Sola Sound - Tonebender Mark II Professional  [schematic]

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

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 09 May 2009, 23:43

Lol ah cool, cheers anyway for posting it up, ah maybe I wont bother with vintage caps, probably end up being unworthy hassle, I probably wont be able to tell the tone difference, i'l just use up the carbon comps, only wanted to use the parts for recycling really.

As for those tranis I'l be socketing them anyway so I guess i'l just try them all out and see what either works or sound best, there all vintage germaniums so i'm sure i'l end up with some pretty good original mojo tone...
Scruffie
Opamp Operator
 
Posts: 1727
Joined: 13 Mar 2009, 18:59
Location: London.. ish, Uk
Has thanked: 27 times
Have thanks: 136 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 00:03

yeah, check out what works best for you..
you could socket the caps as well, to see what difference different types can make. or use a breadboard...
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 10 May 2009, 00:09

Me and breadboard have a troubled past lol, Something about converting layouts from schematics to vero or breadboard I just can't do, I understand the schematic, I get how the circuit works once it's layed out on vero or bread but I can never get it to do it right unless i'm building the circuit myself and follow it as I go, but if someone has a breadboard layout done would be handy, as it would be nice to check out the variables and I don't wanna ruin a piece of vero by socketing everything then wanting part stability so soldering the parts back in and ending up with an unclean board.
Scruffie
Opamp Operator
 
Posts: 1727
Joined: 13 Mar 2009, 18:59
Location: London.. ish, Uk
Has thanked: 27 times
Have thanks: 136 times

Re: Sola Sound - Tonebender Mark II Professional

Postby yeeshkul » 10 May 2009, 15:12

JHS wrote: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


This makes me confused - are you talking about 2 or 3 tranzistor bender?
User avatar
yeeshkul
Breadboard Brother
 
Posts: 92
Joined: 19 Jan 2008, 13:41
Has thanked: 1 time
Have thanks: 2 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 15:55

he's talking about both.
I have never seen one with a 1k instead of 470R. Units with OC81D transistors have 100k instad of the 47k, maybe he confused it?

JHS wrote: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


early units were made with OC75s on MK 1.5 boards. (picture here: http://stompboxes.co.uk/History.html)
furthermore, scruffie just reported us that his Mullard OC81Ds are higher gain.
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 10 May 2009, 16:35

As for your layout electric warrior, where do I place the trimmers? Not the 8k2 as I thought?
Scruffie
Opamp Operator
 
Posts: 1727
Joined: 13 Mar 2009, 18:59
Location: London.. ish, Uk
Has thanked: 27 times
Have thanks: 136 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 16:40

8k2 is right. you can tweak the other collector resistors as well.
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 10 May 2009, 16:45

Oh I thought from the previous comments it Didn't really work biasing that transistor. I would bias the other transistors... but I only have 1 10k trimmer lying around lol plus with the big caps and tranis, not enough spare room really to stick in more trimmers without using a bigger board which i'd rather not do.
Scruffie
Opamp Operator
 
Posts: 1727
Joined: 13 Mar 2009, 18:59
Location: London.. ish, Uk
Has thanked: 27 times
Have thanks: 136 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 16:47

it's probably better for you to make two. one with sockets to find out what you like and a smaller one with the parts that you liked the best..
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 10 May 2009, 16:51

That's a good idea, i'm not actually building this for myself, a friend wants a Mk II with all mojo parts (physcological thing probably, and I can see the attraction it does look pretty in the old ones) so if I built a second one with sockets could have it for myself.
Scruffie
Opamp Operator
 
Posts: 1727
Joined: 13 Mar 2009, 18:59
Location: London.. ish, Uk
Has thanked: 27 times
Have thanks: 136 times

Re: Sola Sound - Tonebender Mark II Professional

Postby yeeshkul » 10 May 2009, 18:00

keeping the Q2 collector resistor 47k helps a lot to the Q3 biasing. 100k is makes too strong a divider and you can have troubles with just 10k trimpot in Q3 collector.

