Tone Bender Mk.II - Help Needed

ljn · Post by **ljn** » 02 Feb 2016, 23:29

Hello, everyone. I've been working on a clone of the Sola-Sound Tone Bender Mk.II professional. It will pass signal, but the distortion is uncontrollable and fades into a bunch of weird oscillation and motorboating sounds. Turning the attack control to it's minimum setting makes a small difference, but it's still putting out a wild sounding, gated distortion there. The transistors are AC128 with gains in the 60s and 70s with leakage in the 200-300 uA range. The base resistor on Q1 is 10k and the collector resistor on Q2 is 47k. I started out with 100k in both positions and changing them seemed to have no effect. Please help me figure this out. Thanks.

ljn · Post by **ljn** » 03 Feb 2016, 00:01

Also, I left out power supply filter cap. Would that cause any problems? I didn't think it would matter since I left the filter cap out of the germanium fuzzrite clone I built and it works fine without it.

ljn · Post by **ljn** » 05 Feb 2016, 21:29

I managed to get it working, but the sound is way off. Here's what I have in terms of hfe and leakage. Q1 hfe is 62 with 299 uA leakage. Q2 hfe is 63 with 218 uA leakage and Q3 hfe is 68 with 182 uA leakage. It's really gated and doesn't clean up like it should. So what's wrong here? Too much leakage? Not enough? Or, is it simply a gain issue? I really need some answers on this one. Thanks.

ljn · Post by **ljn** » 06 Feb 2016, 08:04

Okay, so I figured out I was using a bad battery to power this one. It read almost 8 volts on my meter, but something is wrong with it. I put a different battery in there and it sounds great now. It's very bright, which I don't mind. There's plenty of sustain, too. Even with the attack control at minimum, it has more gain than the silicon Fuzz Face I built a couple years ago.

DrNomis · Post by **DrNomis** » 06 Feb 2016, 10:39

It sounds like your Mk II build is suffering from what's called motorboating, that 47uF cap from the -V supply to ground is there to prevent motorboating in the Mk II circuit, you'll probably find that if you add the cap your Mk II build should work normally.......

ljn · Post by **ljn** » 06 Feb 2016, 11:06

Thanks. I'll put one in there and see how it works out. It's sounding pretty good right now, though. Still, I guess it wouldn't be right to leave that cap out.

ljn · Post by **ljn** » 07 Feb 2016, 04:20

After trying my three tone benders through my old Sears amp, I noticed that the mk. II can do the "Dazed and Confused " tone very well, but it doesn't get the "Communication Breakdown " tone at all. I can, however, achieve that particular sound with the Mk. 1.5. Is it possible that Led Zeppelin I was recorded using both circuits? That's what I'm beginning to believe.

DrNomis · Post by **DrNomis** » 07 Feb 2016, 05:30

ljn wrote:After trying my three tone benders through my old Sears amp, I noticed that the mk. II can do the "Dazed and Confused " tone very well, but it doesn't get the "Communication Breakdown " tone at all. I can, however, achieve that particular sound with the Mk. 1.5. Is it possible that Led Zeppelin I was recorded using both circuits? That's what I'm beginning to believe.

It's possible, I'm thinking that Jimmy Page might have been doing some Beta-Testing for Gary Hurst (designer of the Tonebender Mk I) during the recording of the first two Led Zeppelin albums, I seem to remember reading somewhere that Gary Hurst made a custom Fuzz pedal for Jimmy Page around that time.

ljn · Post by **ljn** » 07 Feb 2016, 06:03

Well, he certainly knew what he was doing. He designed some of the best fuzz circuits of all time. Plus, considering the endorsement deal that Mr. Page had with Sola-Sound, he probably used every one of the Tone Bender pedals. It would make sense, because he was such a big name back then and that would've really helped with advertising.

