DIY Sampler from cheap digital audio recorders

[th0mas]

As the title says.  I just bought 6 of them, wanted to bring it to any interested party's attention:

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=5799268272&ssPageName=ADME:B:EOIBSA:CA:11

[stryd_one]

These will probably be too high latency to use as a sampler :( Although these kind of voice recording devices (also available as just an IC) would be useful for doing soudbites on radio shows etc, where accuracy of timing is not so important.

Thanks for the heads-up, and good luck experimenting with these!

[Therezin]

If I were stateside, I'd probably end up getting one for my old Palm IIIx and another to take apart an' see what makes it tick... Oh well, guess I have enough stuff laying around here for me to play with for a while  :P

[th0mas]

Latency is very low, and device doesn't seem to mind being fed 5v instead of 3v from batteries ;)

more/pics to come..

Could a moderator move this to maybe "Design ideas" or somewhere else similiar?  I'm now in the process of turning these devices into a DIY sampler and am going to have a series of questions.

cheers,

Tom

[stryd_one]

How low is 'very low'? nanoseconds?

[th0mas]

If only I could determine nanoseconds with my eyes/ears ;)

Basically, I tried humming a constant tone, and pressing record, waiting a second, pressing record again to stop the tone.  When I hit play, the tone starts without apparent delay - feels about the same as pressing a trigger on a real sampler would, and faster than most virtual samplers I've played with.  Some characteristics of the device aren't the greatest for a sampler:

- the sound apparently has to stop before it can be retriggered, you can't go "Yo-Yo-y-y-y-Yo" for example.  I might be wrong, and it might actually just operate such that hitting play while the sample is playing stops the sample.  There might also be some glitchy way to accomplish this that I haven't found tinkering yet.

- no sample editing capabilities, period.

- while you can store multiple sounds on each device, the only interface to swtich sounds are "previous sound / next sound" which makes for a weird MIDI implementation to select patches.

- most often recording has a 'click' right at the start, which would suck.  A simple noise gate might minimize this but then it'd probably mess up the recording sound's envelope.  Wouldn't be too bad if we're dealing with recorded loops instead of one-shots.

As of now I have not looked up the datasheet for the controller, I've only been playing with ideas of connecting the already existing switches to transistor relays to two 74HC595's to connect to J10 of a core module.

Seems they only take up ~10 mA current when either recording or playing.  Needs a battery in order to save patches.

I'm interested in turning this into a lo-fi weirdo instrument, so I hope to be able to 'bend' the circuit a bit, maybe be able to modify pitch/timing on the fly with a potentiometer, stuff like that.  There's no crystal that I see so maybe timing's determined with a resistor/capacitor combination, which I could bend pretty easily.  That is, if I remember any electronics, and I probably don't ;), so I don't really know.  In terms of MIDI implementation, I'm expecting it to just respond to specific note events on a midi channel and trigger the corresponding device.

I'll try to post pictures in the next couple days, along with the start of an infinite number of questions ;).

[th0mas]

Here's my conceptual schematic:

http://th0mas.sixbit.org/mbsampler-1.png

In reality I'd like to think this schematic would be a general purpose MIOS->relay circuit, pretty much based on how the SID module goes from serial->parallel access, then to transistor relays on the pads of the play/record switch for each recorder (only 1 shown in the schematic).  Any flaws?  If flaws are major just say "there are major flaws" and I will go re-learn basic electronic knowledge I'm probably forgetting, or never really learned ;)

edit: note that I forgot OE#->GND on both of the ICs.

[smashtv]

Easy latency measure:

Sample a click noise (anything with fast attack) and wire to the loudest tact switch you can find for the trigger.....then record both the tact switch press and the sampler output click into any audio ware that shows the waveform, then measure the time between clicks on the waveform view.

Best

Smash

[th0mas]

datasheet for the microcontroller used:

http://magnachip.com/download/GMS97CL2051_1051_Manual.pdf

Conceptual question:

Instead of using transistor relays attached to the contacts for each switch (play/record), could I instead just:

- reclaim a bunch of pins that are unused on my CORE PIC (IE, pretty much all of them, since I'm not using an LCD or anything else.. maybe a DIN if it's needed at most)

- tie the GNDs together for the CORE and the audio sampler (already will be; same power supply delivering 5v)

- connect PIC output pin to the sampler's microcontroller input pin

edit: update (to avoid double posting ;) )

I have a dedicated core running MIOS v1.9 and a small application that raises PortB (all pins) on note on, and turns them off on note off.  I have one wire coming off of port B (D7).  Now, to get it to trigger the sampler and we're in business! :D

side note:

I can't believe how freaking easy this is.  Seriously, between MIOS, surrounding applications, and the C function wrapper, and the quality boards I got from SmashTV, I am in the community's debt!  Thanks all!

[th0mas]

(this deserves a double post :) )

It works!  I used an NPN transistor from some random board I had to connect the 'record' input pad and ground.

Time to wire up a couple :D

[th0mas]

D'oh!

It's too slow as stryd_one predicted :(

Oh well, I already have another plan for them - plus this was a great 'hello world' application for myself :D.

[stryd_one]

That's been prophecised for many years now :( I was hoping it wouldn't be true but feared the worst...

But at least now, we know for sure! Thanks for trying it! I'm sure it was a pretty intense "Hello World" but hopefully you will benefit from it, as the community has, by learning stuff :)