Dual expression pedal in a stomp box for "preset switching" EHX Dlx Mem Boy

mike257

Wondering about how I can get more out of my fave delay pedal, the Deluxe Memory Boy, and I'm thinking of building a foot switchable "two preset" expression pedal in a box to give me a choice of two preset delay times as well as the tap tempo.  Am I right in thinking that all I need to create a single expression pedal is to stick a 10k pot in series between the tip and ring?

The plan, then, is to put a 3PDT in an enclosure with two 10k pots and two LEDs.  I'll use the first two poles of the switch to swap between the two pots and the third to switch power between the two LEDs to indicate which "preset" is active.

The way the DMB works is that the delay time is set by either the "Delay" knob or the tap footswitch, whichever is the last used.  Essentially, this will give me the ability to switch between tap delay and two fixed times instantly, so it'll be almost like having three presets on board.  

Any thoughts on this?  Am I missing anything obvious that will cause this to fail miserably, or other cool tricks I could do while I'm at it?

If this works out, I'm tempted to stick a similar box in the effects loop of the pedal to control the feedback level so I can flip between a "sensible" setting and unity repeats too.  Fun times!

mike257

Had a quick rethink and I'm going to use a bi colour LED and two different coloured knobs to match so I know which one I'm tweaking/using.  Priced the parts up and it comes in at under 20 squid from Musikding.de including a pre-drilled enclosure - if it works out, this might bump the Carbon Copy off the board too.  Think I'll be placing the order when the next paycheque lands.

@ICBM - if I've missed anything daft that will make this not work, you'll probably spot it instantly.  Any thoughts?

mike257

Duplicate post, oops!

ChrisCox1994

I have no idea about how this would be done, i'd be interested to see the results as ive always wanted a 2nd preset on my DMB, as I also use an exp pedal to go from 'normal' to feedbacking delays...

ICBM

Sounds OK, but be aware that some pedals need a full potential divider and not a series resistance for the expression function. You can still do it with a pot but you'll need a TRS ('stereo') cable.

You still only need a DPDT to switch between two of them because the third connection is common (and usually ground, but don't assume so), so it doesn't need switching.

This also assumes that switching between two fixed pots settings is enough to trigger the 'last used' function in the pedal, and I can't help with that, sorry!

mike257

Well, the expression pedal is just a pot with a big pedal stuck to it - I figured if I just stick a couple of pots in a box and a switch to bounce between them, electrically it's the same as jumping to two different spots in the travel of a normal expression pedal so the DMB should see it the same way.  I want to use it to alter the delay time, but would be equally effective with any of the parameters you can control with the expression pedal - if you're using it to alter feedback, you can just set the feedback level for your normal delays on one pot and crank it up on the other and you won't have the guesswork of trying to sit an expression pedal in the right spot for what you're after.  

I've not ordered the parts yet as I'm a bit strapped at the mo but as soon as I do I'll update here and let you know how it works out - a video demo might be in order!  For under twenty squid it's worth a go at least.

ICBM

mike257 said:

Well, the expression pedal is just a pot with a big pedal stuck to it - I figured if I just stick a couple of pots in a box and a switch to bounce between them, electrically it's the same as jumping to two different spots in the travel of a normal expression pedal so the DMB should see it the same way.

Probably. But it might be looking for a changing value, rather than a sudden step. I don't know, and you'll most likely only find out by trying it.