tonebender pro MKII sounds mindblowing but Q3's Vc is too high?

[hellwood]

i just finished this thing and i cant even imagine it sounding any better! im not sure how that would be possible so...like i always do for reference, i measured the transistors voltages and Q3 seems way off. the collector is -7.57v? so, i put in a trimpot, knocked it down to -4.5v and tihe pedal seemed smoother, but  NOT  BETTER? it took a 33k to do what 8.2k should have done? also, it lost its ballsy edge and understandably some volume and i know that when a FF is this out of bias, its as good as a paperweight. so, is this normal or should it too sound like crap when its this unbiased? is this circuit more forgiving? WTF? any suggestions or smart-ass comments welcome. THANKS!

Q1 c. -8.59, b. -.036, e. 0
Q2 c. -.206, b. -.085, e. 0
Q3 c. -7.57, b. -.206, e. -.130

http://fuzzcentral.ssguitar.com/mkII.php

[mac]

Mine sounds a lot better at 4.5v than at 7.5v.
Any idea of transistor's gain and leakage?

mac

[R.G.]

i just finished this thing and i cant even imagine it sounding any better!

I have some good advice for you.

If it ain't broke, don't fix it.

What do you do if your tinkering makes it sound worse and you can't get it back?

Make a second one and do your tinkering on that one. Having a pedal you can't imagine sounding any better is rare.

[jonathan perez]

right on the head, RG! 

[hellwood]

Mine sounds a lot better at 4.5v than at 7.5v.
Any idea of transistor's gain and leakage?

mac

Q1 Hfe- 66   / leakage .079
Q2 Hfe- 73   / leakage .213
Q3 Hfe- 131 / leakage .399 (a little leaky but my 136 / .274 tranny read about the same)

I have some good advice for you.

If it ain't broke, don't fix it.

What do you do if your tinkering makes it sound worse and you can't get it back?

Make a second one and do your tinkering on that one. Having a pedal you can't imagine sounding any better is rare.

thanks for the good advise. i have done that to my quarter mile car too many times to count, and because of that im a compulsive-note-taking-madman and i only make one change at a time.
another thing i noticed when the bias was at -4.5 was how it did clean up a lot better when i rolled off the guitar volume. is this pedal supposed to clean up? ive never actually heard one of these pedals so i dont know how they behave/misbehave. THANKS!

[GREEN FUZ]

I haven`t built the Tonebender but I believe a common phenomenon of the design is that it cleans up beautifully when the volume knob is decreased.

[Toney]

 There's a place for the carefull methodical builder in us, and a place for the musician.

Sounds excellent and is stable?

Who cares why! box it up!! (musician)

[mac]

Don't care about Q3 leakage, since its hfe & leakage changes does not alter Vc3 much. Q2 is another story.
Finger heat Q2 and Q3 one at a time, and see what happens with Vc3.
Given your values it is not surprising that you need a 33k at Q3 collector to get 4.5v. Mine bias at around 12k to 14k depending on the day, with Q2's (70; 50ua) and using a 47k not a 100k at Q2.

But if it sounds better at 7.5v...

Who cares why! box it up!! (musician)

I wish I could separate the musician from the hobbyst in me...

mac

[hellwood]

Finger heat Q2 and Q3 one at a time, and see what happens with Vc3.

finger heat on Q2 makes Vc3 increase and finger heat on Q3 makes Vc3 decrease

Given your values it is not surprising that you need a 33k at Q3 collector to get 4.5v. Mine bias at around 12k to 14k depending on the day, with Q2's (70; 50ua) and using a 47k not a 100k at Q2.

what is your Q2 Vc?

[ulysses]

my hfe's are 70 70 and 140

i think 140 is way to high - at higher voltages on q3 it does sound a lot better - i think i currently have mine set to 5.5-6volts

all the other voltages on my build match the recommended ones so there is nothing wrong with the build.

it sounds flabby and farty with q3 at 4.5volts

when i get around to it i will hunt down a ge tranny with a 100-110hfe.

cheers
ulysses

[mac]

finger heat on Q2 makes Vc3 increase and finger heat on Q3 makes Vc3 decrease

Yes, but vc3 is more sensible to Q2 variations.

