Sola Sound Yellow Hybrid Tone Bender

Julian A

New member
Another thing: in the photos I've seen, the large red cap was always a 470nF, other than the old, tropical fish pedals (they used 100nF).
I've never been able to confirm the value of the small blue one between Q2 and Q3. Not to say that they didn't change the values, but could those two be mixed up on the part value photo? Just making sure!
 

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music6000

Well-known member
Another thing: in the photos I've seen, the large red cap was always a 470nF, other than the old, tropical fish pedals (they used 100nF).
I've never been able to confirm the value of the small blue one between Q2 and Q3. Not to say that they didn't change the values, but could those two be mixed up on the part value photo? Just making sure!
We are better off sticking with the Original post Layout!
It's a 2018 version so any bugs have been sorted, it uses standard Alpha Pots & you can see where the legs are connected.
It has the correct NPN OC140 Germanium.

What we need is super clear close up pictures of the Yellow MLCC's for now !!!
 

mdc

Active member
I have a friend who also has a recent NPN version - I’ve asked him to crack his open and see if the values on the smaller MLCCs are more readily visible.
I’m still getting wild measurements off of my DMM, unfortunately.
 

mdc

Active member

 

mdc

Active member
On the two lower caps, I get the recorded values consistently with the terminals in one position; swapping the terminals yields a fairly random number briefly and then it drops to zero (this is the cap discharging?). I get no reading in either position on the upper cap.
 

Julian A

New member
We are better off sticking with the Original post Layout!
It's a 2018 version so any bugs have been sorted, it uses standard Alpha Pots & you can see where the legs are connected.
It has the correct NPN OC140 Germanium.

What we need is super clear close up pictures of the Yellow MLCC's for now !!!
Right, just wanted to be sure they changed the values and the bright blue near Q3 & red Wima values weren't mixed up, since 470n and 10n are quite different. New photos fully prove the 10nF. Same Wima package and everything!

Reading caps in circuit can be quite an endeavor. I can see the upside down 471 (470p) on the first photo, I'd hope the rest are others are the same. We'll see!

Seriously appreciate this! This pedal has been on my mind since my initial "clone" project, knowing some small details or values were missed.
 

mdc

Active member
I just realised you were asking for confirmation on the smaller blue cap, not the larger/darker one—sorry! I'll double check it later today, but iirc it has a numeric code rather than an actual value printed on it. It's good to double check all the printed values either way, so I'm happy to take a look. Similarly, if any of the resistor values look suspect just let me know and I'll take another look at those. I tried to be methodical about it, but I'm not fluent in band codes so it's a bit of a painstaking process and easy to fumble a value.
 

mdc

Active member
Turns out the nice thing about using the 5% tolerance resistors is that they're a lot easier to read than the 1%—way less worry that you're reading it backwards.
 

mdc

Active member
OK, here's an attempt at a trace— @Julian A let me know if this matches up with the one you drew out?
I'm sure there are some mistakes in here, I just kind of muddled through it.
As of now it's missing values for the 3 small caps, the zener diode, and the pots.

[updated schematic below]
 
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mdc

Active member
OK, got a few more photos of a different unit - there's a 471 code visible on the mlcc cap closest to the Ge diode, so I think that means that between all three 471 has been visible on each cap. Safe to assume they're all 470pF I think?

There's a partial code "55c" visible on the zener diode, which makes sense with the BZX visible on mine - BZX-55C
 

Mir9

Member
Mdc, how loud is this pedal compared to the bypass signal?

Also would Julian A's idea of a Muff type tone stack on the previous page make more sense?
 

mdc

Active member
It's entirely likely that I just followed the traces on the PCB incorrectly and the tone stack should be a more traditional BMP-style. There were a few lines that were obscured by pots and the battery clip. I think everything up to the 1uF cap after Q3 is ok-ish (please correct me if you see something different!), but the tone stack may be a mess.

EDIT - just took a quick look and realised I left off a 100nF cap going to ground in the tone section. I'll fix it.
 

mdc

Active member
Oh, and I've never noticed the pedal lacking in volume or anything. It definitely gets above unity.
 

Julian A

New member
Great progress! Schematic is looking good. Only difference with the overall layout I can see is the 1uF after Q3. I have mine directly on Q3s collector. Would have to check my circuit board photos to see how I found that.

It indeed has a muff style stack. Not as scooped or wild though. Can be simulated in the tone stack calculator. 10K Linear pot is what I saw in one bad photo, which makes sense in the circuit. I used a 47nF cause that's what was used on the old 2010 tropical fish one.

If it means anything, my build is exceptionally loud. One of my louder fuzzes. It's even louder with the zener switched out of circuit. The lack of clippers seems to overcome the mere 3 stages & muff stack at the end w/ no recovery.
With that said, I'm using either 50K or 100K for volume and fuzz and currently a Russian transistor with about 90hfe and low leakage. BC178C for the silicons.
 
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