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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pietro_moog
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Post by pietro_moog »

I adjusted a few resistors and caps, and the Q3c voltage is like -8.05v
I don't what to make of Q2C: it really depends from the voltage divider, so i tried 180k (-1,2v) and 430k (-5v); i don't know what i like more, i can't decide.

Q1 is the strange one: it has very low hfe and leakage, but everything works. i tried to reach the suggested voltage (around -1v) changing the bias resistor, but i only get to -0,4v with a 4,7M resistor. There is a noticeable effect though, it doesn't SAG anymore.
With 1M on Q1B i had a HUUUUGE Sag, i wasn't expecting this (but i like it).
Is this suppose to happen?
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pietro_moog
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Post by pietro_moog »

I forgot: my transistors are

Q1 = MP40B, 30hfe, 20mA L

Q2 = gt308b, 64hfe, 5mA L

Q3 = MP42 , 52hfe, 50mA L

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Post by Manfred »

Hfe depends on collector current at which current Hfe was measured.
The unit for the leakage current is certainly Microamps not Milliamps.

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Post by Tomrcarre »

I know it’s stretching back a long time... (10 years!) but I was wondering if anyone has a copy of the schematic for the silicon MK1 sonicVI posted back on page 7, I’ve tried using the internet way back machine to get a copy of it but sadly the link is dead :(.

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Post by Seiche »

you could probably trace it from the gutshot in this reverb listing
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Manicstrat2112
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my favorite amplifier: Egnater Rebel 30 MK I
Completed builds: Partial list: Creepy Fingers EQ Exciter Fuzz, Tonebender MK II, Silicon Tonebender MK II, Fuzzrocious Ram the Manparts, Thunderdrive, Fuzz Face. Silicon Fuzz Face, EHX Muff Fuzz, Brian May Treble Booster, DAM Grease Box, DAM Meathead, Lovepedal Woodrow, Lovepedal Eternity, Silicon Fuzz Master, Fuzz Factory, Mastotron, Super Hard On, 73 Rams Head BM, Katzenkonig, Phase 45, Black Dust, RAH, Tentacle, MXR Distortion +, DOD 250 Preamp, Distortron, Naga Viper, JHS Andy Timmons, Pro co Rat, Celine Mark 4, EQD Dunes, EHX OD Glove,, Lemon Drop, 59 Sound, Formula No 5, Formula No. 55, Black Ash, Plexi Drive, 65 Deluxe, Hummingbird, Fuzzolo, Univibe, EQD The Depths, Guzzling, Maestro FZ-1 and FZ-1A, Tonebender MKI, Harmonic Percolator, Zonk Machine, Hybrid Si/Ge Zonk Machine, MBP Harbinger 1.5, MBP Pork Barrel (to original CE-2 specs) and it all started with the Bazz Fuss =)
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Post by Manicstrat2112 »

Ever since I got to play through a genuine MK I Tonebender, I have been chasing that sound. There are lots of pedals that come close, but none sound and feel like an original MK I. Unfortunately I don't have thousands to fork out for an original specimen, so I set out to build one. It has turned out to be a monumental task. I've been building pedals for a few years now so I figured it wouldn't be THAT tough right? Wrong! The circuit itself is easy....it's the tuning of said circuit that is a pain in the ass.
I have heard people talking about "simulating leakage" with a 1M resistor to help with biasing. Could someone please explain how to do that? ....and how it works exactly? Also, I haven't really been able to find any information about voltages or gain (hfe) targets. ANY information or tips concerning this circuit would be greatly appreciated!
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andy-h-h
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Post by andy-h-h »

Use this method to work out how and leakage of your transistors.

http://tagboardeffects.blogspot.com/201 ... r.html?m=1

Then add resistance across the base and collector until the leakage reading is in the correct range. Check hfe during the process.

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Manicstrat2112
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my favorite amplifier: Egnater Rebel 30 MK I
Completed builds: Partial list: Creepy Fingers EQ Exciter Fuzz, Tonebender MK II, Silicon Tonebender MK II, Fuzzrocious Ram the Manparts, Thunderdrive, Fuzz Face. Silicon Fuzz Face, EHX Muff Fuzz, Brian May Treble Booster, DAM Grease Box, DAM Meathead, Lovepedal Woodrow, Lovepedal Eternity, Silicon Fuzz Master, Fuzz Factory, Mastotron, Super Hard On, 73 Rams Head BM, Katzenkonig, Phase 45, Black Dust, RAH, Tentacle, MXR Distortion +, DOD 250 Preamp, Distortron, Naga Viper, JHS Andy Timmons, Pro co Rat, Celine Mark 4, EQD Dunes, EHX OD Glove,, Lemon Drop, 59 Sound, Formula No 5, Formula No. 55, Black Ash, Plexi Drive, 65 Deluxe, Hummingbird, Fuzzolo, Univibe, EQD The Depths, Guzzling, Maestro FZ-1 and FZ-1A, Tonebender MKI, Harmonic Percolator, Zonk Machine, Hybrid Si/Ge Zonk Machine, MBP Harbinger 1.5, MBP Pork Barrel (to original CE-2 specs) and it all started with the Bazz Fuss =)
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Post by Manicstrat2112 »

