DIY looper?

[jim p]

Has anyone made a looper using the ISD1964 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ISD1964SYI01-ND
I am getting a demo PCB for the ISD1964 for free so that will make trying the IC out easier. Looking at the data sheet I should be able to add a pitch control and maybe a low frequency oscillator for a tremolo on the playback. Got to get through my current project of building two 5902 amps first. If all goes well I may have to layout some PCBs and get three from ExpressPCB.

[jim p]

I received a demo board for free for the ISD1964 and have been checking it out.
I messed up a bit because it has a class D pulse width modulated output but with a couple of resistors and a capacitor you can get a regular audio waveform out of it. Just playing with ideas for the input and output circuit to get the best possible tone from the IC. Plan on having a switch for either two 32 second clips or one 64 second clips. If I do layout a PCB I may use two ICs so you could run two loops at the same time. I have a design for a two footswitch box that would use a regular mono ¼ cable so you would have a separate footswitch box connected to the looper. Also still need to see how best to modulate the playback clock for tremolo effect on the recorded loop.

[Commodore 64]

This is way beyond my understanding, but it sounds cool, and I would build one if I had directions :).

[jim p]

Just to continue my posting on the DIY looper using the ISD1964 IC. Right know I am not so sure I want to spend the bucks to mare a PCB for the IC. The fidelity of the sound from the IC is like an old cassette tape without Dolby, limited dynamic range and constant background hiss. I still need to try hooking a low frequency oscillator to the frequency input for tremolo that may make it worth while. So far the best sound I have is by creating a differential signal with a transistor to connect the input to the plus and minus microphone connections. When I get to the final interation I will post schematics of current state if anyone else wants to give it a try.

[Ch0jin]

What was your reason for selecting that particular chip?

I'm just curious because most DIY looper projects I've read about involve really low quality samples due to the silicon they use (chip from voice recorder, answering machine etc etc)

Is there a reason for not starting with the hardware design from a good looper?

Surely with all the loopers on the market now -someone- knows what silicon they are using. From there, datasheet and some reverse engineering etc etc etc.

Been wondering about that for while.....

Also, just scanned the datasheet for that chip. Doesn't seem to list frequency response or noise characteristics, but the poor quality could be a result of the low sample rate (depending how you have it configured) I guess.

[Ch0jin]

OK so I decided to answer my own question...

I just ripped my RC-2 apart to find out for myself what sort of silicon it uses to get me 16 minutes of crystal clear loops, and found out why people aren't copying the design..

At it's heart is what appears to be a proprietary microprocessor. It's a Roland ESC R04010990. The only mention of it online I could find was a Russian guy mentioning he found it in a Boss DD7 pedal (which makes the plot even more interesting)

There's also Samsung memory chip that its datasheet describes as 32M x 8 Bit 16M x 16 Bit NAND Flash Memory.

There are a couple more 8pin SMC's that I didn't bother to check after I realised I wasn't going to be able to copy it....

So I guess that's the answer huh.