Building an Analog Delay (guitar effect)

[sebgar]

What's the basic circuit behind an analog delay? How do you create a delayed signal with the option of adjusting time and feedback?

Thanks!

 

[keith1200rs]

I think most are digital now but I think you can still get hold of the old analogue 'bucket brigade delay lines' as well.

Keith

 

[dick_freebird]

The oldest reverb units were long springs with transducers
at both ends. Back in the day you could also get a reverb
off a reel-reel tape deck (divorced record & pickup heads,
selecting the speed changed the delay)/

Later on the CCD "bucket brigade" analog shift registers
were popular with hobbyists.

You could do this nowadays with one of the uCs that has
a decent A/D, stuff the audio data to memory and pull it
out with an offset index and push it at a DAC. Variable as
you please.

 

[sebgar]

Hmmm. Idon't think analog is going to work for me then. Any recommendation for digital? what uC should I go for?
I just wanna build something simple. I'm not interesting in a high quality delay circuit, just want to learn the basic circuit/principle.

Thank you,

 

[Ricky761]

hi,

you might be interested to browse and check each circuit on this site:

tonepad -- a resource for d.i.y. music projects

cheers.

 

[leo_o2]

Oscillator+ counter

 

[keith1200rs]

So no need of any memory to provide the time delay? Or ADC and DAC?

Keith

 

[TuAtAu]

can we try to have some lag phase shift to create the delay?

 

[audiomik]

sebgar

Keeping in the Analog vein, have a look for the Panasonic MN3007 BBD analog delay IC and it's application notes.
MN3007 Datasheet pdf - Microcomputers/Controllers - Panasonic
These IC's are still available.

It is suggested as a replacement for the SAD1024 IC in a number of applications and datasheets for these will also give you much info on how to use them for a wide range of 'time domain' Instrument effects.

hope this assists
Mik

 

[FvM]

So no need of any memory to provide the time delay? Or ADC and DAC?

Of course you need all of these. Some single chip processor have low or medium resolution AD/DA, but rarely sufficient RAM. Also analog delay chips don't have mind blowing delay times. They are better suited for time base manipulations imvolving short delays, e.g. flangers. But I guess, no new analog delay effects have been designed since 20 years or so.

I just wanna build something simple.

Any idea about the maximum delay time and analog bandwidth?

 

[leo_o2]

Of course, you can do. However, it can't be accurately controlled.

can we try to have some lag phase shift to create the delay?

 

[FvM]

can we try to have some lag phase shift to create the delay?

Most contributors (me to) assumed, that analog delay is referring to an perceptible delay amount, which would mean at least 50 or 100 ms. Practically, it can't be generated by "lag phase shift" (low-pass) circuits with acceptable bandwidth. For time base manipulations in a short time range, e.g for a flanger or frequency modulation (leslie effect), it can work. Effects of the analog age have been often using tunable allpass or lowpass chains for this purpose. Accurate control isn't an issue, but the limited number of stages is.