Momentary switch for signal & LED bypass (using opamp)

[Kevin Mitchell]

Trying to wrap my head around implementing such a thing to all projects. Inspired by the luxury of soft touch momentary switches and jfet switching (boss and ibanez bypass methods) I'm trying to understand how to go about it with some parts I have lying around.

Edit
-What I was looking for is similar to what is used in the danelectro bypass method. Will share results to this thread.-

[hymenoptera]

You mean to use opamps to replace the jfets??

I'm not sure I understand.

[R.G.]

If I understand what you're after, you want to make a flipflop out of opamps. Is this right?

A flipflop needs two amplifying elements. Two transistors, two comparators, two logic gates, two opamps can all be used.

While it's possible to do this with opamps, they are not necessarily the best way to do it. Opamps are high feedback amplifiers, and using them in a saturated switching setup like a flipflop will expose many of those imperfections that the manufacturers put in tiny print on the datasheet.

My opinion is that it would be good for you to acquire some CMOS hex inverters to have lying around. They're almost ideal for the purpose and need much less RC glue than transistors or even comparators.

Again - possible, with more or less trouble expended to get it to work.

If you were trying to replace the switching JFETs with opamps, I don't know of any way to do that with TL0xx opamps.

[Kevin Mitchell]

Yes I was talking about using the opamps to replace the jfets. I'm not familiar with any of these bypass methods and have been scratching my head finding some of these nice stompbox builds using a momentary in place of the true bypass relay. Not sure if it was just a dummy switch for appeal or if there was a jfet flip/flop bypass circuit hooked up to it but I can't imagine where it's hidden.
These images of a Zero Point Super Deluxe;
Inside
Outside

I'm trying to familiarize myself with bypass methods using a soft touch momentary stomp switch as the pictures above suggest. After viewing the schematic of the Zero Point Super Deluxe2 I do not believe that particular build includes what that person has done. I am very curious.

[Kevin Mitchell]

So what is a good flip flop circuit to use these days for using a momentary switch as the bypass/led switch? I suppose there are chips out there that may simplify thing?

[R.G.]

Yes I was talking about using the opamps to replace the jfets.

OK, normal opamps won't do that. There are some advanced opamps with a muting/disable input that might be used for that, but I don't know personally if the muting produces an audible click or not.

A momentary switch requires some help to switch a pedal. Normal alternate-action switches combine both the signal-routing connections that change when they're pressed, plus a mechanical flipflop that keeps the contacts where you put them until the next time you press the button. A simple momentary switch often doesn't have enough contacts to do the complete switching job, plus it doesn't (by definition) have a memory.

So we use the momentary switch to flip an electronic flipflop. There is an article containing that information at geofex. The fourth illustration, down at the bottom of this page: http://www.geofex.com/article_folders/cd4053/cd4053.htm tells you how to make a very capable flipflop from a cheap CMOS hex inverter chip. I have used that same circuit in my day job for over a decade. It's quite reliable. The rest of the article tells you how to use a CMOS CD4053 to do the complete bypassing. Two cheap CMOS chips, you're done.

I'm not familiar with any of these bypass methods and have been scratching my head finding some of these nice stompbox builds using a momentary in place of the true bypass relay. Not sure if it was just a dummy switch for appeal or if there was a jfet flip/flop bypass circuit hooked up to it but I can't imagine where it's hidden.

Read the articles on bypassing and switching at geofex. There's a lot there. Keep digging.

[Kevin Mitchell]

Wow thanks R.G. I've been meaning to snag all of the ICs for a sequencer experiment ironically.

I guess manufacturers like danelectro use a similar bypass method? This schematic for example.

The CD4053 can be used as 3 SPDT switches, correct? This would be ideal for input, output and a bypass LED.

Your work shows the use of a 4013 and also a 4049 as a control which allowing a spst to flip/trigger the 4053 switch. So those 2 CMOS chip circuits (control and switch ICs) and a momentary stomp switch is exactly what I'm looking for to replace the common 3pdt relay. I could also add more 4053 ICs - 2 making it a 6PDT relay circuit.
This is the switch I've got my eyes on;


Just validating my understanding of the design's capabilities 

[Kevin Mitchell]

Ehh Accidental post. I'll share a schematic and possibly a pcb layout later.

Thanks again for the info I was looking for!

[bloxstompboxes]

R.G., your site is down at the moment. Getting:

Service Unavailable

--------------------------------------------------------------------------------

HTTP Error 503. The service is unavailable.

[R.G.]

So it is. I'll go ask the hosting company what gives.

[Kevin Mitchell]

Ehh Geofex is still down.

Any examples floating around using a spdt, CD4053 and a CD4049 for a "latching" bypass as your diagrams shown?

[hymenoptera]

Ehh Geofex is still down.

Archived at wayback machine while RG gets his hosting figured out.

Main page:
https://web.archive.org/web/20150905100930/http://www.geofex.com/

Here's one of the articles (I think.. I didn't really dig too much):
https://web.archive.org/web/20150701010908/http://www.geofex.com/Article_Folders/cd4053/cd4053.htm

[R.G.]

Geofex is back up now. Hosting company had a server go funny on them. All better now.