Cable question

[Ben Kennedy]

Hello all -

I have a Zoom H1, which has a stereo line input. I have a cable that is 1/8" male to two 1/4" TS male connectors. I can successfully connect them to two Aux outputs on an Allen & Heath mixer, which has TRS balanced outputs. When I record, I successfully capture each Aux output on the left and right tracks. My understanding is that this because the "Hot" portion of each of the TRS Aux ports are getting connected to the Tip and Ring portions of the 1/8" plug, so it all works great.

Previously I had been using a 1/8" to 1/4" TRS cable to attach the recorder to the mixer. This resulted in a recording that had the aux signal on the L channel (which I expected), but nothing on the R channel - when looking at waveform in Audicity, it is blank. Now, my understanding is that the Ring of the 1/8" was connected to the "Cold" side of the TRS Aux output. So why was my waveform flat?

Is a cold signal incompatible with the analog-to-digital converter in my recorder? Or does it read it and suppress the output because it knows is actually connected to a TRS source? Or is the mixer clever about it and not sending anything to the recorder when connected that way? Thanks in advance for any insight.

 

[John Roberts]

Re: Cable question

1/4" TRS jacks are commonly used to feed +/-/ground of a single balanced mono signal, and less commonly the unbalanced Left+/Right+/ground of a stereo signal (most often found on headphone jacks). OTOH 1/8" TRS are predominantly unbalanced stereo connections.

JR

 

[Timo Ulkuniemi]

Re: Cable question

Hello all -
Now, my understanding is that the Ring of the 1/8" was connected to the "Cold" side of the TRS Aux output. So why was my waveform flat?

Hello

If your TRS-output was true banced - electronically or transformer - you would have signal in both channels of your recorder - same signal with opposite polarity,

Many mixers have trs-outputs, that are not balanced, but ground-compensated - hence no signal on R-channel.

 

[Ben Kennedy]

Re: Cable question

If your TRS-output was true banced - electronically or transformer - you would have signal in both channels of your recorder - same signal with opposite polarity,

Many mixers have trs-outputs, that are not balanced, but ground-compensated - hence no signal on R-channel.

Thanks! The manual says "Each aux send is available on an impedance balanced TRS" - so this makes sense now. I now understand why "impedance balanced" is a somewhat misleading term, since electrically balanced TRS is also impedance balanced. A lot of the descriptions of balanced connections make it seem like the opposite waveform is the critical thing for noise cancellation, when the reality is that it is the impedance that matters so that interference produces the same voltage spikes in both lines. Is that a fair comment?

 

[John Roberts]

Re: Cable question

Thanks! The manual says "Each aux send is available on an impedance balanced TRS" - so this makes sense now. I now understand why "impedance balanced" is a somewhat misleading term, since electrically balanced TRS is also impedance balanced.

Impedance balanced is probably the best marketing bang for a pennies worth of resistor ever spent. That said the impedance balanced termination is generally all you need for anything but crazy long lines.

A lot of the descriptions of balanced connections make it seem like the opposite waveform is the critical thing for noise cancellation, when the reality is that it is the impedance that matters so that interference produces the same voltage spikes in both lines. Is that a fair comment?

You are correct sir...

JR