Building the Power Amp Section ONLY

[jonyoungyi]

Was curious if anyone here has built just the power amp section of any amps. I've been thinking about building the wampler Black 65 and Tweed 57 and using those two for my "preamp" section and feeding them into a full blown AB763 power amp section. Of course I'd have a 9v transformer to power the two pedals.

Is that a thing? Do people build just the power amp sections of amps? haha

[eleventeen]

Certainly. But define or clarify what you mean. Including the phase inverter?


There's nothing out of the ordinary building a power amp that needs ~~1 volt to drive it. That would be entirely conventional, and could be easily done with your 2 output tubes and a single 12A_7. Easy. Well, maybe not easy, but simple. 

[jonyoungyi]

Yup, including the phase inverter. The AB763 is a Push Pull, so I'd need the phase inverter.

The idea would be similar to adding a passive fx loop, but just adding the "return" path and connecting the output of the 2 pedals to that path. (hope that makes sense).

I'm just curious if anyone here has done that before. It sounds easy on paper, as I've built several amps already. Just gut the preamp section and replace with pedals, right? haha

Wonder if there is something unexpected I should.... expect... in my thinking hahaha

[shooter]

Wonder if there is something unexpected I should.... expect... in my thinking hahaha

I'm doing one now, breadboarding 1st, and there is a lot to consider, how much drive do you need to bend the PA the way you want, tube type, Bias, B+, OT.  A lot of your "tone" comes from bending the power tube/s.

[silverfox]

It's well worth it for the learning experience. But, rather than do it again, I'd most likely buy a used Peavey stereo power amp. Classic 50-50. I got the schematic off the Web but it's too large to post. They have what appears to be the Recovery section of an effects loop feeding the phase inverter. Some good ideas. While I was building mine I ran across one in a shop for $275. Hard to beat the price when the Iron cost me about that alone... But the build experience- Priceless!

silverfox.

[Ed_Chambley]

I have built all the amps I want to play and on every build I have a loop that will allow me to use only the Power Amp section.  Now I build preamps to patch into any of the amps I have built.  So much cheaper to build a preamp, which IMO where the basis tone is.  Most I tire of quickly, but my building of amps got really out of hand to the point where the amps began owning me.  I sold all but 6 of my builds.  I still do not want to admit how many tube radios and amps I still have and I still bought a Philco am last weekend.


What is cool about doing what you are considering is if you take your time and consider building a Tube Power amp that has enough current to run large tubes, but low enough voltage to run all octals.  Make it with a switching rectifier from SS to tube and you can achieve a multitude of different voltages.


Tubenit like to build with 330-0-330 I think.  Maybe he will see this and chime in on all the different voltages he gets simply by changing rectifier tubes.


Brian Wampler makes some very nice pedals, but if you do not run them into the front of a preamp tube you will hear diode switching more easily.  If you can, put you overdrive pedals in a FX loop on a tube amp amp and play and listen.  This will give you an idea of what you will have. Some folks pay no attention to diode switching, but I hear it and it drives me nuts.  I don't notice it much at all in front of a preamp.


Don't take me the wrong way, I love all pedals simply because it is fun to me.  I don't use a lot,  but have quite a few.  Also recording the output from a pedal and playing at amp volumes through a stereo will reveal some of this sound too.


Forum Member Jojokeo builds some really nice pedals as well.  The FuzzShway he sent me if a blast and I am still finding new ways of using it.  I'll bet if you PM him he will have some great insight on using a pedal as a preamp.  Brian's pedals have active preamps and a really hot when turned up a little.

[jonyoungyi]

Hey Ed!

Thanks for the insight! I definitely should test this before going off and building a power amp. To be honest I read reviews about the pedals and listened to demos and they sounded great, but of course the demo wasn't running the pedal like how I want to run them haha

I just finished a 5E3 that I'm having issues with and am finishing up the Black 65 pedal soon. I'll be sure to fix that 5E3 and try the pedal in it's effects loop to get a idea of diode switching vs preamp tubes!

Thanks, all!