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Wednesday, 10 April 2013

Soft Latch True Bypass (Relay) Switch For Guitar Effects Stripboard veroboard Layout



People often like to retrofit their guitar effects with "true bypass" switches but this usually means wrecking the pedal case by drilling holes in it and stripping out the buffered section etc.

Personally I don't like doing this modification, I like there to be a buffer because there is always a degree of signal loss in pedal chains but this is here for those who do like to do it.

as it uses a mechanical relay (which can be found at Rapid Electronics or wherever - the one I used is the 12v version of this one ) it is exactly the same as a true bypass switch and adds nothing to the signal.
it is quite small so it can fit in some pedals (like a tubescreamer) or you could use it externally to maybe bypass a whole group of pedals (or just one of course)

it's worth mentioning that this has many other uses such as controlling high power relays with a little tact/push switch and so on

NB: if you find you're getting misfire clicks you can make the capacitor a higher value - that part acts as a crude debounce - the higher it is the more stable it becomes but the slower you can turn it on and off but I found 220n was fine for guitar bypassing

hope you like.



for the purpose of perspective

26 comments:

  1. hi, i´m a beginner so i wold like to ask something, the relay is rated 12v?, there is no problem with 9 v input to activate? can i use relay rated 9 or 5 v without component change? in the photo between Q1 and Q2 seems like a 9th resisitence is placed is that right? thanks

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  2. there is no problem - the relay I used is a 12 volt one. a 9 volt one would be fine but not a 5 volt one
    in the photo the "resistor" you can see is a zero ohm jumper resistor - it doesn't actually have any resistance, they just look nicer

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  3. Very quick response Paul, thanks a lot

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  4. Hi Paul,

    Nice layout! Thank you!
    How would you include a status LED in this layout?

    Thanks in advance

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  5. thanks for sharing your work. this is quite amazing. and this really will add nothing to color my tone?
    if that is really true, this is AMAZING and i am gonna build me like 6 of these lol
    all my boss pedals are gonna get made over

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    Replies
    1. no it won't add anything to your tone - a relay is exactly the same as a mechanical switch except that it uses an electro-magnet to turn it on and off instead of your hand/foot.

      the tact switch is to turn it on and off - so you wire it to the tact switch in your boss pedal

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  6. btw....what is the TACT switch for?

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  7. Hi Paul! This looks like just what I was looking for. Is there any way to add an LED on/off to this? All the best.

    James

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    Replies
    1. yes there is - I think I'm going to add it to the circuit cause just about everyone has asked me that - it may mean an extra transistor (which is why I left it off in the first place) but check back in a couple of days

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    2. Thanks Paul!

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  8. Very nice Paul, I experience only a little popping problem when I discarge, I can I solve it?
    Thanks a lot

    All the best

    Paolo

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  9. thank you for answer
    What can I use instead of the BC557?
    thank you very much

    You can not edit this project, with momentary switch and relay latching?

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    Replies
    1. the circuit latches the relay so you just need a normal one.
      you can probably use any general purpose PNP transistor as long as you get the pinout right
      but personally I just get 100 of the cheapest BC557/547 transistors from china on eBay and never run out.

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  10. Hello, Paul,

    I was trying to source a relay locally and I'm wondering if I could get your opinion on if you think it would work in this project:

    http://www.te.com/catalog/pn/en/5-1462000-1

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  11. Right on :)

    I'm not a big poster or anything, but just so you know, I've got several of your projects kicking around. Really great stuff. I'm also quite fond of your music.

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  12. Hello Paul, could you please tell me what changes should I do for using this circuit with a 5v relay? I was looking for 12 or 9v but in my country all I could find was 5v relays...

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  13. Could I use a normally open spst soft switch if I just want to turn on the effect momentarily. Ie I just want the effect to turn on when I depress the switch, so non latching.

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    Replies
    1. Its the relay thats latching not the foot switch I think .

      Rob

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  14. Hi !
    no free wheel diode ?
    thx
    mika

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  15. Is the tact switch a momentary switch? I'm trying to find a circuit that will let me use the existing momentary switches in a Pod XT Live (I took the broken main board out, I'm filling it with Veros of the effects I'm building) to engage/bypass the signal. It looks like this circuit will set up one of those latching circuit using momentary type tricks... so push it once, the circuit closes the relay engages Com to NC, push it again, the circuit opens, the relay returns to Com to NO... is this correct?

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    Replies
    1. yes - but be careful when desoldering them - they damage quite easily with excessive heat.
      and yes - push it once it engages push it again it disengages

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    2. Hehe, the good news is, I don't have to desolder the existing momentary switches... they're attached to daughterboards in the XT chassis, still attached to the main pedal, AND the boards are wired with a 16 pin ribbon connector... Already pinned them out, just need a circuit to run em to. That's why I wanted to know if I could use em, I'd rather not take the buttons out and try to replace them with spdt switches.

      Thanks for this!

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