Alesis Semi / programmable DSPs

[drew]

Hi... I remember some posts here a while ago about a possible DIY kit or at least a collection of information on some DIY reverb/delay/modulation effects using Alesis Semi parts... I don't remember who it was from (sorry!) but I was wondering what happened to it.

I'm always looking for interesting effects, especially time-based effects.... I have an alesis Ineko but it's noisier than anything I've ever used before. Positively terrible, not even worth the $80 they're charging these days for 'em. I'm hoping that the DIY stuff might be at least slightly better quality...


drew
toothpastefordinner.com

[Peter Snowberg]

The DIY DSP project got delayed thanks to (or no thanks to) life making some unexpected turns. It's still very much on..... but I need some more disposable capital to finish things off.

If you open up that box, I'll bet you'll find a single AL3101 DSP along with support components.

Alesis took some really cheap turns to make this stuff accessible to consumers without a lot of cash. They use (at least in the stuff I've seen) cheap op-amps in very minimalist configurations. They're also pushing the DSPs to their limits and beyond. Those Alesis DSPs are really more like MAC cores than full DSP-CPUs. Even with 24 bit I/O, if you code a 10 band graphic EQ, your dynamic range is reduced to 18 bits. Alesis-Semi has better chips in development, but for $3.50 I'm amazed by what you can get.

My design tries to address some of these limitations while simultaneously making a DSP development platform that's musically useful. I hope they'll be "slightly" better at the very least. I've got a couple designs and I'm going back and forth a little about what to include in each.

In my opinion, Alesis is trying to push the envelope with their new effects and they've gone a bit too far to appeal to serious musicians, but the market is really elsewhere and Alesis almost died a couple years ago so they had to reach to where the money is. That's capitalism for you.

If you want studio clean and powerful audio DSP, you really need more capable chips like the 24/56 bit Motorola DSP56K line at the least. Those have 56 bit accumulators, giving more dynamic range than analog will give in the real world. Unfortunately that quality comes at a cost.

If you want to mess with their hardware in the mean time, Alesis Semiconductor (a different company under the same umbrella) sells evaluation kits for their AL3101 and AL3201B chips. Both kits also use their matching A/D and D/As. I don't recall the costs, but they were typical ($$$$) as eval kits go. You pay more, but they're engineering tools and not consumer products. At least you get complete control.

Stay tuned for more.

If you want to hack your current unit, check out the data sheets for the A/D and D/A. You could rebuild the analog sections with better parts and I'm sure you'll get better results. Some of what you hear now is the result of cheapo ceramic caps and TL084 op-amps. Switch to NE5532s with film caps and it's a whole new world.

Take care,
-Peter

[drew]

I have a bunch of burr-brown op amps sitting around so maybe I'll drop those in (socketed of course!) I just assumed all the noise was due to super-super-super low quality digital stuff... but I guess digital is garbage in garbage out, huh?

I'll probably wait on the development kit since they're usually $100-ish and one can get the parts for much cheaper, assuming you know what to do with them.

Thanks for the suggestions... you know, I have a Microverb III that sounds great but it's a little noisy. I prefer it to most other digital reverbs in the same price range, or pretty much anything under $300. I could probably crack that dude open too.... and get another for pretty cheaply if I break it!


drew
toothpastefordinner.com

[drew]

So I popped open my Alesis Ineko this afternoon...

It's got two TL082 surface-mount opamps in there... and guess what else? An AL3102, AL3201, and AL1101. It's got an LM339 (this is a comparator; I assume it's for the input/overload LED control) and microprocessor as well.

Screenprinted on the top side of the board is the message, "We're glad you're interested in our designs. Alesis ICs are available at WWW.ALESIS-SEMI.COM". I think that's great

I might dead-bug some burr browns in there, but before I do, d'you think there'd be enough of a difference between a TL082 and a BB2134 or similar to make a difference?


drew
toothpastefordinner.com