You couldn't get what you wanted. You have a device that exposes pentacon - but is behaving a circuit like unbalanced 3/4 jack.
That's sad. I am showing empathy.
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I can hear my PC think through my speakers
- Thread starter Rainier939
- Start date
That's sad. I am showing empathy.
Please do I understand correctly that your measurement was PC -> USB Khadas Tone 2 via USB-C data+ power -> E-MU 0204 again powered via USB? If so, your chain's ground loop would be between grounds of the two USB connectors of your PC, no PE wires, no loops involving the PSU ground wires. Very likely there are basically zero ground noise currents running between these two adjacent grounds. It would be very unusual if ground-loop effects showed in your spectrogram as there would be basically no ground loop currents in such a chain.
Please can you give some links to those threads? I cannot recall any such case. IIRC in the end those complaining about PC noise always identified some SE connection somewhere in their chain which mixed ground loop and return signal currents.
audio_tony
Addicted to Fun and Learning
You're not hearing 'coil whine'. What you are most likely hearing is caused by a ground loop, which when dealing with a PC can be an issue.
Take a look at these measurements which show the issue that can be caused by a ground loop.
Peterinvan
Senior Member
We had a computer at my first programming job, with a ferrite core memory. The full time tech that kept it going used to place a transistor radio next to the core to “hear” if the computer was booting up properly when the operating system was loaded from punched paper tape.
Sokel
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I should have stated the conditions,rookie mistake.
So,it's PC>E-MU 0204 > 6 meter cable (as I want to measure everything as they sit at the rack) > Grounded-boxed-powered by Salas RefleKtor D KTB+ESS Controller > 5 meters USB cable > PC. (Same rig I have shown lots of times here,as I like to measure my whole gear as a whole black box)
A lot of chances for returning currents (my main danger though is the low impedance of E-MU's input,some hints are evident)
It will be meaningless to show you a couple,or run across the forums to gather them,but they are there.I make similar remarks at some of them,I sound like a broken record at the end.
AnalogSteph
Major Contributor
What's a "3/4 jack"? Does it only play waltzes?
Anyway, a headphone is a floating transducer that does not care one iota whether a voltage of say 4 V across its terminals is the difference between +4 V and 0 V or +2 V and -2 V. It needs a balanced output about as much as a hole in the headband. If you can achieve the same performance with an internally single-ended circuit of lower complexity with higher supply voltages (which generally makes it cheaper to produce), there is absolutely nothing wrong with that.
Shared return resistance common to both drivers is a potential issue as it can lead to weakened bass, however that is 95% about headphone cable construction. If it properly bifurcates its left and right driver returns directly at the plug like Sennheiser HD6xx ones have been for 30 years, that only leaves maybe 50 mOhms of contact resistance (and that's a 3.5 mm too if memory serves, 1/4" is better), as opposed to typically about an ohm. Now as a rule of thumb, you ideally want shared resistance to be <1% of nominal driver impedance. I struggle to think of any headphones with 5 ohms or less, so that basically means the problem is solved. Should there be an oxidized jack, they make isopropyl alcohol and contact cleaner for that.
On the other end of the signal chain, a phono cartridge is another example of a floating transducer. Balanced turntable connections have so far remained rather exotic because you can do without them pretty well.
Balanced connections help when there are disagreements about ground potential on both ends to be expected, i.e. neither end is floating. The more complex a system becomes, the more likely you are to introduce multiple ground connections in it, and then the performance of unbalanced connections simply breaks down. In a sprawling studio, trying to maintain exactly one ground connection like it may still be possible in a classic hi-fi with exquisite juggling would become maddening, and the modern audiovisual world has plenty of other things to offer that can introduce new ones: Network cabling, TV cable, terrestrial antennas, satellite dishes... - and yes, computers.
