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Balanced to unbalanced cable to make up.
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Uncle Krunkus
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PostPosted: Sat May 12, 2007 3:54 am    Post subject: Balanced to unbalanced cable to make up. Reply with quote  Mark this post and the followings unread

Hey everyone,
I'm fairly sure of the answer to this, but I thought I'd post it so others might be able to reference it.
I'm re-making up the cables from my new cabinet to the computer and back and wanted to know how to make: -

Two 6mm balanced mono outputs --> One 3.5 unbalanced stereo input

Yes, I know I'm taking a half decent compressor and plugging it into an Audigy sound card. (I can hear everybody's blood curdling from here! Laughing ) When I suddenly have the kind of job that allows me to buy a new input/output box for the computer you will all be the first to know. Very Happy Till then I'd like to make the most of what I've got.

I'm pretty sure that I should do this: -
Hots --> Tip/Ring(L/R)
Colds --> Sleeve(combined at the 3.5mm end)
Sheilds --> Covering right up to the 3.5 but not connected

What do ya reckon?

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EdisonRex
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PostPosted: Sat May 12, 2007 5:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Let me get this straight in my head. (good day, by the way)

2x balanced mono outputs from compressor output, and you are wanting to turn it into an unbalanced stereo mini jack for a computer sound card input.

The way you are proposing isn't really staying balanced, you don't have a good decouple on the computer's side. I suppose it'd work, but it won't be balanced. I was taught not to short colds. Maybe I was taught wrong. You're combining the colds? Won't that introduce channel crosstalk on the colds?

you could just take an unbalanced output since you don't really have a balanced input on the computer end. I think that'd be simpler.

So pick tip or ring from the balanced output. One or the other, but make sure you pick the same one for each channel. Say tip for both channels.

So left tip out becomes tip on the input, right tip out becomes ring on the input, and shield should go all the way along because it's unbalanced.

Hopefully your impedance won't be an issue, I'm guessing your outputs are like 600 ohms and who knows what the input impedance is. The level out the compressor is probably like +4 anyway so you'll be driving hard, so I suppose that'd work okay anyway.

Anyway, that's what I usually do in these situations, balanced outputs don't matter to me practically for short runs IMHO.

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Uncle Krunkus
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PostPosted: Sat May 12, 2007 7:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, actually you're completely right. I thought that I could improve it in someway by trying to use the balanced outs. But it would crosstalk like you said.
If I use mono 6mm plugs to do it like you described, the sleeve will short the cold to the sheild inside the socket on the compressor, yeah? Is that okay?

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EdisonRex
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PostPosted: Sat May 12, 2007 9:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Yeah, actually you're completely right. I thought that I could improve it in someway by trying to use the balanced outs. But it would crosstalk like you said.
If I use mono 6mm plugs to do it like you described, the sleeve will short the cold to the sheild inside the socket on the compressor, yeah? Is that okay?


yup they will, and that's basically okay. When I said don't short colds, I meant at the far end. You can (and should) do it at the near end. Mind you, if it's a transformerless connection you might want to consider using a TRS and leaving the cold isolated. But if my memory of these things is right it shouldn't matter. FWIW, I always use a TRS plug and then open the cold to unbalance.

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EdisonRex
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PostPosted: Sat May 12, 2007 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

You made me have to go look it up. Yes, short the cold (-) at source, and if you really want to properly equalise the level from +4 to -10 then put a 3.9k and a 1k resistor in series across the cable at the computer end, and connect the input end's tip to the junction of the two resistors.

Code:

(+)------------------------------|
(-)\                               3.9k
    |                             |-----------------------tip
(c)/-----------------------------1.0k----------------- sleeve


you'd have to do the same with the second channel but connect to ring at the input end.

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Uncle Krunkus
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PostPosted: Sat May 12, 2007 4:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

So the resistors form a 1:4 divider. Cool

I can switch the output of the compressor between +4 and -10. I've always left it on +4 because I thought a hotter signal would mean less noise when I get to the computer. I can drop the level in software, and have never noticed any overdrive. I figured if I go with -10, I'd just have to compensate by turning up the gain of the card, and that's bound to create more noise. Does that make sense?

BTW, thanks for digging out such a comprehensive answer. Very Happy

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elektro80
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PostPosted: Sat May 12, 2007 5:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just noticed this thread. I guess I should reread the lot when I am 100% sober and then post something.

Anyways, the advice given by EdisonRex seems intuitively OK. Implied here is handling of an analogue gain structure and then how to handle digital recording levels.

And yes, the traditional way to do this is to work with a reasonably hot signal. How hot depends on what you want to accomplish signature wise with the various decvices you have in the signal path. You mention a compressor. Which one? You should consider having a neutral EQ or a filterbank in front of it. It is always smart to be able to shape the signal you put into a compressor.

When recording to a DAW, it is standard to keep the main beef of the signal at say -18db to -15db. Peaks are allowed, but it is smart to round these off at say -6 to -3db. However, I think -3db is a bit too hot when tracking. Record at 44.1 khz/24bit. If you want a better recording go for 88.2khz/24bit. You might choose other samplerates, but unless you have a damned good reason, stick to 1X or 2X.

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Uncle Krunkus
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PostPosted: Sun May 13, 2007 6:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I was also going to use some nice balanced Canaire cable I found in my "good stuff" box. I s'pose that would be a waste now. The old one was just a thin fig8 dual line cable, surely I could do better than that? I think I've also got some nice unbalanced instrument cable around here somewhere, I'll just have a look.
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