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Discussion Starter · #1 ·
postulation...

with the ever abundance of VCR's that are being thrown out...is it possible to re-wire the input to use a VCR as a echoplex? it already has a tape (there's lots out there), and the heads...so...even if you needed to wire in a pre-amp with a switch to turn on/off...would this work?

after my last big mod...now i'm thinking electronically again...
 

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postulation...

with the ever abundance of VCR's that are being thrown out...is it possible to re-wire the input to use a VCR as a echoplex? it already has a tape (there's lots out there), and the heads...so...even if you needed to wire in a pre-amp with a switch to turn on/off...would this work?

after my last big mod...now i'm thinking electronically again...
Having a record and playback head is great, and having lotsa tape to store things on*** is also great, but there are two big challenges with this:
1) there is no way to deliberately space out the record and playback head, as on an Echoplex;
2) there is no simple way to be able to vary the playback or record speed so as to be able to generate different delay times.

So, a lot more trouble than it's worth. I will note however that for a brief period, VCRs were being adapted to be ADAT recorders...before flash RAM got real cheap and real small.

***Because of how video heads operate, the tape is recorded to diagonally, making it functionally equivalent to recording on mag tape that is many inches wide. And if we think of 2" tape as representing the best that studios could offer, then recording on tape that is effectively several times wider ought to deliver fabulous fidelity. But then, fabulous fidelity is not exactly what we crave tape-based delays for, is it?
 

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SVHS decks actually have very good audio quality (there was a fad of using them as mixdown decks for a while back in the early 2000s) and consumer line level is remarkably close to HiZ instrument level. If the playback head is before the erase/record head(s) then in theory it could be as simple as hacking up a VHS tape so that it has a loop of tape vs a full reel and a take up reel. Since there is no speed or tape length adjustment the delay time will be fixed by the length of the loop in the cartridge and static motor speed of the VCR. You could add delay time adjustment in 1 of 2 ways:

1) voltage control (pot) on the power connection to the playback drive motor or
2) changing the length of tape loop inside the VHS cartridge (this may not be easy as you want the tape to be taught around the spindles; in theory you could add some pulleys in there to fold the tape around in to increase length; motor voltage adjustment seems counter-intuitively easier).
 

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Discussion Starter · #7 ·
Having a record and playback head is great, and having lotsa tape to store things on*** is also great, but there are two big challenges with this:
1) there is no way to deliberately space out the record and playback head, as on an Echoplex;
2) there is no simple way to be able to vary the playback or record speed so as to be able to generate different delay times.

So, a lot more trouble than it's worth. I will note however that for a brief period, VCRs were being adapted to be ADAT recorders...before flash RAM got real cheap and real small.

***Because of how video heads operate, the tape is recorded to diagonally, making it functionally equivalent to recording on mag tape that is many inches wide. And if we think of 2" tape as representing the best that studios could offer, then recording on tape that is effectively several times wider ought to deliver fabulous fidelity. But then, fabulous fidelity is not exactly what we crave tape-based delays for, is it?
Yep..you're right...i forgot that the heads were no moveable,..and in most cases, one in the same


I have a book that shows you how to turn a regular cassette player into an Echoplex, but seeing as I'm not electronically inclined, I don't know how to do it.
Id be interested in this...but...in the other hand...the heads would be the same as a vcr
 

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We've seen numerous relatively successful attempts to make a homebrew Echoplex with cassette tape, over on the diystompbox forum. But it starts to turn into something like a person deciding to make their own pizza by growing their own wheat, turning it into flour, and making their own mozzarella cheese. If one has the time, resources, and dedication, fine. But the project is likely far more involved than anyone who enjoys playing as much as they enjoy building, would like to commit to. Unless one has a quixotic commitment to near-impossible tasks, one might be better off spending the time at a second job and buying an Echoplex. And we haven't even begun to get into the issues of finding and maintaining mag tape.

Get out while you still can.
 

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VCR's (VHS and Beta) all used helical scan heterodyne recording.

They had one or two audio tracks and a control track recorded at the bottom of the tape and the rest of the 1/2" was diagonal recorded stripes that Mark referred to. The video heads would spin on a drum that the tape wrapped more than half way around, and the heads would 'paint' diagonal recording stripes on the tape.

All the high freq (video and Hi-fi audio) were recorded in that but you need to demodulate it to separate the component signals when playing it back. Because of that, the tape speed and spinning heads had to be sync'd on playback - that is what the tracking stripe was for. That track was read to position the tape with respect to the spinning video heads. That was what the old tracking knobs adjusted, going from noise to a clear picture. That control was eventually replaced with an automated circuit that did it for us.

Because of that, tape speeds were very low (to achieve 2, 4 and eventually 6 hours of record time). The bandwidth was achieve by the much larger tape to head speed of the spinning heads used for the video portion.

As an aside, video recording only ever used two heads 180 degrees apart. Four head and six head machines only improved picture when using pause or slow motion / high speed playback. The only used two heads for recording and regular playback. But you better believe 4 and 6 head labels sold a lot of machines.

Summing up, the one or two longitudinal audio tracks are nearly useless because the tape moves so slowly, even at the highest speed. Cassette is better quality and easier to mess with. The hi-fi tracks will only play back sync'd audio and you can't delay it by modifying tape speed, so again useless, without some sort of outboard digital manipulation (time base correctors).

They did make pretty good audio recorders though, if you don't need the effects. Sony made a box that allowed you to record hi-quality audio using the video bandwidth. They were small and sounded excellent (great noise numbers, no wow and flutter) and were used a lot for remote recording before more convenient digital methods came along.
 
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