Developing a powerful digital looper project for the DIY community

[aziltz]

any new developments on this project?

[Taylor]

Do you mean the original idea, which was to make a hi-fi powerful looper, or the tangent I went down, which was a glitchy lo fi looper?

The former is not happening at the moment. I have begun learning DSP and will be investigating hardware for it. Since it's such a large project and beyond my personal abilities at the moment, it's a long-term project for sure. It would be great if some of the heavier-hitters w.r.t. DSP would volunteer, but as long as it's just me working on it, it might be a multi-year project.

I have been getting into PICs, and am envisioning a looper based on the ISD chipcorders, which would have something like 4-6 of the chips all linked up by an MCU which would step through them, recording on one while playing back the others. The Tone God said they don't sync up perfectly, but that's not a huge concern of mine. This unit would be more for e experimental/ambient/drone types.

[aziltz]

I've decided to take a look at the ISD17000 series and take a stab at programming a controller for it, much in the same way your tremolo design was done.  I think I do enough programming in research that it shouldn't be to hard to figure it out the logic and the language.  The hard part will finding the time.

[Taylor]

Ok, sounds cool. So this'll be in the tradition of the Payback, etc. more than a modern digital looper? I'll be interested to check it out. Did you get an email from some musicians asking you to build such a thing by chance?  I got the mail as well.

[aziltz]

Ok, sounds cool. So this'll be in the tradition of the Payback, etc. more than a modern digital looper? I'll be interested to check it out. Did you get an email from some musicians asking you to build such a thing by chance?  I got the mail as well.

yes, I've received a few emails and eventually found that thread.  I've made myself a ISD2500 looper in the past, but I won't be making any loopers for bassists anytime soon.  They all want tiny, lovepedal-sized single loopers and I had more of a vision to create a Echoplex-voiced Payback style thing.  Tone God may still beat me to it with v2, but I'm more interested in learning a way to program chips with a fun project.

Both the ideas proposed in this thread were very interesting, I hope they eventually pan out.

[Taylor]

Cool, that sounds interesting.

You forgot to mention that they want those hand-made teeny tiny loopers for less than a Boss pedal! 

Have you looked into the "Where's the party at?"? It's a DIY project that does overdubbing, multiple separate loops, and all kinds of crazy granular loop slicing. It basically does all the usual pedal looper stuff but adds a bunch of weird stuff as well. The only real drawback is that it is 8-bit quality, but you can tack a lowpass filter on the end and it should sound similar to the ISD chips but with a lot more functionality. I bought 2 of the PCBs and chips and hope to start building soon (haven't gotten the boards yet). It looks like a really cool thing and I think this in combination with a Payback 1.0 I'm building will probably end up replacing my EHX 2880. The EHX is of course more clean, but I'm not sure that matters too much for me.

[mth5044]

Sorry if this is a rediculous question, but what is wrong with the example circuit on the ISD1740A/50A/60A or whatever those numbers were?

[aziltz]

Cool, that sounds interesting.

You forgot to mention that they want those hand-made teeny tiny loopers for less than a Boss pedal!  

Have you looked into the "Where's the party at?"? It's a DIY project that does overdubbing, multiple separate loops, and all kinds of crazy granular loop slicing. It basically does all the usual pedal looper stuff but adds a bunch of weird stuff as well. The only real drawback is that it is 8-bit quality, but you can tack a lowpass filter on the end and it should sound similar to the ISD chips but with a lot more functionality. I bought 2 of the PCBs and chips and hope to start building soon (haven't gotten the boards yet). It looks like a really cool thing and I think this in combination with a Payback 1.0 I'm building will probably end up replacing my EHX 2880. The EHX is of course more clean, but I'm not sure that matters too much for me.

is there a thread on the "where's the party at?"  I've been search to no avail.

EDIT: found it

[Taylor]

Sorry if this is a rediculous question, but what is wrong with the example circuit on the ISD1740A/50A/60A or whatever those numbers were?

Eh, well it doesn't have buffers or mixers, and the switching is a little awkward, and the input expects a microphone signal rather than an instrument signal. I think it does have an analog output rather than the speaker out only of the earlier chips, though. Oh, and it doesn't loop AFAIK, so you'd have to retrigger playback each time.

[JKowalski]

"where's the party at?"  I've been search to no avail.
EDIT: found it

[lil PopTart kid]

You guys are being silly!  USE A PIC.  They have 1G of memory they are dirt cheap and easy to work with.  I have been thinking about programming a looper for a while now.  This was just the motivation I needed.  I'll make one and post my finding somewhere on here.  A few questions first how do you guys think it should function?  What would be the best way for all of you?

[Taylor]

Which PIC has that much memory? What kind of bit depth and sample rate does the ADC have? Sounds cool to me, hope that comes to fruition.

You won't get any real consensus, since this is a really open-ended kind of unit and people use them in different ways.

I really like multiple layers that can be independently controlled for continuous pitch/speed control, feedback level, and volume. Something like 4 simultaneous loops would be great. Reverse is important.

[JKowalski]

You guys are being silly!  USE A PIC.  They have 1G of memory they are dirt cheap and easy to work with.  I have been thinking about programming a looper for a while now.  This was just the motivation I needed.  I'll make one and post my finding somewhere on here.  A few questions first how do you guys think it should function?  What would be the best way for all of you?

There isn't any PIC with 1GB of memory!

