Here's an idea some may wanna try

[John_P_WI]

Cool we have moved from soul to vibe to tantrum. Sounds like a move in the right direction to me.

[Reeltarded]

NFB is Dippity-Doo for amps. Yep.

[Ang3lus]

correct me if i'm wrong, but doesn't turning the NFB up takes the presence out of the circuit ? or is it always in regardless ?

I hate to say it, but i've had NFB pots since day in all amps i ever built (which is closing on 3 years now)

I even shared the idea on my #102 build thread, and I've found it way way way back when on some forum someplace, so i reckon it's been around for a long time ?

[iknowjohnny]

correct me if i'm wrong, but doesn't turning the NFB up takes the presence out of the circuit ? or is it always in regardless ?

Sure, if you remove *enough* NFB. Thats part of my point.

1-remove enough nfb to get the kind of aliveness i'm getting now, it's harsh and bright in a very bad way with a P cap. Before you get to that point it possesses none of the qualities i'm harping about and theres no in between.

2-remove the cap and before you get to that harsh bright point, the amp takes on the GOOD qualities of brightness with none of the bad, IE: cut, presence, alive quality, super dynamics/touch.

In short, removing the cap lets the nfb signal remain full and unaltered and the ability to cut NFB now leaves you with a much fuller livelier tone who's cut and presence can be added to a perfect degree. All i can tell you is it's VEY different from how my amp is with a prenec pot or no nfb and a cut control. VERY different, and the best tone this amp has had to date.

I hate to say it, but i've had NFB pots since day in all amps i ever built (which is closing on 3 years now)

More than 3 for me ! I built this amp 8 years ago and had a NFB pot in it within the 1st year. But again, it's NOT the nfb pot thats making this tone i'm talking about. Its nfb WITH the presence removed and lots of resistance.

I can see some are becoming Irritated that i seem to have found a tone tweak that pleases me to no end so i've leave the subject alone. Just trying to share something that you may feel is worthless but may be the best tweak i have found after 8 years tweaking this thing. To those who think no nfb and a cut is better, just tell me you've tried this too. I HAVE done both and i see no comparison, just a much better working version of the same sort of tone. carry on...

[Ang3lus]

not irritated, just curious.

I will try it, btw, did you try a 1M pot too ? does it have more travel ? or is 250k kinda the max noticeable thing ?

[Darkbluemurder]

Sounds very interesting. I hate the normal presence control on high gain amps. Decoupling the NFB only for the highest frequencies (that's what the regular presence control does) makes it only harsh when turned up full, with very little adjustable range.

I guess you ditched the presence control in favor of the NFB control - 33k (or slightly higher) in series with the 250k pot as a variable resistor, and 4k7 to ground, right? Did you mount this pot in the location of the presence pot?

Thanks for sharing this idea,

Stephan

[ampdoc1]

Iknow,

Don't get yourself flustered. You've found something that you know works well for you. Others have things that work for them. You been kind enough to describe it and offer it up on this forum,...some may try it,...most won't. That's just the nature of the beast.

A lot of us have had our own AA-HA moments and shared them here. But if anyone tried to implement every good idea offered here, they'd never get a build finished.

adoc1

[iknowjohnny]

Iknow,

Don't get yourself flustered. You've found something that you know works well for you. Others have things that work for them. You been kind enough to describe it and offer it up on this forum,...some may try it,...most won't. That's just the nature of the beast.

A lot of us have had our own AA-HA moments and shared them here. But if anyone tried to implement every good idea offered here, they'd never get a build finished.

adoc1

Thanks. But i have to admit something here. It may be that this idea is NOT what i thought after all. I don't understand what happened, but the reason i haven't posted is i've been going over and over this to try and figure out what happened. At one point it changed and i'm not sure why. I don't think i touched anything between where it sounded so good and then didn't aside from one resistor change (nfb 33k to 100k) which i even changed back when this happened, even tho turning the nfb pot down should have been the same effect. All i know if the tone is now worse than it was before i changed it. I have no idea whats going on, but i swapped all the tubes hoping there was just a coincidence like a tube going bad right around the time i did this mod. But no joy. The thing is, it's far too different to be a hearing thing, one of those day to day changes we often hear due to weather, our physical state or whatever it is that causes that. One way i know that besides the big difference in just tone quality if the amp had this much more middy sound to it when i first got excited about the change. In fact, that was the only downside because it was too middy, and i LIKE mids. But i found i could tame that with the mid control. Now after the amp seems to have changed it no longer has that and the mid knob is now best turned back up to where it usually was. So i know something changed but i can't for the life of my figure it out. I also built and installed a new board a couple days afterwards, which i had planned to do a week or 2 before and was just awaiting the parts and has nothing to do with my "find". I figured whatever the issue was when i installed a new board with all new components it should bring the sound back. But nope. And since the tone went to he|| the amp sounds crappier than it ever has. I'm so bummed about this i don't wanna look at the thing now let alone play it. I even put the presence back in and the tone is ok but compared to how it was after the mod i just don't want to play the damn thing. I spent all last night just staring at the guts trying to figure out what could have happened. But i can't recall making any changes, and with a new board.....well, all i could imagine is a tube, but as i said i swapped them all. I feel like tossing the POS.

[matt h]

(deleted)

[ampfab]

No negitive feedback on a jcm800, I thought i invented that. best jcm800 mod i've ever found. definitely more "alive"