Pedal switching matrix with the AD75019

[R.G.]

I get sucked in by shiny things every so often.

The AD75019 crosspoint switch that got mentioned and I picked up on has done so. It looks like a good solution to making an any-order programmable switch setup for a pedal board.

I got carried away with it and did some trial layouts. Looks like the chip itself is, as expected, trivial compared to the mess of wiring needed for the jacks. I set the jacks part of it up as a modularly expandable array, an input jack and two loops, and output jack and three loops, and a section of five loops, so you can have a five-pedal router, or a ten or 15 by inserting one or two five-loop sections.

The odd arithmetic is because one in and one out of the 16x16 cross point array is taken by the input jack and output jack, so only 15 ins/outs are available for pedals. The switching chip is a tiny wart on the wiring and PCBs for the jacks. A 15-loops setup will be as much as 30 inches wide. Possibly this can be cut a bit by using vertically stacked jacks, but those are hard to deal with in setup, I think.

The tougher questions then becomes how a user will interact with this mass of switching. I don't like menus and scroll bars for controllers. I'm still working on how to let the guitarist see what he's doing. A 16x16 crossbar switch is a seriously capable setup. Any one of the inputs can be connected to any one *or up to all* of the outputs at any time. So can the other inputs. It's entirely possible to tell this thing to do things with signal routing that you do NOT want it to do.

So some kind of processor needs involved to read what the guitarist says, then interpret that into a sane routing setup inside the crossbar that does what a human would expect it to do. I'm actually thinking of hexadecimal (0-9, A-B-C-D-E-F) loop names rearranged on a screen showing the actual routing order and which one(s) are on in a set of loops. It gets tricky because there is no longer any physical connection between the order of the footswitches and the order of the effects in the chain, nor to which effects are on at any time. There's probably a two-beers limit on using this in a sane way.

[R.G.]

Hmmm. Display is a REAL problem. I may have been right: the right display is an old, otherwise useless laptop.

The fundamentals of working this (IMHO) require that the user needs to see a definitive display that tells him what set of stuff is playing. There are two situations that need covered, one a quick-and-dirty one while playing and another which may need to be more detailed while programming the unit.

On stage, you want one stomp to give you one set of pedals active and a rearrangement of those. You also want one visual indication that you got what you wanted when you stomped. And audio indication is OK when engaging a distortion from clean, maybe, but for subtler rearrangements and selections, that is (IMHO) not quick and effective enough for on-stage operation.

Yeah, sure, you can do the MIDI banks/programs number thing. Sucks (IMHO). The objective of music is not to make the musician memorize letters and numbers in so far as it can be helped. If the difficulty of displaying which pedal is on in a fixed order of pedals is N, the difficulty of displaying which pedals are on and which order they're in is at least N²; worse, the nonblocking crossbar offers you the possibility to do combinations and selections of sets of pedals (I/Os) in parallel/series/mixed. That is maybe N³ difficult.

Maybe text is the way. Perhaps you could just call your newly minted selection/rearrangement/series/parallel combination "Mellow Atomic Laser Blast" or something.

I'm currently chasing using a setup using 2" high 16 segment LED displays on the top of the unit. But velcro-ing a laptop to it is about the same cost and more flexible. 

[mth5044]

I was thinking something way dumbed down from that. One wide rectangle, 15 loops, in and out, with each loop have a dual sevens digit number display number display. The only interaction would be the up or down button next to the display. No bypassing footswitches, no loops within loops, just straight up a row of 15 loops. Set in the back of the board, rather than the front so the user would still use the bypass switches of the pedals themselves. I think the days of the LoopMaster-esq true bypass strips are over (or maybe everyone already has one).

Them simply rearrange you're pedals as you want with the number system. I'd the board reads 1 - 15, they are in the order you want them in. If you want that wah fourth in chain instead of first, push the button until 4 comes up on it's display.

Perhaps using the chip in this way isn't taking advantage of all the possibilities.

[R.G.]

It's a reasonable idea. It's another variation of the number-per-loop thing. It is actually kind of my current favorite turned inside-out.

I was thinking that each loop would be a fixed number, right to left of 1 to 15 (Hexadecimal "F"). You'd set up the thing so that each footswitch would bring up one of 15 (or "N") possible rearrangements of those loops, and the display would show something like "8237A41" for one footswitch, then when you pressed another footswitch it would change to maybe "4B31" and another footswitch could be "F2AC57681347". Gibberish, yes. But as a name for one "program" it's highly recognizable to the guy who set it up. And for tinkering and setup, you could recognize that '4B31' was the fourth pedal from the right, the B-th (i.e. 11th) pedal from the right, the third pedal from the right and the first pedal from the right. A simple string of pedals in order from left to right is "123456789ABCDEF" if all pedals are in.

