Effects Loops in pedals (delays mostly)

[lotus_eater]

Would it be hard to mod an existing delay pedal to have an FX loop (one that affects the delayed signal)? I've been looking for the last couple of day and can't find anything on the internet so I thought I would ask around.

[multi_s]

it will depend on the specific delay circuit.

most analog delays id say yes, most digital delays you will probably be out of luck, but it depends. delays based on the 'pt2399' chip for example, which is digital, coudl still be modded to do what your thinking.

[lotus_eater]

So something like the echobase ( http://www.diystompboxes.com/smfforum/index.php?topic=60662.0 ) this could be modded that way?

[multi_s]

i would say so.

[crazynoises]

I think Keeley has a DD-3 mod that does it, but I have no idea how he pulls it off.

Rather than try to cram an effects loop into an existing pedal, I just built one of these:
http://www.guitarpcb.com/apps/webstore/ ... ow/3456364

Or you can build the ROG splitter/blender or a paralooper. There are PCB's and/or tagboard layouts for all of them lying around.

The disadvantage is that you are using two separate pedals instead of one. The advantage is that the split/blend thing is basically a mixer so you can use one channel for any kind of fx loop you want. You aren't limited to just using it on the tails of a delay. And you don't have to crack open and quite likely rehouse your delay pedal.

[mysteriousj]

Yeah man you can do it. To do it properly you need to add on a dual op amp and use two switched jacks, I can post a schematic from one of my projects if you're keen?

[Chankgeez]

Doesn't the DMB Lunar Echo have an effects loop?

[crazynoises]

There are several pedals that have them.

If they don't, it's a matter of whether there is an easy place to splice the signal out and insert the loop. I guess for most modern, lots o' knobs, boutique-ish pedals there are pots to set the character of the echoes even switch between types of echo like tape or something. And I suppose right there or right before it is where you would look to splice and reroute. But you have to find some extra space to put the jacks and stuff.

There might be a simpler way I have missed.

[mysteriousj]

Another thing too.. is whether you put the loop before or after the feedback. If you put it before the feedback any change in gain makes self oscillation much easier, any change in frequency response means every repeat gets more and more filtered each repeat etc.

If you put it in after you just simply get the effect on the repeats. This can be the safer option in some ways basically because any even small change in gain or frequency response can make things start to get crazy - which can be cool but sometimes annoying - some pedals simply won't work either. So really depends what you're after.

[Dr. Sherman Sticks M.D.]

it will depend on the specific delay circuit.

most analog delays id say yes, most digital delays you will probably be out of luck, but it depends. delays based on the 'pt2399' chip for example, which is digital, coudl still be modded to do what your thinking.

yea i have a delay that i'm pretty sure is based on this chip and it has an fx loop. its def a digital delay

its called the space time continuum or something like that. it was made by experimentalists anonymous.

here is a link to some discussion regarding it: http://experimentalistsanonymous.com/board/index.php?topic=1684.0
might be helpful for your research/doing your own mod

[lotus_eater]

Yeah man you can do it. To do it properly you need to add on a dual op amp and use two switched jacks, I can post a schematic from one of my projects if you're keen?

That would be fantastic!

[mysteriousj]

Alright, so the two op amps are just buffers and so remove/add bias as well as prevent things being loaded down etc. In some designs you might get away with only the 2nd op amp but this way makes things pretty much universal. Note R93 won't be needed in most cases but it will be if you want to do this on an echo base as above.

For the jacks, they have to be switched. Something like these http://www.ebay.com/itm/4pcs-1-4-STEREO-PCB-PANEL-MOUNT-HEADPHONE-JACK-2340-/121025994946?pt=LH_DefaultDomain_0&hash=item1c2db620c2
You can also get NYS2152 from smallbear which will work.

In the diagram above Pin 4 of the jacks is the contact that makes a connection with the tip. When a plug isn't inserted pins 3 and 4 are a short. and so if there is nothing plugged in it will just bypass the fx loop. If you insert a plug pins 3 and 4 are open and so it will run through the FX .

You could also just use normal jacks and use dpdt to switch the loop on or off. But I prefer the above and just turn off the fx in the loop if I don't wanna use them.

[lotus_eater]

Sorry I havent had internet for a while! Thanks so much for posting this!