Hi all, great forum!!

Thank you in advance for any replies, this is probably a dumb question as I know very little about electronics :/

I would love to one day build some kind of analogue audio device however my main interest is in digital sampling. Could anyone give me a little education here? My question is this. .

Basically, why can't we do "Sampling" with analogue electronics, why does it have to be done digitally?

Analogue recording is well established and a beautiful thing, the first sampling machines like the Melotron were based on analogue tape, but is there no way to do this using analogue electronics rather than tape? Can signals really not be stored within a circuit?

The essence of a sampler is that it allows storage and instant playback of an audio waveform, if we could do this in an analogue circuit I'm sure it would be amazing! How could it be done? And why hasn't it been done already?

Many thanks.

Signal Jacker.

 

Interesting question. I don't have an answer off the top of my head for you - but the bucket brigade chip comes to mind. I believe before digital delay units were feasible, economically viable, or commonly used - there was the bucket brigade IC chip. I think Radio Shack might have even sold a chip - back in the day. However, this is a delay unit - not a long term storage unit - so you'd have to constantly refresh the bucket brigade. Not only would special circuits be needed to continually refresh the bucket brigade, but refreshing would lead to the audio quality degrading rapidly (like seconds or minutes). Then there's another issue with starting the sample using a bucket brigade at an arbitrary time. So, the bucket brigade may not be a feasible method for storing and recalling analog sounds at any moment in time.

If the samples you'd like to store are permanent then there may be an analog way of hardwiring a sound.

I assume you'd also need to play the sounds back at different speeds. True?

 

Look up analogue delay pedal and see how the signal is delayed. here is a place to start.

Q: What's the Difference between Analog and Digital Delay Pedals?

https://www.sweetwater.com/.../q-whats-the-difference-between-analog-and-digital-del..
How does a pedal actually work? Let's get technical ...

https://www.reddit.com/.../guitarpedals/.../how_does_a_pedal_actually_work_lets_get...

 

Thank you FuirierSerie.

I too thought of analogue delays as they use similar temporary storage.

The signal degradation in analogue delay units sounds very pleasant (imo) It's a nice characteristic which software delays emulate as well.

I appreciate the huge developments in digital signal processing and the amazing possibilities digital has brought us, though a lot of them are based on analogue signal processing like variable resonant filters, LFO''s Envelopes etc, it would be cool to be able to build a sampler that really had these analogue features and didn't just emulate them digitally.

I personally feel re pitching may not need to be a feature of such a device, but looping and slicing and filtering would be very cool, if it's "do-able".

 

Analog samples can be taken and stored, but the storage would typically be in a capacitor which is subject to leakage, so the sample can only be stored for a short time without serious degradation.
Also it would take zillions of capacitors to store all the samples for even a short segment of music.
The one practical example of this technique is the bucket-brigade circuit mentioned by FS, but that can only store the signal for a few tenths of a second at most, before noticeable signal degradation occurs.

So the reason it's done digitally is that digital samples can be taken at a very high precision (20-bits or more) and stored indefinitely as digital words in digital memory or digital CDs with no degradation.

There's no sound quality or other advantage in trying to do this in an analog fashion.

 

OK, thats cool.

Now I understand, I thank you guys for the education

 

I remembered something with tape recorder technology: Tape Loop