Can you describe the ruckus? Anyone care to guess this?

[pucho812]

This is a puzzler...  This is the aux master of a channel on a desk. Of the 10 aux masters this is the most offending one.  The others do it as well but not nearly this pronounced.  Aside from crosstalk/bleed of steely dan's two against nature,  We have this buzz.  I  am trying to figure out what exactly it is. I would guess it's capacitor related. If I run an eq to remove the buzz in pro tools, I have to have the frequency upwards around 1-2K with a medium wide Q and a good amount of cut to get the buzz out.  I am assuming the 1-2K frequency is do to being a harmonic and not the fundamental.

The set up for  recording this was literally aux masters out directly into the daw machine. The Aux masters did not have any signal  on it, and when there is signal the buzz is still present just not as noticeable at times.  I do know it's not the wiring to the daw because when we use the console busses or direct out from the channels into the daw we do not have this buzz.  I do know it is isolated down to the aux masters themselves which their outputs show up on  our patch bays. I do not schematics but such is at times. At least we got ye old o-scope and probe...

(audio sample Below)
https://drive.google.com/open?id=1Q5lZLGkLgeYdSfgHxWjlHSACW7uWqhbd

 

[ruffrecords]

I hear nothing at all.

Cheers

Ian

 

[pucho812]

I hear nothing at all.

Cheers

Ian

no way really?  We got buzz over here, so much so that there was a client complaint. 

May I ask what you are playing it back through?it's there, I have not run an analyzer on it yet,

 

[JohnRoberts]

are there hard assignments to the aux bus or do some have a different number of sends to them.  This could affect the noise gain of the sum amp, so ground potential noise gets amplified more or less due to different noise gain.

JR

 

[pucho812]

are there hard assignments to the aux bus or do some have a different number of sends to them.  This could affect the noise gain of the sum amp, so ground potential noise gets amplified more or less due to different noise gain.

JR

This is with nothing assigned to the aux masters, just the aux masters at unity.

There is a screen shot attached of the file from the free FFT  called span by Voxen go.

I have also uploaded a wav of the same audio for better resolution

https://drive.google.com/open?id=13-WfhgDoYWvbmMU6GdhEt8LngQSJC-eN

 

[moamps]

It sounds and looks to me as a ground pollution problem with a SMPS.

 

[pucho812]

It sounds and looks to me as a ground pollution problem with a SMPS.

No SMPSU's however I started testing components today and found a few leaky caps, so starting there.

 

[radardoug]

What kind of desk?

 

[pucho812]

What kind of desk?

our lovely trident A range....

 

[radardoug]

Could you do a clip where you put audio on the bus at 0 VU, and then the noise? Do you have the masters wound right up?
That noise is 50 dB down from digital clip, but we need to know where your zero reference is. I wouldn't expect the Trident to be any better than - 70 wrt 0VU. And Tridents did crosstalk, (but so did Neves)

 

[pucho812]

Could you do a clip where you put audio on the bus at 0 VU, and then the noise? Do you have the masters wound right up?
That noise is 50 dB down from digital clip, but we need to know where your zero reference is. I wouldn't expect the Trident to be any better than - 70 wrt 0VU. And Tridents did crosstalk, (but so did Neves)

the crosstalk is not optimal but it be what it be. The big concern is the buzz, while yes their spec is not always the highest in quiet I would suspect this kind of action to be far from normal.  as mentioned I do not have schematics, but I did find bad caps so away I go from there.

 

[Brian Roth]

Does the level of the buzz vary as you adjust the Aux master pot?

Bri

 

[boji]

I can confirm 60Hz goblin. And ever the slightest bit of crosstalk- mixbus (gtr+drums)

Sound I get with my fluorescent desk lamp.

 

[ruffrecords]

no way really?  We got buzz over here, so much so that there was a client complaint. 

May I ask what you are playing it back through?it's there, I have not run an analyzer on it yet,

Just playing it on my computer speakers with the volume turned up full.

I cannot hear much above 10K these days so maybe its just my ears.

Cheers

Ian

 

[synthiaks]

Doesn't the Trident A have a lot of Tantaliums in it?

Maybe one has short to ground? It sound like a cap problem to me.

S

 

[mrclunk]

It sounds and looks to me as a ground pollution problem with a SMPS.

I agree but you lot are far more experienced than i!

I had similar sounding issue from a failing screen SMPS next to our desk.  Turned things off one by one until it disappeared.
Is the Aux 10 circuit / amplifier physically closer to something that could interfere?

 

[JohnRoberts]

This is with nothing assigned to the aux masters, just the aux masters at unity.

There is a screen shot attached of the file from the free FFT  called span by Voxen go.

I have also uploaded a wav of the same audio for better resolution

https://drive.google.com/open?id=13-WfhgDoYWvbmMU6GdhEt8LngQSJC-eN

Master section ground noise can be amplified by a stray impedance from a virtual earth bus to ground. I've seen solder blobs and stray strands of wire cause such mischief.

Good luck

JR

 

[pucho812]

Does the level of the buzz vary as you adjust the Aux master pot?

Bri

Yes...

Doesn't the Trident A have a lot of Tantaliums in it?

Maybe one has short to ground? It sound like a cap problem to me.

S

the pants have been replaced over time. yes I can concur a cap issue, I found 4 x 470uF/63V caps in each aux master that are leaking. Starting there.

I agree but you lot are far more experienced than i!

I had similar sounding issue from a failing screen SMPS next to our desk.  Turned things off one by one until it disappeared.
Is the Aux 10 circuit / amplifier physically closer to something that could interfere?

There are 10 aux masters, this noise is in varying degrees on all of them regardless of slot on the frame they go in.  location is not an issue and we do not have a SMPSU in use on the desk or near it.

Master section ground noise can be amplified by a stray impedance from a virtual earth bus to ground. I've seen solder blobs and stray strands of wire cause such mischief.

Good luck

JR

thanks JR.

As always a wealth of information.

Thanks everyone, let's see what progresses.

 

[pucho812]

replaced 4 dead caps in one module. They tested as leaky in circuit with my cap tester.  The new ones tested the same but according to peak electronics who make the cap tester, it's possible they do that based on can size. We'll see. So far testing yields less buzz but still there. I need to take some AP measurements and see what is what.

 

[jdurango]

Fair warning, I have nowhere near the level of experience as most of the guys in this thread, but I'd check the patchbay (assuming you have one). I'm guessing you've tried turning up auxes on each channel to see if one of them is behaving strangely or injecting noise? If there's a suspect channel, pull it and see what happens. Or worst case, pull one channel at a time to rule them out.

Again, I'm no expert tech, but that's where my caveman monkey brain would go. Good luck! I know how frustrating that stuff is!