Tone Bender Mk. I

ljn · Post by **ljn** » 07 Jan 2016, 00:01

Hi, everyone. Last night, I decided to build the Sola-Sound Tone Bender Mk.I. I've been wanting one for a ling time. It worked as soon as I powered it up, but I'm getting too much low end in the sound. There's plenty of fuzz, but I don't think it's supposed to be so dark sounding. I used all of the stock values except for the electrolytic cap. For that, I used a 22 uf axial lead. My transistors are AC128 with hfe and leakage as follows: Q1 hfe 60 with 0.10ma leakage, Q2 hfe 73 with 0.06 ma leakage and Q3 hfe 62 with 0.06 ma leakage. Are my transistors the cause of the problem, or is it something else. I'd really like to get this one straightened out. Thanks.

ljn · Post by **ljn** » 07 Jan 2016, 04:23

I managed to reduce the bass response, but the fuzz is pretty gated and there's a sizzling noise when the signal fades. Could this be a problem with the amount of leakage in my transistors?

mictester · Post by **mictester** » 07 Jan 2016, 07:30

Check the collector voltage of the second transistor. If it's much away from -4V5, your output will be gated.

ljn · Post by **ljn** » 07 Jan 2016, 07:44

Do you mean with the attack control at full? How would I change the voltage if it's not right?

ljn · Post by **ljn** » 07 Jan 2016, 08:12

Okay. Here are the voltage readings. Firstly with the attack control on zero: Q1- C: -9.61v, B: -1.80v, E: -2.31v. Q2- C:-7.47v, B:0v, E: 0v. Q3- C: -6.47v, B: -0.02v, E: 0v. Now, with the attack control at full the voltages are as follows. Q1- C: -9.60v, B:-1.59v, E: -2.05 v. Q2- C:- 0.13v, B: -0.14v, E: 0v. Q3- C:-6.81v, B: -0.03v, E: 0v. Are these even close to what it's supposed to have?

ljn · Post by **ljn** » 07 Jan 2016, 08:15

mictester wrote:Check the collector voltage of the second transistor. If it's much away from -4V5, your output will be gated.

I believe you're referring to the mk 1.5. I already built one of those and it sounds pretty good.

ljn · Post by **ljn** » 08 Jan 2016, 03:45

If anyone on here has built a good sounding Tone Bender Mk.I, could you please recommend some acceptable voltages? It would really help to solve this problem. Thanks.

ljn · Post by **ljn** » 10 Mar 2016, 07:45

I have a "matched" set of AC125 transistors on the way. They should be here tomorrow or the next day. Can't wait to give them a try! In the description, the hfe for each was specified as Q1 60-70, Q2 110-120 and Q3 90-95. There was no mention of leakage readings, but the seller assured me he tests them thoroughly to make sure they'll work in the Mk.I circuit. We'll see.