True bypass a BOSS pedal (w/pix 56k warning)

[cd]

First of all, thanks to transmogrifox and Philip Bryant!  Without their info this project would not have been possible.

This question comes up a lot.  How do I true bypass a BOSS pedal?  Answer(s):

- you can't
- you can't stuff a DPDT switch in there
- don't bother putting one in, the buffer is high quality and sounds good
- don't bother putting one in, just build an external TB box with four switches and a jack etc.
- you're an idiot, BOSS pedals rock why would you want to mess one up

Alrighty then!  Well, I had an SD-1 lying around so I decided to mod it to "another pedal" specs.  "Another pedal" is true bypass, so I figured I'd go whole hog and change the whole thing.  SO, here's a pic of a BOSS pedal with true bypass:



I know what you're thinking: HUH?  That's just a regular SD-1, it's not true bypass.  Well, let's open up the battery hatch and see what's in there, shall we?  HMMMM, did CD manage to stuff a DPDT in there?!?!?!!



OH.  That was a bit underwhelming.  There's no DPDT in there, it's just a regular SD-1.  Which isn't true bypass.  Well, you're right.  That's the stock BOSS switch in there.  So I didn't manage to stuff a DPDT in there.  But I thought it was a BOSS pedal with true bypass.  What did you do to the insides then?  OK, here's the last pic:



On the bottom right you can see the small bit of perfboard that houses a latching relay and the associated control circuitry.  The relay is a DPDT which is used for TRUE BYPASS.  Since it's a single coil, latching type relay, battery drain is minimal (even though I use a power adapter exclusively).  Two opamps are used to drive the relay (circuit by transmogrifox - search for "latching relay" and a website with a link will pop up with the schematic).  I used the stock BOSS flip flop as a latch to control the relay, so the momentary switch is left in place, as is the stock BOSS indicator LED.  The whole thing works beautifully, with a tiny tiny bit of switching noise - nothing you wouldn't experience from a regular 3PDT though.

At first I thought I would rewire the stock BOSS switching FETs to a "Clinton Bypass" (see GEOFEX) since the FETs are already there, and FETs are good at that.  When I opened up the pedal there was a lot of room so I thought if I'm going to rewire the damned thing, I might as well get rid of the FETs and go real TB with a relay.  It took a bit of shoehorning in - the relay perfboard is a smidge too tall which made the backplate a bit tough to get on.

It would have been MUCH easier to use a 2 coil latching relay, that way you could use the latching relay driver on GEOFEX - but I couldn't find any locally so I went with the single coil.  Thanks to transmogrifox for his relay driver circuit, and Philip Bryant for his excellent SD-1 schematic - without it I would have probably went blind figuring out all the connections.

I don't have the time or inclination to post up a full tutorial on this mod (and I don't want to help the commercial modders), but all of the relevant info can be found at the usual places: searching the forum, GEOFEX, Google, etc.

[Hal]

sweet idea.  Where'd u get the relay/how much can they be had for?

[cd]

I got the relay at a local store, cost was $2.  You can get them at all the usual places though, Mouser, Digikey, etc.  The relay I used was a 5V, single coil latching relay.  You'll want to get one that is low profile (5mm or shorter).  I used a socket for the relay so it's actually about half as high as it looks.

[Gilles C]

Nice job!

I like it because you didn't modified the box, so it looks original. And I like to keep the feeling of a Boss pedal even when modified. And you kept it.

Gilles

[dubs]

That's very cool!
Apparently  you can true bypass boss pedals. I saw a pic that someone removed the top of a blue 3pdt footswitch and drilled the hole larger where boss one is to fit the footswitch..

[Kleber AG]

I'm not the one who posted the pictures, but after looking that pics I did it to my Boss Delay, removed the top of the switch, sanded for lowering the height...
BTW: You don't need to drill a bigger size hole for the 3pdt !!!
Now my Boss Delay makes "clank"  when I switch on or off!!!

Works nice, I've been giging with it and it's perfect!!!

Search the archives, now I can't remember all the details, but it's on the archives for sure.

Kleber AG

[syzygy]

cd,

Where did you connect your relay into the flip flop circuit?  I have a schematic from Phillip, too.

Thanks!

[cd]

cd,

Where did you connect your relay into the flip flop circuit?  I have a schematic from Phillip, too.

Thanks!

The flip flop is used as a switch to signal the relay driver to turn on/off.

[Roberto]

nice.    

I designed a small and simple circuit that can translate the internal BOSS flip-flop collector voltages into pulses (few mS) well suited for drive a two coils latching relay. Basically is a high impedance input buffer, a differentiator  and a driver for each coil.

this is the PCB version:    






and this is the really small version (some boss pedals don't have too much free space): :lol:

[Fp-www.Tonepad.com]

VERY nice.

Inspiring.

Fp

[wui223]

nice.    

I designed a small and simple circuit that can translate the internal BOSS flip-flop collector voltages into pulses (few mS) well suited for drive a two coils latching relay. Basically is a high impedance input buffer, a differentiator  and a driver for each coil.

can u post the schematic to share with us?

[petemoore]

Slick !!!
 IIRC There was some demand for that kind of thing.

[Freddy205]

That is brilliant Roberto. I would also like to see the schematic for that. I have a bunch of boss pedals I'd like to true bypass.

[Roberto]

Thanks. I'll try to post the schematics tonight.

[syzygy]

Roberto,

Looks awesome!  Very james bond.  Where did you get the ..ehh.. red electrical condom?  :shock:

syzygy

[Melanhead]

Thanks. I'll try to post the schematics tonight.

That would be much appreciated ...

[Bernardduur]

Roberto,

Looks awesome!  Very james bond.  Where did you get the ..ehh.. red electrical condom?  :shock:

syzygy

I would guess a red shrink tube; can be bought here everywhere

[Roberto]

Yes is  shrink tube.

This is the schematic:  



and this is the internal boss flip-flop where the inputs are connected:

[Melanhead]

Thanks that's great ...

[Bernardduur]

Yes, thank you! Will try it soon on my Boss pedals.