[sdiy] Tape Delay

[John L Marshall]

Years ago I built several tape delay units using  broadcast tape cartridge
machines. NAB cartridges are the same size as the 8 track but the pinch
roller is attached to a swing arm on the machine not inside the cartridge.
These machines are robust and are usually easy to work on. The heads on mono
units are half track, with an acceptable S/N ratio. The other track is for
signalling, start next device, que up, etc.

Use back lubricated tape in the cartridges. The tape needs to slide easily
while looping inside the cartridge.

The spindle motor speed can be controlled the old fashioned way, with a VFO
and a power amplifier.

The machines and cartridges are no longer being used by most broadcasters.
They should be available as surplus, cheap.

John

----- Original Message -----
From: Tony Clark <clark at andrews.edu>
To: John Lamb <jlamb3 at nc.rr.com>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, August 22, 2001 10:42 AM
Subject: Re: [sdiy] BBD for delay and other things


> > Speaking of tape echo, is there a tape loop cartridge similar to the
> > echoplex cartridge that will fit over a standard home-stereo
> > audiocasette head?  I'm on a quest for analog echoes, and if I have to
> > resort to tape delay, I'd rather do it via commodity components from
> > busted tape decks instead of building an echoplex and using those
> > funny cartidges.
>
>    Heh.  Well if you are adventurous enough, you could buy an old
> 8-track player to modify, specifically one that can record.  8-tracks are
> cheap and cartridges a dime a dozen (literally!).
>    There's a lot of modification that would have to be done to get it to
> work though.  The heads have to be reversed around so that the
> record/erase head is in front of the playback head.  In fact, depending
> on how keen you are on the audio quality, the heads should be replaced
> with two-track versions for better bandwidth.
>    You'll probably also want to figure out how to adjust the speed of
> play to get different delay times out.
>    The cartridges of an 8-track have a special metal splice in the tape
> that signals the player to switch tracks.  It will have to be removed and
> the tape respliced.  Easy enough to do since I doubt anyone would need
> all the tape that's in one of those things anyway!
>    You could also probably do this with a conventional tape player, but
> it would be harder to set up a continuous loop tape with one of those.
> Besides, 8-tracks are bigger and probably easier to work on.  :)
>    It'd probably be far easier to buy an old reel-style tape recorder to
> do this on, but I like the compact space that a small 8-track unit takes
> up.  :)
>    Anyone ever seen or done anything like this?
>
>    Cheers,
>
>    Tony
>
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