Buffered Feedback loop!

[djwackfriz]

Hey Folks! I've been messing around with this idea for a bit, and just had some time to throw something together. It's essentially a feedback loop with 2 LPB's in it, as suggested by Colin from EA (Thanks for all the suggestions on your site dude!)

I'm having some trouble figuring out the switching, since my needs are kind of different from the typical bypass loop. I actually don't want bypass; Instead, I want a "Feedback On Demand" type of routing, with signal always passing through the box, and buffered feedback when I activate the switch (my pedals are all true bypass, so I don't really need a bypass box at all). Also, I only want the buffers to affect the feedback loop when engaged, and not when the switch is off.

I started to draw a signal path but am having trouble:
1) figuring out how to route the signal through the buffers by way of the switch, and at which point to place the buffers themselves (Colin suggests one "within the loop" and one after it)
2) wiring the switch!

Anyone able to make corrections to my diagram or offer advice?
Thanks again in advance for any help, I really appreciate all the knowledge on this site!

[djwackfriz]

Bump! Am I way off on this?

I know I need to always connect the Input to the Send and the Receive to the Output for when the effect is diseganged, but I'm not sure how to organize the loop from Receive back to Send utilizing the LPB's and the switch!

[ambulancevoice]

hi, sorry i didnt reply to the email, i forgot all about it
so i might aswell reply here

this is what you need

[djwackfriz]

AWESOOOME! Thanks a lot dude, I actually had a dream about this circuit last night and it involved a DPDT, I guess I'm starting to get the hang of this!

One last question - I have a 500K pot to control feedback amount, where does that need to go? On an unbuffered FB loop it goes between send and receive...

[ambulancevoice]

on an unbuffered version, the feedback pot would be wired like a volume pot between the send and the return
on this buffered version, the lpb (between the feedback loop) volume/boost pot is also acting as the feedback pot here
so the 500k pot isnt needed

[djwackfriz]

Awesome! And when this circuit is off, will the pedals in the send/receive loop function normally?

[ambulancevoice]

yeah they will
because you cut of the feedback connection, the pedals no longer feedback bettween eachother, and the signal just runs through them normally
also, the first lpb make the input signal louder even when the feedback is bypassed, the boost level can lowered still, but you might wanna make sure thats ok with that guy your making this for

[djwackfriz]

OKOKOK, one more question -

What would be the drawback to using just one LPB between the Send and Return, and making it switchable ON/OFF? Would this create noise issues or screw up the buffering? Because I'm finding that that second LPB may/may not be necessary or helpful in the permanent signal chain... would this setup still create feedback that is audible?

Edit: I decided to try to find a way to bypass both LPB's in the OFF position, and then Turn them all on in the ON position. I switched to a 3PDT, and moved the +9V of everything to the switch. I also tried to route the INPUT to the SEND on the third column of lugs. Does this look at all correct? I'M NEW!

[ambulancevoice]

actually, doing it that way would just cut out the signal entirely
probably the betterway to do it would be to use a 3pdt footswitch to bypass the input lpb (with an led) or just using a dpdt (with no led) and keep the other switch that cuts the feedback as it is
like this

for no led on the 1st lpb bypass, just use a dpdt and cut out the led part of the 3pdt bypass

also, i added a output volume pot cause i just remembered that a feedback loop can make very loud sounds if your not careful

[djwackfriz]

This is looking pretty cool! Thanks for all the help Alex, I owe you beer if you ever come to NYC!

I wonder if we can eliminate one volume pot by just moving LPB#1 over to the line between Return and Out...? That way the feedback loop has a volume, and then there is an output volume that is bypassable with the 3PDT when the FB loop is not active... or maybe it could act as a booster on its own!

[ambulancevoice]

nope, the first lpb needs to be there to buffer the input signal and help it drive the feedback loop
at the output it would be useless, but you can always put another one there, besides another boost/buffer at output isnt really needed at all