Hi Tech TB Looper?

[swinginguitar]

Have been wanting to build a true bypass looper. Was thinking today that rather than use the traditional 3PDT and mess of wires method, I could use it as an opportunity to explore some new techniques (and because I want some of the loops to be stereo and 3PDT won't cut it). So, let me throw out a few ideas that sprang to mind, and invite some comments from all of you in terms of feasibility, relative complexity,  etc.:

1) mechanical relays controlled via transistors, or a PIC, or .....?
2) reed relays (DIP package could be an advantage)
3) multiplexer chip (these probably can't be true bypass...or can they?)
4) anything else?

[Mark Hammer]

All been worked out and done.

Look for Dean Hazelwanter's past posts.

[swinginguitar]

Is this the thread in question?

http://www.diystompboxes.com/smfforum/index.php?topic=56264.0


edit:
That's all I found....doesn't answer my questions....

[Mark Hammer]

Okay, go to GEOFEX and poke around there a bit, then go to The Tone God's site.

[crane]

I'm afraid I do not understand your problem.
If you want to use relays - do that (for example - Line6 DL-4 uses relays for bypass)
If you want to use analog multiplexer ICs - do that but don't call it true bypass
Reed switches sound wrong to me - too many problems with mechanics (moving the magnet etc) - or is there something I don't know about advanced reed switches?
After all - you can use 4pdt push buttons for stereo loops.

Conclusions
1)if you want an easy build - use 4pdt
2)if you want a very cheap build - use relays
3)if you want an even cheaper build but no true bypass - use FETs for switching loops

[swinginguitar]

Had not seen the tone god site...wow lotsa reading to do.

as i understand reed relays come in DIP packages and thus could be compact and fit in a PCB layout easily.

[swinginguitar]

The Wicked Switch on Andrwe's site is a good read.

Anyone have any comments on the fidelity of the 4066 arrangement? Signal wise, is it equivalent of the mechanical switched we typically use, or does the internal resistance load the signal?

[swinginguitar]

If I went with a PIC controlling a relay (either directly on a 5v relay or via a transistor switch on a 12v relay), can I assume that I need 2 pins per loop (1 for the actuator and one to signal the relay)?

[Beo]

If you want to use analog multiplexer ICs - do that but don't call it true bypass

Do you say this is not true bypass because there is no mechanical switch? Are you implying that there is some tone loss with cmos switching?

[crane]

If you want to use analog multiplexer ICs - do that but don't call it true bypass

Do you say this is not true bypass because there is no mechanical switch? Are you implying that there is some tone loss with cmos switching?

I said thait because there is no mechanical switch which AFIK is the only way to make TB (no matter if the switch is a relay, push button or reed switch). If there is any tone loss doing analog multiplexing depends on schematic, layout and parts used.
A good buffered bypass can sound as good as true bypass but you still shouldn't call it true bypass.
If chicken tastes like beef - do you call it beef?

[swinginguitar]

Can you guys recommend a PCB mount relay? Any experiences with particular units?

I sit safe to assume the SSR's aren't techically true bypass since there's no mechanical switch?

[harmonic]

I've read here and elsewhere that you don't want to be putting audio through SSRs as they're not designed for audio.

I've had good results with Omron G5V-2.

I've been working on electronic switching and trying all the 4013/4016/4049/4053/40106 combinations. I've settled on a 555 driving a relay as the least number of compone ya (its a use case where minute footprint is paramount). The relay I've been using is the aforementioned Omron, specifically the High Sensitivity variant.

Hope that helps.