Playing around with a long delay

[goroth]

I think the hype is right dude. There is so much boutique stuff put together by people who don't know anything about anything, they can't even solder their 35 year old circuit right. And then they charge a couple of hundred for that privledge. You think outside the bis, have the skills to implement it, an eye for the aesthetic and you're musical enough that it's not just random crap but actually cool for people who love making music/noise.

[cloudscapes]

[fever606]

Bonkers. In the absolute best possible way.

[oscillofuzz]

So cloudscapes, when designing such a delay (with long delay times possible), is it doable to include fx send/return jacks for the repeats in the circuit like the TimeLine, Deluxe Memory Boy, Moog MF104 etc. have? There's currently no delay pedal with as long delay times as yours has that also has the fx loop option for the repeats, but I have some sweet ideas for using such a feature...

[cloudscapes]

It's doable, but kind of needs to be designed with it in mind, rather than hacked in. It's hackable, but awkward. I may or may not include that in a future revision. For this first pedal, I didn't because I absolutely wanted to keep it that size. For my personal use at least.

[oscillofuzz]

That it's doable means I should really get into circuit designing instead of 'just' building kits, and because it's digital I guess I should learn a programming language too? I wouldn't have the slightest idea of where to start...
Got any tips maybe?

[cloudscapes]

Got experience with DIY in general, though?

The easiest way to start a delay would be one of the million pt2399-based projects/kits that are all over the web. One of the Rebote versions, they're the most popular. I'm sure there's more than one of them somewhere that have a send-return on it for exactly what you mentioned, external effects in feedback loop. No programming needed for these.

But the pt2399 is limited. It can't do reverse, and you can't do longer than <1 second unless by hacking several together. I know it's been done, though I haven't looked into how.

For programming a delay, the "easiest" way to start off with just be arduino. Everything they make is user-friendly and a lot of it geared towards people just getting into that sort of stuff. A lot of people take it up without any experience in the hardware, since arduino supplies ready-made boards, but then you'd end up bolting an arduino board inside a pedal. It would "work".

I don't have any experience with arduino personally, though, so I don't really know what it's capable of. So I apologize for not being able to give something specific . I do know there are several kits available of different "computing power". The lower end ones might enable you some very short very lo-fi delay, "worse" than any pt2399 based delay, while the higher end ones might enable something comparable to mine, thoguh at a much steeper learning curve.

[mathias]

Since we're talking chips like Arduinos, have you tried designing a pedal around an ARM chip for more processing power and memory, cloudscapes?

[cloudscapes]

Since we're talking chips like Arduinos, have you tried designing a pedal around an ARM chip for more processing power and memory, cloudscapes?

That's next on my list. Learning ARM.

It won't give me more memory though. The PIC32s I'm using have a comparable amount of memory to ARM equivalents, and I use external memory chips for this delay anyway. ARM will be a bit more powerful than PIC32, but it won't automatically make my effects better. I'm probably not using the PIC32's at full efficiency either, and in the delay, I'm running them at 72khz, doing all sorts of stuff at the same time, the ringmod, normal modulation, sampling the 4 digital pots, other stuff. I'm not really bottlenecked by the PIC32's speed at the moment, and more by my lack of knowledge of how to do proper DSP and just being bad at math. Somebody smarter than me could take the same hardware and do something that seems more "powerful", I'm sure.

[mathias]

Would a chip with DSP built in (again, there's a learning curve) be any more useful? I guess it isn't so much about whether it will make the effects better but more processing power might give more breathing room for worrying about timing and how many things can happen 'simultaneously'.

I'm at the other end of the spectrum, programming at a very high level on small ARM computers that are running a full OS.. It's nice when I want to integrate some hardware and the programming is high level and timing is never really a concern (other than debouncing, and there are simple ways to deal with that.) That said, I haven't tried to create a digital or digitally-controlled analog guitar effect. Just analog kits and some simple fuzz circuits in my hobby builds in the past.

[cloudscapes]

(continued)

The reason I want to (eventually) move over to ARM is more subtle.

They have better on-chip ADCs. 12bit instead of 10. I don't use these for sound, but it'll give me a bit higher precision for the smoothness of pots.