[darwin_deathcat]

I've been working on an idea to get a second ISD 1700 chipcorder to quantize to the loop point of a first one. Basically, it's the same way you get the first one to loop: route the signal from the -sp out lead to the play input lead. When play stops, the voltage drops to ground, and the chip (almost) instantly starts playing again. My idea is to just route the -sp out lead to BOTH the play switch input of the 1st AND the second chip. You could have the second chip be switchable to quantize either with the loop point of the first chip, or to itself. Adding a third chip, you could then have much more permutations of quantization for the second and the third chip (both to the first, second to the first and third to second, second to itself and third to second, second to itself and third to first, second and third to themselves). Loop length doesn't matter. Say first loop is two bars, and second is 1 bar. Second starts with first, and then stops. When first restarts, -sp goes to ground, and triggers both. Say loop one is 2 bars and loop 2 is 4 bars. Same idea, first loop will go twice, but will trigger the second loop when it ends. The trick will be that you will need to end the second loop a little shorter than an equal increment of the first (ie, if first is EXACTLY 2 bars, you'll need to end the second at 1.99 bars). Otherwise I'm not sure if it will trigger at the right time (ie, if it is too long, it will not get triggered until the NEXT time around).

All the audio is taken from the +sp lead, and will need to mixed down together. I suggest "volume control" style passive mixer circuits for each loop.

I've successfully built a single looper with this concept. It self-quantizes just fine. Not totally seamless, but perfectly adequate for my needs. I need to buy a second ISD 1700 board (the fully populated test boards from digikey are AWESOME time savers!) and some more momentary switches in order to test this idea (slaving the second loop to the quantize point of the first), but I am 99% sure it will work.

[Lurco]

I don`t understand that quantize thing? Is it like synchronizing?

[Taylor]

If you are using two chips in parallel, to record separate parts, you need these two chips to remain in sync. So let's say you record an octaved bassline, then a lead on top on the other chip. If the chips don't remain in sync with each other, then after a little while it sounds like your lead guitar is dragging behind the bass player (perhaps more realistic this way, but most don't want the "guitarist-has-had-3-Jamesons" effect). So you need to work out a scheme where they are clocked together.

That is if sync is a big deal to you. My looping interests tend towards droney stuff where sync is not a real issue.

[aziltz]

Hey Taylor, what was the programmed chip technology used in the Tap Tremolo?  I want to start reading up.

[.Mike]

Hey Taylor, what was the programmed chip technology used in the Tap Tremolo?  I want to start reading up.

PIC16F684. Code, datasheet for the TapLFO: http://www.electricdruid.net/index.php?page=projects.taplfo

Mike

[lil PopTart kid]

There isn't any PIC with 1GB of memory!

Excuse me ment 1MB.  However you can easily hook up extra memory. 
Also If I can come up with a smart way of going about making the circuit
and the program all the memory isn't needed.

And oooo a reverse! I think I saw that one time on an electro harmonix
looper and it was AWESOME.

[darwin_deathcat]

I don`t understand that quantize thing? Is it like synchronizing?

Well, yes, sort of. The Quantize point is the loop initiation trigger point. In more sophisticated loopers, you can set the quantize point to be any even increment or divisor of the loop. So for example, you record a loop that is 4 seconds long. Normally, the quantize point is 4 seconds, so the loop plays for 4 seconds, then starts at the beginning. With a sophisticated software looper like sooperlooper, you can set the loop to quantize at, for example, 8 seconds. So you get 4 seconds of playing, 4 seconds of silence, then 4 seconds of playing again. If you have two loops, you can make the second loop quantize to the start of the first loop (which is the way it "normally" works), so that regardless of how long or short the second loop is, it will always start at the "beginning" of the first loop. With very sophisticated loopers (again, like sooperlooper) you can set the quantize point to be, for example, the nearest 8th note, and thus trigger the second loop BEFORE the first loop ends. If you use such complicated quantization schemes with multiple loops, you get very cool polyrhythms between the multiple loops.

  However, with the way I'm suggesting to trigger the loops with the ISD chips, there is only 1 quantize point per loop. That point is the start of the loop. If you have more than one chip, each chip has it's own quantize point (starting point) that has the potential to trigger the loop to restart. In the case of only two ISD chips, you can either opt to have the second loop trigger based on the starting point of the first loop, or you can have the second loop trigger based on it's own starting point. If it is important that the loops be "aligned", then one ought to take the first option. If it doesn't matter, then you can do the second one. Doing the second one also gives you the option to build looped polyrythms, depending upon the difference in loop intervals and the timing of your loop triggering. Doing this all with the ISD chips and such "analog" triggering methods means that if you want to have multiple loops and have them all aligned on the same beats, you have to be much more precise while setting the loop point than you do with other loopers, who "do it for you".  The advantages of doing it this way are that it's actually cheaper than buying a commercial hardware looper with multiple loops, the whole thing can be powered off of 3AA batteries (ie. it's ultraportable for street performance), you can set up the control layout to be exactly the way you want it (ie. you can put the switches in the box so they fit your needs), and it's totally cool to build your own! The disadvantages are that you can't actually overdub with sound-on-sound, but instead can only just have two independent single loops that are syncing their initial loop points together, you have to be more precise when setting the loops because there is less "fudge factor" than with commercial units, and finally, you have to build the thing yourself which means sourcing all the components, testing everything, assembling, retesting, debugging, retesting, etc, etc., before everything works.