Sola Sound - Tonebender Mark II Professional [schematic]

[JimiB]

I am trying to create a really accurate MKII and I was looking at the D.A.M. stuff and he is using a trimpot but also the 8.2K resistor. Do you think the trim pot is a 100K in series with that 10K and subbing for the Q2 collector r?

http://www.stompboxes.co.uk/gpage2.html

Anybody have any ideas on this?
I guess it might just be a 10K pot in series with the 8.2K resistor. I measured the 20K trim pot in mine and it was set fairly high (14K or so) to get 4.5V on a stable 120hFE germ. tranny.

[nomorph]

Hi,
I am trying to implement a sag/starve pot for the tone bender MKII.
My MKII is built in positive ground.
My first question is do I have to put it on the -9v or on the +9v of the battery ?
Basically I tried to put a 50k pot in series with the -9v (which feeds the circuit board)and it only reduces the volume.
Any idea ?

[noelgrassy]

I built the Solasound Mk II using OC75. Great sounding, fattish fuzz. But, there's nothing remotely
clean about it even with my axe's volume rolled waaaay down. Is this typical for this circuit? I have
no experience with the original pedal. Or these xistors for that matter.
Thanks for any and all advice, NG.

[JHS]

The org. TB MK2Pro circuit was designed for the use of the weak OC81D (hfe max. 40, and made for the use in driver and phasesplitter stages in radios).

OC76/44 and similar trannies (hfe app. 70-80) don't match the 2pro circuit specs. as perfect as OC81D, yielding in an dist. sound even at min. gain. and an overcompressed fuzz when maxed. Sola never adapted the circuit for trannies with higher hfe but used them in the later made TBs.

JHS

[noelgrassy]

Thankyou JHS. That helps explain my FX's condition quite clearly.
I'll build another pedal using the circuits discussed at the begining
of this thread.

I think I'll try some of the Si NPN versions with these old, low hFE
xistors I've pirated out of an old Hammond organism.
As always, very nice of you wiser folks sharing the knowledge.
Or, "dropping science" as some would say.
To that I intone, "werd".

[JHS]

Some further infos I got from a well known British FX-builder/-modder from the early '60th.

The 1st trannie had been addded to the circuit because OC81D didn't had enough hfe to work well in the old TB Mk1.5/2 circuit.

You can archieve the sound of the early TB Mk2pro with OC81D if you built a F-Face with OC44, 5uF I-cap, 47n O-cap and a 100k pot for vol. Adjust the voltage between C and ground on Q2 to app. 5,5V.
Maybe the R on the collector of the 1st trannie must be altered a bit too to set a perfect working point for Q1.
You can trim the highend futhermore by adding few pf to the output and/or the trannies.

BTW:
If you want the original Jimmy page sound from a VOX TB MK2pro or clone (his secret fuzz box, modded by RM), use OC81D and swap the 1k on the collector of Q2 for a 1,8-2,2k.

JHS

[noelgrassy]

I did score a fistfull of OC44's. I'll breadboard the FF circuit with OC44's and try the changes you've suggested.
I've had my feelers out for some OC81D's for 3 or 4 months and have yet to see any for sale on Ebay.
If you've seen any or know where else I should be looking PM me if you feel inclined. I adore
Page's tone and would be happy as a pig in shit if that's a sound I could get near.

slightly OT: There's a wicked thread on the LP Forum about two fellows blueprinting his custom HiWatt he apparently
used until 1971 or so. I always think of his Marshall backline 'cause that's what I saw in 1974. This HiWatt was sorta
"daisy chained" with a Marshall for much of the early years. It was also sculpted to be a low gain Plexi affair by
the tone of the thread I read. Not the usual "headroom for miles" sound associated with 100 watt HiWatts.

[JHS]

In an interview Page mentioned he used the Hiwatt only for rehersal not on stage.

JHS

[noelgrassy]

Dude, they posted copious photos of Page in action, on stage [w/ Pork Pie Hat, no less] rockin' that very box.
If you see the two disc Led Zep DVD, the jam in the Netherlands, on a TV stage, has him using it as well.

Sometimes I get the feeling more musicians than just Billy Gibbons have a way of telling none truths.

[Bernardduur]

Some further infos I got from a well known British FX-builder/-modder from the early '60th.

The 1st trannie had been addded to the circuit because OC81D didn't had enough hfe to work well in the old TB Mk1.5/2 circuit.

