Tonebender Mk1 Transistor sets at now at SmallBear

The numbers look good but be prepared to tweak the resistors because it's a finicky circuit, especially if you want to get more than one sound out if it.

Looking forward to seeing and hearing your build since I'm an MK1 buff.

Have you heard the new ones Sola Sounds just sold? All sound different and all sound amazing.
 
Cvoxdog said:
Just curious, which resistors are you more likely to tweak and which direction would you go?
Click to expand...
The 15k resistor on Q3c so you get the right voltage. The 470k before Q2 is useful to tweak the amount of gain. That was as low as 180k in vintage units.
 
Big Monk said:
I second this. Small Bear, even under Steve, had a dodgy record of knowing exactly what they were doing with tuning.

For instance, and this never changed, they always sent MK II sets to bias to 4.5 vDC on Q3.
Click to expand...
Yeah, I bought a TB mk3 set and I could never get it to bias correctly (even with a trim pot) until I swapped in different transistors.
 
andare said:
The 15k resistor on Q3c so you get the right voltage. The 470k before Q2 is useful to tweak the amount of gain. That was as low as 180k in vintage units.
Click to expand...
Thanks, I have the zonk which sounds good but I'd like to tweak it to see if I can get a little more gain.
 
spi said:
Yeah, I bought a TB mk3 set and I could never get it to bias correctly (even with a trim pot) until I swapped in different transistors.
Click to expand...
What hfe and leakage did you go for with the TB MK3?

I have one on a breadboard that sounds great but it's very quiet. I had to get rid of the 220k before the volume pot to get it to unity. Also the collector voltages are at -5V but apparently they should be at -3.5V
 
andare said:
What hfe and leakage did you go for with the TB MK3?

I have one on a breadboard that sounds great but it's very quiet. I had to get rid of the 220k before the volume pot to get it to unity. Also the collector voltages are at -5V but apparently they should be at -3.5V
Click to expand...
What they sent me hfe/leakage:
Q1: 60/30
Q2: 82/250
Q3: 110/35

What I ended up using (and liking better):
Q1: 60/30
Q2: 11/23
Q3: 82/250

The low gain Q2 ended up working well in this darlington pair configuration.
And the high leakage in Q3 isn't causing any issues for me, but I don't think it was ideal in Q2 because that one would not bias.
 
spi said:
What they sent me hfe/leakage:
Q1: 60/30
Q2: 82/250
Q3: 110/35

What I ended up using (and liking better):
Q1: 60/30
Q2: 11/23
Q3: 82/250

The low gain Q2 ended up working well in this darlington pair configuration.
And the high leakage in Q3 isn't causing any issues for me, but I don't think it was ideal in Q2 because that one would not bias.
Click to expand...
Interesting. I read that Q1 and Q2 should be at the same gain but maybe because they're darlingtons it doesn;t matter. Like I know what a darlington pair is :)

Sooner or later I'll have to read up on what transistors are and how they work because I still don't know what biasing is haha
Just painting by numbers here. I'm astonished that my pedals even work.
 
Received my order today

Q1 OC75 B = 74 L = 140
Q2 2N1305 B = 128 L = 80
Q3 2G308 B = 102 L = 35

Put them in this

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Tonebender MKI

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Pedal is barely audible with the volume and gain knobs maxed. Have to crank the amp to 10 just to hear it at all. Gain is not fuzzy at all.

Voltages

Gain pot min

Q1
C = 8.81
B = 8.75
E = 0.31

Q2
C = 0.93
B = 0.74
E = 0

Q3
C = 0.74
B = 0.59
E = 0


Gain pot maxed

Q1
C = 8.79
B = 8.73
E =0.30

Q2
C = 6.25
B = 6.05
E = 0

Q3
C = 0.76
B = 3.08
E = 0

Where do I go from here? What needs to be tweaked?
 
You should be getting between - 8-8.5V on Q3c.

Look at my build report to see my voltages and other useful info.

Tone Bender MK I - Vintage Edition

Hello everybody. I'm very happy to present my most rewarding build to date: a Tone Bender MK I. I built it on turret board with 1W carbon film resistors (but there's a 1k8 1/4W metal film resistor in there too) and big axial capacitors. The coolest thing about it, however, is the vintage style...
forum.pedalpcb.com forum.pedalpcb.com
 
Oh FFS, I forgot the voltage inverter. I should not build when I am tired. Why can't I ever learn this lesson?

With the voltage inverter

Voltages

Gain pot min

Q1
C = 8.78
B = 0.90
E = 1.17

Q2
C = 8.72
B = 0.04
E = 0

Q3
C = 8.6
B = 0.02
E = 0


Gain pot max

Q1
C = 8.78
B = 0.87
E = 1.13

Q2
C = 4.5
B = 0.16
E = 0

Q3
C = 8.27
B = 0.01
E = 0

Works just fine. Loud and gainy.

It is a bit bassy and farty. Any tips to lower bass/increase treble and/or reduce fartiness a bit?
 
Reduce the 25uF and maybe the 100nF caps for less bass.

What do you mean by farty exactly? Listen to the new ones on Sola Sounds Channel for reference.
 
Not sure if gated is the right word, but it spits/sputters with too much bass throughout the first half of the Attack pot and it sounds - for lack of a better word - farty. I read your linked post and changed the 470k resistor to 330k like you had tried and it smoothed up the pedal right away and the fartiness was gone but so was some of the grit as you mentioned. I also played with the input and output caps and that changed things nicely as well but too much. So I think the right answer is to change the resistor to something between 330k and 470k and then adjust one of the caps as necessary. Going to box it and keep playing with values as it does sound pretty great it just needs some fine tuning.

Also, that gold pedal of yours is gorgeous
 
Freshmex18 said:
Not sure if gated is the right word, but it spits/sputters with too much bass throughout the first half of the Attack pot and it sounds - for lack of a better word - farty. I read your linked post and changed the 470k resistor to 330k like you had tried and it smoothed up the pedal right away and the fartiness was gone but so was some of the grit as you mentioned. I also played with the input and output caps and that changed things nicely as well but too much. So I think the right answer is to change the resistor to something between 330k and 470k and then adjust one of the caps as necessary. Going to box it and keep playing with values as it does sound pretty great it just needs some fine tuning.
Click to expand...
Gated is the word. I'm sure you have no background noise with this pedal. That's what it does.as you can hear in the demos of the Sola Sounds MK1s.

Mine doesn't have too much bass at all. In fact it has a lot of midrange but the bass isn't lacking.
Freshmex18 said:
Also, that gold pedal of yours is gorgeous
Click to expand...
All thanks to Temol who made the enclosure.
 
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