Tuesday, 27 October 2015

Tech 21 SansAmp Classic

Here is a layout for a very famous pedal.
05/11/2015 Layout updated and verified!








60 comments:

  1. This is very scary and intimidating... I commend you for your hard work in tracing this pedal!

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  2. Haven't traced it.
    I've used someone else schematic.
    I'm planning to build it one day to check if it sounds like my original.

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  3. Hello. Tx for the layout! I am planning on building it. I was wondering: In the second vertical row on the left side there is a transistor drawn with the letters 'clr' on it. Could anyone please tell me what those letters mean? Thanks in advance.

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    1. I meant a 'resistor' with 'clr' on it, not a 'transistor'.

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    2. Its the resistor for your led. How bright or dim you want it. If your not sure socket it and try values from 1.2k to 4.8. Its personal preference.

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    3. It's Current Limiting Resistor
      I'd say 1-15k depending on the LED you use.
      I use a personnaly use a 10k CLR with ultra bright leds

      Alex, awesome layout again, amazing how you managed to make it so compact with so much wiring !

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  4. Thanks for the explanation!

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  5. http://www.tech21nyc.com/support/manuals/sansamp/Classic-OM.pdf

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  6. Great layout buddy, you have posted some really amazing layouts.

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  7. Awesome work as always! Is there any differences between this and the gt2?

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  8. i own a original and this pedal is a AC/DC in a box, real nice Marshall sound and decent AC30. you can tweak it til you die with all dipswitches ;)

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  9. Wow - this looks very cool. And I think I have everything for this build. Thanks once again Alex!

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  10. Can you use a rotary switch instead of dip switch if you can how would you wire the rotary.

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    1. I don't think you want a rotary here. The idea is to select the eight different settings on or off as you wish. For example, you may turn on Mid-Boost 1 and Vintage Tubes and leave the rest off. You could use a bank of 8 submini spst switches in place of the DIP switch.

      I have a question about the zener diodes. Can we substitute higher voltage zeners for these as I don't have the 1N755s?

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  11. Oh man I didn't think about that were u can turn on turn off the switches individualy I will just go buy the dip switch thanks for the info.i think the higher zeners would be fine better than going lower voltage

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    1. The hard part now is drilling a rectangular hole in your enclosure haha.

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    2. I will probably mount the 8 DIP switch by first soldering the 16 connection wires to the switch, drill 16 small holes to fit each pin (oversized) on the enclosure, thread the wires through the access holes, and then securing the body of the switch to the top of the enclosure with some epoxy. You can protect the pins from shorting with some heat shrink insulation.

      If you want to cut a square hole, it shouldn't be too bad. Just drill out the area with regular twist drills then finish up with flat files. Aluminum works very easily with files.

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  12. Yeah that's going to b a challenge a square hole will have to get the dremel tool out.

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  13. Actually I haven't built this yet still thinking about it.This pedal sounds great but I found a vero layout for the sans amp gt-2 it's sounds a lot better than this pedal.

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    1. I saw the Aron Nelson vero - it could probably be improved. There's a schematic at the Tonepad site, so maybe Alex could do the GT-2 vero at some point. The classic still looks like a worthwhile build. :)

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    2. Personally, I prefer the "Classic". I think it's a more complete pedal.
      I'll give it a try but the problem with the GT-2 layout is that it uses 3 2P3T Toggle or Rotary Switches.

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    3. I built the tonepad's version, it's best to use 3 slide switches, in Europe Musikding sells them. Still a lot of wiring and 3 square drillings...
      http://www.musikding.de/Sliding-switch-2x-ON-ON-ON-2P3T

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  14. Tayda sells them too... But back to the Classic: i can use 8 spst switches instead of the dip switch right?

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    1. Yes you can if you are brave enough

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  15. hi there Alex!
    that's a fantastic effect!
    and a very nice layout again mate!

    i've bought everything to get it working, and as i was reading the schem i've found a tiny mistake.
    on the board(not at the notes) where you say dip sw16, it should be 13.

    and i also have 2 questions:

    1.from ic2 pin2 there is a 1k resistor that goes to presdrive1,2. on the schem it's a 100r.is that correct?and i can also see a 330k from pres3 to pres1,2 that i can't find anywhere at the schem.

    2.at the note 3 on the schem for that unknown cap in parallel with the 1m resistor, it says 47pf-220pf and in your layout it's a 2.2nf.

    the schematic i'm talking about is this

    http://freestompboxes.org/viewtopic.php?f=13&t=4375&p=163417&hilit=Tech+21+SansAmp+Classic#p163417

    shit...i'm out of dpdt on-on-on...i'll build it just with bass and normal..

