Quadrafuzz

[jimbeaux]

Shielded cable is recommended in the instructions for any runs longer than a few inches, and although it looks like a lot of work - it purrs & growls but doesn't hum.

[Mark Hammer]

Here are pics of my QuadrFuzz build.

I don't think I've ever seen that much RG-174 in one place.   

I was going to say that I was taking it on faith that there was a circuit board underneath all that.   Indeed, the only reason I *knew* there was a circuit board was because I recognized the colour of a PAiA board!

[phaeton]

Btw, I presume that the progression of input caps on the opamp inputs  (.001, .01, .02, .033) is what does all the frequency dividing, and they are roughly set an octave apart?  They seem kind of small though, and I always thought that to single out a certain section of the spectrum, you need a filter on BOTH ends....

In the circuits I've played around with, i usually carve each set of freqs with a hi-pass/lo-pass RC filter pair.  Is this less than optimal?  I also split the signal into 3 pieces of roughly 1.5 octave (instead of 4 like the Quadra, but I've often mused going for 7 or more bands).  I guess I should also note that I use different types of clipping arrangements for each band, and i've (so far) used transistors instead of opamps, but I've always planned on trying it with TL082s or similar.  Mine's also really knobby- gain/volume for each band, plus a master volume on the output.

Mine have been pretty crude, I've got a few iterations I've breadboarded with varying success, and there are a lot of places where I've got quesitons, but I think in the right hands (or enough time in mine) it could turn into something interesting.

[soggybag]

I was looking at Mark's edited version of the Quadrafuzz:
http://img.photobucket.com/albums/v474/mhammer/moddedQUAFZSCH.png
I don't get what the two op-amps on the far right are doing. Its seems the first (top right) is used to sum the fuzz outputs. The network of resistors and caps and the op-amp below is not clear to what clear to me what the purpose of this is, can anyone explain that? Especially the two pots between these two.

It looks like these were meant to be a dual ganged pot, they seem to be named R46a and b. But they do not have a name so it makes me think these were meant as trimmers.

It looks like the last op-amp, bottom right, is a final output buffer. It seems to me you could sum the fuzz outputs to this last op-amp and leave the other two out?

[Nasse]

I´m not sure but that other circuit looks like a filter, lo pass maybe taming too much harmonics. I wonder if anybody has tried different kind and four times post distortion filters with this, that would be complicated animal but could sound interesting...

[soggybag]

Another thing that is perplexing me, can anyone explain the four switches leading from the input buffer into each of the filter stages? Except for the first, it seems that each just adds a parallel resistor along the signal path into each filter stage. Does this just act as a boost for any particular filter stage? I would this could be left out to simplify things a bit more.

[Dave_B]

Another thing that is perplexing me, can anyone explain the four switches leading from the input buffer into each of the filter stages?

Aren't those Q switches?

[soggybag]

It looks to me that the switches in question adds another resistor in parallel leading to the input buffer for three of the distortion stages. The first stage seems to add a .005 cap in parallel to another .005 cap.

I had originally thought that this changed the input impedance. After looking at the original schematic I noticed this was already covered before the input buffer.

I'm not really sure but I'm guessing this extra resistor changes the filter range in some way.

[MartyMart]

Here are pics of my QuadrFuzz build.

http://s79.photobucket.com/albums/j133/Jimbo_99/

I did use break-out jacks to tap into the individual fuzz outputs.

Have split the fuzz outputs to separate amplifiers, and the stereo image sounded great.

That looks like an "Ancient build" Jimbeaux !!   
( bet it's still working though ! )
MM

[donald stringer]

I am going to take a guess and say the switches either [labeled resonance] may transform the that section into an inductor or just change the knee. I may be wrong though but I have been studying a little on filters.

[grapefruit]

When the 4.7k resistor is switched in parallel with the 22k resistor the gain of the filter section is increased, thereby increasing the Q or resonance of the filter.

Stew.

[grapefruit]

I may be a bit off on that assumption. This is different to your usual bandpass filter arrangement....

[RaceDriver205]

Is anyone willing to record a sound sample of their Quadrafuzz unit?
I believe the last request for a sample of the QF was in 2003, and yet still no sample!
C'mmmonn! One for the team!

[Doug_H]

Here are pics of my QuadrFuzz build.

Crimeny! All that to distort a signal?!?!? 

No, seriously... Nice looking build.


And re. low battery drain:

Try using a TL06* series op amp like John Hollis did for the Easy-Vibe.

[RaceDriver205]

Jimbeaux, gis a sound sample! 

[WGTP]

http://www.harmony-central.com/articles/tips/multiband_distortion/

I posted this elsewhere, but it is very relevant to this thread.  From the master himself.