You can archieve the sound of the early TB Mk2pro with OC81D if you built a F-Face with OC44, 5uF I-cap, 47n O-cap and a 100k pot for vol. Adjust the voltage between C and ground on Q2 to app. 5,5V.
Maybe the R on the collector of the 1st trannie must be altered a bit too to set a perfect working point for Q1.
You can trim the highend futhermore by adding few pf to the output and/or the trannies.

BTW:
If you want the original Jimmy page sound from a VOX TB MK2pro or clone (his secret fuzz box, modded by RM), use OC81D and swap the 1k on the collector of Q2 for a 1,8-2,2k.

JHS

Hey man!

I can't seem to find the 1k in the schematics of the Vox TB MK2Pro....... on the collector of Q2 is always a 47k resistor (or am I going crazy)

[JHS]

In the Mk1.5/Mk2pro are 2 R (1k/8,2k) connected in series to the collector of the 2nd transistor, though some units have 470E instead of the 1K.

The 47k is connected to the collector of the 1st trannie and I recommend to subs the R with a 50k trimpot for biasing Q1.
If you set the value of the trimpot lower than 33k you have to decrease the FB-resister too or Q2 will be misbiased.

JHS

[Bernardduur]

In the Mk1.5/Mk2pro are 2 R (1k/8,2k) connected in series to the collector of the 2nd transistor, though some units have 470E instead of the 1K.

The 47k is connected to the collector of the 1st trannie and I recommend to subs the R with a 50k trimpot for biasing Q1.
If you set the value of the trimpot lower than 33k you have to decrease the FB-resister too or Q2 will be misbiased.

JHS

Thanks! I was looking at the right resistor

[JHS]

It seems that the trim is for biasing Q1. You can see in their pics that even D*A*M uses pf-caps to trim the highend in many of their circuits.

What is accurate?

RM and GH tuned a lot of average sounding benders by replacing the stock trannies. They select the trannies for a given Fuzz-circuit in a listening test by ear and then soldered them in. Sometimes they replaced a cap or resister for further finetuning.

JHS

[Bernardduur]

Wow.......

I just finished a version of the unit...... as JHS mentioned......

Wow

I used some Russian MP21D transistors that were measured around 40 Hfe....... it sounds really nice!

[vanessa]

I tried it will all 40 hfe's over the weekend. It cleaned up well but lacked gain. I did not really like it. And with transistors that were a little leaky it sounded like a mosquito. I did like the tone with a little bit leaky transistor in Q1 at 40 hfe.
I tried several transistor combinations with some performing better than others. With two 40 hfe's in Q1, Q2 and a 70 hfe in Q3 I liked it better. I think I will try a 50 hfe (med leakage) in Q1, 70 in Q2 and a 100 in Q3 and see what that yields. I'm thinking they might have used the same beta order as the MKI, who knows? They probably just grabbed them indiscriminately from a parts bin.

[gght]

Tonebender with guts shot and $$$ pricetag!

http://cgi.ebay.com/Yellow-Sola-Sound-Tone-Bender-1972-Fuzz-Rare-Tone_W0QQitemZ220227779531QQihZ012QQcategoryZ41418QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Professor SourTone]

I believe this is a Tonebender Mk1.5? I lent it to Steve Macari so he could copy the casing. Maybe some of the circuit stuck too. Mr D*A*M has a current auction for a modded reissue which goes into it a bit!

http://cgi.ebay.co.uk/D-A-M-DAM-SOLA-SO ... dZViewItem

[analogguru]

The guts from the yellow one are identical to a standard SolaSound 3-knob Tonebender. The Macari´s Reissue is suspicious since it uses at least a silicon diode which the original doesn´t have. Also the first two transistors seem to be silicon. Will not be much audible, but IMHO if it is a reissue (in the same case) it also has to be identical circuitwise to avoid confusion with the real thing.

The D.A.M. auction seems to be indeed a MK 1.5 clone. Basically nothing much different to a Fuzz Face. Funny where he found the old Wima electrolytics.

analogguru

[bobo]

Anyone know Hfe Q1,Q2,Q3 of Tone Bender MkII. I will install OC-75.

[noelgrassy]

Very good question. I've seen what David Main likes in a Gary Hurst type Tonebender. Q2=120, Q3=92 & he had "?"
shown for Q1. I know, not much help. It's the only info I've found for the hFe of any of these early fuzzes.
Good luck, NG.