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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
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45 comments:

  1. Anonymous19 April 2013 at 22:29

    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

    ReplyDelete
  2. DrStevenson19 April 2013 at 22:33

    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. Anonymous19 April 2013 at 22:40

    Very quick response Paul, thanks a lot

    ReplyDelete
  4. Cylens27 May 2013 at 11:07

    Hi Paul,

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

    Thanks in advance

    ReplyDelete
  5. Unknown25 June 2013 at 01:33

    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

    ReplyDelete
    Replies
    1. DrStevenson25 June 2013 at 06:11

      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

      Delete
  6. Unknown25 June 2013 at 01:36

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

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    Replies
    1. ferekidis10 February 2015 at 23:35

      This comment has been removed by the author.

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    2. ferekidis10 February 2015 at 23:42

      This comment has been removed by the author.

      Delete
  7. Anonymous25 June 2013 at 19:52

    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. DrStevenson25 June 2013 at 20:36

      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

      Delete
    2. Anonymous25 June 2013 at 21:44

      Thanks Paul!

      Delete
  8. Sonicguitars3 September 2013 at 11:08

    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. antonio7 November 2013 at 20:48

    hello
    I need a latching relay?

    ReplyDelete
  10. antonio8 November 2013 at 08:19

    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?

    ReplyDelete
    Replies
    1. DrStevenson8 November 2013 at 09:00

      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.

      Delete
  11. Bohemian H15 January 2014 at 12:14

    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

    ReplyDelete
  12. Bohemian H15 January 2014 at 17:06

    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.

    ReplyDelete
  13. Dios10 March 2014 at 07:09

    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...

    ReplyDelete
  14. Matt9 April 2014 at 16:23

    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. Anonymous14 April 2014 at 06:20

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

      Rob

      Delete
  15. Anonymous14 November 2014 at 12:12

    Hi !
    no free wheel diode ?
    thx
    mika

    ReplyDelete
  16. Tkrain18 November 2014 at 04:30

    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?

    ReplyDelete
    Replies
    1. DrStevenson18 November 2014 at 08:11

      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

      Delete
    2. Tkrain19 November 2014 at 00:27

      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!

      Delete
  17. Unknown21 August 2015 at 02:35

    I already simulate the circuit but does not always work.
    can anyone tell me if they did, if it works well?
    thanks

    ReplyDelete
  18. Unknown13 December 2015 at 21:14

    Hi everyone, my build is working, yet is really unreliable. Sometimes the Relay just won't switch off... I have to press the switch several times then.... any ideas how to fix this?

    ReplyDelete
  19. Unknown21 March 2016 at 20:23

    I had the same problem. Make the (220n) into a 470 n. This made a huge difference and didnt add any noticeable delay in the switching.

    ReplyDelete
  20. Unknown21 March 2016 at 20:24

    I have a problem of sorts. I made several pedals with this setup here recently. I went to daisy chain them and I have a couple of pedals that turn on and off when i hit a different pedal. I noticed it only did it when they were daisy chained . Any ideas for the fix?

    ReplyDelete
  21. Unknown28 March 2016 at 14:44

    This comment has been removed by the author.

    ReplyDelete
  22. Unknown28 March 2016 at 14:46

    This looks like the sort of circuit I'm looking for, but I'm wondering if it's overkill. I have set up a RF remote control footswitch for my effects rack (having disassembled the keyfob and put the workings into the footswitch - with a momentary action). What I want to do now is have an led indicator on the footswitch to show that the effect is "live". Therefore, I don't need the inputs and outputs for the instruments/effects, just the LED.

    If possible, I would like to go one better and have a red LED for when the effect is off and a green LED for when the effect is on.

    My knowledge of electronics is a liitle sketchy (it's 30 years since I did my City and Guilds), and I have spent the Easter weekend going around in circles trying to find the right solution, so any help you can offer would be very much appreciated.

    ReplyDelete
  23. Unknown28 March 2016 at 14:50

    This looks like the sort of circuit I'm looking for, but I'm wondering if it's overkill. I have set up a RF remote control footswitch for my effects rack (having disassembled the keyfob and put the workings into the footswitch - with a momentary action). What I want to do now is have an led indicator on the footswitch to show that the effect is "live". Therefore, I don't need the inputs and outputs for the instruments/effects, just the LED.

    If possible, I would like to go one better and have a red LED for when the effect is off and a green LED for when the effect is on.

    My knowledge of electronics is a liitle sketchy (it's 30 years since I did my City and Guilds), and I have spent the Easter weekend going around in circles trying to find the right solution, so any help you can offer would be very much appreciated.

    ReplyDelete
  24. timN14 August 2016 at 17:34

    any updates? is this 100% working?

    ReplyDelete
  25. Nacho21 October 2016 at 23:47

    Works with 5v relay? or only 9v? pin 8 and 9 have to be join? Thanks

    ReplyDelete
  26. Willy17 August 2021 at 14:16

    Gudday Paul,

    Just wondering if there's any way to set up a bi-colour LED in this....?

    ReplyDelete
  27. Willy13 October 2022 at 10:16

    Also, is there any way to make this engage only while the switch is held down?

    ReplyDelete
  28. Anonymous13 March 2023 at 09:47

    What so I need to extendto get a stable state at Power on. At the moment it is "on".
    I wann to be able to choose with a switch if it is "on" or "off(bypass)" when I Apple voltage.
    It is a great thing.
    Axel

    ReplyDelete
    Replies
    1. Anonymous14 March 2023 at 12:52

      I get it ! Add a 0.1uF to R4,R5,R8 (the connect of one side of the tact switch) and the other side of the 0.1uF to the middle pos of a switch. Left Pos of the switch to ground, right pos to VCC.
      If switch is grounded, the Power on not activates the effect otherwise the effect is "ON" when applying the Power.

      Delete
  29. Al19 July 2023 at 20:59

    A reverse-biased 1N4148 across the relay coil will prevent the destruction of the right-most transistor in the schemo. For those of you that want to use a 5V coil relay, omit the LED as drawn in the diagram, and put your LED in series with the relay coil. The LED will drop about 2.5V if you use a Blue one, and you could put a couple of 1N4148 resistors in series too. to drop a further 1.3V, so then you'll be close to the 5V the relay coil is looking for!

    ReplyDelete
  30. Anonymous26 October 2023 at 10:11

    Some mess in the schematic? Should Q3 be a Q2 and another way, if you are looking the vero picture....am I right ??

    ReplyDelete

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