Some questions before I buy a Coyote-1

[sammay]

Hi everyone,

I've been seriously considering buying a Coyote-1, but seeing as it's a fair amount of money (for me) I thought I'd ask a few questions first.

I'm an electrical engineering student who's planning to specialize in digital signal processing, and has embedded systems programming experience (in C/Python/asm). I'm also a bass player who works as a live sound engineer so I figure I'm pretty close to the perfect audience for this unit. I'm involved in the Audio Electronics club at uni and we're thinking about maybe getting one of these for the club to work on projects.

I'm a little worried about being an early adopter though. It's really hard to find any recent reviews with substance. What's the build quality and reliability like - has anyone had issues? If I order from Australia, do I get an Australian power adaptor?

On the software side, what's the state of the non-windows development environments for Mac and Linux? Will I be compiling software from dev sources?

Finally, I notice this thing has a video output. Is the Coyote intended to have more general purpose DSP capabilities - could I use it as a general DSP board? If so that would be really cool. What are the limits for input and output signal voltages and power? (Someone mentioned input signal clipping on another thread)

Thanks a lot for your time.

EDIT From the wiki:

Theoretically Linux compatibility is not far behind, but I have not had time to test the serial port functionality under Linux. Under OSX it was the serial communications which required the most attention.

I have experience with Linux PySerial development and might be able to help here

[howard]

I'm sort of in the same group and bought one. I work in IT(sys-admin), have an electronics interest as a hobbyist(have worked professionally as a guitar and guitar electronics tech), play guitar/bass and have worked as a sound tech.

So far I would say the build quality is very good, that's not really an issue as far as I can see. As an early adopter I can clearly see room for improvement on the software side, but it's not a bad product at all! Sound is good, usability is ok, possibilities are great.

I have several posts here on suggestions so far, mostly on kinks in usability. It doesn't store changes in patches on usage, you have to connect to a pc to do so, which is a bit of a pain.
I'm also eager to see more effects, reverb and flanger/phaser to name a few. The patch editor is quite capable, mostly lacking in proper effects. I think Eric is working on a new distortion, as the one in there kind of sucks...

I'm the one that mentioned signal clipping on the input. One of my guitars have really hot Dimarzio pickups that can be a challenge to amps and effects in general. This one is very hard to use with the Coyote, as it appears to clip before the adc. It doesn't complain in the same way it does when there is a signal overflow(it has an indicator in the display). Unfortunately this is my main guitar, and I'd love to see this work. When time permits I'll probably mod the input stage.

The Mac port is ok, it crashes once in a while(I've used it for some time) and I guess the Linux port will be more or less the same for now, as they both rely on Mono. The is no compiling involved, Eric has made an App bundle, at least for mac. I suspect a deb or rpm will be available for Linux.

This is a Propeller, it can be made to do a lot! I guess Eric can answer the questions about using it as a general purpose dsp better than me.

I live in Norway, where we run 220 volts. It came with a proper switchmode psu with various adapters for different countries, so no problems there.

Activity has been a bit low on the forum lately, don't really know what Eric is up to. Hope he's not letting this go, as it is a great product, it just needs some more development. Feel free to ask more!


Howard

[sammay]

Thanks for replying. If Eric doesn't reply in the next couple of days, I might try and send him an email. The other pedal I'm looking at is the Line 6 ToneCore DSP development module, not sure if you've had any experience with that.

I'm also eager to see more effects, reverb and flanger/phaser to name a few.

Flanger/phaser should be pretty easy to do as a digital effect, in fact it was the first project I was going to work on! Both of those are types of comb filters, that cut out several frequencies with a very specific dip or notch in the frequency response. The filter frequencies are modulate with a low frequency oscillator to produce the swooshing.

I would definitely be buying this pedal to develop my own effects.

I'm the one that mentioned signal clipping on the input. One of my guitars have really hot Dimarzio pickups that can be a challenge to amps and effects in general. This one is very hard to use with the Coyote, as it appears to clip before the adc. It doesn't complain in the same way it does when there is a signal overflow(it has an indicator in the display). Unfortunately this is my main guitar, and I'd love to see this work. When time permits I'll probably mod the input stage.

Have you tried using a compressor/limiter with that guitar? You could get a cheap Boss or Behringer compressor pedal and put it at the front of your effects chain.

It doesn't store changes in patches on usage, you have to connect to a pc to do so, which is a bit of a pain.

What, every time you turn it on you have to re-download all the patches!? That's a pretty serious kink. Although having a laptop on your pedal board would look very hardcore...

[howard]

Haven't tried the Line6. I'm thinking of getting this little puppy when it hits the stores:
http://www.wired.com/gadgetlab/2010/01/ ... es+2%29%29

I suppose they are quite easy but I have no experience with dsp programming(only small amounts of programming in general, actually, but part of my plan when I bought the Coyote was to get up to speed on this), hope to see them surface soon anyway.

I could always run a compressor in front(I have several) but I don't like the sound that much, especially not those of Boss and Behringer...
It's a small design flaw, but fixable. I guess Eric didn't have a really hot guitar to test with.

A compressor in this pedal would be nice though, just for kicks. One of my reasons for buying this pedal was to reduce the amounts of effects, as the Coyote can do pretty much whatever one wants. At some point I will sit down and make an adapter for an expression pedal(to hook up on the i2c bus), will just have to wait for someone to cook up a parametric eq or wah...

The thing with the Coyote is that all patch editing is done in software. You build patches from a bin of effects, wire them up the way you want and preset the levels and then store it. When playing and not connected to a machine you can tweak various parameters on each patch(you have 4 knobs and the two stomp buttons) but they won't stick. Right now I can't remember wether they stay during patch changes, but definitely not after reboot. This sucks a bit, as the sound is always a dynamic process...
I've had some mail and forum exchanges with Eric on this, but we haven't reached a conclusion yet.

[sammay]

I got my Coyote-1 on Saturday and I've just started trying to write a flanger effect. Damn this is hardcore programming though. No multiply instruction! Manually fetching bytes from SRAM with raw bus commands! There really should be an OS api for that.

...wait for someone to cook up a parametric eq...

That reminds me, I actually designed a digital filter for a parametric 4-band EQ for an assignment last year (theoretical, just did the maths and simulated it in Matlab). Here's the response with the low mid frequency boosted by 1dB gain, mid by 1.75dB, high mid by 2.5dB, high cut by -0.75dB (low freq is off the scale):



I'll dig that out and have a look at implementing it.

[eric_admin]

Sam,

It's a good idea for me to provide a multiply API somehow. I'll give it some thought and see what I can come up with. One possibility is to create a math module and hand the operands through the socket interface, but the result wouldn't be synchronized until the next microframe (sample) so it would take some care (basically pipelining) to use properly. The OS modules are pretty saturated from a performance standpoint so I think it would have to go in some kind of a dedicated support/utility cog in any case, but whether that's a proper "module" or an OS mod to create a dedicated math cog could be debated. I'll stew on it while I'm driving today; it's good food for thought, thanks!

[sammay]

The OS modules are pretty saturated from a performance standpoint

The Propeller is an awesome microprocessor and all, but what would be really nice would be access to a dedicated DSP chip of some kind. Forget optimising multiplication, we'd be able to do a Fast Fourier Transform every microframe.

Would the I2C expansion port be fast enough to transport a few samples to and from external DSP hardware every microframe? That would be a cool hardware mod.