Experimenting on a Si Tone Bender MkIII - how to get less decay?!

[Renegadrian]

Gents, I just started experimenting with the Tone Bender MkIII schem - here is for reference from fuzz central.

now I just made it with negative ground, using pn2369 or 2n3904, with a 1n4148 as diode, or a LED.
took off the 220k res before the volume.
The pedal sounds quite good that way, but I found the notes die just after a moment, not infinite sustain you have.
Like the trannies "gate" and the notes decay in a fizzy way...
Thought...Well, maybe I just have to bias trannies in a different manner...so I tried wiring pots instead of the resistors that go from 9V to the trannies (220k, 10k and 18k) also putting the pot to q3 before the 10k res that lowers the voltage.
none of these experiments made substantial changes to the sound...
What could I try to get a less fizzy sound?! Thank you!!!

[LucifersTrip]

are you getting proper voltages when you have the poor decay?

did you remember to flip the diode?

[Renegadrian]

made a search but couldn't find a voltage reading table to compare...
all polarized components (diode and electrolytics) are flipped
thx for the reply

[Renegadrian]

reading with 2n3904

voltage in 9.77
Q1 (cbe)
3.68
1.64
1.12
Q2 (cbe)
3.66
1.12
0.53
Q3 (cbe)
4.75
0
0

my schem

[Solidhex]

  It's that Q3. In the original the darlington pair only has to push the base of Q3 about a tenth of a volt to turn it on. The diode isn't needed here since its more an effort to keep the leakage of the germanium from turning the transistor on without any signal hitting it. What you need is a pull up resistor to bring the base of Q3 closer to .7v so it will turn on and stay on (more sustain) when playing notes. Either from the positive supply or across the collecter/base of Q3. it won't behave exactly like a germanium version but you should at least start getting some longer decay that way...

[LucifersTrip]

Also, in a bunch of the build reports (original ge version), many have found the best sound when Q3 C voltage is lower, in the 1.5 - 2.5v range


good luck

[Renegadrian]

@LucifersTrip - as I wired a pot at Q3 collector I was able to go from 4.8v to almost 0, but that wouldn't make it sound better. thx again for your answer!

@Solidhex Yeah As I read in fuzz central the first two trannies aren't that important, while Q3 is the one that shapes the sound.
as for the diode, it it almost gated at all without, while is almost playable with. I got a 1n4148, but also a recent 1n260 and tried a couple of leds too. more or less the same result.Think I'll follow your precious hint and wire a pot at the base to find the right value for a fixed resistor...thank you!

[Renegadrian]

It seems that Solidhex knows his $hit...definitely right with his hint!!! put a 1M res. to Q3 base - works a lot way better...infinite sustain, man!!! and I was on a Zoom with headphones, don't wanna think about this MF just before a raging tube amp!!! The gain pot could be better, yeah it works but it never goes clean...btw it frekin' rocks!!! \m/ Updated schem

[bwanasonic]

It seems that Solidhex knows his $hit...definitely right with his hint!!! put a 1M res. to Q3 base - works a lot way better...infinite sustain, man!!! and I was on a Zoom with headphones, don't wanna think about this MF just before a raging tube amp!!! The gain pot could be better, yeah it works but it never goes clean...btw it frekin' rocks!!! \m/

I have always found that the guitar volume pot is better for this than the fuzz/ gain pot, which I usually prefer on full. Of course this equation is not so straightforward, once you introduce things like Zooms and headphones, and various pickup styles.

[azrael]

Setup a standard gain pot with a limiting resistor, works well in place of the gain pot.

What are your voltages now?

[Renegadrian]

You mean signal from 220n to pin 3, wiper to Q3 an pin 1 to ground?! yes that could be tried...maybe it'd sound better...
I guess playing late at night with headphones won't get you the same sound as a real amp, but yeah you understand how that gain pot works and how much clean you can get...

After my "1M res. to Q3 base" mod, collector voltage is really low (like 0.3), but who cares (as long as it sounds good) - I have base at 0.6

[mac]

Check my simplified version at my gallery using just 2 silicons which has some filter caps, a trimmer from q3 C to B to set the desired voltage, and a buzzaround-like drive control.  Just some ideas you can use now that you solved the decay problem.

mac

[Renegadrian]

Yes Marcelo, I already knew your layout and thought I'd give a try soon, but this time I wanted to stay true with the original layout, hoping it would work the same...after all it went that way, just that minor change about the q3 base res and no diode. Now the ckt gives a good fuzzy tone but has infinite sustain, no fizzy gating...
thank you for your suggestion and your work! it's really a nice variation on the mkIII

[Solidhex]

 Theres a couple alternatives to their fuzz control. You can use a pregain control in front of the circuit or you can use a 5K pot in parallel with a 10K resistor to replace the 3K3 resistor on the emitter of Q2 then wire it with the electro on the wiper of the pot like a Fuzz Face. Another thing to do is make the 10uf switchable to 4.7uf for crunchier lower gain tones.

[karolisd]

Hi, I know this is an old thread, but I'm currently breadboarding a silicon tonebender MK3. I've replaced q1 and q2 with a MPSA14 darlington transistor and q3 with a 2n3904. As stated above it had very little sustain, so i put a 1m resistor between the collector and base of 2n3904. However, after this mod a lot of hum appeared. Did you notice this in your builds? How can this be solved?