i made a test circuit for fiddling with TB parts and found out this (applied for 80-120 Hfe trannies):
1. if i use 10k bias resistor for the Q1 base, the unit gives no more fuzz than Fuzz Face. When i push it up to 100k (= base voltage up) there is a hell lot of fuzz coming out of it in comparing to FF (easy comparison due to the FF/TB switch).
2. even a small starve/filter resistor (divider on the battery) helps with the overall volume a lot - because it works like a common collector resistor for all 3 stages.
3. using 47k resistor (instead of 100k) for Q2C helps a lot with easy biasing Q3C(!) wia 25k trimpot. Using 100k res. you can have troubles to push the bias down to 4.5V.
4. pushing bias of Q3 to 6.5-7V doesn't affect the sound as far as i can judge and helps with the overall volume.
User avatar
yeeshkul
Breadboard Brother
 
Posts: 92
Joined: 19 Jan 2008, 13:41
Has thanked: 1 time
Have thanks: 2 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 18:37

I built one with OC75s.
1. It has plenty of fuzz with the 10k at Q1's base. Much more than a Fuzz Face.
2. I have no volume issues at all. It's very loud.
4. That's roughly where bias for Q3 ended up with stock values.

Scruffie has some OC81Ds, so he should definitely start out with the 100k bias resistors, imho. There must have been a reason why different values were used for these.
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby yeeshkul » 10 May 2009, 18:59

"There must have been a reason why different values were used for these."

Sure! 100k = more fuzz. Weak trannies -> we need more fuzz -> we use 100k :) (1.)
User avatar
yeeshkul
Breadboard Brother
 
Posts: 92
Joined: 19 Jan 2008, 13:41
Has thanked: 1 time
Have thanks: 2 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 19:23

I don't think they were weak compared to OC75s..
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby yeeshkul » 10 May 2009, 19:32

What Hfe were your 75's? JHS mentioned that 81D's were about 40 ... that is really not much but it makes perfect sense regarding the different resistor values.
User avatar
yeeshkul
Breadboard Brother
 
Posts: 92
Joined: 19 Jan 2008, 13:41
Has thanked: 1 time
Have thanks: 2 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 19:36

between 70 and 90 iirc.
Scruffie wants to use some old Mullard OC81Ds that measure 90-110 on his multimeter. If they don't leak too much they're in the same gain range as my OC75s.
The new production DSIs are supposed to be in the low thirties..
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Sola Sound - Tonebender Mark II Professional

Postby yeeshkul » 10 May 2009, 19:38

"on his multimeter" that sounds dodgy :). i suppose he knows they leak and so he can't measure them straight :wink:
User avatar
yeeshkul
Breadboard Brother
 
Posts: 92
Joined: 19 Jan 2008, 13:41
Has thanked: 1 time
Have thanks: 2 times

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 19:43

I suspect he hasn't built the circuit to measure leakage, yet :)
The guys who have built pedals with Mullard OC81Ds always complain about the low gain new production ones...
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

Re: Tone Bender MkII OC-75

Postby playon » 10 May 2009, 20:33

bobo wrote:
Torchy wrote:http://fuzzcentral.ssguitar.com/mkII.php

The transistor gains for the MKII should be something like 70 for Q1 and Q2 and 100 for Q3.


Thank I already tried Q1, Q2 = 70 and Q3 = 100. The sound is not so good. Someone said Q1& Q2 must have high Hfe than Q3. What's the correct statement.? I tried many hfe of OC-75 but it could not complete with AC-128.


I had the BYOC kit of the MKII... is sounded not so good with the three OC75s they included with the kit. It sounded much better when I messed around with different trannys, at the moment it has Q1 AC128 90 hfe, Q2 OC75 80, and Q3 OC81D 40 hfe. It sounds better but I'm going to keep messing with it as there is still room for improvement. I think if you are looking for info on how to build the best sounding MKII, the D.A.M. site is your best resource... Dave Mains probably knows more about these pedals than anyone, and he's shared a lot of info, you may have to search for it.
playon
Resistor Ronker
 
Posts: 253
Joined: 01 Jan 2008, 03:09
Has thanked: 0 time
Have thanks: 1 time

Re: Sola Sound - Tonebender Mark II Professional

Postby Electric Warrior » 10 May 2009, 20:51

seconded! David knows his Tone Benders. I luv the D*A*M forum!
User avatar
Electric Warrior
Diode Debunker
 
Posts: 709
Joined: 23 Feb 2009, 04:37
Has thanked: 20 times
Have thanks: 78 times

PreviousNext

Return to Vintage Stompbox Corner ( ... - 1975)

Who is online

Users browsing this forum: Bing [Bot] and 10 guests