big long question re PPIMV and NFB

[Fred G.]

Here's the background:

Blackface Bandmaster, modded heavily (OK, I know. I was young - but I learned TONS from this, and it's my amp, dammit).

I put in a Torres post PI MV 11 years ago. I have wrestled with this amp for 11 years trying to tweak it into sounding good, but always had an annoying problem with excessive shrill high end, no matter what I tried. It always "almost" sounded great, but continually frustrated me when I tried to tweak it into "that sound".

Tonight, I decided to get drastic (for me, anyway). I first disconnected the NFB. Noticed "some" difference, but nothing earth-shattering (keep in mind I have a sleeping wife on the second floor, so I couldnt crank things up too much, even though I'm in the basement).

next thing I did was to "standardize" the PPIMV, since the Torres version is "backwards" (the wipers are "fed" from the first set of caps, instead of the wipers "feeding" the 2nd set - did I get that right?).

anyway, now the amp is a whole different critter. The shrill highs vanished, as if by magic. The excessive rumbly farty bass has been tamed. It doesn't have the same amount of grind that it did before, but it just sounds "better".

I feel like I have something to tweak and work with now to finally get this amp where I want it!

I'm not real sure why "reversing" (or "standardizing") the post PI MV connections made such a big difference. I don't think disconnecting the NFB wire was the big factor as much as changing the PPIMV connections was.

Can somebody explain to me just what I really accomplished here?

Thanks,

Fred G.

[Noel Grassy]

I hate to say it cuz Torres was near me and got me started on the amp thing but but many of his circuit mods were either poorly thought out or uninformed alltogether. The mods he sells in packages are just crap. His book was elementary but lacked the knowledge necessary to cover a wide range of one model or even amps with similar topology. You've just done done a Torres re-treatment, glad it worked out for you and obviously you know what you've done in the amp. Hell yeah it's your amp, MOD it till it's correct for you.

[Fred G.]

Hi Neil,

I'm with you on the Torres thing. I honestly think he performed a great service for me by getting me started, but that's about where it stops. I do like his book, though. It's disjointed and poorly written, but he does give you a lot of basic stuff to work with. I would still recommend it as a starter book for somebody.

As for his mods - well, I don't need 'em anymore!

Fred G.