The problem with all of this is having to make a guess which form of displaying the information is better for the variety of human minds reviewing it as they punch footswitchs in the middle of the song. And humans being humans, some will like raspberry and hate avocado, while others will prefer chicken with garlic sauce. And once you've decided how to accommodate the humans, it has to then be buildable, and then it has to be buildable at a reasonable price and difficulty.

Pesky humans.   

[PRR]

> thinking of hexadecimal (0-9, A-B-C-D-E-F) loop names rearranged on a screen
> The objective of music is not to make the musician memorize letters....

Every Good Boy Does Fine?

Hex-code initially (or just A-0); then ask user for "names". Muff, HardOn, Phazer, etc. There is a compromise between a fully descriptive name "Roland BOSS Special Edition distortion pedal with next-generation technology" and display space "Roland BO"; let the user work it out.

> the right display is an old, otherwise useless laptop.

I'm having bad luck with not-so-old laptops. While I have one working flaptop pushing 10 years, others have failed in 3. (FAILED, not just user-garbled, which happens a lot.)

Also think a pack-up nightly gig will be harder on a laptop than "normal" laptop life. When I laptop just to laptop, I carry it carefully. Gigging, it gets thrown in a bag in the truck and then the trap-set falls over on it.

And MS/Apple ecosystems are about forcing you to new versions, which sometimes break old code. I am very peeved at Win7 because real-simple DOS apps are just shut-out, and some XP programs fall-down.

Raspberry Pi with its linux. Old unix code usually just works, and new code should just-work for many years. RaspPi is flash-drive and fan-free, mechanical wear-out is nil. Cost is small. Various displays are possible, from 2-line LCD to 84-inch TV. Display configuration will be a problem as long as we are on X-windows from 1980, but change may happen in our lifetime.

There is a sound-path program JACK for unix (and others). http://www.jackaudio.org/ For software interconnect (virtual pipes), and JACK itself is a daemon, there are various user-interfaces available. I have not explored it. However many musicians use it post-processing (maybe live?), so there is community support. The several interfaces may suggest what works for users. The fact that it is poking a hardware matrix instead of data-streams doesn't really change the interface issues.

> A 15-loops setup will be as much as 30 inches wide.

Studio patchbays have a large number of 1/4" jacks in small or very-small space. Yes, they are tight and can be a pain to re-patch; also to navigate. And the archetypal telco plug/jack is not the Switchcraft cheap copy, so may not be best even if you can afford the startlingly high prices and can find a configuration without excess frills.

You could sell (extra profit) dual-1/4"-to-1/8"-stereo cables; Fit pedals one end, compact at the other. But I hate affordable 1/8" plugs (had a synth-ful) and also special cables.

[PRR]

Raspberry Pi

https://www.adafruit.com/categories/105

Raspberry Pi 2 - Model B - ARMv7 with 1G RAM $39.95
Raspberry Pi Model B+ 512MB RAM $29.95
PiTFT - Assembled 320x240 2.8" TFT+Touchscreen for Raspberry Pi $34.95
HDMI 7" 800x480 Display Backpack - With Touchscreen $89.95
Adafruit Blue&White 16x2 LCD+Keypad Kit for Raspberry Pi  $19.95
5V 1A (1000mA) USB port power supply - UL Listed  $5.95
And much more......

$30 gets a camera. Point it at pedalboard. Snag images for pretty display. Watch player's finger point "here" "here" and make that connection. (Much ambiguity processing needed....)

Well into $100 for "display" on a $14 matrix. However your box and jacks will force a high price. Interface makes/breaks the idea. (If it frustrates me, I'll go back to hand-patching.)

[dschwartz]

What's the goal?
Making a looper that allow the user to change the position of each loop on the chain? And with a user friendly interface?

If that so, i think these things..
- it is really necesary that all of the loops are movable? Do you think of someone that uses 15 pedals and needs 15x15 combinations? will this guy ever going to use 1% of those combinations? Like putting the reverb before the distortion and compression is something attractive to users?

What about a looper separated in blocks..you have 12 loops, and you separate them in 3 blocks, first, middle and last.. So for each loop program, you assign the parameter "position" for each loop..so instead of scrolling  12 times for each loop, you select if it goes first, middle or last..the order inside each position block is given by the natural position of the loop..visually you could see in what position block each loop is by a 3 color led..and just a number for each program.

If 15x15 combinations are needed, the simplest, most friendly interface is the dot matrix, where x is the loop number, and y is the loop position..

[R.G.]

What's the goal?
Making a looper that allow the user to change the position of each loop on the chain? And with a user friendly interface?

What goal??    I was just distracted by a Shiny Thing.

[PRR]

> distracted by a Shiny Thing.

While I was writing that, a new shiny thing appeared: a $7 Rasp Pi.

Sold-out in 12 hours, but is clearly going to be a stock-thing.

Doesn't help with the high cost of jackery and panel space.

[R.G.]

I replaced the single jacks with vertical stacked pairs and got the total length down to about 17", so it would be simpler, but still it's a lot of space. Not to mention the sheer thickness of 32 phone-plug cords in and out of it.   

