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Discussion Starter · #1 ·
Anyone ran audio from one building to another?

Currently sharing the computer in the spare room with my wife's job.

I only make one-take demos for the other guys to learn the latest creation -- mp3 via email using Audacity.

I am building a garage this year. I am planning to record on my reel-to-reel in the garage and occasionally upload to the band. I had the foresight to install a PVC conduit from the house under the sidewalk to the driveway, so when the electrician is here the audio can go in too. I have done zero research so far...

Could be handy to cue someone in the house or garage via microphone (two tin cans on a wire? Lol)

Any thoughts?. Thanks team!
 

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How long is the run? is the tape out signal balanced? What is the input on the computer?

If balanced just run mic/line cable terminated to XLR or TRS as appropo (may have to debalance and drop to consumer line level on the computer end using an appropriate interface device - depending on what audio card you're using). If the run is really long or the signal is unbalananced it would be ideal to convert to LoZ balanced (mpro mic level) fiorst. Radial makes a set of boxes to do this for long runs of guitar signal (the SGI), but depending on the output of the tape machine you'd probably need a differernt box - some sort of passive DI in reverse ont he garage end (and a second DI the right way round on the computer end).

If you want to run other signals besides the (I assume ) 2 track (stereo) tape signal - a mic whatever - you can get multicore cable (anywhere from 2 up to 16 channels of balanced mic lines bundled into one cable) - like a stage snake, but without the fan/stage box so you get run it through the pipe first.



Are you handy with a soldering iron?


Quality snake cable (4 channel) can be had for as cheap as US$87 per foot (obviously the Mogami pictured above is going to be at least double that; it ain't 2 times better.)
 

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Discussion Starter · #3 ·
Thanks Granny. The distance couldn't be better. Garage/four-foot sidewalk/house. The spare room is right there.

I am using the jacks on the back of the computer. Tape deck is unbalanced.

This is not a recording project, it is a "work-on-this-song-boys" project. So lost-cost, easy-implementation are the specs.
 

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If the tape deck is on the wall closest to the house and the computer is close to the garage so the total distance is 6-8', you could probably get away with running unbalanced - 1/4" TS or RCA (whatever the tape machine has) to a (I assume) 1/8" (3.5mm) TRS minijack input on the computer (aka small headphone jack).

I suppose the conduit is plastic, but if it was metal, you could just ground one end of it for shielding and then it'd almost definitely be alright.
 

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Discussion Starter · #6 · (Edited)
Thanks Humoungous! "Been there, done that."

The reel-to-reel is all about retro now. Lol.

Nothing better about it. Just clinging to "the good old days". Start tape. Start jammin.

Thanks again GG. Actually down one wall, across the conduit and up into the computer room will be twenty feet or more, eh?

I record with a single large diaphram condensor into a vacuum tube preamp with "tune-able" acoustic tubes around the mic to control early reflections. Basically a mono recording of what is going on in the room (also the garage will be acoustically proportioned with a bit of trapping, diffusing, and absorbing).

So why not run the balanced mic line to the house and have the tape deck in the house beside the computer? The preamp should buffer the line, no? Solves communication problem -- one mic for everything:

" Take one", count off, start playing. Bobs yer uncle, if the "control room" is paying attention.

Maybe a window for visual contact as well? Maybe two balanced lines for sending mixes if I want to get fancy.
 

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As I understand it, when driving loads over a long distance, what you want is a high-current buffer/driver. It is both the low output impedance, plus the higher current drive, that serves to overcome the cable capacitance.

Think of it this way. In a conventional single-pole lowpass filter like this:

The cable provides a series resistance, and also capacitance between the conductor and the shield. If the distance is short - as in a 1/4W resistor and capacitor - the formula for identifying where the high-end rolls off is given by 1 / (2 * pi * R *C), where R is megohms and C is in microfarads. If R = 10k and C = .01uf, then those two components roll off frequencies above 1591hz at 6db/octave. The cable you will use to connect the open-reel machine and the rest of your system, also has a linear resistance, and a linear capacitance (i.e., both increase the longer the cable).

The rolloff is partly dictated by how fast the resistor/resistance permits charging up the capacitor. Since the resistor is in the series path of the signal, and higher resistance reduces how much current can pass, increasing the resistance lowers how much current is available to charge up the cap, lowering the rolloff (e.g., if R = 100k in our example, rolloff begins around 159hz).

Working the other way, though, if the resistance is fixed, then trying to pass more current through that same resistance allows the cap to charge up faster, and so results in less high-frequency loss. That is, the resistance will reduce current flow from whatever you started out with. But if you start out with more, then more gets through.

So, since you can't do much about the linear resistance of a cable connecting the tape machine in one part of the house, and where you're running the signal to. And since you can't reduce the cable capacitance (apart from using the lowest capacitance able you can find), then the next best thing is to use a lot of current drive to send the signal over that cable.

There are different ways of achieving that. One of the simpler ways is simply to parallel stages. My buddy Jack Orman has a simple project for a "super buffer", intended to address this very problem: AMZ Super Buffer for Guitars

Filters at work prevent me from linking to the schematic, but you can see that it consists of 4 paralleled versions of the exact same buffer stage. Their combined current output allows for it to drive a very long cable. This is the sort of thing one might use for feeding a mixer 100ft back from the stage to a power amp right in front of the stage. There may be other sorts of devices, for example those that use transformers, but this is cheap and simple, and small.
 

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Discussion Starter · #8 ·
Thanks mhammer. Good reference for when the time comes.

Same info applies if driving a mic or mix from the garage to house (with recording in house) as opposed to recrding in garage and driving to computer in house.
 
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