[sdiy] Delays: how?

[harrybissell]

Hiya all... Inline

Ken Stone wrote:

> I'm going one step beyond this. I have a Schober Reverbatape. 1 record head,
> and 3 playback heads. The mechanics already designed for loop tapes :)
>
> Ken

nice.... more inline...

>
>
> >Or how about a nice low-tech analog solution?
> >
> >Old reel to reel tape deck (I'm sure you can pick one up pretty easily),
> re-fitted with a variable speed motor, and a continuous loop of tape.  Vary
> the tape speed for the delay time, vary the erase head current for the
> feedback control.

no no NO !!!  You run the erase head FULL at all times... or not at all
(for sound on sound)...

You get the decaying repeat by feeding back a portion of the signal from
the play head preamp to the record preamp.

Three head reel to reel machines can usually do echo with no modification
... as is. Feedback from the play head to the record head and you're there.

BTW... you can use a regular tape without looping.... but it runs out in 30
minutes
or whatever. Stop and rewind.  Or listen to your jams on the echo tape.... VERY
trippy without the direct sound.

I modded a cassette player by removing the erase head... move the record head
to the erase position... add a new head where the original used to be (with
preamp).  Put the deck in record mode (the stock electronics are working
normally) and feed back that new preamp into the line input.

NOTE: Many cassette decks (cheap-os) use the erase head as part of the bias
oscillator... so you remove the head (physically) but leave it connected
electrically...
just keep it away from the tape.  Your results may vary.

With this rig... you run the cassette until it stops... then you can flip it
over and play again... then use a bulk tape eraser to er.... erase it.

I'm sure the electronic peasant would approve. I was a serf once upon a time
;^P

H^) harry

>
> >
> >It might be a bit noisy, but I bet it will sound good as you modulate the
> tape speed.
> >
> >Seb
> >
> >
> >
> >
> >MED wrote:
> >
> >>         Okay, the BBD source seems to have dried up (along with the whole
> >> "sounding horrible") and this raises the question: what now?
> >> I want to make a delay with a decent time (something like 1 second).
> >> Feedback should be adjustable from same level (feeding back until
> >> hard-clipping catches it) to silent. Preferable would be control over
> >> the feedback loop, like an effects chain (pitch shifting craziness, et
> >> cetera)
> >> I have the feeling that a modern-component delay will be a
> >> some-decent-bit-number ADC into a LOT of shift registers (same number of
> >> lines as the resolution of the ADC/DAC, times however many are needed
> >> for the delay time) into a DAC. Is there a better technique? Preferably
> >> something simpler?
> >>
> >> Should I just try to make a tape echo? How are *they* done? MM doesn't
> >> have any schematics for the rolands, just vague descriptions that whet
> >> one's appetite.
> >>
> >> -MED
> >
> >
> _______________________________________________________________________
> Ken Stone   sasami at hotkey.net.au
> Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
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