Relocation for 3PDT and bypass switching mechanisms.

[plex]

Greetings DIYstompboxes forum. I'm a student in EE (about 90% of the way through) and I hope to be able to eventually contribute to the forum. I'm new to making pedals/guitar effects and had a question about the bypass switch.

I want to route the bypass switch outside of the pedal, up to a distance of 5 feet from the effect circuit. The switch needs to be easy to activate (little force required) as well. A concern of mine is interference, would using a grounded cable wrap mitigate that (at least for RF)? What would be a good solution to this relocation issue?

Also, could one route multiple effect signals (say overdrive, whammy, and clean) through the use of a decoder and multiplexer?

Thank you,
plex

[Brisance]

when in doubt, use a relay.

[plex]

I just put this together. Would this even work for audio signals? It was one of the first things that came to mind. (Forgive any inaccuracies, the long winter break made me rusty).



I sadly have little experience with relays.

[R.G.]

My best wishes on your chosen profession. I got into EE largely because of my urge to build amplifiers and pedals, but that was back in 1969. It's been a long, tangled road, as yours no doubt will be too. Hang in there and make the best of it!

I would say that running the signals out to the switch is the answer that would have been current up to about 1974. Since then, professional practice has been to keep the signal path as short as possible and use local switching elements controlled by logic, a process called "cold switching" in the biz, at least back then. I believe cold switching may be so accepted that it doesn't have a special distinction any more.

My advice is to use either a relay as a local switching element and run the controls for the relay out to the physical switch, or use an analog switch setup ( I like the CD4053 ) as the local switch. I have an article on my web page [http://www.geofex.com] on the use of CMOS switches like the 4053 for signal routing, and also some info on relay switching, among other things.

In my professional dotage I have graduated to my own personal dream job and I now do all the pedal design for a commercial manufacturer. We use CMOS switches and/or relays in the pedals for other reasons. But the switching is just fine with these elements instead of hard switches.

Mechanical footswitches are actually the 1950s solution to routing. They let you do signal bypass for pedals, but have problems of their own. You'll hear "true bypass" bandied about as the holy grail of pedal switching. Actually, true bypass is the solution to a problem that we largely don't have any more.

[krister]

Midi switching works quite well too, but that puts you into the digital realm. The actual switching does not carry any audio signal. Listen to RG.  He knows way more than me.

[plex]

Thanks for the advice guys!

R.G. I'm studying EE to hopefully design microprocessors or analog IC design (if genetic algorithms haven't kicked analog designers out by then )...but audio circuits are really great too.
CD4053 seems awesome, I checked out your site and it has been really helpful.

For multiple bypass I thought about chaining two CD4053s together...3 effects; clean, effect 1, effect 2. 2 control switches, when nothing is pressed the sound is clean but when either effect switch is pressed then that effect becomes active (only when the switch is active, think of a tactile switch)...The tact switches will run to a decoder to control the CD4053s.

Does this seem like it would work? I also boxed in red two resistors which I don't think I'll need to use if I chain the 4053s together.



The tri-states would prevent conflicts on the A0/B0 control line... I think

[Albrecht]

essaydune

Hello guys, I'm finishing my last course project on Digital IC Design, Test, and Validation at Portland State University. I tried to open/download schematic diagrams by Alexandre Ernandez (The true bypass, is that really good?) but my antivirus blocked them. I can't access the images on the forum either.. @plex, could you please resend those in a zip file? Thanks.