About to build a Tonebender MKI. Any advice?

[jrod]

Thanks, Mac! Any idea on what could be causing it? I thought it was just me until I found the example I posted.

Mhhh, hard to say. When do you get that noise, near Vcc? Maybe one transistor is too off. In that case try to turn it on a little more.

Hey Mac! I'll try to set it up tonight on the breadboard and get some measurements. But, IIRC, I had Q3C at about 8.5V, Q2C varied from about 2V-8V, and Q1E about 1.5V & collector at Vcc. So, all 3 transistors were close to Vcc with Fuzz pot maxed.

When you say to "turn it on a little more" are you saying to feed more voltage to the collector?

Thanks!

[fuzzymuff]

Im a bit late on this discussion, but I'm glad I found this thread as I'm about to breadboard a sola sound tone bender MK1.  I've read about this particular tone bender being difficult to get the sound right as it is very picky with tranistors.  I've was informed that Small Bear sells a transistor set and specifically matched for the tone bender mk1, http://www.smallbearelec.com/servlet/Detail?no=1311  I figure ordering one set of these transistors for the tone bender MK1 would be a great idea, so wouldn't have to do the leg work in buying a whole bunch of trannys and sorting them out.  Has anyone sucessfully built a tone bender MK1 using the small bear tranistor set?  

[Merman]

I ordered the generic and OC75 mki sets a little while back when I was first playing with this on breadboard. Tax refund has let me grow my ge collection a lot since then. Mainly some OC75 and a bag of ac125z vi from the ebay. A lot of the difference between a small bear set and one I pick out after some swapping is really a matter of personal taste, I think. The OC75 set I got just popped in and sounded very good. Seems to be kinda representative of what I can get using that type or similar transistors, I guess. The generic set was a 3ax31c for q1, 2n508 for q2 and q3. The 2n508 I got seem to have *just* enough leakage to work. I had to go with 180k off q2 base, and I think I doubled the 1.8k or something just to line up one of the cooler sounds with 0 attack. So a little more fuss, the end result was a much weirder sound, attack knob sweep was a little more askew... but still awesome in the end. Maybe not for everyone though. I live in an apartment, and one of the neighbors from the complex asked with a bit of concern about "those weird sounds" the day after I was fiddling around with the generic set.

I say go for it! Unless you have scary neighbors...

[Arcane Analog]

I am pretty sure the OC75 sets from SB are simply gain audited for the "general consensus" as to HFE preferences although I know many would not agree. The two sets sent to me were not leakage audited. They will work fine in a MKII but I don't think they will always drop in and play in a MKI and you will almost definitely have artifacting. It is also worthy to note that the SB MKII sets are audited to get 4.5V and not 7+V so buying one of these sets will not guarantee success without some understanding of the circuit(s).

[mac]

Hey Mac! I'll try to set it up tonight on the breadboard and get some measurements. But, IIRC, I had Q3C at about 8.5V, Q2C varied from about 2V-8V, and Q1E about 1.5V & collector at Vcc. So, all 3 transistors were close to Vcc with Fuzz pot maxed.

When you say to "turn it on a little more" are you saying to feed more voltage to the collector?

Exactly. Q2 depends on the fuzz pot, so tweak Q3 to decrease its voltage a bit, 7.5v-8v.
Q1E seems ok, but have you tried a resistor from Vcc to B, say 1M, to increase the emiter voltage. I'm wondering if Q1 below 1.5v is too low...

For those having decay noises, maybe, and I say maybe, the lack of Vcc to B (or C to B) resistors at Q1 and Q3 can cause this.
That and/or the 22uf cap.

If I were to build it, I would add a pot at Q3 to adjust the collector at will.

I say go for it! Unless you have scary neighbors...

The basement of my building has displaced 10 feet since I moved in 

mac

[fuzzymuff]

I ordered the generic and OC75 mki sets a little while back when I was first playing with this on breadboard. Tax refund has let me grow my ge collection a lot since then. Mainly some OC75 and a bag of ac125z vi from the ebay. A lot of the difference between a small bear set and one I pick out after some swapping is really a matter of personal taste, I think. The OC75 set I got just popped in and sounded very good. Seems to be kinda representative of what I can get using that type or similar transistors, I guess. The generic set was a 3ax31c for q1, 2n508 for q2 and q3. The 2n508 I got seem to have *just* enough leakage to work. I had to go with 180k off q2 base, and I think I doubled the 1.8k or something just to line up one of the cooler sounds with 0 attack. So a little more fuss, the end result was a much weirder sound, attack knob sweep was a little more askew... but still awesome in the end. Maybe not for everyone though. I live in an apartment, and one of the neighbors from the complex asked with a bit of concern about "those weird sounds" the day after I was fiddling around with the generic set.

I say go for it! Unless you have scary neighbors...

Great to hear that.  I placed an order for those transistor MK1 set.  So a bag full of OC75 can still be had for a reasonalbe price, or should I just go with a bag full of Russian Ge trannies?

I don't live in an apt, I have an extra room near behind the house that I use as a "Man Cave" with all my musical stuff work area and my neighbors can't hear me and I can't hear them 

[fuzzymuff]

I am pretty sure the OC75 sets from SB are simply gain audited for the "general consensus" as to HFE preferences although I know many would not agree. The two sets sent to me were not leakage audited. They will work fine in a MKII but I don't think they will always drop in and play in a MKI and you will almost definitely have artifacting. It is also worthy to note that the SB MKII sets are audited to get 4.5V and not 7+V so buying one of these sets will not guarantee success without some understanding of the circuit(s).

I can verify the SB MK2 set audited for Q3C at 4.5v.  I used the included resistor that came with the set and indeed set the Q2C voltage to 4.5v, but if I didn't use the included resistor and use 47K or 33K, it brought the voltage closer to the 7.5-8.5v range.

[Arcane Analog]

The leakage is arguably more important than the gain in the MKI so it will be more effort to get the circuit where it is supposed to be.

[rousejeremy]

I'm thinking of building another one of these. Someone slap me.

[BetterOffShred]

I have enough Ge stuff now to probably make an attempt.. but reading this whole thread I'm not sure it's worth it   I built a Mk IV and still can't get it to sound right