Electric Warrior · Post by **Electric Warrior** » 07 Feb 2016, 16:24

DrNomis wrote:
ljn wrote:After trying my three tone benders through my old Sears amp, I noticed that the mk. II can do the "Dazed and Confused " tone very well, but it doesn't get the "Communication Breakdown " tone at all. I can, however, achieve that particular sound with the Mk. 1.5. Is it possible that Led Zeppelin I was recorded using both circuits? That's what I'm beginning to believe.

It's possible, I'm thinking that Jimmy Page might have been doing some Beta-Testing for Gary Hurst (designer of the Tonebender Mk I) during the recording of the first two Led Zeppelin albums, I seem to remember reading somewhere that Gary Hurst made a custom Fuzz pedal for Jimmy Page around that time.

We simply don't know which circuit was inside Jimmy Page's Tone Bender. Could have been a MK1.5, could have been a MKII, could have been a Supa MKI.
By the time they recorded Led Zeppelin I these were probably all out of production. Sola Sound had moved on to the MKIII and I think Gary Hurst had gone back to Italy.

Whatever that pedal is, Page had been using it for quite a while in the Yardbirds.

The rhythm guitars in Communication Breakdown sound a lot like amp overdrive to me.

ljn · Post by **ljn** » 08 Feb 2016, 01:51

You may be correct. Mr. Page really knew how to get the best out whatever gear was available. I can't find a schematic of that Mk. I supa fuzz. I'd like to build that one very much. It seems quite interesting, being essentially a Tone Bender Mk. I , but with a Tone control. Thanks.

ljn · Post by **ljn** » 10 Feb 2016, 21:34

I just can't help thinking that this pedal should clean up more when backing off the guitar's volume control. Is it supposed to? As it is right now, it doesn't. It does get more treble, but also more gated. Thanks.

Electric Warrior · Post by **Electric Warrior** » 11 Feb 2016, 14:10

Time to rethink your transistor selection. Swap out Q2 until you find one that works better for you.

Bret608 · Post by **Bret608** » 11 Feb 2016, 19:23

If I remember correctly, I got better clean up on mine by going with lower leakage for Q2. Either way, it seemed like that was the one to experiment with to dial it in to taste.

Electric Warrior · Post by **Electric Warrior** » 11 Feb 2016, 19:52

Yes, indeed. Touch Q2 in a MKII with great cleanup and as the leakage increases, things are gonna be more gated in a matter of seconds.

ljn · Post by **ljn** » 11 Feb 2016, 21:42

I have a couple with lower leakage, but the hfe is also lower (in the 40s) .

Electric Warrior · Post by **Electric Warrior** » 11 Feb 2016, 22:16

Maybe try using higher leakage transistors for Q1 and Q3 then?

Oh, and voltage readings might be helpful..

ljn · Post by **ljn** » 11 Feb 2016, 22:36

Okay. Here are my options for Q2 all three are AC128. one has a hfe of 45 with 117 uA leakage. One has hfe of 48 with 105 uA leakage. And the third one I have has a hfe of 53 with 149 uA leakage. These are not in the pedal, but in my parts box. I have higher leakage in Q1. It has 299 uA leakage (hfe is 62). Q3 only has 182 uA leakage(hfe is 68). Thanks. I will try and get you some voltage readings later.

ljn · Post by **ljn** » 11 Feb 2016, 23:28

Here are the voltage readings from my clone. These were taken with the battery reading 8.92 volts and the attack control set to maximum.
Q1: C-7.11, B-0.04, E- 0
Q2: C-0.08, B- 0.05, E- 0
Q3: C- 8.08, B- 0.07, E- 0.05.
I hope this will be helpful in figuring out the problem. Oh, and I should mention the resistors are all stock values. 10k from Q1 base to ground and 47k on Q2 collector. Thanks.

ljn · Post by **ljn** » 12 Feb 2016, 04:02

I improved the clean up by placing a 100 k resistor in parallel with the 47k resistor on Q2 collector. It still has plenty of fuzz, too. With my guitar volume set to about 8, I was able to achieve a nice "In My Time Of Dying " style tone while using my Zippo lighter for a slide (a technique I've been developing because I like the sound and extra sustain it produces) . I think it will do until I can order a matched transistor set. Thanks.