ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: Doc Mark:I want to seco... -- 2/15/2000 7:52 PM

Re: Mushy Breakup on a Princeton Reverb

2/16/2000 3:58 PM
Mark	Re: Mushy Breakup on a Princeton Reverb Thanks to all that have replied. I think that I need to dig in a little deeper to get to the root of the problem. First, I think its safe to rule out the speaker being an issue since I put an Eminence 10" 50W ceramic in there and that made a significant difference in tone and loudness. The trashy stock speaker was the first thing I ditched. Secondly, my tech put in JAN Phillips 6V6's and a 5AR4 rectifier and rebiased before I recapped it and dismantled the pull-boost circuitry. Assuming my tech rebiased it optimally, I should be in good shape as far as bias goes. But if and extra 2ma can make such a big difference as in PTJohn's reply, maybe I should get that rechecked. Since I am becoming a DIY amp guy, I should learn how to rebias anyway. Can anyone guide me as to how I can install a bias adjustment pot? I hear its real easy but I don't know what parts I need and where exactly in the circuit it goes. Thirdly, I did try a .0047 mfd in place of the .022 PI coupling cap and the low end farting improved but only marginally. I'm beginning to think this is just a Fender thing - keep the bass under 4! Fourthly, I am planning on trying the B+ mod but after curing this particular problem. I would try it now if it is being suggested as a cure, but I don't believe it is, is it? Lastly, I have heard that if the .1mfd caps feeding the output tubes are not well matched, I will get crossover distortion. Torres is an advocate of this, but there are a lot of non-advocates of Torres. He sells matched .1 / 600v caps for $10. Is this worth a shot? Thanks again guys! Mark

2/16/2000 3:58 PM

Mark

Re: Mushy Breakup on a Princeton Reverb

Thanks to all that have replied. I think that I need to dig in a little deeper to get to the root of the problem.

First, I think its safe to rule out the speaker being an issue since I put an Eminence 10" 50W ceramic in there and that made a significant difference in tone and loudness. The trashy stock speaker was the first thing I ditched.

Secondly, my tech put in JAN Phillips 6V6's and a 5AR4 rectifier and rebiased before I recapped it and dismantled the pull-boost circuitry. Assuming my tech rebiased it optimally, I should be in good shape as far as bias goes. But if and extra 2ma can make such a big difference as in PTJohn's reply, maybe I should get that rechecked. Since I am becoming a DIY amp guy, I should learn how to rebias anyway. Can anyone guide me as to how I can install a bias adjustment pot? I hear its real easy but I don't know what parts I need and where exactly in the circuit it goes.

Thirdly, I did try a .0047 mfd in place of the .022 PI coupling cap and the low end farting improved but only marginally. I'm beginning to think this is just a Fender thing - keep the bass under 4!

Fourthly, I am planning on trying the B+ mod but after curing this particular problem. I would try it now if it is being suggested as a cure, but I don't believe it is, is it?

Lastly, I have heard that if the .1mfd caps feeding the output tubes are not well matched, I will get crossover distortion. Torres is an advocate of this, but there are a lot of non-advocates of Torres. He sells matched .1 / 600v caps for $10. Is this worth a shot?

Thanks again guys!

Mark

Replies:

Bruce q{Lastly, I have heard that if the ... -- 2/16/2000 4:28 PM