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Strange awakenings

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Strange awakenings

Postby Mike Shand » Mon Jul 15, 2019 2:42 pm

I have an Audient ID4 interface connected to a pair of Neuman KH80s by balanced TRS cables. The ID4 is powered via USB from a windows desktop running win10, with the latest Audient drivers.

All works fine. Except...

I have my KH80s set to go to standby in the absence of signal. Currently after 30 minutes. They do go to standby, BUT they randomly (or more strictly one or other of them... not the same one each time and usually not both at the same time) awaken from standby quite frequently (every hour or so, but not at a fixed time).

This happens whether or not the audient is muted or the volume turned right down.
It happens whether or not the computer is running or in sleep mode. Note that while sleeping USB power is maintained.
It happens even if I unplug the USB cable from the ID4, so it has no power!

However is DOESN'T happen if I unplug the TRS cables from the ID4 and leave them dangling.

The KH80s are not grounded through the mains cable, so their only grounding is via the TRS cables. I hear no hum or other extraneous noises.

I have checked continuity between the computer ground and the USB shield, and between the USB sheild and the case of the ID4 and the sleeve of the TRS sockets.

I have tried adjusting the threshold of the KH80s via the Neumann control app, and it makes no difference at either extreme. (it is a rather unclear to me what the meaning of the threshold level is).

I do not have any other inputs or outputs connected to the ID4.

There is a fridge the other side of the wall but I have not been able to correlate the waking with the fridge switching on and off. Nor with switching on and off lights etc. etc.

I am at a loss to know what I can do to cure this problem. Not the end of the world obviously, but having the speakers continually powering up and down throughout the day and night is something of a nuisance. It kind of defeats the object of having a standby mode in the first place.

Any ideas folks?

Mike
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Re: Strange awakenings

Postby Hugh Robjohns » Mon Jul 15, 2019 3:20 pm

Mike Shand wrote:However is DOESN'T happen if I unplug the TRS cables from the ID4 and leave them dangling.

What Fun! :-)

The first thing to check is that you're running the latest firmware in the speaker, just in case there was a known programming glitch that has been corrected since you bought the speakers.

Since the wake-up doesn't happen if the speakers are left to their own devices, it has to be some sort of external signal reaching the speaker via the audio cables, either in the form of RF interference, or a disturbance relative to or via the ground connection.

If it was RF then I'd expect it still to happen with the input cables disconnected from the ID4 since they would then make even better aerials. As it doesn't, it seems more likely that it is a disturbance on the ground reference that's somehow triggering the wake-up command.

I think since you're using balanced audio connections anyway, I'd experiment by isolating the signal grounds to each speaker -- the speaker doesn't need a ground reference for the audio, and it is a double-insulated device so doesn't need a ground for safety either.

So, either snip and insulate the screen/sleeve connection in the TRS plugs at the speaker end of both cables, or insert a line-transformer isolating box in the speaker signal paths, such as the ART DTI or similar.

You shouldn't suffer any hum problems with these mods, and it might cure the problem if it's related to noises on the ground connection.

I'd also contact Neumann and tell them what's happening, just in case it's a known condition. Often a manufacturer needs several independent reports of a weird 'fault' like this before they take it seriously and come up with a solution...

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Re: Strange awakenings

Postby Mike Shand » Mon Jul 15, 2019 4:37 pm

Thanks Hugh.

Yes, I’m running the latest Neumann firmware.

I’ve got a spare art DTI somewhere. I’ll see if I can dig it out when I get home and report back.

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Re: Strange awakenings

Postby resistorman » Mon Jul 15, 2019 5:27 pm

I’m not being snarky. But why not just use a power strip?
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Re: Strange awakenings

Postby Mike Shand » Mon Jul 15, 2019 5:52 pm

resistorman wrote:I’m not being snarky. But why not just use a power strip?
Yes. I thought of that, but wasn’t sure the speakers would like having their power cut all the time, rather than being powered off or going to standby. When you power them off they go through a shutdown process, which would be circumvented by cutting the power.
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Re: Strange awakenings

Postby Mike Shand » Mon Jul 15, 2019 5:59 pm

Mike Shand wrote:Thanks Hugh.

Yes, I’m running the latest Neumann firmware.

I’ve got a spare art DTI somewhere. I’ll see if I can dig it out when I get home and report back.

Mike
Curiouser and curiouser. I couldn’t find the DTI, so tried cutting the screen on one of the leads at the kh80 end. As Hugh said, this *should* be fine. However, there was a slight hum when I plugged it back in with the id4 usb cable disconnected. But when I connected the usb cable the hum rose to intolerable levels.

I just checked the ID4 specs and the outputs are indeed balanced.

As an aside, I noticed there was a firmware update for the ID4, so have applied it, but it wasn’t supposed to solve any issues like this, so I’m not holding my breath.

Anyway, I’ve reconnected the screen and we’ll see what happens over the evening.

Mike
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Re: Strange awakenings

Postby Mike Shand » Tue Jul 16, 2019 3:41 pm

So... as expected, no improvement with the firmware upgrade.

