Making my own interconnect XLR to RCA

[Ropeburn]

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 trcks and get a decent RCA-RCA cable?
Stupid blind me...

Well that settles that. BUT now I'm intrigued by those serial and parallel control connectors!

I want a service manual more than ever.

Edit:

https://www.tascam.eu/en/docs/CD-A550_A750_Manual_RevB.pdf

Page 45. Omg NICE

 

[mhardy6647]

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.

So -- this will be light on details (due only to the passage of time and my own flagging memory) but a hifi friend and fellow traveler was trying to isolate the source of noise (audible) from the output of (if memory serves) a power amplifier (this is with unbalanced inputs). He'd tried open-circuit inputs and still heard... whatever he was hearing. I encouraged him to short the inputs and see if the noise level changed -- so he did (powered down of course) and he was greeted (upon power-up) with a horrific howl from the loudspeakers.

No permanent damage done, but... as I said... there are some determined idiots out there, and some of them apparently design and build amplifiers.

 

[Ropeburn]

No permanent damage done, but... as I said... there are some determined idiots out there, and some of them apparently design and build amplifiers.

That's the polar opposite of a, let's say, soldierproof design. The worst village idiot is supposed to be able to use it without burning down the building. In this context that's the typical clueless musician, drunk and on three other drugs, sleep deprived, randomly plugging things wherever and turning everything up to eleventyone.

A real proper design accommodates the worst case scenario!

 

[mhardy6647]

Determined idiots, mein Freund -- a formidable force of nature.

 

[antcollinet]

So -- this will be light on details (due only to the passage of time and my own flagging memory) but a hifi friend and fellow traveler was trying to isolate the source of noise (audible) from the output of (if memory serves) a power amplifier (this is with unbalanced inputs). He'd tried open-circuit inputs and still heard... whatever he was hearing. I encouraged him to short the inputs and see if the noise level changed -- so he did (powered down of course) and he was greeted (upon power-up) with a horrific howl from the loudspeakers.

No permanent damage done, but... as I said... there are some determined idiots out there, and some of them apparently design and build amplifiers.

Presumably the short kicked the amp into oscillation. It's difficult to imagine how this could happen - it would require some sort of feedback from the output right onto the input terminal that then needs some non zero impedance there for stability. With any non zero impedance, the feedback would change the input voltage and behaviour would be dependent on the output impedance of the source.....

No, whoever designed that was an imbecile. Hopefully they went out of business due to the unutterably uselessness of their amps.

 

[Sokel]

The best outcome of this thread is that, people hopefully understand that there's no point buying balanced gear if the next link is not balanced.

We have seen cases that even if a source has both balanced and unbalanced outputs, people try use the balanced one despite all warnings, solely based at the higher voltage derived better THD+N !

Even if this higher voltage ability will result at far worst SNR (when digital attenuation is used) if the next stage's input only accepts the traditional 2V or less for older gear.

 

[staticV3]

The best outcome of this thread is that, people hopefully understand that there's no point buying balanced gear if the next link is not balanced.

We have seen cases that even if a source has both balanced and unbalanced outputs, people try use the balanced one despite all warnings, solely based at the higher voltage derived better THD+N !

Even if this higher voltage ability will result at far worst SNR (when digital attenuation is used) if the next stage's input only accepts the traditional 2V or less for older gear.

What's more, without a few trafos or Opamps between XLR source and RCA sink, you cannot get more than 2V out of the 4V source anyway, even with the volume maxed out.

 

[Sokel]

What's more, without a few trafos or Opamps between XLR source and RCA sink, you cannot get more than 2V out of the 4V source anyway, even with the volume maxed out.

I remember vaguely a post, with someone trying to reverse cold and then sum them passively, with just a cable

 

[mhardy6647]

Presumably the short kicked the amp into oscillation. It's difficult to imagine how this could happen - it would require some sort of feedback from the output right onto the input terminal that then needs some non zero impedance there for stability. With any non zero impedance, the feedback would change the input voltage and behaviour would be dependent on the output impedance of the source.....

No, whoever designed that was an imbecile. Hopefully they went out of business due to the unutterably uselessness of their amps.

Yes, did you read my posts?
We are talking determined idiot. It was a commercial product, though. We are in violent agreement.

 

[antcollinet]

Yes, did you read my posts?
We are talking determined idiot. It was a commercial product, though. We are in violent agreement.

Yes I know - I thought I was building on the agreement

 

[mhardy6647]

We're good.

 

[Steve D.]

Tests underway here.
I mentioned above that cheapo XLR Female<->RCA Male cable I got - quite an ordinary version, Pin 1 and Pin 3 shorted.
Meanwhile I found some RCA<->RCA wires - also a plain and cheap type.
Plugged them one by one, tested each of them for hours. First tried XLR out player to CD RCA input amp. Then CD line out RCA player to CD in RCA amp.
Absolutely no difference can be heard - no noise, no hum with XLRs, normal signal, music playing and everyone happy... the same with RCAs - same volume, nothing to note, nothing to underline, nothing to complain about.
Maybe kind of strange, but a fact.

 

[Ropeburn]

Tests underway here.
I mentioned above that cheapo XLR Female<->RCA Male cable I got - quite an ordinary version, Pin 1 and Pin 3 shorted.
Meanwhile I found some RCA<->RCA wires - also a plain and cheap type.
Plugged them one by one, tested each of them for hours. First tried XLR out player to CD RCA input amp. Then CD line out RCA player to CD in RCA amp.
Absolutely no difference can be heard - no noise, no hum with XLRs, normal signal, music playing and everyone happy... the same with RCAs - same volume, nothing to note, nothing to underline, nothing to complain about.
Maybe kind of strange, but a fact.

Not strange. It's exactly what I'd expect from properly designed devices. It's supposed to work like that. Nice it works!

 

[antcollinet]

Tests underway here.
I mentioned above that cheapo XLR Female<->RCA Male cable I got - quite an ordinary version, Pin 1 and Pin 3 shorted.
Meanwhile I found some RCA<->RCA wires - also a plain and cheap type.
Plugged them one by one, tested each of them for hours. First tried XLR out player to CD RCA input amp. Then CD line out RCA player to CD in RCA amp.
Absolutely no difference can be heard - no noise, no hum with XLRs, normal signal, music playing and everyone happy... the same with RCAs - same volume, nothing to note, nothing to underline, nothing to complain about.
Maybe kind of strange, but a fact.

Not strange at all - exactly what I'd have expected.

EDIT : Ninjad by @Ropeburn - almost word for word.

 

[mhardy6647]

Not strange at all - exactly what I'd have expected.

EDIT : Ninjad by @Ropeburn - almost word for word.

Twin sons of different mothers.

 

[Steve D.]

Don't know... maybe was expected some tiny, slimmy difference - more/less noise or hum, level mismatch, etc.
Nothing like that - shorted XLRs sound could not be differed from RCAs, even with a blind testing, done by myself and other 2-3 inhabitants of the house, wandering around without anything meaningful to do...