Thursday, 11 April 2013

Throbak Overdrive Boost

Very nice adaptation of Colorsound Overdriver with a few very nice mods. And the manufacturer isn't shy about telling us where the circuit came from. Very nice.

Throbak Electronics offers the Overdrive Boost. Throbak has reproduced and improved the circuit of the original Colorsound Overdriver (also known by the name Power Boost). The original was used by Jeff Beck and was an integral part of his 70's signature tone. The Colorsound Overdriver was also a favorite of Marc Bolan and is considered by many to be the best overdrive/booster ever made.





61 comments:

  1. Trimmers Q1: 5.0k, Q2: 2.0k (5v) and Q3: 1.5k (6.5v) true?

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    1. Yup. Those voltages are mentioned in the schematic, but i think it would be better just to use your ears. Most transistors won't bias exactly the same..
      +m

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  2. Which transistor would you suggest for Q4?
    Thanks

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    1. Original has 2N404, but any bad, leaky, othewrwise unusable NPN Germanium would be fine. For example, if you have bought a batch of AC176s through ebay, there has to be a few of those which are unusable for any other purposes. I have something like 160 pieces of those, and about 12 reads as diodes on my Atlas DCA55. Those would be really good cadidates as it's only used as a diode.

      You could use any Ge diode there as well. Anode as collector and cathode as base.
      +m

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    2. Should it be a PNP or an NPN? The diagram says PNP.

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    3. My bad. It is PNP. 2N404 is PNP... I think that NPN will too as it's only used as a diode.
      +m

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  3. Mine works so you can call this one verified! I followed your tip of using a Germanium diode for Q4 as I didn't have any Germanium transistors. I had to look at a Colorsound Overdriver schematic to verify the 5.6k resistor (on your vero layout, I couldn't tell if it was 5.6k or 56k)and I also noticed that the 3.9 resistor next to it is a 39k on the Colorsound Overdriver schematic. Is your value a typo? Anyway, I used 39k in mine and think it sounds awesome! Your layout also has two Treble 1 POT connections - I used Treble 2 to make the connection at the 5.6k resistor.
    Thanks for another great layout!

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    1. No that's not a typo. Just checked the Throbak schem and those values are correct. I'll set the cap down one layer :) Sorry for that. Fixin' and taggin' right away. Thanks Frank!
      +m

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  4. Hi Miro,
    Looking at the schematics, shouldn't there be a 100nF cap between Bass 1 and Bass 3 ?
    Thanks

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    Replies
    1. Don't know how i missed that. It's an easy fix though. Layout fixed...
      +m

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  5. Ok, I updated my build with the 3.9k resistor and 100nF cap between Bass 1 and Bass 3 - and I also made an audio clip incase anyone is interested.
    Thanks again!
    http://snd.sc/11gigm9

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  8. anyone have trouble with the germanium switch?  i get a serious volume
    drop when switched on.  dont get me wrong, it sounds great, but i
    wired it up to a footswitch so i can toggle live so i'd like to
    eliminate the volume drop.  ive got a 1n914 diode in Q4 because the
    ac128 i had in there sounded awful and volume drop was even more
    intense.  i opted for sockets until i find a good combo.  any ideas?
    is the ac128 just too low gain to make a it a decent choice?  i must
    admit i'm not very well read on the subject, so any advice would be
    greatly appreciated.

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    1. a germ transistor or diode is going to cause a substantial volume drop. that's the nature of the beast (they have a low forward cutoff voltage), but any diode clipping in this pedal is going to cut some level since without the ge switch clicked in there are no diodes in the clipping circuit.

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  9. i just finishing building and testing this one. IMO, it's an AWESOME pedal, and it works great on bass with no mods too! thanks for posting it.

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  10. BTW, as previously mentioned, the layout still shows two treble 1 contacts! the lead labeled treble 1 that is four rows up from the bottom right should be labeled 'treble 2' (the one that connects to the 5K6 resistor). other than that, the layout is perfect.

    and here's a pic of my vero build of it:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Throbak/ThrobakODB-03.jpg

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  11. Is anyone else experiencing the drastic volume drops when switching in the germanium diode/transistor ? I am about to build this and was just wondering . YouTube demos don't seem to mention this .

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    Replies
    1. anyone that is familiar with this type of circuit already knows that there's a big volume loss when switching the ge diodes in.

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  12. well i could have squeezed it into a 1590B like the original but I don't like the footswitches so close to the controls so I went with a 1590BB instead.
    here's a couple of pics of it:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Throbak/ODB-01.jpg

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Throbak/ODB-02.jpg

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    1. John, yours looks amazing. How did you wire the pregain switch with the 3pdt switch? I'm confused at how you used to other poles.

