#161843  by Hitime
 Mon Jul 09, 2018 10:52 am
When using only the preamp part of a twin what happens to the power amp ,is it shut off ?can you remove the power tubes?
 #161849  by waldo041
 Mon Jul 09, 2018 8:39 pm
Hitime wrote:
Mon Jul 09, 2018 10:52 am
When using only the preamp part of a twin what happens to the power amp ,is it shut off ?can you remove the power tubes?
Depends on how you are preamp tapped. You want the input into the phase inverter to be shunted to ground at the same time the tap has a jack in it. You also want to remove the speaker plug so that the jack shunts the output to ground. With both the input and output shunted to ground the power amp section will just sit idle. You can at this point keep them in for one type of voltage or remove them and raise the voltages across the entire amp. Of course you want to make sure your filter caps can handle whatever voltage increase happens. Check your voltages, know your amp. Lethal voltages involved so a competent tech is HIGHLY RECOMMENDED.

~waldo
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 #162150  by Beggars Tomb
 Thu Aug 09, 2018 11:38 am
Waldo....
I was thinking of adding a separate jack just for preamp out. I was going to wire it how I saw on article on dozin.com and that got me thinking of adding a spdt switch to input of phase inverter.....one side would be for normal operation and be wired to output of phase inverter cap with other side of switch for preamp out being wired to ground.

You think this would be a viable option for shunting phase inverter input to ground while in preamp mode?