cool reverb apart from switch spdt 'pop' issue

[deadastronaut]

yeah i tried pulldowns on both sides of sw2 at those points...

yeah i guess there are no guarantees with electronic switching either...

it will add a lot more to the circuit, but IF it works, it will be worth it to have 'clean' switching on this..without reverberating pops  


i don't quite understand the schematics for this switching though..its something ive never dealt with, so it will be a learning curve for sure...

and how it would be incorporated into the schemo...hmmm..

take this SPDT version for example as i think i have 4066 and a 4093.. ( lifted from andrews the tone gods site )


so the spdt is a physical switch..(as in footswitch)

and the result is a virtual ( where we connect to where the sw2 was? ) but only using 2 connections?.

[deadastronaut]

So if my head is on straight, it should be like this then..

but just take 2 switches out for the R21/R22..thoughts?



seems like a tank to crack a nut....but hey if it works..

[deadastronaut]

just for my own reference..

[samhay]

I'm not sure how happy the 4066 is when playing with signals that are swinging around ground. Isn't most of Andrew's 'wicked switches' about biasing up to half supply to prevent popping?

Edit: http://www.diystompboxes.com/smfforum/index.php?topic=74935.0;wap2
There is more out there, but my memory is failing me at the moment.

[deadastronaut]

hmmm not sure!..

edit: resistors to vb on inverter inputs?.

[samhay]

^you mean the switch going to Vb.
It is a bit more complicated than that, but got me thinking about one other thing you can try - DC coupling most of it.
You could even remove C5 and/or C13 if you wanted, but they are probably doing some useful filtering.
The feedback, mix and volume pots now have DC on them. You might find this distasteful, but it is probably not an issue.

[deadastronaut]

^ right i see...remove C2/ C1 / C15..

i'll give that a whirl...

edit: WHOOOAHH... deadly massive pop.

[samhay]

did you see that the feedback and volume pots now connect to Vb?

[deadastronaut]

oops no...ok i'll try again.


nope that pops like hell..

[samhay]

I assume the 3 switch lugs are all at Vb now?
Is the popping worse this way?

[deadastronaut]

sw at vb..

you mean with the caps removed etc..

i didn't measure the sw lugs, but it was massively popping..


its quite a little bugger as it only pops while playing and switching, when no sound is going through its as totally silent when switching...hmmm..

[samhay]

Hmm, there is probably a clue in that somewhere.

Do you fancy any more experimentation? If so, here are a couple of things to try:
- does it pop when the volume is all the way down?
- make R22 1k and R12 22k - any change?

[deadastronaut]

yep there is still a little pop with reverb vol fully off..

no difference on swapping/changing the resistors.


i was looking at sabrotones reverb by harald..but i bet that pops too..
http://www.sabrotone.com/?attachment_id=2763

[samhay]

It might, but it's working a little differently - the dry signal is never lifted (it won't do 100% wet) and is high-impedance going into the non-inverting input of the output op-amp.

The bypass arrangement you have came from slacker right? Might be time to see how much joy he has had with it in the real world.

Edit - actually, thinking of slacker. You could try to go back to FET switching and use his FET switch-with-an-RC (http://www.diystompboxes.com/smfforum/index.php?topic=101126.msg939855#msg939855). You can still do the switching with a DPDT this way...

[deadastronaut]

yeah, i'll ask him by pm and see if his experience is any different..


going back to the electronic switching..

what was the bias lark?..

[samhay]

If I recall, the bias lark involves putting the signal at Vb, which is what you had on the breadboard earlier today.

For another approach, see my last post - you would need two FET switches.

[deadastronaut]

ok, cheers man, i'll check that out.

2 fet switches?..

[bluebunny]

Not sure if you've seen this before, Rob (or if it's already been mentioned in this thread), but R.G. (who else?) has a handy article on CMOS switching here.  Talks about biasing, too.

[deadastronaut]

cheers marc: i was looking at the 4066+4093 setup as i have those..

but will they be properly 'silent' though?

[samhay]

Not sure if you've seen this before, Rob (or if it's already been mentioned in this thread), but R.G. (who else?) has a handy article on CMOS switching here.  Talks about biasing, too.

Ah, that's what I was think of.