Pedal switcher ideas

[Mattnezz]

I've been using my diy programmable effect-loop-switcher for quite some time now and I don't want to gig without it.
It has 9 TB loops and an A/B/Y switch, all programmable to 8 presets over 10 banks. I have a booster under the 9th loop which can be activated regardless of the mode (edit or preset) but can be programmed aswell. Same goes for the A/B/Y-switch.
I use a modified Roland FC-100 to do the switching and programming, from there I run a 5-wire cable to my pedalcase full of relays, effects and jacks.

Awesome, but I thought of an update...

I'd like to switch 8 fx-loops in any order and add a programmable level-control to each (A and B) output to skip the need for my current underdrive/boost situation. Maybe a switchable inputbuffer. These are the basic needs.
When you put effects in any order, I guess the user-interface poses the biggest challenge. I use an Arduino, or the bare 328P chip, and my beginner-program-skills are not that good. But I managed to get the user interface working, 'though maybe inconventional.

Like my other switcher it has a 'preset-mode' to call presets and an 'edit-mode' to edit them.
To tackle the order-problem I used 2 modes under edit.
Mode 1: effects are added to the chain in their physical order, so if you have a Fuzz in the first loop, it stays there.
Mode 2: effects are added to or removed from the chain in the order of activation.
So if you first press loop4 (phaser?) on and then loop1 (fuzz?) on, the order of fx will be: IN>loop4>loop1>OUT.
If you press loop4 again, so it's off, the order will be: IN>loop1>OUT
If you press loop4 again, so it's on, the order becomes: IN>loop1>loop4>OUT

To keep track of all this switching mattnezz, I use a small cheap 128x160 pixel TFT-screen. (The 16-bit colors remind me of Nintendo's  )
It displays patching, output selected and I gave all loops/pedals a designated color.
So-far it looks like this. (drawn pixel by pixel    )


How to do the actual switching? Well, I'm really in doubt what physical switches to use!
To realize this I need a couple (10 pc) of digitally controlled say 1P8T switches. But I really need to be able to send that 1P to one or more of the 8 throws for splitting/summing purposes.
I first designed a solution consisting of a 74HC595 or a CD4094 SR controlling 2 CD4066's, but had problems with headroom and/or logic level-shifting. I also opted for the DG112 as an e-switch to solve headroom en levelshift problems. My code works with this setup, I just shift the switch/gain/led-data bytes and magic happens.
Looking further for an electronic solution i stumbled upon this topic on the AD75019, a mighty matrix switcher indeed! I consider this solution, as one of the cheapest, but my lack of programming skills worries me (how to make the 32-bytes data toggle the right switches?) and I worry about electronic switching (in large quantities) in general.
It needs buffering for each input to get the sound through. Guitars and a lot of stompboxes are fairly high impedance, while most e-switches seem to perform best at low impedances.
Now I'm really considering an old-skool solution too... relays. Bulky and expensive, but I found someone selling Chinese reed-relays under 50ct a piece. Nice, since I need about 80 of 'em.  specs: 5V, coilR=500 ohms, so a single relaycoil draws about 10mA. This means that if I only activate a couple of the 8 reedswitches at a time, I could even drive them directly with a cheap 74HC595. Most of these SR's can source/sink 20mA/output and something like 30~40mA per package.

What to do, what to do? 

[antonis]

Nice, since I need about 80 of 'em. 

Perhaps you'll also need about 80 of 1N4004 for back-bias..
(or about 80 of 100R + 47nF for RC snubber in case of ac relay driving..)

[Mattnezz]

I guess a couple of 1N4148's over the coils will do, they come cheap in bulk.
I'll drive the relays fairly simple, DC, and try to let the 595 sink current for active ones.
I'll try to use the 595's as a low-current ULN2803.

I like to put the 1x8 switches on small pcb's, to be able to mount them vertically on a 'motherboard'.
Something like this sketch:

If the reeds are too close and the coils interact (do they do that?), I might solder half of them to the underside of the pcb.

This way a 1x8 switch will cost about $6~$7 a piece, I don't know if it's worth the money though.
Yes it has 200Vpp headroom, but I dont know how many cycles the switch will survive and if it's better or worse than the electronic solution...