And once again, by the time you pay for the box, the switches and the jacks, the electronics may as well be free.

[stallik]

And once again, by the time you pay for the box, the switches and the jacks, the electronics may as well be free.

If someone wanted to build a whole number of effects into one big box, you'd save the jacks and cables but then it would be a whole different beast

[PRR]

> vertical stacked pairs and got the total length down to about 17", .... 32 phone-plug

The traditional fill for 17" rack, double-stack 1/4" telco, is 48 (2 rows of 24).



This may not be possible with our usual guitar-amp jacks.

Telco jacks were *designed* to fit close. (There was a time that every telephone customer had a jack on an operator's panel.)

[mth5044]

This would pretty much be a no-go for anyone who uses those HOSA pancake cables.

[R.G.]

Seriously, folks. The jacks and wires are not the problem. The user interface is the problem.

[kleber.kag]

Yes it is, anyway I like these ones from Amphenol
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTjUx-ATTZrdxVmdueogIufmysac0Y9263pX6gNxNQ0RHQxJpPB

[kleber.kag]

I mean, the user interface is the problem.

[jubal81]

For simplicity and as few knobs as possible, what about one of those rotary encoders with a built-in push button?

Hold down stomp switch for a loop to go into program mode for that selection, then cycle through the loops with the encoder and press it on the selections you want active on that preset. A long press on the rotary encoder button could put it in manual, on-off operation on each loop.

[stallik]

I'd  go for a touchscreen interface looking like a visual representation of a pedalboard. User can simply move any pedal to a different location and other pedals would move out of the way, patching would re route automatically and rules could be put in place to prevent stupid loops. Tap to turn pedal on and off.
This part, I can do. Prog would output the required sequence in any format required but Interfacing with the switching circuit however, is rocket science as I don't understand what's required.
And. The cost has gone up yet again with the addition of a tablet or at least a pi & touchscreen

[digi2t]

So, one of these....



into one of these...



OK, a bit of a simplistic view, but I'm digging it.

R.G., if it helps, I can email you the complete manual for the AM-16, which includes the schematics for it (too heavy for gallery upload, 7+ megs pdf). I also have the bin file for the eprom on file. It might give you some insight as to how this 16x16 matrix was set up back in the day.

Personally, I love my AM-16's but the buffers could be much better.

[R.G.]

I'd  go for a touchscreen interface looking like a visual representation of a pedalboard. User can simply move any pedal to a different location and other pedals would move out of the way, patching would re route automatically and rules could be put in place to prevent stupid loops. Tap to turn pedal on and off.
This part, I can do. Prog would output the required sequence in any format required but Interfacing with the switching circuit however, is rocket science as I don't understand what's required.
And. The cost has gone up yet again with the addition of a tablet or at least a pi & touchscreen

Yeah, I was trying to find a way around that, something that's more palatable to DIY hackers that have only a meter, a soldering iron and a stone axe.  But it may be that the optimum interface is something like a Raspberry Pi and a touchscreen, which is what I think you meant. I didn't do a complete rundown, but it looks like touchscreens for RPs are in the US$80 and up range, the RP itself is US$35-50 depending on supplier, so the UI, before programming, costs something like $125 by the time you actually get it running.

I have messed a bit with using LED character displays, something like a 14 or 16 segment display per loop. It's far less capable than a touchscreen. The parts cost runs up there too. Per-channel cost is about $2.50 for the display, $1.00 for the drivers, another $0.50 for the miscellaney, so you're up at ~~US$64 and up even using the cheapo setup.

Both of which merely confirm that conveying both on/off status and order for 15 loops (one is needed for the box in/our) is complicated if you don't make the user do the heavy mental work of remembering that a Bank 6 Preset 3 is the sound they set up back in the studio when they were prepping for the gig, and two beers ago.   

Like Einstein said: everything should be as simple as possible - but no simpler. There is a limit to how simple you can complex setups for people if they're to be self sufficient with the tools.

So, one of these....
...
into one of these...
...
OK, a bit of a simplistic view, but I'm digging it.

Pretty much right. The single-chip crossbar makes the actual switching easy. But it won't easily replace the three multi-digit LED displays, dot matrix display, and multiplicity of up/down/sideways and other buttons on the front.

R.G., if it helps, I can email you the complete manual for the AM-16, which includes the schematics for it (too heavy for gallery upload, 7+ megs pdf). I also have the bin file for the eprom on file. It might give you some insight as to how this 16x16 matrix was set up back in the day.

Thanks, but I don't know what I'd ever do with it. Hold on to it for now. That unit does this kind of task, but differently in both the matrix switch and user interface. In fact, it's an example of the user interface I don't want to do. I've been working with computers since 1974, and I still don't like forcing the user to match the machine instead of otherwise. People should be free to think and conceptualize, machines should do the heavy lifting to let them think.