Collector resistor (Bazz Fuss)

[Sam]

I spent last night trying out the simple "Bazz Fuss". Can someone explain how the gating-effekt works? I liked the basic sound of the effekt - thick synth-like fuzz and would like to expand the circuit somewhat.

Well, this is what I know: I know that the input cap at 4.7uF filters out DC and low frequencies. Being a large value it lets more bass into the circuit (right?). I understand the output cap, the basic principle of the transistor but do not understand what the diode (from collector to base) do in the particular circuit. Has this diode something to do with the gating effekt or is it a clipping diode? I tried bypassing it with a wire but that made everything totally silent. I know the low input impedance makes the effekt very thick and bassy by loading down the guitars pickups.

I tried two different collector resistors, 8.2k and standard 10k, without any audiable difference.

I've read all the brilliant texts on stompbox technology at GEO. So, if somebody feels they've got the time to help out a newbie I would really love to get a very short "The technonoly of the Bass Fuzz".

[B Tremblay]

There are others who are infinitely more qualified to answer your questions, but I believe that the diode simultaneously biases the base of the transistor and clips.

[Sam]

I've been thinking that the guitar signal (which is connetced to the base through a 4.7u cap) is gated by the trannie when the voltage gets to low. At higher voltages (when the diode "opens up") the collector voltage is fed back through the diode to the base and clips the singal.

If this is the case - do I have to put another trannie stage in front of the existing one to eliminate the gating? Or is it just a matter of picking the right component values?

I think the Bazz Fuss has great potential to become a good sounding fuzz for bass guitar.

[davebungo]

If you think about it, the base of the transistor will be at about 0.6V (as it is a forward biased pn junction).  Similarly, the collector will be clamped at about 0.6V above the base because the diode will also be forward biased.  So the collector is effectively prevented from going much above 0.6V+0.6V = 1.2V and no less than 0V (so severe clipping).  I have seen some modified circuits using a darlington configuration which will provide even more gain and more intense clipping.  Don't take my word for it though as I haven't played with this circuit.

[Sam]

Yeah - I think I get your point.

I used the 2N3904 transistor. If I put a large resistor in paralel with the diode to keep the base biased or between ground and base. Will that eliminate the gating or severe lack of sustain?

Still, I like to have the gating as a switchable option...

[jmusser]

Sam, check out "first bass effect:bazz fuss: pics and clip" on page 6 by "zyzygy", and post on page 2 for "simple distortion for bass guitar, by "shawsofhell". I thought the bazz fuzz clip for bass sounded great, but then again, I'm not a bass player.

[Sam]

Thanks!  

Now I found all the articles about the Bazz Fuss on ROG and Home-Wrecker.

I did some experimenting with the circuit. I used a 10k collector resistor where there should be a 100k when using a non-darlington transistor. I used a 2N3904. The severe gating seemed to be an effekt of the small resistor value. Why?  :oops:

Now there is much longer and more natural note decay - but I liked the sound better before. Some of the thick beefy buzz went away. I think I'll try a 2N5906-darlington next.

I really love the Bazz Fuss and will spend the next few days tweaking this wonderful little thing. If I put a second Bazz Fuss stage after the first though a switch (to give it a Buzz Box mode) - where are the best points to connect the switch?

Hope you don't mind the ambarrisingly newbie-oriented questions...  :wink: