Multi Face Build - Too MUCH Output??

[amonte]

I finally got around to building the Multi Face project as detailed on home-wrecker.com

http://www.home-wrecker.com/multiface.html

It works really nicely, but I seem to be getting too MUCH output from it.  It sounds best when the volume knob is at least above the first 1/4 or so, but even that low on the volume knob, I'm already much louder than the bypassed signal.  In order to get it around the same level as bypass, I'm literally on the first few ticks of the pot - and I noticed that there's definitely a difference in the quality of the fuzz sound this low on the dial.  I've got a 100K audio taper in there now.  I originally had a 500K on there, but even switching to the 100K didn't seem to fix it.

Any ideas?  Anybody had similar problems with this?  I suppose the other solution would be to simply use it a little louder and raise the volume of my other dirt pedals to compensate, but I really don't want to go down that road.

Thanks!

[midwayfair]

You can try giving it fewer volts to work with. You'll have to rebias after running them down of course, but a 100K pot between the + power lead and the +9V board input should do the trick. You can hardwire it in the finished product by measuring the pot at a setting you like.

Untested in this circuit, obv, but I've done this in other projects.

You can also try other transistors. As a last resort, if you get all the way down to VERY low gain transistors (in the 60 range?) and it's still too loud for your taste, find a couple leaky ones and turn them around. Of course, it might no longer be a fuzz at that point!

[wilrecar77]

Hey man. Maybe try a normal voltage divider before the volume pot? You might try dividing it in 2 (like how you get the 4.5v for an opamp circuit running off of a 9 volt battery) as a starting point. If it changes the tone, raise or lower the values.

I say that because I had an opamp muff fuzz on the breadboard using 1M's for the voltage divider to get the reference voltage and it whined like crazy. I knew my power supply was noisy so I changed it to 10K's and it got rid of it. I think that the 1M's had a high impedance so it let in the high frequencies of the power supply whine more readily than the 10K's which would present a low impedance.

Basically, if the voltage divider works but changed the tone, keep the ratio between the resistors but experiment with the values.

[amonte]

Wow, thanks for the replies guys, I will give these a shot.

midwayfair, I kind of like starving the battery to 4.5 volts.  That sounds interesting.  Rebiasing the Multi Face is easy, so that might work nicely.

wilrecar77, I like the voltage divider idea to - but wouldn't that change the output impedance of the circuit?  Might not be a bad thing though - could tame some of the high end.

[wilrecar77]

It will definitely change the output impedance. If I knew more about the math behind it, I'd recommend some values but thats why I suggested experimenting. I *think* that using high values will present a high enough impedance for it not to affect the tone very much.