cool reverb apart from switch spdt 'pop' issue

[samhay]

slacker - nice idea.
Rob - This is proving to be even worse than preventing a little pop.
With respect to my idea, the brick may be struggling with the 10k load of the feedback pot. You could try increasing this to 100k (which is what I have on the breadboard with my design, but can't remember if this is because 10k didn't work right). The output of the brick will be ~ half, so dropping the 33k resistor was a good idea.

[deadastronaut]

slacker - nice idea.
Rob - This is proving to be even worse than preventing a little pop.  yeah i know.  
With respect to my idea, the brick may be struggling with the 10k load of the feedback pot. You could try increasing this to 100k (which is what I have on the breadboard with my design, but can't remember if this is because 10k didn't work right). The output of the brick will be ~ half, so dropping the 33k resistor was a good idea...just tried a 100k pot, and messing with the 33k...no difference really..

''Or bypass the whole shabang, that will definitely work, it feels like a horrible bodge though.''

may have to be the way to go...hmmm...

[slacker]

slacker - nice idea.

Cheers. shame it didn't quite work, handy little snippet to have around though

The reason taking feedback from the output of the brick doesn't work too well could be down to phase. The datasheet doesn't say but I assume the output is notionally in phase with the input, as much as it can be for something like reverb. The current scheme inverts the output of the brick and then inverts it a second time before feeding it back in, so it's in phase. Taking the output from the brick and just feeding it back through IC2C inverts it so it's out of phase.

Give this a try, this hopefully gives "in phase" feedback. The "Fback" resistor sets the max feedback level start with a jumper and adjust to taste, assuming it works. Might not need the new "R6" try it with and without, with it R19 might need tweaking to keep the levels right.



If this works then we're back where we were about 4 pages ago, you just need a second fet switch to lift "dry/mix" from VB in bypass.

Fingers crossed  

[samhay]

slacker - you are quite right, I had forgotten about the inverting op-amp.
hopefully that will do the trick.

[deadastronaut]

cheers ian and sam for going way beyond the call of duty to help solve this bugger..

i'll give that a go a little later, and yep, i'll have my fingers crossed

back in a bit..

[samhay]

No worries Rob.
Sorry for not catching a few, rather obvious in hindsight, issues sooner.

[deadastronaut]

@ian,  that works and we now have tails with clean guitar.....

however ... immediately i noticed the reverb decay is dramatically cut short. even on max feedback...

and feedback pot is doing nothing.

[samhay]

What value is the feedback resistor you chose?

[deadastronaut]

morning..

i tried from 100r - 4.7M. (using  resistor sub box)

i also tried lowering R5 but it distorted too much.

[samhay]

I'm confused, even if this was an impedance issue, then I would expect the feedback pot to do something - just less than before.

[deadastronaut]

i'll double check it over...i wondered why the feedback pot did nothing too..

back in a bit..

[slacker]

Yeah the feedback pot should at least do something, unless there's something I'm missing what I've done should have positive gain with pot turned up so you should get oscillation.

[deadastronaut]

nope.. just checked,

no change on fb pot at all.....i swapped it for another too..checked connections.

i even tried the 22 to vb, no difference....weird.

[slacker]

I'm stumped, I don't see how this can't work. Have you tried taking feedback straight from pin 5 or 6 of the brick?

[deadastronaut]

just tried that..no difference..on 5/6


just to confirm....pin 10 has a 1M to VB..and pin 10 also goes to 100nf....100k pot>resistor>100nf...>..to junction of 10k pot/10k resistor..

thats how i have it..

just checked my Vb's..all sitting nicely at 4.55v.


from pin 10 to the 100nf i have 4.5v...pot side of 100nf is 0.00v.....resistor>100nf..output 5/6 side of 100nf is 4.5v..

measured resistance on pot..working fine..

[slacker]

Yeah that's it. I think we need to do some testing, disconnect C12 from the junction of the 10k and 10k pot, and instead of plugging your guitar into the input of the pedal plug it into C12, this should then give you wet reverb on the output. The pot should control the level. Does that work.

[deadastronaut]

hold on...

aha...dumbass that i am...   (just slapped myself and the cat .)

i still had a wire from pin 10 to vb....whilst connecting the 1M from pin 10 too...

so now we have oscillation again....and switch works....but cuts tails off quick still. (even at oscillation)

[slacker]

Yaaahhhhhhhhhhhh, thank fook for that, I was just about to drive down to the big smoke and throw the fecking thing through the window for you 

Does adding the extra 22k help with the tails? If it does you could try making it smaller which will increase the gain.

[deadastronaut]

ha ha your welcome to throw my cat out too...

tried the 22k, i just turned my mixer up and there is a faint hint (but noticable ) of verb when bypassed (plucked hard) (fet switched off)

if i put that 22k lower it brings out more verb...and tails oscillation. (fet switch off)

if i turn feedback right down there is no background reverb at all.....

tails are better but still unaturally decay quick when switched.

[deadastronaut]

heres a little sample , fully wet, with delay...

ahhhhhhh chillll.....

https://dl.dropboxusercontent.com/u/7464107/deadastronaut%20wet%20reverb%2Bdelay.mp3