Allen Old Flame mods

Phase inverter bypass cap? What is that?

If you want to tighten up the bottom end a little you might try reducing the value of the preamp gain stages cathode bypass caps. If they are the typicla Fenderish 25uf, try going with 4.7uf instead. You might also try smaller coupling cap sizes if the cathode bypass cap changes doesn't tighten it up enough.

 

That .001uf (or later, .01uf) cap is usually called the PI input cap or coupling cap. It isn't a bypass cap in the normal sense.

I'd probably try a 10uf as the cathode bypass cap in the first gain stage, then listen to it for a while. If that didn't do it, I'd put the 25uf back in, then reduce the coupling cap from that stage to the next one by 30% or so, then listen to it for a while. I'd reverse the coupling cap and then do Hasserl's tone stack cap mod next, and listen. Next I'd put that cap back in, then reduce the PI input cap by 50%, then listen....

Just take the time and do the changes one by one and really evaluate the results. A combo of these changes will fix it, but your ear has to be satisfied. What you pick up here will help you mod future amps!

Tons of good info here:
http://www.unclespot.com/AmpINFO.html

just my ramblings; YMMV.

Slick51

 

Contact Dave Allen himself at his website. He's a heck of a nice guy, and I'm sure he knows exactly how to accomplish what you want.

 

Really? He has helped me through several mods to all three of my Allen amps. Most of my complaints had to do with too much low end being passed through -- typical blackface Fender sound. I ended up changing several caps in the amps, some of which had a more significant effect than the others.

One change that helped a lot was altering the values of the caps that are in the input and output to the master volume. You'll see two, .1uF caps that input to the master volume, and two, .1uF caps that come out. I changed each of these to .022uF caps. This was David's suggestion.

Another change I made that had a significant effect was in the tone stack. The standard slope resistor is 100K. I changed this to 56K. There is a .1uF cap and a .047uF in the tone stack. I changed each of these to .022uF. That made the tone controls more workable. I got this change from Dave Funk's Tube Amp Workbook.

Another change I made to my 40 TONESavor was to convert it to accept either 6L6 or EL34 power tubes, with only a bias change. I run EL34 tubes in that amp, and it tightened up the bottom end.

 

Another difference is the fact that my Old Flame and TONESavor each has the smaller OT. I built the 40 watt TONESavor (2x12) first, with the larger, Bassman-sized OT, but I decided I didn't care for that much iron. It was just too clean and too loud. I preferred the smaller OT, which is what I also have in my Old Flame (2x10).