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  13. Cool layout, Do you have the shcematic for this pedal. I wanted to make one on a pcb.

    Thanks

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  14. Hi,
    which offboard wiring is best used so that both switches are footswitches, and is it possible to have LEDS for both switches?
    Hope someone can steer me in the right direction,
    Thanks in advance,
    matt.

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  15. After four months of continually messing my first pedal up I got it to work last week. Whoosh...
    This week I built Two (Not the same ones) - and got them right first time.
    Now I have the Bug and Need to Move on to bigger things... the bits for the throbak pedal arrived this week so...before my bubble bursts
    Can anyone please advise on the best offboard wiring and LED position.
    I'll be eternally grateful.
    Thanks,
    Matt

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  16. I've built 2 of these now and they sound awesome. However when played through my practice amp I'm hearing very little difference in treble and bass when turning those 2 knobs. Is this usual or is it supposed to be a lot less subtle?

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    1. the treble and bass knobs are NOT subtle at all. they add a TON of bass or treble so there must be an error in your build.

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    2. John (Kallas) I would like to build one in the same arrangement as your photos shown above and I am itching to get started. Could you please advise me on how you wired it up with two footswitches and two LEDS. Thanks in advance

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    3. Thanks John, The weird thing is that it happened on 2 separate builds. Perhaps it was simply my amp not being able to handle the extra bass and treble, it's one of those mini practice amps. I guess I'll have to try it with a bigger tube amp next time. I've double checked the soldering, wiring, and placements of components on both builds and they were exactly the same as on the vero layout.

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    4. Hi,
      Something doesn't sound right with mine.
      My transistors readings (CBE) are:

      Q1: 1.26 0.84 0.28
      Q2: 5 1.24 0.94
      Q3: 6.5 5.36 4.66

      Does anything seem dodgy?
      Is the Hfe important?
      Thanks for the help

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  17. HI,
    Can anybody help?
    To re-itterate, I want to build this pedal with a (3PDT I have in stock) stomp switch instead of a toggle for the pregain so am I right to assume Its wired the same?

    My main problem is that I am unsure of how to wire an LED to indicate this pregain footswitch is on and would really appreciate if someone could advise me.

    Other than that I intend to use the normal offboard wiring for a single stomp shown on this site (shown at the top of this page:http://tagboardeffects.blogspot.co.uk/2012/02/offboard-wiring.html)

    Am I right to do so?

    'Any' help would be greatly appreciated as I have already populated the board and are just hanging on a response from one of you benevolent chaps to point me in the right direction..so if you can answer 'any' of my questions You'll make me a very happy man.
    Thanks,
    Matt.

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  20. Hi Matt,
    It should be connected like this:

    PGSW 1 ---1 4 7
    PGSW 2 ---2 5 8--- Ground
    PGSW 3 ---3 6 9--- LED-

    Normal single stomp wiring for the main switch.
    Don't forget the resistor for the PreGain switch LED.

    ReplyDelete
    Replies
    1. Alex You are a 'STAR'
      Thanks a million.
      Am I right in thinking the LED goes to 9Vdc input like so:

      PGSW 1 ---1 4 7
      PGSW 2 ---2 5 8--- Ground
      PGSW 3 ---3 6 9--- LED---resistor----9Vdc

      Again thanks of the highest order.
      Matt

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    2. Hi Matt,
      No problem.
      LED---Resistor---+9V is correct.

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  21. Hi,
    I so wanted to post a success, but after days of troubleshooting I cant see anything so I hope someone can help. the pedal works but only when both the pregain switch and the ON switch are on, I get no sound when just the ON switch is pressed.

    I wired the pregain switch exactly as below:

    PGSW 1 ---1 4 7---- pregain 3
    PGSW 2 ---2 5 8--- Ground
    PGSW 3 ---3 6 9--- LED---resistor----9Vdc

    I followed the vero build exactly and used the standard single switch offboard wiring.

    Is there anything additional I need to do?
    Hope you can Help,
    Matt.

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  22. Hi,
    I almost finished wiring the pedal. Only thing I can't understand is where the two grey wires on the left go. do they go to pregain pot. 1 and 2? and from there to PGSW?

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    Replies
    1. Yes, so for example, the first wire would go to pre-gain lug 2, and also directly to PGSW lug 3. You could take a wire from the board to the pot, and then the pot to the switch, or two wires straight from the board, to the pot and switch respectively.
      Hope that helps
      Dave

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    2. great! thanks!
      is there a point to connecting the bottom grey wire on the left (in the layout) to pregain pot? it connects to nothing on the board after all.