I guess that vc2 is about half a volt in mine.

***
I'm going to breadboard one with a 150-200 Ge at Q3 and play with vc3. Maybe the first tranny has something to do because it is boosting the FF section. Just a thought.

mac

[hellwood]

my hfe's are 70 70 and 140

i think 140 is way to high - at higher voltages on q3 it does sound a lot better - i think i currently have mine set to 5.5-6volts

all the other voltages on my build match the recommended ones so there is nothing wrong with the build.

it sounds flabby and farty with q3 at 4.5volts

when i get around to it i will hunt down a ge tranny with a 100-110hfe.

cheers
ulysses

let me guess...you are using humbuckers.
__________________________________

OK, for anyone who gives a sh**. i have biased Q2 and Q3 all kinds of ways and have found some interesting things. when Q3 Vc is where it should be (-4.5), the strat/tele single coil thing is happening in every possible way(lead, rhythm, palm muting rhythms, chords, rolloff, etc). its ALL happening bigtime at the expense of a little volume drop, however the les paul/sg humbucker thing is NOT (at least for ripping rhythms). when i crank up Q3 Vc(>-6.5v) the humbuckers start to work w/ various rhythm techniques but the singlecoil loses its scooped mid effect and clarity along w/ some rolloff capabilities but its more in your face(probably the mids). Q2 Vc doesnt seem to have as much of an effect on things other than Q3 Vc. for my last experiment i will try a recommended 100 Hfe Q3 just to see what that helps/hurts and ill post the results.

[Toney]

I give a sh.. , I mean I'm interested in your findings and mostly play buckers.
I have never heard anyone mention these results before.
Keep em coming!

[Toney]

Hmmm, so once you have established the two ideal bias points for Q3 relating to single coils and 'buckers, it may well be the best idea to make the difference in resistance switchable with an external toggle, or fix resistors up to the lowest  usable point and have the rest as a dialable range via a small value external pot.

[petemoore]

I've got to figure the value again, new guitar Needs bigger treble bleed caps.
  This time it's burstbuckers and 500k pots, that should lend itself nicely to the treble bleed mod on the neck especially and bridge, Volume pot bypass cap mods.
  I have them in there already, caps marked 221, they aren't big enough I can tell they're actually in there.
  figured I'd play a gig [I just finished] and see...nope gonna take more to get treble out of these.

[hellwood]

Hmmm, so once you have established the two ideal bias points for Q3 relating to single coils and 'buckers, it may well be the best idea to make the difference in resistance switchable with an external toggle, or fix resistors up to the lowest  usable point and have the rest as a dialable range via a small value external pot.

we think alike, and if the 100 Hfe experiment for Q3 doesnt pan out, thats exactly what i will do!
at least that way i can have one smokin hot pedal that works for both guitars instead of having to have a pedal that is just OK or great for one and not the other. im thinking a toggle will do the trick because im not really interested in the range the pot would give me. in fact, im thinking of doing this to all of my pedals!

[hellwood]

i have added a sound clip. tele 52RI>TB>74 champ>SM57>windows sound recorder

http://www.theharshcarpets.com/my_tonebenderProMKII.wav

my formula for this was Q2Vc -.550 and Q3Vc -4.5. i used the original Hfe's posted on the top of the thread (66,73,131). i could not get the humbuckers to my satisfaction no matter what i tried. they seem unresponsive and flabby(for palm muting/fast rhythms) but not totally useless because they scream for solos! i tried a Q3 of 100Hfe and it sounded great but still some of the meat was missing and still was not as responsive as i need. i tried a Q2 of 82 w/ Q3 of 100Hfe and 131Hfe and the magic just progressively disappeared. everyone was right. i got lucky and had all the right combos from the start. the only things i changed in the end were Q2Vc -.550 and Q3Vc -4.5. i originally thought Q3Vc of -7.57 was the best, but after cranking my amp to compensate for the volume drop at -4.5, it sounds the same but a little more controlled and less chaotic. its chaotic enough w/ a Q3 of 131Hfe. im boxing it up! thats it! i hope this is of some value to someone!