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/diy/ - Do It Yourself

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File: 7 KB, 489x143, sampleAndHold.jpg [View same] [iqdb] [saucenao] [google]
22870 No.22870 [Reply] [Original]

Hello /diy/,

I been wondering if it would be possible to build my own sample and hold circuit that can take input (say from a guitar or drum machine) and sample that and keep looping. Maybe make that into a pedal or something.

>> No.22884

>>22870
Needs to be done digitally.

>> No.22897

You can do it in analog with a delay line, but it will take many stages. The easiest thing will be to sample the input with an ADC, and then add a delay before output to a DAC and mixer stage. If you want to look into the analog approach, look for the work by Reid Harrison.

>> No.22901

>>22897
>add a delay
Circular buffer.

>> No.22904

You could try to mod a tape recorder by "looping" a short section of the tape and adding a playhead, but I agree it would be much easier done digitally

>> No.22913

u could do it with tape also
before digital they had tape delays

>> No.22920
File: 13 KB, 709x621, singlechipsampleandhold.gif [View same] [iqdb] [saucenao] [google]
22920

>>22884

Thanks.
I looked up the Boss RC series and noticed they were digital.

What about something like this? http://www.musicfromouterspace.com/analogsynth/singlechipsampleandhold/singlechipsampleandhold.html

>> No.22932

>>22920
I think that's just an add-on for something more complicated.

>> No.22946
File: 108 KB, 640x384, choruspcb.jpg [View same] [iqdb] [saucenao] [google]
22946

Analog you can only do tape delays, or get BBD (bucket brigade delay) chips but usually they don't store much information (512 -1024 samples) and must be used with a compander section to reduce noise. The NOS ones are quite expensive and the chink clones are not very well regarded. To have an effect like the EH Memory Man you must line up several of those.

Digitally there are inexpensive and easy to use chips like the PT2399.

>> No.22954

The issue is that you want to delay a signal, not just sample and hold it. In the link and schematic above, you would have just a moment in time. Let's say that you wanted to sample at 1kHz and then have 1sec delay. You'd need 1000 of them in parallel with a sequencial selector. How the circuit works is that the JFET (Q1) disables the voltage change on C3, which is buffered and seen at CVOUT. Seriously, a digital solution will be your best bet.

>> No.22955

>>22946
excuse me I remembered it wrong th Memory Man use the now gone and expensive 4096 stages MN3005 BBD. Lining up severals is not a suitable option.

>> No.23024

>>22954
>>22946

Thanks alot guys.

>> No.23049

>>22954
That is (was) a BBD chip, essentially.
http://en.wikipedia.org/wiki/Bucket-brigade_device

>> No.23071

>>23049

Very interesting.