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Some Discussion on Amp EQs

#122
ejsagun said:
i have been trying to wrap my head as to how to do it with fets (SVT) style. I read your posts on the first page and it got me wondering on how to execute it. opamps would be easier but wheres the fun in that.
Click to expand...

op amps by far are easier to do that with. You can drive a passive james/bax then afterwards use an active mids control (quite a few out there) which do not even need inductors but give you a good approximation of that control.
 
#124
I don't know how much peaveys VB-2 & 3 have in common with my older Classic 400, but it also has the resonance control.

Schematics here Link Removed

Turning that control up makes the lowend really big...and "looser" the higher you go. I always kept mine pretty far left as that amp sounds deep and strong as is.
 
#125
if its a negative feedback control, then it decouples the negative feedback in low frequency resulting in more low end or less low end in the output of the amp.
 
#138
Here is a new one for the thread. This is a VB-2 EQ, which is a negative feedback type that is unique to Peavey. This is with one setting of the mid shift switch. The frequency seems a little off from the actual amp, but I'm going to blame the tube models in this case. This is also just the EQ, not the actual speaker output curves.
VB-2 low sweep.JPG

VB-2 mid sweep.JPG
VB-2 high sweep.JPG
 
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#139
Again...what a nice thread. It may seem simple for you designers and techs out there, but for the rest of us simpletons it goes a long way towards explaining what's really going on. Especially with things like the losses you get in circuits, and makeup gain, NFB, and the fact that when we say things like we're adding or "boosting" something in the sound we're really not, we're just losing less of it.


I'd like your take on B-strings question quoted here when you have time...



B-string said:
What do you think of combining shelving and active bandpass such as Gallien uses.
Click to expand...

I have schematics for these I could dig up if need be, tucked away in old crashed computer hard drives and old emails. A bit outside the jist of this thread as there isn't a tube to be found in the amp anywhere. :)

But, I find the older Gallien-Kruegers, where the treble shelving is set low enough to have a nice effect on regular paper cone speakers rather than being a sort of quasi tweeter knob, to be extremely musical and useful for our instrument. Simple, intuitive 4-band but the frequency centers, slopes, Q widths, etc. are just spot on to my ear. Notable for musical sounding boosts as well as the "cut what you don't want" approach.

If I could get that eq coupled to some big honkin' power tubes and iron, with a nice wide range between too clean and too dirty, it might well be my last amp. :)
 
#140
BbbyBld said:
Here is a new one for the thread. This is a VB-2 EQ, which is a negative feedback type that is unique to Peavey. This is with one setting of the mid shift switch. The frequency seems a little off from the actual amp, but I'm going to blame the tube models in this case. This is also just the EQ, not the actual speaker output curves. View attachment 430912
View attachment 430914 View attachment 430915
Click to expand...
Nice to see an amp designer from a big company get in on the fun. Thx for sharing, Bobby!
 
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