andy-h-h wrote: 26 Oct 2020, 08:21 Then add resistance across the base and collector until the leakage reading is in the correct range. Check hfe during the process.
Thanks!
I have a transistor tester that gives me hfe and leakage readings.....so I assume I can use it while adding resistance across the base and collector to adjust leakage?
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Post by andy-h-h »

Yep - even better if you have proper test gear.

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Post by modman »

Remember the Stones' Statisfaction was only released June 5th of 1965...

In September of 1965 the Sola Sound Tonebender features prominently in Beat Instrumental magazine, with a full page ad and a big Fuzz giveaway:


6509-Beat-Instrumental-1965-09 01.jpg
6509-Beat-Instrumental-1965-09-OCR contest.jpg
6509-Beat-Instrumental-1965-09 02.jpg
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Post by nightraven »

And one of the winners of that competition was tracked down more recently by Macari's, who reacquired the pedal for their own collection.

There's more general (and verifiable!) historical information about the 'MKI' here: https://fuzzboxes.org/tonebendermki
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Post by modman »

nightraven wrote: 05 Nov 2021, 15:14 And one of the winners of that competition was tracked down more recently by Macari's, who reacquired the pedal for their own collection.
Contact these people to hopefully score one of these yourself ;-)
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Post by Electric Warrior »

As if not enough stompbox collectors were bothering those people :D

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modman
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Post by modman »

I was really joking, just to find my own post reported to myself by nightraven for exposing these people while he's already contacted 3 of them himself.
I did not publish the names, the magazine did. Now at least the hunt is open to everybody rude enough to bug these old people...
This is the whole schematic hysteria all over again. Over a stupid square wave fuzz...
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Post by nightraven »

There's nothing to hunt -- if any of the other (surviving) dudes on the list still owned the pedals, then the pedals would've prized away by Ant Macari or me by now. It really is just a courtesy thing, because they're already aware of the mistake they made, not holding onto what are now £5000+ artifacts, without getting spammed any further.
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Post by modman »

nightraven wrote: 06 Nov 2021, 22:31 There's nothing to hunt -- if any of the other (surviving) dudes on the list still owned the pedals, then the pedals would've prized away by Ant Macari or me by now. It really is just a courtesy thing, because they're already aware of the mistake they made, not holding onto what are now £5000+ artifacts, without getting spammed any further.
What about the 12 other pedals? Please share some information!
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Post by nightraven »

modman wrote: 06 Nov 2021, 23:11
nightraven wrote: 06 Nov 2021, 22:31 There's nothing to hunt -- if any of the other (surviving) dudes on the list still owned the pedals, then the pedals would've prized away by Ant Macari or me by now. It really is just a courtesy thing, because they're already aware of the mistake they made, not holding onto what are now £5000+ artifacts, without getting spammed any further.
What about the 12 other pedals? Please share some information!
Are you referring to the contest in Melody Maker, in Spring 1966? I'd imagine that the 'MKI' had been discontinued by then, because we know for certain (based off an verifiable owner's testimony) that the 'MK1.5' was already available. I don't think the winner's list was published for that one though.
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Post by modman »

Melody-Maker-1966-03-19-IDX-9 tonebender mki.jpg
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george giblet
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Post by george giblet »

You gotta love the internet sometimes. It's great for digging up old documents.

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Post by MarkL »

I know I'm a bit late with this post, but I've gone through the thread multiple times and I'm seeing conflicting reports on ideal Q2 leakage: some are reporting that Q2 works well with very low leakage (if Q1/Q3 are sufficiently leaky), while others have suggested that Q2 requires moderate leakage, or even high leakage.

In my current build-in-progress, I have Q1 at 65 with 350uA leakage, and Q3 at about 100 with 400uA leakage. If my Q2 is very low leakage (100uA or lower) but is sufficiently high in gain (120-130 Hfe), would that work well within the circuit? I should note that I'm using a 470K for the Q2 to power rail.

I'd appreciate clarification and thoughts here. Thanks.

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