On a side note, the important part of balanced interconnections is on the receiving end. Any unbalanced output can be turned into a balanced one with relatively trivial measures. (Such an output may expose worsening of distortion performance in inputs susceptible to common-mode distortion, but that's a different issue. Basic interference rejection can be made to work just as well.)
Balanced Interfaces
ESP - Balanced Interfaces - how they work, what goes wrong, and why
No, balanced connections are SPECIFICALLY for rejecting ground current noise (ground loops). USB interference does not pollute the signal until the ground voltage difference between analogue sender and analogue receiver adds the noise at the input to the receiver. Balanced connections prevent this from happening by adding the noise simultaneously to the + and - signals so that it cancels out.
Roland68
Major Contributor
There is nothing sad about that, the performance is the same and you don't lose anything. Maybe a few things aren't clear to many people.
SE HPA with balanced connections are now normal and also allow the connection of balanced cables, which is very practical and saves additional cables and costs.
BUT, and this WARNING goes out to everyone, never connect SE headphones with an adapter/pseudo BALANCED cable to a BALANCED HPA! This can damage your HPA and your headphones!
- Symmetrical signal connections between devices are used to eliminate interference in the cable, just for that reason.
- The signal routing in the devices is normally not symmetrical, this only happens at the output and is de-balanced again at the input.
Balanced headphone amplifiers
- Have nothing to do with symmetrical cable connections.
- Interference in the cable of balanced headphones can have an effect, it is not prevented.
- Have 2 power amplifiers per driver/channel, which drive the driver push-pull.
- Where there is light, there is also shadow. The noise can add up with 2 amplifiers per channel. The developers can reduce this, but with most HPAs it is well below the audible limit anyway.
- With 2 power amplifiers, the performance per channel can double.
- But you can also simply build an SE HPA with higher performance. - There is absolutely no difference in sound between equally good SE and balanced HPA, really none at all.
- There are no real differences in terms of measurement either, 2 SE HPA even top the SINAD list.
And to get back to the ground of this thread, neither balanced connections nor balanced HPA can change anything about the problem discussed in this thread.
Roland68
Major Contributor
You are right and you are not.
However, you misinterpreted my statement, which only referred to the thread creator's problem. Perhaps you overlooked the "It can absolutely not help with interference, such as occurs with USB, which already gets into the signal path somewhere beforehand and pollutes the signal.".
However, the statement "No, balanced connections are SPECIFICALLY for rejecting ground current noise (ground loops)" is not correct.
Symmetrical connections originate from analog telecommunications and were definitely used to remove interference that was radiated into the cable. That is the original reason and was therefore adopted in the pro audio sector. You can read about it in enough specialist books.
Suppressing ground current noise (ground loops) is an additional point, provided that both devices and cables are wired correctly. The fact that this is not always sufficient and works 100% can be seen in many threads on this problem in all forums.
Then your understanding of the problem is different from mine. I am not understanding how usb generated noise is “getting into the signal path somewhere beforehand”
My understanding is what we have (most likely) are PC currents from it “thinking” getting onto the PC ground, and hence the USB ground. From there they are conducted via a typical ground loop, through the analogue interconnect ground between DAC and Amp, causing the voltage difference between the two devices that is then added to the signal at the input to the amp.
Regarding the purpose of balanced connections - IMO specifically in audio applications, they are more often a solution for ground loop type problems than they are for radiated interference problems. (Excepting that ground loop currents can often be caused by magnetic coupling into the ground loop - which could be considered radiation.)
I accept that in analogue telecoms with somewhat longer interconnect, this might not be the case.
audio_tony
Addicted to Fun and Learning
It's typically a difference in potential between two grounds (the ground reference for the PC and the ground reference for the DAC / amp / preamp).
This causes unwanted currents to flow in the grounds between the devices resulting in the noise we hear.
Some older preamps and power amps had earth terminals (similar to those for a turntable) on the back to bind both devices to a common ground which mostly solved the ground loop issue.
Of course later double insulated products largely cured this problem, but as a PC has a switch mode PSU a safety ground is a requirement.
