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Re: Fuzz Face for the people!


 
3/5/1998 5:07 AM
GFR
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Re: Fuzz Face for the people!
If I'm using a Wha, the Wha is first, if not, the FF is first. If you want to use a Wha, you will need the Fuller mod to the input (50k pot in series with input) or it won't work very well (the FF will load the Wha circuit because of its load input impedance).  
 
My guitar is a Squier Contemporary Stratocaster, made in Japan. Has rosewood fingerboard and classic fender trem. Pickups are the humbucking provided with the guitar (not very hot output, with a lot of mids) at the bridge and an old PAF copy at the neck (it's loud - I used a bridge pickup). I have a rotary switch that will give me:  
1) bridge  
2) bridge//neck  
3) neck  
4) neck in series with bridge (very high output)  
5) neck in series with out of phase bridge (very high output)  
6) neck // out of phase bridge (very low output)  
7) neck with capacitor to ground (woman tone)  
There's also a switch for single coil operation of bridge pickup.  
The FF tends to work better with the options that give me less output (the dynamics are more responsive). Also it prefers the lower output impedance and brighter sound combinations. The exception here is option number 6) that sounds very thin and weak.  
 
I think the dual sounds will sound good, especially if you can switch them to single coil.
 
3/5/1998 11:30 AM
CJ Landry
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"you will need the Fuller mod to the input (50k pot in series with input"  
 
Just for clarification sake, Colorsound was doing this with 2 - 100k resitors in series and to GND at the output of their wah way before Fuller mod'ed any wah wah's or FF's. If you look at pictures of Jimi Hendrix, he put the FF first before his wah Colorsound wah pedal.  
 
Christian
 
3/5/1998 8:32 PM
Greg
1) Change the value of the 33k resistor (decrease it). This  
will increase Q1's collector current and so the voltage  
drop at its base. You will probably need to increase the  
value of the 1k also. Roger Mayer used 5k6 for the resistor  
and 2k2 for the pot in his "Classic Fuzz".  
 
Little background here: I have a Mayer Classic Fuzz that I've been wrestling w/ for the past 6 months or so, off and on. It just sounded really blatty. Replaced all the caps. No change. Tried different values for the fuzz pot. No change. I then gave up, figuring that the AC128's must be sick. Well, I recently ordered a couple of them from RG and this evening I put them in. No change!! So, after reading your post I figured I'd start working on the resistors. I tried going lower w/ the 5k6 w/ no success. So I started working my way up in values. At 18k, I began getting some more appropriate sounds. I settled on 27k. Never did try 33k. Might still do that. Anyway, the sound of this thing is still not quite there and it's a bit bright. Anything I can do to change that? RG mentions putzing about w/ the 100k resistor. What can I expect if I were to do this? I guess the obvious answer is just to do it and see what happens but I'm burnt out for the night, so I thought I'd see what the Sifu's (teacher) might have to say about it. Thanks for any input.  
 
Greg
 
3/6/1998 12:51 AM
Preben Hansen
I have read RG's technologi document about  
the FF. I am going to experiment with the different circuits mentioned here.  
One topic affecting the tone seames to be the input impedance of the FF and the load of the input from the guitar PU.  
I have seen a schematic, the JSH-fuzz somewherw on this net. It uses an emitter-follower at the input. I will try that some time in the near future.  
Any comments/suggestions ?  
Preben
 
3/6/1998 4:25 AM
MHelin
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Preben:  
 
One topic affecting the tone seames  
to be the input impedance of the FF  
and the load of the input from the  
guitar PU.  
I have seen a schematic, the JSH-fuzz  
somewherw on this net. It uses an  
emitter-follower at the input. I will try  
that some time in the near future.  
Any comments/suggestions ?
 
 
Input impedance of FF is about hfe*25/Ic. If hfe=84 and Ic .25 mA, it's about 8.4k, which is not much, as that 8.4k is quite typical output impedance for a guitar PU, and at PU's resonance frequencies it's much more (about 50k or so). A rule of thumb for the input impedance is ten times the output impedance, that's why the 500k is quite usual.  
 
However, the Ic is 0.25 mA only when the transistor is conducting and the base voltage is then most negative (with PNP Q1). When the transistor is not conducting, there's just the base current of Q2, which is not much, and the input impedance is much more, I'd say it's close to 100k (the feedback resistor is there). So during negative phase input impedance is low and during positive phase it's high, and this is one way to see how the asymmetric distortion is created.  
 
If you add an emitter-follower or other buffer circuit between PU and FF, you'll get rid of this asymmetric input impedance and loose the tone, so it's better not to use any input buffers. Instead the recommended mod for the collector resistor (33k --> 5k6) is good, as it lowers the input impedance (for the negative phase). It also lowers input impedance for the positive phase, and to be able to adjust it for your guitar PU's, it's better to put there a pot. 50k pot could be fine for humbuckers too, maybe a logarithmic one as it makes it easier to adjust at the lower end. Put a 1k resistor in series with it in order to avoid accidents (or how much current these ge transistors can take, 5 mA must be safe, so 9V/5ma = about 2k). This is the tone control for FF :-),  
 
-Mikko
 
3/6/1998 8:36 AM
MHelin
email

I wrote:  
However, the Ic is 0.25 mA only when the transistor is conducting and the base voltage is then most negative (with PNP Q1). When the transistor is not conducting, there's just the base current of Q2, which is not much, and the input impedance is much more, I'd say it's close to 100k (the feedback resistor is there). So during negative phase input impedance is low and during positive phase it's high, and this is one way to see how the asymmetric distortion is created.  
 
Just one thing to add, when the input voltage at base of Q1 goes positive (towards the ground) the voltage at the collector of Q1 goes negative, as well as the emitter of Q2 thus charging the cap bypassing the 1k pot. When the cap is being charged the negative voltage affects on the base of the Q1. As the frequency of voltage is quite fast the cap just levels all the changes and changes the operation point of Q1 so that when the signal dies the asymmetric distortion disappears (I think so). So a bigger cap would change the attack/decay times longer. Now the internal re of Q2 with the cap sets the time constant RC for it, but you could connect a pot there between the cap (or actually the 1k pot) and the emitter of Q2 to limit the current charging the cap and so adjusting the time constant. Maybe with two diodes and pots you could adjust both attack and release times separately, except that the minimum 0.3 V voltage difference may create some problems with only a modest changes. Now if somebody only could find out how to get the tone with silicon transistors!  
 
-Mikko
 
3/6/1998 9:13 AM
MHelin
email

 
Now if somebody only could find out how to get the tone with silicon transistors!  
 
 
If the problem is that PU's just can't drive the silicon as smoothly as the Ge ones? Extra amplifier stage will raise the voltage, but the nice tone is lost. What if we used a transformer to raise the voltage level just enough to be able to drive the silicon transistor? This way the PU's are still loaded as before (I think so) and the tone resulting of this is not lost. Please correct me if I'm wrong here.  
 
-Mikko
 
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