They have more timers, something like 12 instead of like 5 for the PIC32. It doesn't affect sound quality, more like affects features. Like in the delay, I have the main samplerate as one timer, the low-speed pot update stuff on another, modulation on another, ringmod carier oscillator on yet another, and I think I have one left. More timers just means I can have more stuff running at different speeds and with different control over speeds. I could put it all on the same timer, but it wouldn't be optimal, or elegant. And performance would probably suffer,

The extra MHz ARM have over PIC32 certainly would help, even if I can't use either to their full potential. And as I've said, I'm not currently bottlenecked by that at the moment (getting close, though).

Some other stuff. ARM have a hardware FPUs, meaning they can juggle floating point (fractions) pretty well. I won't have to hack it as much as I do in PIC32.

The PIC32 IDE I use unfortunately doesn't support I2S very well. Actually in its listed supported chips, it has none that have I2S, which is really perplexing. I2S is an audio protocol when connecting the microcontroller (whether arm or pic) to a codec/adc/dac. The makers of the IDE I use perplexingly don't support PIC32s who have I2S. Some people on the forums have guessed it might have to do with some legal things, but who really knows. Anyways,

[cloudscapes]

Both similarly speced ARM and PIC32s have DSP stuff built in, even if they aren't dedicated DSP chips. Some have even said that they have enough of it that it's not worth using a real DSP anymore unless your're doing complex physical simulations and whatever. ARM can do floating point better. And like I said, I'm more limited by my lack of DSP education/knowledge than by the power of the chips I'm using.

ARM OSs are neat, I wonder how much overhead they take away.

[mathias]

Ah, when I say OS I mean Linux -- so it's basically a full computer that you could use as an underpowered desktop/laptop (with a usb keyboard and mouse, and an monitor adapter) -- the Raspberry Pi (which seems to be the Arduino of cheap Linux boards) is a good example. Haven't tried to do any audio stuff with a Raspberry Pi, it's been mostly buttons, LEDs, and sensors like motion and temperature sensors for a project I built with a RaspPi in it.

[oscillofuzz]

Oof, that escalated quickly. I'll start by responding to the first post made you made after my last one.

Got experience with DIY in general, though?

The easiest way to start a delay would be one of the million pt2399-based projects/kits that are all over the web. One of the Rebote versions, they're the most popular. I'm sure there's more than one of them somewhere that have a send-return on it for exactly what you mentioned, external effects in feedback loop. No programming needed for these.

But the pt2399 is limited. It can't do reverse, and you can't do longer than <1 second unless by hacking several together. I know it's been done, though I haven't looked into how.

For programming a delay, the "easiest" way to start off with just be arduino. Everything they make is user-friendly and a lot of it geared towards people just getting into that sort of stuff. A lot of people take it up without any experience in the hardware, since arduino supplies ready-made boards, but then you'd end up bolting an arduino board inside a pedal. It would "work".

I don't have any experience with arduino personally, though, so I don't really know what it's capable of. So I apologize for not being able to give something specific . I do know there are several kits available of different "computing power". The lower end ones might enable you some very short very lo-fi delay, "worse" than any pt2399 based delay, while the higher end ones might enable something comparable to mine, thoguh at a much steeper learning curve.

The experience I have with DIY in this context is building kits, so I'm still a total noob to the game. I'm planning on doing a PT2399 build soon for the practice/fun. The next step after kits would probably be to get a breadboard set up so I can lay out/prototype the vero designs you can find online and experiment with component changes.

A PT2399 based design wouldn't get me where I want to be in the end, though. I'm looking for looong delay times (like the times on your Mechanical Sun) with the addition of an fx loop. 1 second won't cut it for the things I'm envisioning, and besides, those needs are covered by what I currently own (Moog MF104M Super Delay).

Getting into Arduino seems like a good start, even if just to learn more, I'll look into what is needed in the next few days. And I'm going to google ARM because I have no idea what that is
How did you get started with programming the PIC32's you use? Which programming language would one need to learn for those?

[cedarskies]

as someone who wants to get into DSP but is too intimidated by it, i really appreciate this page