DACs with switch mode power supplies on the other hand seem to dispense with the safety ground?
Roland68
Major Contributor
I admit, I'm a bit of a pedant when it comes to historical technology and its origins, and I've had a lot to do with symmetrical cabling in IT and industry, especially LVDS.
USB 2.0 connections on simple DACs can react very negatively to a noisy power supply via USB 2.0, as well as to very noisy power supplies. I've also often seen how such power supplies crash Arduino and similar boards.
After I got a simple SMSL DAC from a colleague to test a few years ago and suddenly had a humming sound like never before, I built myself a USB cable with a passive DC filter. This makes it easy to find out whether it's a ground loop, or really the USB output of the PC or the power supply.
With the SMSL USB DAC it was both, but the device also reacted to a super-clean industrial USB HUB from the medical field. It also has a lot to do with sensible development.
I often recommend the SMSL PO100 AK to friends and acquaintances and I also use it myself when I need space at my workstation and put my work equipment away. The device has never made a single humming or noise, even though I have used it with many different HPAs and amplifiers and often touch it, including the ground contacts.
I think that’s what i just said, bearing in mind that ground loops add noise to a signal only on the analogue interconnect. Not between pc and dac. So it is a ground potential difference between two devices at either end of an analogue interconnect
So are you saying that in this case you describe the noise from the USB so disrupted the behaviour of the DAC, that noise was added to the signal on the output of the DAC?.
I”ve never heard of a DAC being unable to reject noise on it’s power input to an audible degree before. And that would presumably have to be differnetial noise between the USB +V out and the USB gnd?
And even if so - my experience is that the type of audible noise the OP is experiencing is far more commonly ground loop than DAC power supply noise getting through to analogue output.
multichannel_guy
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Install a Creative Soundblaster AE7 sound card in the PC. It can serve as a fairly high quality transport. Run the optical connection from the card to DAC and all PC noise is history.
Roland68
Major Contributor
It can be both, individually or together. I don't normally use such devices myself, except for the PO100 AK. At some point I noticed among my friends that these small, simple devices cause problems much more often than the larger ones with built-in power supplies. A USB isolator would solve both problems anyway.
With an E30 I once had the effect that the humming when switching from USB to optical on the PC was eliminated, but the mouse and probably the graphics card could still be heard. But that was a cheap gaming PC from a discount store, and it didn't run very stable either, which suggests cheap and unreliable hardware.
OP
Rainier939
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- Thread Starter
- #98
Well when there is coil whine there is noise in my speakers so i think that is reason enough to claim they have the same origin.
My pc is not top spec but it has a 80plus gold PSU with a mid tier graphics carb.
The entire floor doesn't have grounded sockets and rewiring is not on my to do list. There might be some dedicated circuit, with proper grounding, in the future.
Usb cable is double shielded and it does run close to some power cords but that is unavoidable coming out the back of a pc with a small desk setup
Roland68
Major Contributor
Maybe we can narrow down the problem a little.
- Is the E30's power supply connected to the PC or its own power supply?
- Have you connected the Wiim Mini to the E30 with an optical cable?
AnalogSteph
Major Contributor
Oof. That should have been on someone's to do list at least a decade ago (and arguably two or three). You technically cannot safely operate any IEC Class I equipment there, including a PC - it is relying on a functional protective earth connection to keep you safe in case an internal insulation fault develops. Moreover, the leakage current from built-in mains filters has nowhere to go, so computer ground will be pulled towards about half the mains voltage. Any amplifier connected will exhibit hum on open unbalanced inputs, and you may feel a slight tingle on conductive surfaces.
(I wonder how you got your ground loop issues then, are both the amplifier and the amp on the same power strip?)
This wiring situation is not just inconvenient but actually concerning with regard to basic electrical safety, and I would not be taking that lightly. I would check whether this sort of thing is still up to code, and I imagine your insurance may not be particularly enthused.
