Mix-minus setup: Cannot send computer sound from USB to the caller

[csarami@ncsu.edu]

Hi,

I have a Yamaha MG12XU mixer. I am using FX1 aux to send out my signal to the outside.

I call the other person over the phone. The person I call is able to hear my input channels except, except the USB input.

- I playback music from my computer and I have a USB switch ON for Channel 11/12. I hear the music played from my computer and the PFL meter shows around 0dbFS when I play it.
- I have the Aux 1 knob on the USB input channel (11/12) all the way clockwise to the end! The channel is ON and its PFL is off.

What other settings I should check, please?

Any help would be much appreciated.

CS

[Sam Spoons]

As far as I can tell for a brief glance at the manual the Yamaha MG12XU only routes USB returns to the main L/R bus.

edit :- that is wrong I think, just trying to puzzle it out, it would be so much easier if I had the mixer in front of me

[Sam Spoons]

Ok, can you press two or more of the routing [1-2] [3-4] [L-R] buttons, if so then I'd try sending the stream from a pair of groups rather than the aux send but, that said your aux send method should work so check the attenuator function and the [Line/USB] button as well as the channel [ON] button on the USB channel.

[Kwackman]

As Sam says, the "Attenuation Function" button (page 22,28 of manual) are worth checking out.
Also, from what I can see, Aux 1 is only Pre-fader?
If that is so, it might not be the best for a mix-minus as contributors will hear stuff even if you've faded it out.

[Hugh Robjohns]

If your phone called can hear other channels via Aux 1, then it should work on the USB input channel too.

First thing I'd try is listening to the FX1 output to make sure it's actually coming out of the desk. If your USB source was, for example, polarity inverted on one channel for some reason you'd hear it in stereo on the main mix out and monitoring speakers, but the (summed mono) Aux 1 output would cancel to silence.

[csarami@ncsu.edu]

As Sam says, the "Attenuation Function" button (page 22,28 of manual) are worth checking out.
Also, from what I can see, Aux 1 is only Pre-fader?
If that is so, it might not be the best for a mix-minus as contributors will hear stuff even if you've faded it out.

I think the attenuator, would make the input from USB even softer! wouldn't it?
I suppose Aux 1 and Aux 2 are both post fader. But I will check that. Thank you.

[csarami@ncsu.edu]

If your phone called can hear other channels via Aux 1, then it should work on the USB input channel too.

First thing I'd try is listening to the FX1 output to make sure it's actually coming out of the desk. If your USB source was, for example, polarity inverted on one channel for some reason you'd hear it in stereo on the main mix out and monitoring speakers, but the (summed mono) Aux 1 output would cancel to silence.

I am testing this with ""Echo / Sound Test Service" of Skype.

It seems my mics can only send signals to Aux 1 and the "Echo / Sound Test Service" records them just find.

It seems beside the USB, even when I insert my synth outputs ( stereo) to

1) any input including Mono: Ch 4 ( just one of the cables), or
2) both cables into stereos: 5/6,7/8,9/10,11/12,

I don't hear anything out of them recorded with I try "Echo / Sound Test Service.

[Hugh Robjohns]

I am testing this with ""Echo / Sound Test Service" of Skype.

As I said, it would be a lot more helpful to check the actual Aux signal coming out of the console, just so you're testing one thing at a time.

It seems my mics can only send signals to Aux 1 and the "Echo / Sound Test Service" records them just find.

Looking at the manual, the only obvious difference between the mic channels and the stereo channels is the mono summing to feed the Aux buses. So I can't see any obvious reason why those channels shouldn't make it to the Aux output (assuming the channels are turned on, of course).

It seems beside the USB, even when I insert my synth outputs ( stereo) to
1) any input including Mono: Ch 4 ( just one of the cables), or
2) both cables into stereos: 5/6,7/8,9/10,11/12,
I don't hear anything out of them recorded with I try "Echo / Sound Test Service.

It would be worth trying the stereo channels with only one input connected.

It would also be worth checking that the output level From Aux 1 is roughly the same for both mic signals and line sources.

It's an intriguing problem.

[Sam Spoons]

As Sam says, the "Attenuation Function" button (page 22,28 of manual) are worth checking out.
Also, from what I can see, Aux 1 is only Pre-fader?
If that is so, it might not be the best for a mix-minus as contributors will hear stuff even if you've faded it out.

I think the attenuator, would make the input from USB even softer! wouldn't it?

Not if it is set to max attenuation, make sure it is set to off.

I suppose Aux 1 and Aux 2 are both post fader. But I will check that. Thank you

Aux 1 is pre-fade, aux 2 is switchable. It is normal for the low numbered aux sends to be pre and high numbered post, sometimes with some of the others switchable between pre and post, A post-fade aux will depend on the channel fader as well as the aux knob for it's live, pre-fade will only be affected by it's aux knob.

Next step is definitely to follow Hugh's advice and work through the system logically. If you are using your phone as a streaming device does Skype have a background sounds cancel option (zoom does I believe)?

