Sola Sound - Tonebender MkIII [schematic]

[Electric Warrior]

Nice!
I went the easy way with a vero board:





It's based on the earliest variant of the circuit with an OC75 wired up as a diode:





I used a 250k volume pot for my build. The value is still unconfirmed. I know of one pretty early unit with a 250k volume pot, but that one had a slightly later variant of the circuit.

[Barcode]

Has no one ever figured out that volume drop some of us have even when shorting the output resistor? I've got one on my bench right now that a friend of mine built and neither of us can figure out why there is a volume drop vs. the bypassed signal. I've seen it mentioned in some build reports on tonepad as well, but no fix mentioned

[joeboo88]

Hi Barcode, while our site was down i built one of these from a different layout, its lying naked right now without a switch on it, but I'll put one on tonight and see if mine has a volume drop. I'll let you know.
It is a very loud pedal even without removing the resistor between the tone a volume pot.
I think I got the vero layout off google awhile ago, i cant remember where...the above schematic looks just like what i used.
Ps, I used 3 2n1209's, that i found on an old cct board i inherited but the thing sound gateded on my strat, but not so much on my Tele?
I'm still learning and wondering where i can stick a trimmer on this thing, to get it biased better, but its probably the weird ge trannies ( I didnt want to fork out extra dough on ac128's...I'm low budget...)


Peace love dope! they can have my freestopmboxes.org when they pry my keyboard out of my cold dead hand

[joeboo88]

soorry for being a goof, maybe i used a 2n1202's as i was getting conflicting info on whether a 2n1209 was PNP or NPN...blah blah blah. Too many midnight shifts.....

[joeboo88]

Has no one ever figured out that volume drop some of us have even when shorting the output resistor? I've got one on my bench right now that a friend of mine built and neither of us can figure out why there is a volume drop vs. the bypassed signal. I've seen it mentioned in some build reports on tonepad as well, but no fix mentioned

Hi Barcode, i stuck in a 3dpdt switch (minus led) after i figured out my GE trannies, a 2sb77 on Q3 and 2 sn1309s.
I get lower volume without the effect on and more volume with pedal engaged without adjusting the geetar knob. Is this what your talking about?
Maybe I shouldnt have piped in until I'm firing all cylinders from my midnight shifts. This is the last one!
I remember I politely used the schematic from fuzz Central with the cool little story that accompanied it.
I'm gonna nap now. I hope i helped.

[joeboo88]

There's no edit button here. I forgot to say i replaced a mystery Ge ttannie with the 2sb77 and now i have no more mis biased sound, AWESOME.

[azrael]

Has no one ever figured out that volume drop some of us have even when shorting the output resistor? I've got one on my bench right now that a friend of mine built and neither of us can figure out why there is a volume drop vs. the bypassed signal. I've seen it mentioned in some build reports on tonepad as well, but no fix mentioned

perhaps a wiring the gain control like a volume control instead of as a variable resistor? I dunno.
In the silicon MKIIIs I've built, no problems with output, and that's how it is.

[DrNomis]

I've got three 2N2048 PNP Germanium transistors, one has a gain of 76, one has a gain of 86, and one has a gain of 140, the two lowest gain transistors show practically no leakage on my Digitech QT2216 Semiconductor Component Tester (it looks like one of those Peak Atlas Analysers), the one showing a gain of 140 appears to exhibit 400uA of leakage, so I'm planning on using these transistors to build a Mark Three Fuzz....

[gilmour_pugliese]

I've got three 2N2048 PNP Germanium transistors, one has a gain of 76, one has a gain of 86, and one has a gain of 140, the two lowest gain transistors show practically no leakage on my Digitech QT2216 Semiconductor Component Tester (it looks like one of those Peak Atlas Analysers), the one showing a gain of 140 appears to exhibit 400uA of leakage, so I'm planning on using these transistors to build a Mark Three Fuzz....

good luck man (and happy birthday!)... In two years I've never built a full-good-sounding germanium Tone Bender... sometimes they sound like hell, sometimes there're a fart machines... Now I've found my definitive choice with a CA3046-based Mk2 with treble 'n' bass pot (practically a Mk3)

[Nocentelli]

Now I've found my definitive choice with a CA3046-based Mk2 with treble 'n' bass pot (practically a Mk3)

ooh, sounds interesting.

[gilmour_pugliese]

Now I've found my definitive choice with a CA3046-based Mk2 with treble 'n' bass pot (practically a Mk3)

ooh, sounds interesting.

Yeah, I've used some Texan technology

[azrael]

Sweet! Any chance to see some project files in the Ready To Build section?

[DrNomis]

I've got three 2N2048 PNP Germanium transistors, one has a gain of 76, one has a gain of 86, and one has a gain of 140, the two lowest gain transistors show practically no leakage on my Digitech QT2216 Semiconductor Component Tester (it looks like one of those Peak Atlas Analysers), the one showing a gain of 140 appears to exhibit 400uA of leakage, so I'm planning on using these transistors to build a Mark Three Fuzz....

good luck man (and happy birthday!)... In two years I've never built a full-good-sounding germanium Tone Bender... sometimes they sound like hell, sometimes there're a fart machines... Now I've found my definitive choice with a CA3046-based Mk2 with treble 'n' bass pot (practically a Mk3)

That's interesting, I've never really had many problems with using Ge transistors to make Fuzz pedals, they always sounded good to me, but then again I tend to be pretty careful when I select the transistors I'll use....

[gilmour_pugliese]

For me a germanium fuzz is a tricky pony... in two years I've bought 30-40 transistor, spending a lot of money, without a good result

Also, the transistor tester (Atlas DCA in my case) isn't a good judge... In fact I've tested some AC128 with a 60-140 hfe range and leakage under 300uA, but they never sound completely good... Now, with a CA3046 (which costs a fraction of a good Mullard OCxx) I've my cheap-and-good fuzz sound

[gilmour_pugliese]

Sweet! Any chance to see some project files in the Ready To Build section?

Gimme some time to draw a readable strip layout... I've put together my fuzz without a layout, taking the Recto Chann3l Mk2 scheme and adapting this to a Mk3 specs

[Electric Warrior]

Here's a later variant of the circuit, ca. 1970-'72, maybe even earlier, most reverse board units don't have any pot codes:



If you happen to find a Sola Sound Mark IV Tone Bender, this is pretty much what you'll find inside. They also put that variant into Vox Mark III enclosures. The earliest "batman logo" Tone Benders (silver and orange or black and yellow) also used this variant.

[beedotman]

What are sonic differencies between MKIII and MKIV? MKIII is more fuzzy, while MKIV is more ovedrive sounding circuit?
MKIII has 220K/47K bias string and MKIV - 680K/100K?

[Electric Warrior]

The earliest units had a 1000pF cap in the tone section instead of the usual 2200pf. That should make them a fair bit honkier sounding.
Don't know about the fuzziness and the bias string. I only ever built the early variant. It can get pretty wild at the end of the fuzz pot. Sure can nail this sound:



The 3 knob Rotosound unit that was used to record it has the 680k/150k bias string and a 2200pf tone cap.

I think it's probably the later MKIV ("Batman logo") units ('72-'76) that are being referred to as less fuzzy sounding. They have a 220k/47k bias string.

[Electric Warrior]

whoops, here's the youtube video:

[Electric Warrior]

another whoops (wish I could edit my posts): The MKIII labled units can have any variant of the circuit. Sola made them for Vox from '67 or '68 to mid/late '72. The Sola Sound MKIV labled ones always have the 680k/100k bias string.