Sola Sound - Tone Bender Mark I (1965)  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Electric Warrior
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Post by Electric Warrior »

Dr Tony Balls wrote:side topic but over 8V on Q3 in a mkII? I always heard 4.5V for that circuit.
Yup, the 4.5V myth comes from the people who say it's just a Fuzz Face with a Rangemaster in front and should bias accordingly. Nice theory, but vintage units measure much higher (see the MKII thread, I've linked to some measurements).
I've built the circuit with OC75s. Q3's collector voltage didn't get anywhere near 4.5V. When I tried to force it by adjusting the collector resistor it got all thin and buzzy sounding.

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Post by faj_ind »

my build
box wood Replika MK II with tone my mod
hammond box replika MK I
like overdrive

https://www.youtube.com/watch?v=mOIBHEKipmk

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Post by sinner »

I've added this to the big turretboard tread, but since I see no layout in here I;m adding it again

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Electric Warrior
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Post by Electric Warrior »

That 470k resistor is supposed to be a 180k.

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Post by sinner »

Fixed

Thank you EW

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Post by agoldoor »

Anyone got any idea what the DAM 1965's rotary switch switches between? When I look at the guts photos, it isn't really clear how that works exactly. It looks to me like both wires from the rotary switch are in the same row of vero, so how would they effect anything?

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From this thread (with more gut shots):
http://stompboxes.co.uk/forum/viewtopic.php?f=38&t=2691

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Electric Warrior
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Post by Electric Warrior »

I don't think that's a vero board..

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Post by agoldoor »

Oh, that makes a bit more sense then. Thanks EW!

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Post by dwstanford »

I would figure it switches between different input caps, but its hard to tell from the picture. Its point to pont, but there may be connections underneath.

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Post by nightraven »

it's labelled "Super Zee" so maybe it's something to make it a little more Maestro FZ-y? :)

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Post by agoldoor »

I figured that too, but when I look at it and look at MKI layouts, it has only the caps shown, so I can't/couldn't figure out where the tone change would be, unless it's just a resistor thing, but I would doubt it.

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beedotman
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Post by beedotman »

IMHO there are three options to pass more treble in Super Zee mode:
a) switch is changing output resistor from 2M2 to 1M
b) switch is making brake between 2M2 and 47K
c) switch in Super Zee mode adds in parallel 47K resistor from 470K output pot lug 3 to ground changing pot value to around 42K


My shot is c) - same trick was done in latest 1966 version (Italian Tone Bender).

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Post by beedotman »

Or maybe not :mrgreen: :slap: :block:
Based on photo switch bypassing 2M2 output resistor :thumbsup

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Post by phibes »

A buddy of mine looked into this before. If I remember correctly there's another 2M2 resistor under the board and the switch knocks it parallel with the 2M2 on top knocking it down to 1M.
GuitarlCarl - "TGP = The Gear Polishers"

Image Ken

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Post by beedotman »

phibes wrote:A buddy of mine looked into this before. If I remember correctly there's another 2M2 resistor under the board and the switch knocks it parallel with the 2M2 on top knocking it down to 1M.
thanks for confirmation!

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Post by monkeyxx »

I just wanted to post my build here. at the DAM forum it didn't get much love, but those guys in that thread are PROS and meticulous, I guess the stuff in mine is slightly crooked here and there, need to get more meticulous about that.

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I can say that a lot of what's been said here is true. It's hard to find the right transistors for a good sound without all the fizzly stuff, and on top of that the biasing process is VERY sensitive, and between Q1 and Q3 you have to get BOTH of them right at the same time to get the right sound... took me forever. I used IvIark's layout with the trim pots...I don't see how people do it without them, unless they're doing it on breadboard first before building. I ended up with a 49 hFE 2N404 in Q1 (this part really seemed to bring the sound to life), a 115 hFE 2N404 in Q2, and a 139 hFE AC128K Tungsram in Q3. I ended up taking notes of the voltages from base to ground on Q1 and Q3 once I found the right trim pot settings, which I could offer on here, but I haven't tried using the same settings with another transistor set so I'm not sure if they're universal. Basically I just started with the trim all the way in one direction until there was no sound happening, and then bring it up slowly until just the point where you start to hear the "sizzly fizzlies" and then back it off just a tiny bit from there. There WILL be a slight gating effect on quieter pick attack playing, but I think this is just part of the character of the sound of this circuit, and it sounds nice in a certain way, a lot like the Penny Pedals Fingerprint circuit. I've come to like that sound.

I had to change the 2.2M in my build to 1M to get unity gain with a strat, and for me the ideal value was to lower it to 100K for a "typical" amount of extra volume available on the Level control. I don't think this changed the tone too much other than reducing the gating slightly (which is a benefit) but I'll have to do an A/B with the 1M to see if there is any tonal shift happening. You can jumper that resistor too but then the level is over the top and out of hand.

Humbuckers indeed seem to overload the input of this circuit and create a sag or "squish" sound, which can be used musically for effect on heavy strums. I've found it works best with low/vintage output pickups, or tweaking the volume knob on your guitar as someone else mentioned.

This is a nice sounding circuit, I'm glad I have it around, now. Very "earthy" in the eternal words of Gearmanndude

it did need a pulldown resistor on the input for footswitch popping

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Post by monkeyxx »

the pedal also seems to sound a lot better in a hot or warm room and not as much in a cold one, I've noticed

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Post by nightraven »

monkeyxx wrote:the pedal also seems to sound a lot better in a hot or warm room and not as much in a cold one, I've noticed
my Supa MKI has been really temperature-stable in the short time i have had it. wanna try experiment with it now though - there's no harm in putting it in the fridge for an hour or two is there?

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Post by monkeyxx »

nightraven wrote:
monkeyxx wrote:the pedal also seems to sound a lot better in a hot or warm room and not as much in a cold one, I've noticed
my Supa MKI has been really temperature-stable in the short time i have had it. wanna try experiment with it now though - there's no harm in putting it in the fridge for an hour or two is there?
haha I'd say go for it.

I suspect mine is like that because my Q1 is on the low side of hFE. maybe a higher value part would make it a little more cold friendly. I just know from my R.G. Keen test rig that when you put your warm finger all over a germanium transistor the gain will start to climb and takes a few minutes to equilibrate back to the room temperature

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Post by monkeyxx »

has anyone directly compared the "Gary Hurst" circuit to the "Sola Sound" circuit and is one superior to the other in any way?

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