I found my DTI box and that, unsurprisingly, behaves the same as the removed screen. I’m thinking the problem lies with the ID4. Its as if that needs to be tied down to the kh80 reference.

So maybe the automatic power strip has to be the answer, but I don’t like to be defeated with something that ought to work. :headbang:

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Re: Strange awakenings

Postby Hugh Robjohns » Wed Jul 17, 2019 10:56 am

Hmmm... interesting!

I corresponded with someone who knows a lot about these speakers and his initial thoughts were that the analogue input cables or ID4 are picking up some spikes and the loudspeaker is doing its job reacting to this input signal.

It could be that it is not possible to desensitise the standby setting enough using the 30 dB control, but it would be worthwhile raising the matter with Neumann directly as the firmware has a larger range than customers can currently access...

It might also be worthwhile contacting Audient to see if there's something they can suggest to prevent the iD4 from issuing spikes...

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Re: Strange awakenings

Postby Mike Shand » Thu Jul 18, 2019 2:10 pm

I've contacted them both, and quickly received the following reply from audient.

"Because the issue still occurs when the iD4 is unplugged from its USB (i.e. the iD4 is completely powered off) this would suggest the issue is elsewhere within the system. The speaker outputs on the iD4 are on a relay switch so when the USB is disconnected so are the speaker outputs so no signal can be sent out of the outputs."

That's even more confusing. How is this different from the TRS unplugged case? I can only imagine that there is something in the ID4 which is acting as a pickup for interference even when "disconnected by the relay".

I'm just going to try running a very extended test with the cables unplugged to check I was not deluding myself.
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Re: Strange awakenings

Postby Hugh Robjohns » Thu Jul 18, 2019 2:31 pm

It would be useful to know if the output relays just leave the output connections open circuit, or if they are shorted to ground.

I can't remember if we tried this... but what happens if you provide the iD4 with a solid mains earth? (the easiest way would be to connect something you know is definitely grounded via its mains connection to a spare input/output).

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Re: Strange awakenings

Postby Mike Shand » Sat Jul 20, 2019 4:14 pm

Solid earth didn’t help.

Sorry, the saga continues.

I have an old Roland edirol ua 25 interface. I replaced this with the id4 because Roland don't provide win10 drivers for it. But it does work as a generic output device. Just no inputs or “advanced” features.

So I swapped that with the id4. Same trs cables, same usb cable into same usb socket.

Same problem:-(

So, next experiment was to reduce the input sensitivity of the kh80s by about 12dB using the control app. That’s as low as I can go, and means having the id4 volume control almost at max. I was hoping this might reduce the incidence of waking up...

But no. It still does it.




So now I am trying changing the kh80 standby “level” from 30dB to 0dB (the opposite end of the permissible range, but it’s not clear to me exactly what this means xdB referenced to What?

I’d tried this previously, but with the input sensitivity 12 dB higher....

.... and the result is...

Nope. It still randomly wakes up. I was almost hopeful there for a while.


Ok let’s see if we can capture the offending spikes. I unplugged the TRS leads from the kh80s and plugged them into the balanced line inputs of my zoom H4n. With the computer sleeping and the id4 powered by the usb, and muted, I recorded for 1 1/2 hrs.

Nothing higher than the noise floor( which is just a continuous burbling noise down around -85 dB. From whatever my recording level was.)

Switching mute on and off gives a spike around -50dB and this doesn’t trigger the kh80s to wake up ( when the kh80 standby level is set to 30dB... it does when set to 0 dB. So I think that confirms that 30dB is the correct setting to minimise the wake up sensitivity.) So whatever I have recorded is at least 35 dB below a level that doesn’t trigger a wake up.

The zoom h4n is running battery so no other ground connection. I.e. it *should* emulate the kh80s quite well.

I had a reply from sennheiser, who handle UK Neumann support and they have forwarded it to Neumann technical people for comment. We’ll see if they come up with anything.

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Re: Strange awakenings

Postby Hugh Robjohns » Sat Jul 20, 2019 5:01 pm

Intriguing! Please do let us know what they come up with.
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Re: Strange awakenings

Postby cyrano.mac » Sat Jul 20, 2019 6:40 pm

It"s dry out there...

I'm imagining your electrical system's ground connection is in dry sandy soil. Meaning, there's no ground connection at all.

I'd get a certified electrician in there to measure the resistance to ground, because this not only produces strange inaudible noise on the USB connection, but also weird behavior from "auto-on" devices. That noise usually comes from the PC's PSU, that's either failing slowly, or it has a bad chassis connection somewhere.

It's also not safe, as it would prevent the ground leak current detection not to function when needed.

There's nothing the Audient or the monitors can do about this. And neither will be gained by changing audio or USB cables. What could work, is a USB audio isolator. Unfortunately the real ones are very costly. And the fake ones won't solve the problem.

The only thing worth trying would be to power the Audient from it's own power supply, if possible.
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