Hot Silicon Fuzz R9

[Kearns892]

I breadboarded the Hot Silicon Fuzz using the schematic from the layout gallery http://www.aronnelson.com/gallery/main.php/v/DougH/fuzz/hotsi/GS_Tonebender.gif.html. It sounds great, but has the normal hum expected from a breadboarded circuit next to a computer. However, when I was experimenting with R9, I found that if the resistor was completely bypassed, the hum totally went away. The schematic suggests using a trim pot to tune R9 to taste. I was wondering if someone could explain to me what is actually happening as I change the value of the resistor and why the hum is eliminated when I bypass it all together.

[azrael]

Good question!
I built this layout...
http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/dh_hot_silicon/ulysses_dh_hot_silicon.gif.html

Didn't look too closely at the schem, had no idea about R9. I'll have to try that.
You're adjusting the resistor at Q3's emitter..And Q3 looks like a gain stage. So maybe you're just lowering gain? I have no idea. Just a stab in the dark.

[Gus]

R9 is a different way to adjust the bias of the FF.  At geofex you can find a schematic of a vox fuzz in "the tech of the ff" writeup note the use of a 820 ohm resistor.  With the 1K R9 bypassed you most likely have the FF type section of the fuzz in a gated bias so it is acting like a noise gate.

When I build circuit like that I make the R9 an external pot that goes from gated to compressed sounds

[yeeshkul]

Gus does "gated bias" mean that the transistor is turned off and turns on by signal (like a switch)?

[Kearns892]

Alright, that seems to make sense, thanks a lot Gus. One last thing, want to know if this is normal, mine has really high output, I have to keep it at minimum volume and there is still a significant boost from clean.

[Kearns892]

I couldn't find a perf layout in the gallery so I drew one up. Its no great I know, but I wanted it to fit on half a Medium sized Perf board from smallbear. Unverified as of now, I would like some other people to look it over. If it seems ok I will go ahead and build it and if that works add it to the layout gallery.


Thanks

[Kearns892]

That last layout was really hard to read and contained some polarity issues, I removed the link from the last one so no one gets confused and have the revised version 2 which is easier to read with the latest version of DIYLC. Still looking for anyone to glance over it. Thanks

[jessej]

This looks nice. Are the tone and gain pots still the same value as in the Doug Hammond ver1.0 from May 2008? (link posted above)

You could maybe add the pot values to the gif for future reference.. if you like..   

[arma61]

Hi

is S1 connected in the right way?

according to this

http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/dh_hot_silicon/dh_hot_silicon.gif.html

IN is always connected to C1 and the switch is just adding C2 when swtiched, isn't it ?

as far as I can see from your layout IN is going either to C1 or to C2.

Ciao
Armando

[Kearns892]

I can go ahead and add in the pots later today or tomorrow if people think it will help. And arma, you're right! I suppose I could wire the input wire to go to the switch and then C1 with SPST wired to add C2 in parallel in one position and leave the other lug open, but would it really make much of a difference? Capacitance-wise were talking a .1% difference, which is nothing in light of tolerance values. Is there a value in the switching mechanism of always having a permanent connection there?

Still having problems with a huge volume boost, anything past min. volume is too much to use in home settings. I will run an audio probe through it later and double check all my resistor values, any suggestions on where to start? One last thing, what is the purpose of C8 and is it necessary?

[arma61]

I can go ahead and add in the pots later today or tomorrow if people think it will help. And arma, you're right! I suppose I could wire the input wire to go to the switch and then C1 with SPST wired to add C2 in parallel in one position and leave the other lug open, but would it really make much of a difference? Capacitance-wise were talking a .1% difference, which is nothing in light of tolerance values. Is there a value in the switching mechanism of always having a permanent connection there?

Still having problems with a huge volume boost, anything past min. volume is too much to use in home settings. I will run an audio probe through it later and double check all my resistor values, any suggestions on where to start? One last thing, what is the purpose of C8 and is it necessary?

as far as I can see C8 is a filter on power supply, I think a sort of "to be sure to be sure" a good power is going to the circuit.
About C1 and C2 on mine the difference is quite big, I see it in this way, you're adding 10u to .01u, yes the difference is only 1% on the total, but with the switch connected in that way you're running your signal either through .01u or through 10.01u, that's a big difference!

Armando

[Kearns892]

I think I was unclear. What I meant was the difference between 10uf (the way I have that layout wired) and 10.01uf (the result of running both in parallel with the switching in the schematic). I can't imagine and audible difference between 10uf and 10.01uf, but I am wondering if there is an advantage to having a constant line from the input and adding capacitance to that as opposed switching between two levels of capacitance temporarily breaking the connection like I have it now.

Hope this makes more sense 

[arma61]

ok, got what you mean now! it looks like it's almost the same, so with your connection you have either 10u or .01u, with the connections as in the schematic you have either 10.01u or .01u, that shouldn't be a big difference.

[Kearns892]

I am having computer problems, so I wont be able to fix the layout any time soon, I am also trying to figure out if there is a good way to fit C8 in there with out making any major adjustments, I will probably end up using a jumper just to keep it easy. Thanks for your help.