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A small cable question to record my trio....


Go to solution Solved by fuzzfilth,

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Well, the Yamaha spec-sheet doesn't seem to let me know that, nor the S1 sheet I found, though I don't know what that 'transformer" you mention actually refers too, so I don't really know what I'm looking for.

 

Here are the links to both devices, if you'd have the time to take a look at them, maybe you could figure something out that I can't...

 

https://www.recordcase.de/media/pdf/27/91/5f/Yamaha-MG10XU-Data-Sheet.pdf

 

https://toonz.ca/bose/wiki/index.php?title=S1_Pro_system

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The circuit diagram of the Yamaha shows that there are no transformers used. The Bose manual states that a TRS>TS cable can be used to connect its line out to another input.

 

Here's what I would do: Since all inputs are unbalanced anyway, I'd use normal TS cables and don't push the plugs entirely into the output jacks. There's two bumps which you can feel when plugging into a balanced TRS jack. Pushing into the first bump but not the second should give proper signal (its polarity will be inverted but don't tell anyone) while avoiding a short circuit of half the signal.

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Interesting. I just tried a TS cable in the S1, and you're right. That sounds like a strange solution though. I wish there was a simpler one.

 

This is so confusing. I spent a lot of time reading around, trying to understand this kind of cable connection, and I'm more lost than ever. Dear life...

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I can see that that information is already available, Fuzz, and see that I would need to—really—spend some time with it to wrap my head around it. There are a lot more variables in that whole cable world than I've been aware of. I'm likely to do so eventually, since the gear I have and use calls for it.

 

Thanks for the support.

 

PS: Inserting a cable halfway in doesn't strike me as a simple solution. While I get that if it works, it works.

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I can't. The few things I said in the first post made his eyes glaze over already. :D

My concept of this forum is that while you seem to answer one single person's question, really you'll be helping many, many more people who will now or in the future end up finding this thread as a result of their search on this topic. So think of anyone who could end up reading this in the future, and how interesting it would be for all of us to have that information. ;)

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  • Solution

Fair enough. Ok, here goes:

 

Balanced means the signal is being put out by two actual outputs, each carrying half of the signal, but one with its polarity reversed. These have various names Hot/Cold, +/-, InPhase/OutOfPhase, anything really that emphasizes the fact that both are equal but with opposite polarity, one being the mirror image of the other. On the receiving side, the difference between the two forms the entire signal again.

 

The smart part is that any hum, buzz or other electromagnetic interference introduced into the cable will be equally present in both lines and thus their difference is zero, which effectively cancels any noise that tried to come in this way.

 

Balancing an output can be achieved in two ways:

 

Magnetically by means of a transformer, which, apart from being big and bulky and imparting color into the signal, has two outputs Hot and Cold which have no relation to electrical Ground (more on that in a second)

 

Electrically by means of two amplifiers (one of them inverting the signal), which, apart from being small and arguably without sound color, both have their output referring to electrical Ground.

 

Both ways of balancing have their own rules when going from balanced to unbalanced. Since a transformer's outputs are just the ends of the transformer's secondary coil, both must be used to get current flowing into the receiving unbalanced input. So you connect the Hot output to the input and the Cold output to Ground.

However, in an electronically balanced output, the relation of signal to Ground is already there, so you use only the Hot output and Ground. You should not connect the Cold output to Ground as you'd effectively create a short circuit of the inverted amplifier's output to Ground and poor little inv amp might not like that. There are amps out there who can sense a short circuit on their output and duly shut up to avoid damage but if you can tell whether you have these you wouldn't have to read this article.

 

In practice, when there are 6.3mm TRS (balanced) output and TS (unbalanced) input jacks and you have a transformer balanced output, you can use a normal TS guitar-style cable, which connects both Cold and Ground of the output by the sleeve of the plug, as required.

For an electronically balanced output, you'd actually need a special cable with a TRS plug on one end but with only T and S connected and R left open so as to not shorten Cold to Ground.

 

Well, discussing this type of cable with the guy in the guitar shop is usually fruitless as a) often enough their electrical expertise peaks at reading out the price to you and b) they only have one (the wrong) type of TRS>TS cable anyway, so normally you pull this off by soldering your own cables, unless, and here comes the punchline, you push the plug of that standard TS cable only halfway into that electrically balanced TRS output. Now T connects to Cold, Ground to Ground and Hot is left unconnected (in other words, certainly not shorted to Ground), as required.

Now, since you used the Cold output which carries inverted signal, your unbalanced signal has its polarity reversed. In a true multi-channel, phase aligned environment, this might be a big no-no, but then you wouldn't pull this stunt anyway and work with proper cables instead. However, in most other cases no one will know the difference of whether it has its phase flipped or not (see what I did there?).

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Thanks for taking the time to share all this, Fuzz. I can't follow much of it, yet I'm curious to know what "normally you pull this off by soldering your own cables" actually involves. I have a soldering kit and some experience with soldering—pickups for instance—I have all kinds of cables, and if you care to explain exactly how that kind of cable is made, what kind of cable to use, which wires specifically have to be soldered, and where exactly, I'd like to know that.

 

From what you say, it looks like we can't rely on what's happening inside a TRS to TS cable bought somewhere. So obviously, leaving aside the halfway-in trick, making that cable is the only way to be sure that we use the right thing.

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