Boss SD-1 True Bypass using stock switch

[syzygy]

I've searched but can't find complete instructions and diagrams for doing a true bypass on the SD-1 with the stock foot switch.  Is it possible to do the Millenium or Clinton bypass using the stock switch?  The Clinton and Millenium call for a DPDT I believe, and I don't think that is the same as the stock switch on the SD-1.

Can anyone point me in the right direction?  Maybe I need to use relays..

Thanks,
syzygy

[O]

The stock switch is a momentary switch i.e. it only stays "closed" for as long as you hold down the switch for. A Carling switch, or the "blue" switches aren't momentary. They actually have the contacts touch and stay "closed" everytime you stomp on it.

you _can_ fit a 3PDT switch in there, but it takes some modification.

[Peter Snowberg]

All the Boss pedals use JFET switching so the switch is a momentary SPST. As REM sang.... you can't get there from here.

You might be able to mount a DPDT switch in the same enclosure, but I think you're much better off making a true bypass box which is just a box with a DPDT switch and four jacks. You can use that box to get true bypass without modifying your pedal.

A relay would also work, but relays have advantages and disadvantages. On the plus side they give you true bypass with less switching noise than a stompswitch, but they also consume LOTS of power.

Here's an extreme example, but a small relay requires MORE THAN 50 TIMES as much energy to run as my last distortion design.  Much more of the time it will be more like the relay requring more than 10 times as much as the effect circuit.

[cd]

All the Boss pedals use JFET switching so the switch is a momentary SPST. As REM sang.... you can't get there from here.

You might be able to mount a DPDT switch in the same enclosure, but I think you're much better off making a true bypass box which is just a box with a DPDT switch and four jacks. You can use that box to get true bypass without modifying your pedal.

A relay would also work, but relays have advantages and disadvantages. On the plus side they give you true bypass with less switching noise than a stompswitch, but they also consume LOTS of power.

Here's an extreme example, but a small relay requires MORE THAN 50 TIMES as much energy to run as my last distortion design.  Much more of the time it will be more like the relay requring more than 10 times as much as the effect circuit.

I can't remember if I psoted a whole writeup on it, but I stuffed a latching DPDT relay into a SPDT for true bypass, using the existing flip-flop circuit to drive it.  The latching relay doesn't use much power (only a blip when the coils are energized - otherwise it stays in place with no power).  Try a search with my username and "sd-1 latching relay" as the terms, it should bring it up.  IIRC you also need two opamps (or a dual and a single, for a total of three stages) to drive the relay.  

I still have a problem with switching noise that I haven't solved (or bothered to solve) - it's about as loud as a regular 3PDT so I don't care.  Otherwise it's a really trick setup, the whole pedal looks dead stock inside and out (I posted a pic of the battery comparment, nothing in there) yet it's true bypass with LED indicator and everything!

[Peter Snowberg]

Thanks cd!

Here's the post:

http://diystompboxes.com/sboxforum/viewtopic.php?t=26758

[WorkBench]

Fables of The Reconstruction.  Great album!

[syzygy]

Hey again Peter!

I see.  So you're saying a relay will eat more energy.   Would the output sound be affected at all?  I plan on using dedicated power all the time, instead of the battery, so having the extra drain on energy wouldn't bother me (unless it changes the tone of the circuit).

I'm trying to achieve true bypass without an external box or changing out the SD-1 stock switch, if feasible.  And keep the switching noise at a minimum.

I've looked at some relay schematics at http://www.geofex.com/FX_images/ltchrly.gif but there is no accompanying text on specific parts.  Any idea what my next step should be to implement this circuit in the SD-1 (if this is a good way for me to go, that is)?

Thanks,
sysyzgy

[syzygy]

Wow you guys are fast with the info!  I was writing that last response and two posts came in about a relay solution.

That's a great post from cd.  I need a little more help to understand what you did..  I looked for transmogrifox's site, but the first image was broken.  The only relay schematic listed was an older design.  Which did you use?

A few more questions if you don't mind..
How does the relay hook into the boss switching circuitry?
Which opamps should I pick from?
What is IIRC?
Can I replace the DPDT on the Clinton or Millenium designs with relays and get the same results?

Your guys' info is very helpful!

[jplaudio]

I've done quite a few of these with a low power high sensitivity non-latching relay.
http://www.jpl-audio.com/mods.html
The relay driver uses the existing flipflop for switching.The downside is the extra power consumed, about 10-15 ma. Unlike a latching relay if the power fails the non-latching relay drops into bypass mode. The stock SD-1 draws 4 ma, with the relay it is 17ma. Some of that increase may be due to the new LED that is installed with the relay mod. Email me and I can send you the schematic and/or set you up with a couple of relays to work with.

jl

[cbugatti]

I've modded my own SD-1 too, and the bypassed hiss is to much

does anyone have a step-by-step tuturial of this or is there a "best" way to do this....I've been searching for a while and really want to do this mod...

thanks in advance

[syzygy]

www.geocities.com/transmogrifox/relay

Transmogrifox,

One other question I thought of I noticed in your schematic there is a 4.7M resistor at the input and a 100k resistor at the output.  What do these do exactly?

Thanks!