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 Post subject: Tube switching question
PostPosted: Sun Mar 06, 2011 5:09 am 
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Hi guys,

I'm looking for a little advice on wiring the switch, since I'm deviating from the basic layout. As I'd mentioned before, I'm putting a KT66 in; I'd also like to be able to switch to an EL34. I know from the other threads here that some adjustment to the 6L6 path is needed, probably for both tubes? (It seems to go back & forth between 6L6 being OK for these & needing to add another resistor to get it right?)

I am aware that I also have to switch between the different OT leads for the EL34.

I really didn't plan on using a 6v6 - would be nice to have the option, but I'd give it up for simplicity in favor of switching between the two tubes I've listed. Given this, what are your thoughts on wiring the extra resistors and the tube selection switch?

Thanks! :-D


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PostPosted: Sun Mar 06, 2011 12:21 pm 
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For 6V6, 6L6, KT66 just wire the amp up stock. For the KT66, use the 6L6 setting on the bias switch.

If you want to use an EL34 set the bias switch for 6L6. You also need to use the Brown/White OT lead though, so you'll have to switch that in. You could add another mini switch (in the extra 1/4" hole) to select between the two primary OT leads (brown/yellow, 5K and brown/white 2K5).

I'd wire the amp up stock first though and make sure everything is working before going on to mods...


Chris...

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PostPosted: Mon Mar 07, 2011 4:10 am 
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kurtlives wrote:
For 6V6, 6L6, KT66 just wire the amp up stock. For the KT66, use the 6L6 setting on the bias switch.

If you want to use an EL34 set the bias switch for 6L6. You also need to use the Brown/White OT lead though, so you'll have to switch that in. You could add another mini switch (in the extra 1/4" hole) to select between the two primary OT leads (brown/yellow, 5K and brown/white 2K5).

I'd wire the amp up stock first though and make sure everything is working before going on to mods...


Chris...



So for the KT66 you don't have to change any of the wiring?


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PostPosted: Mon Mar 07, 2011 12:16 pm 
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vortexx wrote:
kurtlives wrote:
For 6V6, 6L6, KT66 just wire the amp up stock. For the KT66, use the 6L6 setting on the bias switch.

If you want to use an EL34 set the bias switch for 6L6. You also need to use the Brown/White OT lead though, so you'll have to switch that in. You could add another mini switch (in the extra 1/4" hole) to select between the two primary OT leads (brown/yellow, 5K and brown/white 2K5).

I'd wire the amp up stock first though and make sure everything is working before going on to mods...


Chris...



So for the KT66 you don't have to change any of the wiring?

Correct

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PostPosted: Tue Mar 08, 2011 12:50 am 
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OK, maybe I wasn't specific enough. I'm talking about setting the cathode resistors up for these two tube types.

In this thread was posted:

coco wrote:
Sergelac wrote:
So in retrospec, it seems that a 1K ohms 5 watts resistor in parallel with the 750 ohms will do the job nicely for a KT66.

Good work Sergelac, I'll actually add this to the manual.


As I said in my OP, I'd like to be able to switch between these two tube types. I already have the 2nd switch ready for the OT leads - what I'm trying to figure out, however, is a way to approach the difference in bias resistors.


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