Adding tube bias pot (pics or info)

[kdove]

Just curious. Sounds like you would not want to adjust the tube bias too high since these amps have pretty hot preamps. But it does sound like balancing adjustments would be a good idea ... rather than depending on tube ranges.

Did a search ... didn't find any pics. Anybody got any pics showing how this looks after the mod? I'd just like to get an idea of what's involved.

I have a Mark 1 but I imagine they are very similar to the other Marks. What resistor has to be replaced with what variable resistor?

 

[Boogiebabies]

If you have a better picture of your power board, we can figure out where the best place to put a pot. It already has a bias adjustment with those two resisitors in parallel, so it is already running a bit more negative bias voltage.

 

[kdove]

I need to locate my digital camera ... I think my daughter borrowed it.

So is it worthwhile to do that mod on a Mark I? Some seem to say NO the amp should be running colder with the boogie preamp. Then others say YES it's a good idea.

Without the mod, what's the best way to check the current status on my amp? Can't I check it with a voltmeter or do I have to have one of the socket testers? Which pins do I check? If so, what should I be looking for in the readings?

 

[phyrexia]

AFAIK the biasing of the power section has nothing to do with how high-gain the preamp section is.

 

[kdove]

AFAIK the biasing of the power section has nothing to do with how high-gain the preamp section is.

I didn't say it clearly ... what I was trying to say is that many think the power amp should run colder SINCE the pre-amp is higher gain (higher than a Fender for example). So too much gain ... from BOTH power amp and preamp might be too much of a good thing ... becoming a bad thing.

But that's why I'm asking the question ... there seem to be varied opinions.