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    1. Hi Savvas!
      I've used this one:
      http://www.diyitalia.eu/forum/download/file.php?id=6401&mode=view
      If you keep reading comments on the FSB it says the schematic you've posted is incorrect.
      Unfortunately it's impossible to perfectly trace a schematic for this pedal for the way it's been built.
      A lot of it is just guessing.

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  16. This comment has been removed by the author.

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  17. I need a little help with the footswitch wiring (haha!)
    i got too much information here i guess.
    i did some masterclass in paint here. can you tell me if this is correct or not?
    http://www2.pic-upload.de/img/28735503/Classictest.gif

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  18. It's correct.
    Don't forget to connect the ground to the negative side of your power supply.

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  20. Anyone know if the on-on-on switches from Tayda are the right ones? I bought some off ebay a while back for the Vibutron and it turns out there are 2 (at least) styles and mine was the "backwards" one and without |V|ark's help, I'd have been straight up poo creek..

    From the Frantone Vibutron page:

    IvIark27 April 2014 at 01:27
    One thing I should add before you build it is to check that the contacts on the Waveshape switch behave as shown in the switch diagrams before soldering it up. The way it is drawn requires 2 & 3 and 4 & 5 to be made in the centre position. If that isn't the case with the ones you buy and instead 1 & 2 and 5 & 6 are made in the middle position, then swap over the poles so:

    Lug 1 becomes 4
    Lug 2 becomes 5
    Lug 3 becomes 6
    Lug 4 becomes 1
    Lug 5 becomes 2
    Lug 6 becomes 3

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    Replies
    1. This might be useful since they vary so much:

      http://allthesound.com/1images/DPDT_switches.jpg

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  21. 99% verified...
    i think it's all about verifing the schematic, cause i'm 100% sure that Alex's layout is as per schem...
    it works absolutely perfect till pin 13 of tl074.
    (also ampdrive pot is backwards.)
    i have signal at lug1&lug2 of high pot, but at pin 14 signal almost disappears. it becomes muddy and farty, and level drops at almost 10% of what pin13 has.
    is that cause output pot is wired that way?
    i've never seen that anywhere else.shouldn't lug 1 go to ground?

    i have to say that i've used a layout that i drew, based on Alex's layout and on the schem he posted above because i wanted to use a dsg pinout jfet,and a dpdt on/on input switch.
    i also put some components on the switches and the 2,2nf cap between lugs1&2 of high pot, and managed to bring it down to 21x21.
    last thing, i didn't have any 7,5v zener so i've used 4,7v.

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    1. now 100% verified!it was i tiny mistake of mine.

      output pot is backwards too. it has some noise with some settings,but you can deal it out with the pres drive. really nice effect. i'll box it for sure!
      dip switch is great!!
      it's like giving you 50 different overdrives...!!!!and i love overdrives!!
      the only thing is that output pot is a bit useless...all the way up, is just above unity so...
      do you guys think it's because of all these 3x100k resistor to ground?isn't that affecting the impedance?any thoughts on that would be great

      anyway..i know my layout is a bit different from alex's layout, but i'm sure like 10000% that it matches with mine and with the schem.

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  22. Yes, the layout should be updated to switch the Output pot connections 1 and 3 (1 goes to the Vbias rail).

    Savas - Re: low output, try changing the 100K to the right of IC2 (pin 7) to 10K and see if that bumps up the output. There are two 100K resistors forming a voltage divider coming out of the second op amp gain stage. That seems like a lot of signal attenuation prior to going through the extensive filtering stage. The last 100K prior to the output jack looks like an antipop resistor. You could increase that to 1M or greater, or simply remove it. I don't think it will affect the output that much either way.

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    1. Frank, once again (you helped me on a similar problem with orange-15 project) your suggestion was right spot on! changed that 100k to a 10k and that did the job!
      now i have a nice output range. thanks!
      you are the "low-output-fixer-master".

      i'll try to make a demo of that pedal in the next days...also i have to make a demo of the or15,collosalus, and a couple of others too...

      and one last thing Alex. you could update the layout for that one too

      "on the board(not at the notes) where you say dip sw16, it should be 13."

      thanks again guys.

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    2. Thanks Savvas & Frank!
      Layout updated. :)

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    3. Thank you so much for verifying this one
      Please post pics when you get a chance to box it :-)

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  23. Great to hear that Savvas! "low-output-fixer-master" hmmm. Sounds like a food blender. ;) It was just a hunch, but I'll mod my build accordingly.