[csarami@ncsu.edu]

I am testing this with ""Echo / Sound Test Service" of Skype.

As I said, it would be a lot more helpful to check the actual Aux signal coming out of the console, just so you're testing one thing at a time.

I have checked it!

I hooked up my small speaker to Aux 1 out and played back from the computer and also from Synth. I can hear both fine. It seems they don't make it to my iPhones microphone/input device.

Here is what I have purchased and my setup:

A) I have an Apple Lightning to 3.5 mm Headphone Jack Adapter
B) l have connected to that a Sennheiser PCV 05 Combo Audio Adapter
C) the microphone end is connected to Aux 1, and the headphones' end is connected to Channel 5/6 with a TRS 1/8inch to dual mono unbalanced TRS 1/4 inch.
D) I have the aux 1 knob on 5/6 channel off so it doesn't feedback to itself.
E) On the master section I have Aux 1 on 0 ( nominal).

I desperately need help with this!
Thank you very much.

Any help would be much appreciated.

[csarami@ncsu.edu]

Aux 1 is pre-fade, aux 2 is switchable. It is normal for the low numbered aux sends to be pre and high numbered post, sometimes with some of the others switchable between pre and post, A post-fade aux will depend on the channel fader as well as the aux knob for it's live, pre-fade will only be affected by it's aux knob.

Thank you. As you see in my image above, Aux 1 is switchable pre/post. So I suppose Aux 2 is sent effect it also adjust the built-in effects of the MG unit.

[Kwackman]

I hooked up my small speaker to Aux 1 out and played back from the computer and also from Synth. I can hear both fine. It seems they don't make it to my iPhones microphone/input device.

Can I double check something- I'm easily confused!
You have checked that audio sources in your mono channels do make it to the iPhone's input, but the USB/synth don't?
Silly question, how do you know what the iPhone is receiving?
I thought the iPhone input would be looking for mic level rather than line level, but if you say the mono channels DO make it to the input of the iPhone...I'm wrong...again!

Aux 1 is switchable pre/post

My fault for bringing that red herring up. The manual confused me as it only shows the bigger models where Aux1 is only PRE. But, in the signal flow diagrams, it shows the MG12-XU with the Pre/Post option. Apologies.

[Hugh Robjohns]

So... it seems we now know for sure that the USB/stereo channel signals are reaching the Aux 1 output, along with the mic channel signals.

Is it also safe to presume that these are all at roughly similar levels? I ask because if the USB channels were substantially louder that could trigger some kind of AGC/limiter that might give the impression of low level...

Given all the above, it appears the problem lies somewhere in the phone or the streaming service you're using, rather than the console... so that's progress!

Someone mentioned an auto-cancellation option in that system and it would definitely be worth looking into that.

Are you sure that your Aux1 mix-minus really is a 'clean feed' and doesn't contain anything coming back from the phone?

[csarami@ncsu.edu]

Can I double check something- I'm easily confused!
You have checked that audio sources in your mono channels do make it to the iPhone's input, but the USB/synth don't?

That is a critical question indeed. "The mono channels make it to the iPhone input If and only if, the source is a Microphone ( dynamic or condenser)

Silly question, how do you know what the iPhone is receiving?

Again a good question. I know it via Skype Echo/Sound test service

I thought the iPhone input would be looking for mic level rather than line level, but if you say the mono channels DO make it to the input of the iPhone...I'm wrong...again!

The Aux1 knob has taken care of this I suppose. Please note I can monitor the signal in my headphones just fine.

Aux 1 is switchable pre/post

My fault for bringing that red herring up. The manual confused me as it only shows the bigger models where Aux1 is only PRE. But, in the signal flow diagrams, it shows the MG12-XU with the Pre/Post option. Apologies.

Thank you for your time.

[csarami@ncsu.edu]

So... it seems we now know for sure that the USB/stereo channel signals are reaching the Aux 1 output, along with the mic channel signals.

Yes. They do reach Aux1 output. As I mentioned in my last post, only the microphone. I just did another experiment:

1. The stereo channel 7/8 have also an xlr microphone input aside from the 1/8" stereo dual unbalanced (line) inputs! When I connect a microphone to its XLR input, it gets recorded in the Skype test service. So I am guessing the issue is with the signal levels of non-microphone sources.

Is it also safe to presume that these are all at roughly similar levels? I ask because if the USB channels were substantially louder that could trigger some kind of AGC/limiter that might give the impression of low level...

At least when I monitor them with a microphone. I attenuated the USB input signal by -9 dB and raised the fader level to compensate here. The PFL meter when I play music from my computer is around 0dB. is how I check the signal levels:

Let say I want to check the signal level of the Channel fader 11/12 which is used for the USB input signal.
1. I turn off the channel fader by pressing the ON button.
2. I press the PFL button.
3. Play music to send signals to the channel.
As I said, the USB doesn't get recorded into my iPhone!

Given all the above, it appears the problem lies somewhere in the phone or the streaming service you're using, rather than the console... so that's progress!

