Analogue Looping

[bssm123]

Hey everyone.

I was wondering whether there is a way to loop an analogue signal, for example;
if I had an input signal of constant frequency which lasted for a second or so, is there a way to loop this signal and create a constant output of this signal until a switch breaks the circuit? Or is the only way to do this kind of looping through digital sampling?

Any help would be great.
Thanks!

 

[ericgibbs]

hi,
You could get these once upon a time.

 

[crutschow]

As Eric noted, there used to be a way to do that with analog circuits, although the total delay time and duration were rather limited. Now the best way is probably to digitize the audio with an A/D converter and then store it in memory where it can be read back to generate an analog signal with a D/A converter for as long as you need, all done under microprocessor control. Some microprocessors have the A/Ds and D/As built in.

 

[MikeMl]

There are VLSIs that do what Carl described.

 

[ronsimpson]

The analog Bucket Brigade works but with every pass through the noise gets worse and the distortion add up. In 20 passes it will look bad.

 

[3v0]

Perhaps if you would let us know what you are trying to build we could provide a better solution.

Your post sent my mind back to the days of early computers. One type of memory that stored data as sound in air. I seen one machine by singer. It had a 2 or 3 foot long tube with a speaker on one end and a microphone on the other.

 

[crutschow]

Your post sent my mind back to the days of early computers. One type of memory that stored data as sound in air. I seen one machine by singer. It had a 2 or 3 foot long tube with a speaker on one end and a microphone on the other.

That would give a signal delay of about 2-3ms.

There also are (were) acoustic storage delay lines that use a piezo-electric solid.

 

[canadaelk]

I still have some of the bucket brigade ICs somewhere.
Some of the ISD soundrecorder ICs can be looped or put into repeat. I do not know if there is noticeable transition period in the cycle.
Not knowing the application, it may be usefull to download a free signalgenerator and use the soundcard to do the tone. E

 

[irbirb]

so kind of a loop/delay - sample/hold thing?
some people really do prefer the old bucket-brigade over digital chips. i for one.

i think it's possible to get classic BBD chips like the MN3005, MN3007, mn3004 etc.
there have been sellers of 'new-old-stock' and i heard that there were operations in china who were pulling used chips from old karoke machines also.
new or used, i also heard that it's important to go for a trusted source.
it's also important to get the clock-chip for driving them.
they're a bit weird in that they operate from a -15 volt supply.
i think you need to include some way to filter out the sound of the clock.

the MN3204 is 512 stage (short) delay, i guess it's a reissue? digikey lists it at least but i don't know if there's a hefty minimum order there.
i'd imagine that the shorter delay chip is what you need.