Yeah it's another Tone Bender.... The Vox was one of the longest running in production, and it's a variation of a Fuzz Face, or vice versa.
VOX TONE BENDER - POINT TO POINT LAYOUT
VOX TONE BENDER MODS
- Increase the size of the output capacitor. 4n7 is pretty small, considering a Fuzz Face is 10nf
- Replace the 8.2k resistor with a trim pot for bias fine tuning
Hey, I have a small problem with my built. I didn't use your layout, but the same values as you did. The problem consists in the Attack Knob. When its full on, it sounds like it should be and it is a fantastic Tone Bender. However, when I turn the Attack knob down, the fuzz disappears quickly. Already past 3 o'clock its gone. Its basically just usable in the last quarter. Do you happen to know what could be the issue? I am considering changing the 820r resistor, as it directly connects to the attack knob. Or do you happen to have a better idea?
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ReplyDeleteQ3? I was referring to the Vox Tone Bender. I am using GT402 with low-moderate leakage. I used the same in the Zonk II (Germanium), which is close to being the same circuit and they work fine with a nice sweep on the 1k Attack Pot. I can't figure out, why I haven't that sweep in the Vox Tone Bender. This is why I thought the 820r might be the culprit, because it doesn't exist in the Zonk II.
ReplyDeleteThis is the gain and leakage I used:
ReplyDeleteQ1: 71, 0,11
Q2: 98, 0,15
This behaviour is usual in this one and with most of the fuzz face family circuits, this is why I usually put a 1k resistor and leave the pot out.
ReplyDeleteIf you want to expand a bit the fuzz in the dial you can try a reverse logarithmic 1k pot for the fuzz.
For the transistors you can try to have a Q1 with low leakage in the 80-100 hFE and a Q2 with low leakage and an hFE as low as in the 30's-40's. This was (approx) the gain ranger of the transistors when they used the SFT363E and SFT 337.
With OC76 they were all over the place bit I built one with a low gain OC76 and sounded like the demos.
Hey! Where did you get this info about hFEs? I've been trying to see if anyone's spec'ed out the transistors from a vintage unit; maybe you have?
DeleteYou can read the info about the transistors here: https://www.freestompboxes.org/viewtopic.php?t=18915
DeleteSorry for the laaaaaaate reply!
What he said ^ ^ ^
ReplyDeleteSorry, getting my tone benders and transistors mixed up..
Can always jumper the 820 and see if it improves things.
Have you seen this before? Has voltages and a bit of info
https://sites.google.com/a/davidmorrin.com/www/home/trouble/troubleeffects/vox-tone-bender