I don't think this is about streaming sevice. I have tested it with Zoom and also Whatsapp. Same result.

Someone mentioned an auto-cancellation option in that system and it would definitely be worth looking into that.

In fact, on Zoom there an option to set the "Echo cancellation". I set it to auto and also aggressive. Nothing changed!

Are you sure that your Aux1 mix-minus really is a 'clean feed' and doesn't contain anything coming back from the phone?

I have the Aux 1 knob set to 0 (turned off) on channel 5/6 (iPhone's input channel).

Finally, I go something. I swapped my brand new "Sennheiser PCV 05 Combo Audio Adapter" with the "Movo TCB2 XLR Microphone to TRRS Smartphone Adapter with Headphone Jack". It seems all the signals microphone, USB and my synth reach the iPhone just fine. The female XLR end of the latter is connected to Aux 1 using XLR Male to 1/4-Inch TRS Male. I need to change this adaptor as the signal is not clean and is a bit noisy, but I cannot find it anywhere and as you see it is sold out

I guess the issue is the incompatibility of the Sennheiser audio adaptor for high voltage ( consumer level) signals! or maybe the seller send me a bad one. I will return it for sure.

Thank you very much, Hugh and everyone for the help! I learned quite a few things from you guys! Again Hardware is the trouble maker!

[Sam Spoons]

I'm not sure if this is the problem but the Sennheiser adapter has 2 x 'stereo' 3.5mm jack sockets, if you connect from the Aux send (a balance output) with a ¼" TRS to 3.5mm TRS cable that could be causing the synth signal to cancel, though I can't work out why summing hot and cold doesn't just remove everything...

The old adapter has a mono connector, the XLRF, for the mic input which should be correctly wired to supply the unbalanced input to the phone. Neither should be noisy, they are just wires and connectors.

[Hugh Robjohns]

Ah... the perils of unknown adapters with unspecified wiring and confused descriptions.

[csarami@ncsu.edu]

Maybe I should get one of these: Sescom LN2MIC-TASDR100 Line Out to Camera Mic Level In Cable.

One more thing: I changed my input to the mixer from Synth to 9/10 from 7/8 it attenuates the signal by -10dBu automatically. But I wish I could do it even more say -20dBu. Is there a way to do that? on Mic inputs 1-4 there are Pads that when I press them, reduce the input signal by -20. However, this option is not available for other

[csarami@ncsu.edu]

Ah... the perils of unknown adapters with unspecified wiring and confused descriptions.

That is correct. I would buy a better one if there was one in the market.

[Hugh Robjohns]

One more thing: I changed my input to the mixer from Synth to 9/10 from 7/8 it attenuates the signal by -10dBu automatically. But I wish I could do it even more say -20dBu.

Assuming you're connecting the line outputs of a synth to the line inputs of a mixer, you really shouldnt need to dial in a lot of attenuation... The volume control on the synth should be adequate for adjusting the levels in concert with the channel input gain control.

The more you tell us, the more confused I am about exactly what is going on...

[csarami@ncsu.edu]

The more you tell us, the more confused I am about exactly what is going on...

This is exactly what the The Heisenberg Uncertainty Principle is all about!

My issue is fixed now! The Sennheiser cable was guilty and I assume I need to put an attenuator on the path to the phone's mic to make it work.

The other cable (with XLR) works now.

I will search later to find a quality one!

Thanks again.

[Hugh Robjohns]

I'm glad it's all solved...

[Mike Stranks]

This is the second time in a couple of weeks that I've come across someone having problems with some Sennhesier adapters...

... which emphasises the point that Sennheiser build adapters for specific kit... their adapters are not generic.

... and as I've commented several times before here... once you get away from the real basics of adapters or adapter leads then all bets are off as to how they're wired. I have an 'interesting' collection of adapters here which are useless - apart from repurposing the connectors. Whoever commissioned them from the manufacturer clearly had no idea about audio connection protocols. Suppliers don't help either, with vague and inaccurate descriptions...

Lessons learnt... to the soldering iron!

[csarami@ncsu.edu]

This is the second time in a couple of weeks that I've come across someone having problems with some Sennhesier adapters...

... which emphasises the point that Sennheiser build adapters for specific kit... their adapters are not generic.

... and as I've commented several times before here... once you get away from the real basics of adapters or adapter leads then all bets are off as to how they're wired. I have an 'interesting' collection of adapters here which are useless - apart from repurposing the connectors. Whoever commissioned them from the manufacturer clearly had no idea about audio connection protocols. Suppliers don't help either, with vague and inaccurate descriptions...

Lessons learnt... to the soldering iron!

I asked Yamaha Support to refer me to a standard or any adapter they use in-house. Here is what they responded to me:

"

We don't have a recommendation on what cable you will need to use. The MG12XU is a mixer used to mix audio from different sources and be sent out to an amplifier or recording device. If the signal is being too strong, then you'll need to adjust the sources gain accordingly.

"