Making my own interconnect XLR to RCA

[Steve D.]

Not normally. In most cases (separately driven hot and cold signals) that will give you exactly the same signal quality as an RCA output.

You mean - in such a case (pin 3 disconnected) XLR has absolutely no advantage over RCA - both signals are equal?

 

[Ropeburn]

You mean - in such a case (pin 3 disconnected) XLR has absolutely no advantage over RCA - both signals are equal?

It has theoretical advantages such as better noise rejection and better SN ratio due to the signal being louder effectively. In most cases that's not relevant in practice and completely inaudible.

 

[antcollinet]

You mean - in such a case (pin 3 disconnected) XLR has absolutely no advantage over RCA - both signals are equal?

Of course not - you are going into an unbalanced input. No advantage of balanced connections (noise rejection) can be obtained. But bear in mind - in most domestic installations, the performance of RCA is still quite capable of transferring an audibly perfect signal. Only if you experience audible common mode noise is there going to be an issue to solve some other way, and this is unlikely unless you position your CD player an unreasonable distance from your amp.

It has theoretical advantages such as better noise rejection and better SN ratio due to the signal being louder effectively. In most cases that's not relevant in practice and completely inaudible.

(my bold)

It isn't - you only get the benefit of higher ouput voltage when both hot and cold are used. Typically both are individually 2V signals - one the negative of the other. When you subtract the negative from the positive (at a balanced input) you get a 4V signal.


Since with an unbalanced input you can only use the positive signal - you only get 2V - just like an RCA output.

 

[Ropeburn]

Of course not - you are going into an unbalanced input. No advantage of balanced connections (noise rejection) can be obtained.




(my bold)

It isn't - you only get the benefit of higher ouput voltage when both hot and cold are used. Typically both are individually 2V signals - one the negative of the other. When you subtract the negative from the positive (at a balanced input) you get a 4V signal.


Since with an unbalanced input you can only use the positive signal - you only get 2V - just like an RCA output.

Right, I misread the pin3 part. If you aren't using that, it's of course identical to unbalanced (proper opamp output assumed).

 

[Steve D.]

Thank you all for everything.

As I get it, it is preferable to use (1) Shorted pins 1 & 3 method - if there is no hum or noise, rather than (2) Pin 3 floating method.

 

[Ropeburn]

Thank you all for everything.

As I get it, it is preferable to use (1) Shorted pins 1 & 3 method - if there is no hum or noise, rather than (2) Pin 3 floating method.

The easiest method to make sure is looking at the service manual of the player, so you can determine how exactly the output works. See if you can find one.

If you can't read schematics, just post the manual or screenshots of the relevant parts here. Our collective membership has more than enough expertise to help you out in detail. (⁠｡⁠･⁠ω⁠･⁠｡⁠)⁠ﾉ⁠♡

 

[antcollinet]

Thank you all for everything.

As I get it, it is preferable to use (1) Shorted pins 1 & 3 method - if there is no hum or noise, rather than (2) Pin 3 floating method.

No it is not.

The only reason for shorting 3 to 1 is if the output from your cd player is a transformer - but it almost certainly isn't.

If you have two actively driven outputs -then shorting 1 to 3 has no benefit but will over load the cold output - and in the worst case, damage it. Again, probably not the latter - but without knowing the output circuit of the interface we can't be certain.

Start with pin 3 floating. If it works, then you are golden. If you get no signal that way, then try shorting pin 3.

Better still find out from the manufacturer or service manual what sort of output you have.


What is the CD player? It might be that someone here is already familiar with it.

 

[mhardy6647]

FWIW, I'd be uncomfortable with shorting anything without being pretty darned sure that whatever is hooked to the source side (indeed, either side) of the short isnt going to mind. I wouldn't assume a priori that there's no possible chance of irretrievable (or even of tedious to repair) damage.

 

[Ropeburn]

FWIW, I'd be uncomfortable with shorting anything without being pretty darned sure that whatever is hooked to the source side (indeed, either side) of the short isnt going to mind. I wouldn't assume a priori that there's no possible chance of irretrievable (or even of tedious to repair) damage.

