Simplified Silicon Tonebender 3-Knob

[mac]

This is a simplified silicon version of the Tonebender 3-knob.
It is intended for those who do not want to mess with ge transistors and avoid thermal runaways.

- As you can see I replaced the darlington pair with just a single transistor Q1 (our well-known friend Mr. 2N3904) trying to keep bias resistors close to the original schem. I also increased the roll off cap a bit. In the original there is a 10k from T1 emiter to ground that adds a little to the overall sound. But my guess is that the designer included it to send some of T1 leakage to gnd. Anyway, this single stage sounds very similar to the original first stage.
- I added a 22k resistor after Q1 to avoid signal hit Q2 too hard.
- The fuzz pot connected this way controls the gain better.
- A silicon diode is a perfect match for a silicon transistor
- R8 feeds Q2 base and sets Q2 collector voltage near 3.2v or so. Experiment with 820k or 680k.
- C5 filter some highs.
- R9 reduces Q2 gain a bit.



Sound clip soon.
Enjoy!

mac

[John Lyons]

Thank you Marcelo! Very generous.

John

[Brymus]

Sweet I will give this a try ASAP ! as I like all your designs.
Its been moved to the top of the breadboard list,I just have to find room for it.

[joegagan]

looks great,thanks for posting this.

[mac]

Its been moved to the top of the breadboard list,I just have to find room for it.

Buy another breadboard!!!

mac

[imbuedblue]

Thanks for this! It's on my vero short list.

[momo]

Just breadboarded this one. Q1 is not biasing and the bias resistors are spot on....., Q2 biases fine with a 1M trimpot. Im getting 1.8v at Q1 collector. 2.4v at base and 1.17v at emiter.
Oh anyhow, im not asking for a debug, ill just go ahead and do a perfboard on it. I was breadboarding to choose input and tone cap and Im sure your schematic is fine

[mac]

Momo, there is an error in the previous schem, R2 should have been 220k and R4 10k    

This is the corrected one:



Sorry!

mac

[momo]

 
Ahhh!....OK then, no problem. At least I know Im not crazy!....I was really scratching my head there.......OK, will try this out now.
thanks again!

[John Lyons]

Ahh, thought that was a little odd. 

[mac]

Ahhh!....OK then, no problem. At least I know Im not crazy!

Good for you! I can't say the same about myself!!!

Ahh, thought that was a little odd. 

It is funny how the mind works. I checked the previous schem a thousand times and since the values were correct but misplaced I didn't see the error.


mac

[momo]

Just tried it, sound great, nice upper harmonics. Id say its a little less brittle or wild than the germ version I also just built. On both builds though the tone cap is kind of weird, on the opposite side of the pot(high end rolled off), there is practically no output. I thought my germ build was kinda off on that but its the same reaction on this one, so this must be part of the design. I have to say, Im still very much following schems and do not fully understand how circuits work so this might be obvious to some of you......
Is there a way to have a tone cap that does not affaect the output as much?

[mac]

This is a quick sound demo,

http://www.aronnelson.com/gallery/main.php/v/mac/sound+demos+of+my+circuits/Simplidied_Si_TB3.mp3.html

Guitar->breadboard->Laney LC30II->dell mini mic->nero wave editor
Tone flat, fuzz 60%, unity volume
Amp low input, clean chn volume at 4, B5, M3, T5.
First take guitar single coil-ish, then HB.

mac

[mac]

I reduced gain a little compared to the ge version, you can remove the 22k before the fuzz pot, or decrease the emiter resistor of Q2.
Both extremes of the tone pot should give you similar output.
The 0.1uf cap is 18k away from the collector, ie, the 0.0047uf cap. R13 shunts some signal to gnd to balance the output signal.

mac

[azrael]

What purpose does the diode serve here? In the original it was to stabilize the temp of the transistor...but here?

Is 3.2V optimal? I'm wondering mostly 'cause I need to bias a Ge one too. :p:

very cool idea, I may build one this weekend.

[mac]

The diode does something, very subtle. I used a silicon to match the transistor Vbe. You can try with or without it.
You can reduce the voltage to 2v or lower by decreasing the feedback resistor. It is a matter of taste.

If you are going to build a Ge one, I'm experimenting with a more stable bias and drive control, much like this one, to avoid extreme thermal runaways.
When I was designing my Ge Big Muff I noticed that Q1,2,3,4 bias are quite stable. I used a similar bias arrangement.
I'm testing this bias with leaky germs which BTW NEED leaky Ge diodes, and/or a resistor from base to gnd. I had good results so far.
A leaky diode and the drive pot connected as in the schematic drain transistor leakage to gnd, and the addition of a feedback resistor make Q3 more stable.

mac

[azrael]

Oh I already have Ge one built, it's just kinda low output, I thought adjusting the bias might help.

Interesting, I glossed over the fact that you had a resistor on the emitter of Q2 here...so mess with that, huh? Perfect, I just got some 500 ohm trimpots.

doesn't the Ge diode already stabilize the bias for the Ge version of the circuit? Just wondering, as I have a Ge diode in my Rangemaster, and I've never had any temperature instability problems there.

[mac]

Oh I already have Ge one built, it's just kinda low output, I thought adjusting the bias might help

In the ge version there is a 220k just before the vol pot. I reduced that value to 100k for more output. Some guys remove it.

Interesting, I glossed over the fact that you had a resistor on the emitter of Q2 here...so mess with that, huh? Perfect, I just got some 500 ohm trimpots.

I put the emiter resistor to tame high gain transistors. This a trick used by those who build a Fuzz Face powered by BC108.

doesn't the Ge diode already stabilize the bias for the Ge version of the circuit? Just wondering, as I have a Ge diode in my Rangemaster, and I've never had any temperature instability problems ther

Yes, but do not trust it is going to keep Q3 stable under large variations of temp.
A rangemaster is far more stable, even the first stage of the TB3 is quite stable. Mine has never moved more than a few mV away from 6.8v.
I cannot live without my rangemaster.

mac

[azrael]

Ah, see I already removed the 220K resistor. But I still have to get it cranked on the volume control for it to be close to or over unity.

Rangemasters ftw.

do you have clips of this silicon design?

[mac]

The output volume has been always an issue. Try a bigger volume pot as well.
The sound clip is some posts above, or go to my gallery.

mac