Tuesday, 29 January 2013

Tech21 XXL

Per request. The original design had couple of things i had to mod to get this stripboard and/or 1590B friendly. First, there are two dual opamps in the original box, and they are used in quite peculiar manner. The first one is TL072, which has other half as input buffer for bypassed signal and other half as first gain stage. Which is fine, until... The second opamp is TLC2262, which has its other half as output buffer for bypassed signal and the other as second gain stage. Since onlythe output buffer is after the gain stages, it should not hurt the sound to omit both buffers. But there's little sense in drawing this with two dual opamps and only use other halves.. So i just used one dual - exactly like all the other aproximations/layouts found on the web. There was another little thing.. As with a few other designs, the volume pot is sometimes used to dump the signal to Vref instead of ground. This is ok, but it just means that we need to have a decoupler capacitor before the conventional volume control. I used 2µ2, which is the same value used as output cap at the buffered output. These *shouldn't* affect the sound, but only way to tell... is that someone builds it :)




Geiri's demo of his build:



Posted by at 17:12
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11 comments:

  1. dexxyy29 January 2013 at 22:54

    swap the tone 1&3 wire positions, drive 2&3 to 1&2 and drive 1 to 3 and tag it. Think i`ll stick this in one of Matt`s enclosures :-)

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    Replies
    1. mirosol29 January 2013 at 23:04

      I just hate it when they don't mark the pot lugs on schematics - usually i percieve them wrong :)

      Thanks man! I'll fix those labels and tag it!
      +m

      Delete
    2. Milkit30 January 2013 at 14:39

      Haha, too cool buddy ;0)

      Wouldn't mind seeing a photo of that finished badboy if I may please Derek?

      Delete
  2. tomo631418 March 2013 at 16:15

    Hi can anyone help with this ??....pedal sounds good however, im not getting much from the warp pot, certainly nothing like on the demo vid, its kinda acting like a subtle tone control, where as in the vid it changes into a kinda fuzz...checked my wiring and board and also changed the pot with no better success....any ideas ????

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  3. tomo631419 March 2013 at 12:44

    OK sorted....it works as it should with my humbuckers....just didnt like my single coil tele...with my LP..sounds like a beast !!

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  4. nicolas.lesage5220 July 2014 at 14:48

    I made it yesterday and I'm sure that the Drive pot must be C100K.
    The Tone is also better with a A100K pot.

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    Replies
    1. mirosol20 July 2014 at 15:03

      I just checked the schematic and it has all four pots marked as "L", so i have no idea if those are linear or logarithmic. But it seems that they are all with the same taper in the original units.
      http://img.photobucket.com/albums/v282/Axiomdrift/XXLpn.gif
      I've updated the labels on the layout to all linear. Yes. It is based on a guess...
      +m

      Delete
  5. giudis21 August 2014 at 10:33

    Hi friends, do you know if there is a layout of the TECH21 VT BASS anywhere?
    thanks a lot
    g.

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  6. Unknown16 July 2015 at 10:33

    Hi,

    What's the difference between the bass version?

    Thanks

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  7. Unknown1 January 2016 at 14:13

    Hi, i have a question, can i use milennium bypass on this project or only 3pdt? I'm from brazil and the 3pdt price here is very expensive,have any way to use dpdt of 6 terminals? thanks and i'm so sorry for bad english.

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  8. Unknown1 January 2016 at 14:38

    Shure!
    Maybe consider buying a batch of 3pdt's from aliexpress or simular? Saves a lot of money!

    ReplyDelete

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