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Long runs of unbalanced cable.

Hey i may have to run some 25-60ft runs of cable from an unbalanced source (cassette machine, reel to reel, Tascam m-30 mixer, record player) to the converter. The sources are on RCA type connections with 1/4" or XLR on the converter depending on what model i get. Im trying to transfer some tapes and records to digital, some personal, some commercial stuff.

Im not sure if there is some sort of di box type device i can use, if there are other devices, techniques, workarounds available, or what compromises I'm looking if i have to do such long longs unbalanced, besides noise.

I an trying to avoid drilling holes in the walls or floor to position the sources closer to the converter, but that is a possibility if necessary.

Thanks as always.


bouldersound Sat, 03/30/2019 - 18:37
Active circuits can have much higher input impedance. For sources like magnetic or piezoelectric pickups that's essential. For active outputs it's not so critical. My normal default with DIs is to use active DIs for passive sources and passive DIs for active sources, but I've found situations where it didn't work out. For that reason I have a collection of different DIs. Your application is simple so I'd bet whatever decent quality stereo DI you get will work.

cyrano Sat, 04/27/2019 - 14:30
Any chance to just try it with a decent cable?

I don't see the need for any DI or other thing, unless you have an impedance mis-match, or a very hostile environment.

I've run unbalanced line level over a 100 ft without any problems. I probably wouldn't do that with mic level, but still...

The record player is another story. It's near mic level, but the simplest solution would be to place an RIAA phono preamp before the long line. A DI surely wouldn't fit a phono level signal over 60 ft.

paulears Sun, 04/28/2019 - 01:19
Clearly it just needs to be tried doesn't it? Connect it up and have a listen. As it's a line level gizmo on the other end, you can send some white noise down the line and then see how much you lose the other end. If it's only a tiny bit, then EQ will put that back. If the cable has loaded the line too much and you've lost too much, you can see and hear.

That said for the price and usefulness of DIs, why haven't you got a couple in the mic box? I've got them all over the place as problem solvers.

bouldersound Sun, 04/28/2019 - 09:38
When I did live sound I had a 100' snake with unbalanced returns. Sometimes it was fine, sometimes it was a buzzing nightmare. Generally speaking, running power from stage so I didn't have to use a remote outlet solved that. Switching to balanced returns also solve it and freed me from having to put out the 100' power extension.

bouldersound Sun, 04/28/2019 - 12:16
Link555, post: 460817, member: 31690 wrote: Mixing with big antennas is never a good idea

True, but I think the buzzing was more from mismatched ground references than extraneous signal getting into the line, ground loop vs. EMI or RFI. The sending and receiving devices had a difference of opinion as to what 0V was, and that difference became part of the signal.

Boswell Sun, 04/28/2019 - 14:57
Distance is only one part of the story. If you are not powering the sending and receiving equipment from the same power outlet, you need galvanic isolation between the two. For audio purposes, this is best provided by transformers: either a bal-un transformer (connected the appropriate way round), or a transformer-based DI box.