will have a real stickers made, but this serves my purpose for now.

Great thread. Would be nice to have clearer photos or link to clearer photos.

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"The only problem with being retired is you never get a day off"

Excellent idea.. Please let me know if i'm correct on how to wire up the Lorlin rotary switch. The original pictures are very blurry and can't really make out what's what. I'm going by the schematic that Coco posted.

1. Set the switch for 6 positions

2. Jumper pins 1 to 4, 2 to 5, 3 to 6 and connect transformer secondary wires as shown on layout

3. Jumper pins 7,8,9 together and 10,11,12 together and connect brown-yellow wire from OT (5k primary) to pins 7,8,9 and then connect brown-white (2.5k primary) to pins 10,11,12

4. Connect switch terminal A to output jacks (same as layout) and then connect switch terminal B to pin 3 (plate) on octal socket

Does this sound correct? I can take clear pictures when this is completed

J., I haven't done the selector switch mod. I just bumped it hoping there are better pictures. I really can't tell you the correct wiring process.

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"The only problem with being retired is you never get a day off"

Thanks Hank, I'm pretty sure what i posted is correct. I'd just like confirmation, just in case!

Also, someone brought it up earlier in this thread and didn't get and answer so i figured I'd ask again.. Can the rotary switch included with the kit withstand the high plate voltages?

Thanks!

Actually, I missed Coco's reply.. I didn't read it as a confident endorsement of using the switch in this way. The 'if in doubt' part of his reply spooked me a bit. If no one replies, I'll just go with the original plan and use a heavier duty DPDT switch.

Jay, I use the heavy duty Carling switch. It's a lot easier to do it that way.

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"The only problem with being retired is you never get a day off"

Yes you can. The current is not that much. The wiring is a bit tricky is all. A DPDT with insulated terminals so they dont arch, is OK too.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Every kind of tube has ideal voltages and impedance ranges for it. Lower load impedance allows EL34s to operate at their peak power and tone. When the load impedance is larger, they may sound harsh or "brittle".
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