Simple Sampler

[PHOBoS]

Here´s a simple sampler I made from a small digital recording device. These little recording devices come in all kinds of varieties, with different recording
times and functions. Some of them produce a beep at the start/end of the recording which is very annoying and makes them not very useful for this purpose.
There are versions that repeat the recording when you keep the button pressed (looper), others just play it once. Some record for a fixed time while others
record as long as you keep the record button pressed. And although I haven't seen them there might be versions that just use one speaker for both recording
(mic) and playback.

The one I used for this simple sampler (labeled "KEYCORDER") has a nice feature. It can record for ±16 seconds, but if you record something shorter it
doesn't erase the rest (similar to a tape). And if you keep the play button pressed it plays the whole recording to the end. So if you record at different
lenghts you end up with a recording containg several snippets. (And now I want to make a similar device using actual tapes ). Sadly I couldn't find any
pitch control on this one, but I have other versions that do have it.

The circuit board has a black blob and for such a small device a lot of components. So I first drew a schematic of the thing, which wasn't very easy,
to see what everything was for. Well, even with a schematic I'm not sure how it works, I also did some measurements but that didn't make things any clearer.
I did find something useful though. As mentioned when you keep the play button pressed it plays the full recording, but if you just shortly press it, it
will only play for the length of the last recording. Untill I disconnected one side of diode D2, without it, it plays the full recording no mather how long
press the play button is pressed. There was only one problem. After that it didn't want to record or play, unless I connected the diode again. I'm not sure
how it works but it seems like "the blob" sends out a low pulse after the last recording is finished playing which stops it. So I tried giving it a low
pulse manually and that worked . So that made it possible to play back the recording for any length off time.

So the next step was to make timers for both recording and playback, and to make it more fun, add voltage control. I started with a 555 timer chip and messed
with the timing cap/resistor untill I could get the full time of ± 16 seconds. But with these values I couldn't get a very short time (3-4secs min.) so I
also added a range pot. And for safety reasons I used optocouplers to replace the original play/record buttons. I also connected the reset of the playback
timer to the record button to make it stop playing and start recording. But this didn't really work, if the playback timer was on and you pressed the record
button then the record timer would just take over the function of the playback timer, so it kept playing instead of stopping. (I think the 2 100nF capacitors
C6/C10 might be responsible for this). By adding a delay (resistor/capacitor/schmitt trigger) between stopping the playback timer and starting record this
was solved. I then did the same thing with the reset of the record timer and the playback button, so it stops recording when you press play.

I also added a switch to disable the timers so it just records/plays as long as you keep the rec/play button pressed. For the record switch I used one with a
center position (only had 1 without) and used it to disable the record function. (like the little tab you can break out of a cassette tape ) A bonus
feature is that when it is disabled the record button acts as a stop playback button. Actually if you press the record button really short it will always
stop playback without starting to record. same goes for the play button (can stop recording without playing).

One idea was to add a random control voltage to both timers and for this I made a Quad S&H with a noise generator (posted here). I made use of
the delay function for sampling the noise just before playing/recording. The audio input was a microphone so to use a line level signal I added a voltage
divider to attenuate the signal. And for the output I used a differential amplifier because "the blob" has 2 output pins with a signal (most likely inverted).

I put everything in a plastic box I had which was just big enough to get everything in. And it came with a nice piece of (non conducting) foam which keeps
everything in place. The 2 unused S&H's are wired to the connectors (gate/Cv out) so I can use those to control something else. No fancy front on this one,
just a fuzzy butterfly sticker (hey, it had the right colors).

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PHOBoS - Simple Sampler.gif
Description:	simple sampler schematic (numbered parts are part of the "keycorder")
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Keycorder.jpg
Description:	original Keycorder
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Simple Sampler - 01.jpg
Description:	Simple Sampler outside
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Simple Sampler - 04.jpg
Description:	Simple Sampler inside
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[dougseidel]

it's astounding the amount of cool stuff you are able to create.

[robsol]

[new voodoo]

thx for the schema. i use the 'Yada Yada Yada' devices in much the same fashion. thx for sharing, really appreciated

[new voodoo]

just curious, around the "record button" and "play button" -it looks like your schema indicates that there is either a LED or a Vactrol and then perhaps the vactrol or the LED lead is connected to one leg of a transistor and the other 2 are what a SPST button connects?
Is that correct?
Sorry to ask, but im uneducated in re engineering so I often, even after quite a while reading these, run into symbols or combinations of symbols I am unfamiliar with for whatever reason.

[PHOBoS]

thanks guys

[RingMad]

Cool. I'm glad you included a photo of the inside, which I take as an example of good layout and wiring organization from board to panel. With each box I build, I learn tricks, but sometimes it seems impossible to do neatly and it ends up a rat's nest. Plus it seems my boxes are more and more complicated and involve more chips and hardware.

James.

[analog_backlash]