Now, now, let's be realistic. If a line level input doesn't stand shorting to ground, it's the most broken one ever designed. One should be careful with output shorting on consumer devices, as they can differ and bad luck is a chance you don't wanna take. But shorting inputs? I'd argue that's a staple method to get zero input with as little noise as possible, for, say, testing purposes.

 

[Sokel]

Now, now, let's be realistic. If a line level input doesn't stand shorting to ground, it's the most broken one ever designed. One should be careful with output shorting on consumer devices, as they can differ and bad luck is a chance you don't wanna take. But shorting inputs? I'd argue that's a staple method to get zero input with as little noise as possible, for, say, testing purposes.

Shorting an input should be ok, agree to that.
But shorting an output and sending that to an input can be very different, if damage occurs for example one can send copious amounts of DC to it.

 

[Ropeburn]

Shorting an input should be ok, agree to that.
But shorting an output and sending that to an input can be very different, if damage occurs for example one can send copious amounts of DC to it.

Generally I agree, but my experienced hamfists are kinda merciless. As long as we're talking about line (=mere signal) outputs as opposed to power ones, I fully expect shorting to be safe. If it isn't, the device is badly designed in my view. Transformers for balanced outputs? That's so 1966, seriously.

 

[mhardy6647]

Now, now, let's be realistic. If a line level input doesn't stand shorting to ground, it's the most broken one ever designed. One should be careful with output shorting on consumer devices, as they can differ and bad luck is a chance you don't wanna take. But shorting inputs? I'd argue that's a staple method to get zero input with as little noise as possible, for, say, testing purposes.

I'd agree, were it not for a couple of actual instances I've seen of weird results (admittedly not fatal ones) with shorted inputs on amplifiers.
You probably know the old saying about idiot proofing:

Never underestimate a determined idiot.

There are some pretty determined idiots out there, especially in the "high end" of the audio industry.

Point taken, though. FWIW, I would be more leery of the outputs (source side), but, appearances to the contrary, I am pretty careful, especially with very expensive things.

 

[antcollinet]

with shorted inputs on amplifiers.

What is the difference between shorting an input - and just sending 0V to it?

 

[Ropeburn]

What is the difference between shorting an input - and just sending 0V to it?

Technically zero, except on broken designs. If you blow those up, it's definitely not your fault but that of the stupid designer. Ground and 0V are literally identical.

 

[mhardy6647]

What is the difference between shorting an input - and just sending 0V to it?

The difference between a dead short and an open circuit.
The hot side (so to speak) is connected to ground.

 

[antcollinet]

The difference between a dead short and an open circuit.
The hot side (so to speak) is connected to ground.

No, I'm talking about an active 0V - indistinguishable by the device from a short to 0V.


I am failing to understand how a short on the input - which is the same (as far as the device is concerned) as an active output from a source putting out silence.

 

[Ropeburn]

The difference between a dead short and an open circuit.
The hot side (so to speak) is connected to ground.

False. Sending 0V is electrically identical to a short, as long as there's a ground connection which is the 0V reference. Open = floating input is different and can very well result in hum/buzz precisely because it isn't referenced to anything. Of course on a properly designed input it still is via the parallel input resistor (10-47k) which pulls the input to ground if there's no input.

 

[antcollinet]

Transformers for balanced outputs? That's so 1966, seriously.

I'm just accounting for the remote possibility that it is a 1966 CD player.

 

[Steve D.]

Please forgive me, I am an idiot.
It's Tascam CD-A750. A combined CD-Tape player.
I looked carefully again, of course it has normal RCA ouputs, I just thought those 3 rows RCA below are for some weird pro-, hi-end-, etc. gadgets.
One of the RCA couples is a plain Line Output.
So, forget all those XLR tricks and get a decent RCA-RCA cable?
Stupid blind me...

 

[antcollinet]

So, forget all those XLR trcks and get a decent RCA-RCA cable?

Sounds the best plan (which means : categorically - yes) - but no need for anything fancy. Amazon basics is fine (see latest cable review here in the last couple of days)

Stupid blind me...

We've all been there brother.