overly ambitious DIY looper

peterleroux

So Mantech has the ISD1730, which looks to be a successor to the chip used in the Zvex Lofi Loop Junky. Reading the design guide, it looks like it should be just about possible to get this working with a record/stop button and a loop button, and the necessary analog wrappers to do mixing, volume, tone etc.

So the question for those who have done some circuit design- would this be an overly ambitious place for me to start with designing a PCB? I'll need to download and learn Eaglecad, then get some PCBs made, but I can't see any massive hurdles here, the chips are available and the control can be done without any microcontrollers. Thoughts/comments?

peterleroux

ah, here is a circuit diagram for a looper based on the 2560, a related chip: http://sounddiy.free.fr/AnalogLo-fiLooper.html
en francaise, but Google Translate should get me close enough

mtmattan

Check out:www.sonictitanfx.com/2012/07/02/lofi-looper/
Did this with the ISD1020 chip.

Haha I really like your spirit!
But this is far out the realm of a say am overdrive circuit.
Will check out the datasheet sometime.

If you can get it working on breadboard I'd be more than happy to assist with a PCB.

As for pros, these ISD chips have loads of character and become a nifty little pedal with the vibrato addition.

As to cons, the quality is VERY lofi and even the cheapest digital looper would far surpass it.

Also perhaps consider the importance of the vibrato feature.
When I built mine, I personally found this to be a wonderfully redeeming feature.

For the vibrato I used that nice little LFO circuit from the ToneGod (check the blog link).
It wobbles the voltage to the chip providing the detune effect.

Another big learning curve for me with this project was using logic gates that starts/stops recording etc.

So ya, definitely an ambitious project!
I don't mean to discourage you at all but I've encountered many instances where the application notes in a datasheet initially seem simple but end up being just a snippet of a far more complex circuit.

What I mean is take for example the TL072/TL074 datasheet. Sure it'll show you how to set up a basic non-inverting op amp - but how do you turn that into a Tube Screamer?

Still need to add input output buffers, RC networks for frequency management blah blah etc.

Anyway, just so you have all the facts before investing your time into something. ? even just trying things, what you end up learning usually far outweighs having an actual working pedal in the end.

peterleroux

Hmm. I think the way forward here is to build a decent breadboard pedal/prototyping rig and have a go. I need to do some shopping at Mantech this week, I might pick the chip up and see how I go from there.
Thanks for the advice. Where did y get the 1020 from? I understand they're not available anymore?