ts2b+@andrew.cmu.edu (Terence Ronald Spies) (04/10/91)
I have completed all the mods in the dynamods file available over anon. ftp at csd4.csd.uwm.edu excepting one. The forward feedback mod worked for a bit and then caused the amp to start howling at various high frequencies. I realize this is probably due to unwanted coupling in the feedback section, but I could not find any problems iwth the wiring. Second, I installed a solid-state version of the 5ar4, which seemed to really tighten up the sound. So, any reasons why the first mod didn't work and any comments on the second? Terence Spies ts2b+@andrew.cmu.edu
jhess@orion.oac.uci.edu (James Hess) (04/12/91)
In article <10915@uwm.edu> ts2b+@andrew.cmu.edu (Terence Ronald Spies) writes: > >I have completed all the mods in the dynamods file available over anon. >ftp at csd4.csd.uwm.edu excepting one. The forward feedback mod worked >for a bit and then caused the amp to start howling at various high frequencies. > >I realize this is probably due to unwanted coupling in the feedback section, >but I could not find any problems iwth the wiring. > Once as a young technician I was handed a modified Audio Research preamp to repair. It was motorboating and occasionally squealing, as I recall. I tried 50 things to fix it; no luck. Finally I sent it off to the manufacturer. They returned it in fine working shape, having removed the a capacitor mod which altered the transfer function sufficiently to destabilize the circut. Some of the tweekers out there are not familiar with the problems of component and assembly variability; therefore they do not follow good engineering practice and design in a margin of safety. Another consideration is that changes to one part of the system freqquently affect other parts of the system. If you applied a collection of modifications each designed independently, it is probable that no one has considered their collective effects. -Jim Hess-