      I connected the PGSW3/pregain 2 as you explained and the pedal wroks, well at least mostly. The bass pot seems to have no effect at all. Also, everytime I move the vero with my finger the gain disappears.. probably a dry joint or a short.

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    3. No, you are right, just connect it directly to the switch. Yeah, check your soldering, solder bridges, component orientation and placement, the usual stuff... I'm sure you'll get it working.
      Cheers
      Dave

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  23. Dave,
    Thanks for the help. You really cleared out for me the stuff that was confusing. I found out that all the problems occur because of bad pots. this is not surprising as it's not the first time that I get bad pots from my local store. Gonna have to wait until I get that ebay shipment haha

    Anyway this pedal is great! The little I got to play with it sounded really awesome. I plan to play this effect in combination with a Sunface Fuzz that I also built thanks to the layout here :D

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  24. Hi there,

    First of all thanks so much for all the info. I'm learning a lot. After building some kits, I thought the next step would be to build some projects 'from scratch'.
    This one was a bit problematic though.. (used an audioprobe to debug, and found out i missed a bridge, very useful experience!) But it's still not right I think.

    I have sound, and that sound is really good, except the following:
    The gain pot doesn't seem to have any effect on the sound at all. The pre-gain pot however, affects the sound even when I have the pregain switched off (When the pregain pot is at zero, I have no sound. Even when it is switched off).
    I checked the wiring and it seems to be correct. The only thing I did different is that I wired the pregain switch to a 3dpt instead of a switch. Does anyone know where I should look for a solution? Cause I really love this effect.

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  25. No one? Or isn't this the place to ask these questions?

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    1. Build this today and ran into the same problem as Marc did. The pedal works and sounds fine except the gain pot. Any help would be appreciated... :)

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  26. F..., biasing Q1 helps a lot :). I recommend omitting the pregainpot/switch, turning down the guitar volume does the same......

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    1. Sorry for the late reply, thanks! Wasn't sure how to bias and used my ears. Was affraid to mess with it when it sounded really really good.

      I iwll definitely do this, thanks a lot!

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    2. Hi guys, I ran into a similar problem - the gain pot does almost nothing, until I put it to the max - there I have a lot of gain - so much so, that it gets really creamy and fuzzy when I engage the pregain and the Ge diode. I didn't have a 10k reverse log pot, though, so I made myself a "poor man's reverse log", by using a 50k linear and a 12k resistor between lugs 2 and 3. Anyway, did just biasing Q1 do the trick for you? Obviously, I'll double and triple check any bridges and cold joints. Thanks in advance!

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  27. well i built this,it makes splat noises and nothing els.i tried a number of different transistors and still the same.What should the reading be for Q1 ECB? When I test C an B of Q1 without the transistor in socket i get C=9.07 and B=8.51 useing 9.5 volt on the power in.when i put the transistor in then B highest voltage is 1.7 and C is 1.4 I dont get it????

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  28. 200pf cap in the left hand top corner- not easy to source. 220's are quite common though. Will I get away with it?

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    1. 220p is close enough. You could try 180p for it too. Either one, i don't think there'll be much of a difference in overall sound.
      +m

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  29. There's also enough room right there to easily put two 100pf in parallel which will give you 200pf

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    1. True.

      On the other hand, Tayda has 200pF ceramics for 1 cent a piece:
      http://www.taydaelectronics.com/capacitors/ceramic-disc-capacitors/10-x-200pf-50v-ceramic-disc-capacitor-pkg-of-10.html

      In this application the material doesn't matter much. It's there to tame possible high pitch oscillations from Q2.
      +m

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  30. Thanks for the input. Much appreciated.

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  31. Help! (again)

    I'm a little confused about an instruction in the diagram which is given as: PGSW1/pregain 3 and PGSW3/pregain 2. Is this an indication to take the wire to the pregain switch and then link directly from that point on the switch to the indicated lug on the pot? That seems a little odd to me at first glance. Can anybody help clear up my misunderstanding?

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  32. Also, the wire marked PGSW1/pregain3 seemsto be connected to a track with a cut right next to it????

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    1. ok, what's happening is that the pregain pot is connected via a switch, so you can either insert it or remove it from the circuit. so when you see PGSW1/pregain 3, what you need to do is have a wire that runs from the board to lug 3 of the pregain pot, and lug 1 of the switch which allows you to engage/disengage the pregain pot.

      yes, that wire should connect to the board at a cut.

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    2. Many thanks. All working perfectly. A great sounding pedal.

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  33. Some description on the net says it uses TO-18 transistors, will this layout work with them?

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    1. TO-18 is just the package (shape) of the transistor. You're probably more familiar with the TO-92 package, the small black semi-circle shaped ones. There is no difference in operation so either can be used.

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