• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Some Discussion on Amp EQs

#84
Pres and Res are most likely the same old NFB eq controls which decouple the NFB loop at low or high frequencies. When you decouple the NFB loop at a frequency that increases the gain of those frequencies in the power amp. i dont have a scheme for its preamp EQ
 
#87
esa372 said:
Great thread!

This caught my attention:
According to the Duncan Calculator, the Alembic F-1X (which is a modded FMV) can be set to have an almost ruler-flat EQ:

The settings have to be pretty extreme to get it, however:
Bass - 0.3
Middle - 5.5
Treble - 0.0

It does appear impossible to get a mid-boost from it, but that's why we have the SF-2. :D
Click to expand...

The TSC is a great visualization tool, but actual measurements are a bit more useful when they're available. ;)

I modified the second channel of my F2B to do mid boost in such a way that you could sum both channels and have controllable mid boost and cut. The guy I sold it to preferred just using the second channel though.

There are some graphs in my DIY tube preamp thread showing various mid boosts achieved with no inductors, starting here. Personally, I like some aspects of the interactivity of the Fender stack, so I tried to do my own riff on that with active bass and mids, and a quasi-passive treble circuit. And being the contrarian that I am, I made the whole thing optimized for active basses only. ;)
 
#89
ImageUploadedByTalkBass1359006479.317487.jpg

This is all I could find. Controls are bass, middle, four way mid toggle switch, treble. And of course presence and resonance.

http://assets.peavey.com/literature/manuals/03595970_4.pdf
 
#90
esa372 said:
Very true!

I don't suppose you have an F-1X on hand to see the actual results of those settings...? :) (I'm not set up for such things, or I'd do it myself.)
Click to expand...

Nope. There was one around here for a while which I worked on and played through, but it's long gone, as is the F2B.
 
#92
dunwichamps said:
Pres and Res are most likely the same old NFB eq controls which decouple the NFB loop at low or high frequencies. When you decouple the NFB loop at a frequency that increases the gain of those frequencies in the power amp. i dont have a scheme for its preamp EQ
Click to expand...

NFB? :hiding:

Never understood how the pres/res controls worked.

dunwichamps said:
thats just a rough block diagram but I was correct about pres and resonance. Thats like the same stuff you might see on a SLO100
Click to expand...
It functions alot like an ampeg tone set up but the mid selector just sounds/reacts pretty different.
 
#93
negative feedback. Its refers to a portion of the output signal that is injected back into the circuit, usually at the phase inverter. It forms a loop which encompasses the phase inverter, power tubes, and OT. Its called negative feedback because it is out of phase with the signal at the inverter. Negative feedback decreases the gain inside the loop but if we select portions of frequency band where we decrease the amount of negative feedback that will increase the gain of that frequency band. Thats what the presence and resonance do
 

Latest posts

Top Bottom
Back