    I even found my 8 pole DIP switch and zener diodes at Radio Shack (hah)!

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  24. Glad to know this layout has been verified and I am planning to give it a go.

    Regarding the 7.5V zener, can I use 1N5236B Zener Diode (7.5V, 1/2W) as a substitute?

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  25. Re: zener diodes. I've been trying to understand what the purpose of the two zener diodes is in this circuit. It looks like it's a voltage limiter of some sort, but I can imagine it having any effect at the input of the overdrive/amp section. I'm going to leave these out and see if it has any effect on the response.

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  26. I've been looking over the schematic and the layout above and I have a few additional comments.

    (1) In the power section, the schematic shows a 430K in parallel with a 100K (equivalent to 81 K), where the layout just has the 430K. This will affect the bias voltage and it probably will not be where it should with the 430K alone (which is usually near 1/2 Vcc or 4.5V). You could either use an 82K or 100K in place of the 430K. I'm going to try 100K in my build as I can't see any reason to not have the bias voltage be 1/2 Vcc.

    (2) The power section also has a 1N4148 small signal diode as a reverse polarity protection. I'm going to use a 1N4001 here.

    (3) I'm definitely removing the 1N755 diodes as they don't serve any purpose that I can see for this circuit, especially if we use this as a simple stomp box.

    (4) The filter section after the gain stage consists of three(!) Sallen-Key low pass filters in series with cutoff frequencies of 9872, 4880, and 3940 Hz respectively (assuming SW7 is open). That kind of filtering must impart some mojo to the final sound and definitely will squash any high frequency artifacts if the gain stage op amps clip.

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  27. Hi Frank!
    The parallel 100K resistor is there, next to the transistor.

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    1. Hi Alex - yeah, I see that now. Thanks! I think I'll just remove the 430K for now and check to see if paralleling it with the 100K makes any difference.

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  28. Would this switch be ok for the input ?
    http://www.ebay.com/itm/2-Chrome-DPDT-3-Way-Guitar-Toggle-ON-ON-ON-Switches-/191044107522?hash=item2c7b1dbd02:g:32kAAOxyhodRySPK

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    1. Those should be fine.
      As Mark (and Heath) suggested:

      You should check that the contacts on the switch behave as shown in the switch diagram before soldering it up. The way it is drawn requires 1 & 2 and 5 & 6 to be made in the centre position. If that isn't the case with the ones you buy and instead 2 & 3 and 4 & 5 are made in the middle position, then swap over the poles so:

      Lug 1 becomes 4
      Lug 2 becomes 5
      Lug 3 becomes 6
      Lug 4 becomes 1
      Lug 5 becomes 2
      Lug 6 becomes 3

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  29. Hi,

    I'm baffled with this input switch thingie.
    I have DP3T slide switch (like http://goo.gl/Od82eo ), would that work, and how should I wire it?

    Thanks!

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    1. Input Sw 1 is A1.
      Input Sw 4 is B1.
      Input Sw 2 is A0.
      Input Sw 5 is B0.
      Input Sw 3 is A3.
      Input Sw 6 is B3.

      A2 and B2 need to be linked together.

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    2. That was fast :)
      Thanks a million!

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  32. I got some problems here:
    The pedal works sometimes. I get R2D2 like oscillation at higher presence drive settings and amp drive settings. Mostly when the 3rd switch (clean amp) is on the off position.

    The oscillation stops somethimes when i switch from humbucker to single coil. and i can modulate the sound by turning the volume knob on the guitar and switching the input switch.

    Help!

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  33. Hi,
    I build this layout. The sound is great!!! But high pot feel no function. Any Bro help me to fix high pot problem !!!
    Thank !!!

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  34. Hi, all!
    How to wire it with the 3dpt button?

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  35. I'm about to start building it. Looking at the layout, it seems to me that it should be simpler to ommit the link going from FS2 to output jack and plug directly the out jack to the FS...

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    1. Built it
      Pres Drive and High are both wired backward
      Some hiss when dip switch 4 is off (clean amp) but that can be dealt easily with the pres drive pot
      Here are pics of my build, along with the GT2 : http://www.casimages.com/u/Alltrax/364703/

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  36. After about a month playing with the classic, it seems there is a bypass issue with the pedal. There is always a tiny distorted signal that can be heard, either in bypass or engaged. I know someone who built it and also has exactly the same issue.
    Just a warning to those considering building it ;-) and if anyone has an idea on how to fix this...

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