A lot of people seem to be asking questions on this circuit as have I! When I first built one the output was extremely low and there was more hiss than anything. I made a new circuit board and this time it worked but there was still very little volume, even with everything on full there was a drop in volume when switching on. There are a number of posts on various websites and most say that the collector voltage of Q3 should be around half the supply voltage. The only way I could achieve this was to bypass the 18K resistor which raised the collector voltage from 2.5 to 4.4v. I have also read that the Q1 and Q2 Darlington pair can be excanged for silicon transistors but when I have tried pnp Si units the circuit has not worked at all.
Bypassing the 18K has meant that the unit now has more than unity gain and the sound has vastly improved.
See my other post on the Axis Face and Mindbender where I have had to INCREASE the resistance to the collector of the final transistor to bring the voltage DOWN to between 4 and 5v! All this may be due to extreme variability in Germanium transistors. The mindbender is the best sounding germanium fuzz pedal I have built so far but needed tweaking to get it right with the transistors I used. I have built a Jumbo tonebender clone which uses BC184C Si transistors, which worked perfectly first time and has seen regular use at live gigs.
About 4.5 volt on collector... IMHO the common emitter stage with the R on collector and output from collector works well when collector is about a 0.5 of POWER SUPPLY. Usually the PS is the voltage on another pin of the collector resistor – 9 volt. But IMHO in this case we have a divider (10k/10k) and a collector R (18k) is powered by NOT 9 but ONLY near a 4.5 volts! And a desirable collector voltage is 2.25 volts?!?! But IF we eliminate 10k-to-ground resistor, collector R will be increased to 18k+10k=28k and now it will powered by a 9 volt and we need 4.5 on collector?!?! Am I right? Some people do this...
A am very glad to read ALL OPINIONS about 3 knob ToneBender and I wish it will be much more, but what about my 1), 2) and 3) questions?
PS to increase out voltage eliminate TONE block and get out from collector (with a capasitor). You will have a +-4.5 volt amplitude of the signal. IMHO it is VERY loud !
Some people do this...
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