Hommade quad tape deck

I love quad as an audio format. I've been recording in quad a lot recently on my tape multitracker. It uses regular cassette tape, and the regular track widths, but uses all four at once instead of two each way. Trouble is, it only has stereo mixdown, and it records at twice speed, so I would need to modify any potential quad tape deck that I build to play at twice normal speed. I've figured out a way to use a 4-part RCA signal, if ran to two stereo amps, to get quad sound to my speakers. Therefore, I would need to modify my homebrew quad tape deck to have 4-part RCA out. I'm still a little fuzzy on the particulars of that. In order to read all four tracks, I'm considering just taking two stereo heads and putting them next to each other, but due to width constraints, that would probably mean being unable to sync their output, let alone record anything. I suppose I could yank the quad head out of a junk Tascam, but good luck finding a junk Tascam! Any ideas on solving this issue? Perhaps work in an output lag somehow on the forward head's output so that they are synced again? One idea that I have, if I can get the outputs synced, is to just pull the head out of one tape deck and make the wires long enough that I can install it in the other deck, still attached to its own electronics, though. Then there would be four RCA jacks out (two from eah machine) and it would require the minimum amount of hacking things up. Then I'd connect the two cases in to uber case (duct tape, porbably), and go on my merry four-channel way. Anyway, is anybody else a fan of this format, and have you thought about making a quad tape deck? If someone has ever ripped up analog tape decks (or knows the nitty-girtty of how they work), please don't hesitate to give some input to this project!

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NachoMahma9 years ago
. To play the tapes you have already recorded, you will need a 4-track head. You'd be surprised how much of that kind of stuff is still available. forgesmith (AKA The E-Bay Meister) can probably provide some good E-Bay links. I suppose you could use two stereo heads, with a delay circuit on one head, but that sounds awfully complicated. . With a little creative work in the pulley department, doubling the speed should be doable, but not easy. . . You really need the technical manual and/or schematics to figure out how to get a quad signal out. Where does the stereo mixdown occur? Why would a quad-head deck have stereo output only?
Rishnai (author)  NachoMahma9 years ago
Sounds daft, doesn't it? It's an entry-level studio multitracker, designed for making master tapes, which would then be mixed to stereo tapes/made into CDs for sale to the great unwashed. At least that's the design, and it was made after quad died a slow quiet death as a commercial format. Tascam 414 mkII, if I remember correctly. In fact, I think I still have warranty, which is pretty wild. I could pretty easily open it up and grab a quad signal, but I'd like to not wreck it. I've got the diagram someplace, but I'm not gonna mess with the mixdown. It mixes four tracks into stereo quite well. No sounds turning up in weird places or anything, and bouncing a sound back and forth works as intended. As for doubling speed, I was planning on probably either sticking a honkin' pulley on there, or swapping it out for sprokets and a fine chain (I've seen a few lurking on RC vehicles), or a gear drive. Mechanical work is fun, though, so I think that'd probably be the smoothest part of the build. As for delay, I can probably get a heavily used delay pedal for right cheap, so unless someone sees a big problem with pulling the delay circuit out of that (tunable amount of delay, too!) and then using the case for some other project, doing it that way seems simple enough.
> I could pretty easily open it up and grab a quad signal, but I'd like to not wreck it. . You know your abilities better than I do, but it shouldn't be THAT difficult, especially if you have the schematics. Somewhere on the tape preamp board you should be able to get all four channels. You'll just be soldering some small wires that you should be able to remove without causing any damage if it doesn't work out. . . I can't imagine ANY chain-type drive being smooth enough to work. Even a helical gear setup is liable to be "noisy." Probably be best to stick with a pulley/belt system, but a good gear set may work.
Rishnai (author)  NachoMahma9 years ago
Watch gears, perhaps? Pulleys are looking simpler and simpler. I might look into getting an identical used recording machine and pulling the quad signal out of that. Having two two decks to bounce off of each other would be handy anyway.
. If you go with gears, I'd use helical cut teeth. Any straight tooth gears will be noisy and introduce flutter (but it may not be enough to be audible). It's hard to get any smoother than a good belt drive (except maybe direct-drive, but I think that's a little too much for this project).