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USB ground loop isolator

iGPR3

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Jun 14, 2024
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Sorry for the 1000th post on ground loops, but after looking at how expensive regular USB isolators are, would something like this cheap aliexpress isolator work? Are there any other ways around a ground loop?

Powered USB hubs are off the table because some hubs only use the mains power for extra juice and will operate on just USB and won’t fix a ground loop.

I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
 
USB DAC like Moondrop Dawn Pro is about $50. 4.4mm to XLR cable is below $20.
The above method is a sure way it will work.

Your method is the cheapest, maybe it will work.
 
I used a cheapo from Amazon for my MiniDSP (for control only) - but it was only for USB 1.1 speeds. Did the trick. It does not appear to be available now...
 
Sorry for the 1000th post on ground loops, but after looking at how expensive regular USB isolators are, would something like this cheap aliexpress isolator work? Are there any other ways around a ground loop?

Powered USB hubs are off the table because some hubs only use the mains power for extra juice and will operate on just USB and won’t fix a ground loop.

I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
As long as you don't use Hi-res and DSD it'll work fine so fine for CD quality and 48kHz audio.
These devices are speed limited but do break ground loops (usually leakage currents from PC/laptop)

When you hear noises that should not be there you should first investigate where the noises are coming from, then look at how devices are powered (3 pin mains plugs for instance not being used in a 3-pin wall socket.
 
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I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
One set of balanced cables to got from the DAC to preamp of whatever is too expensive?
 
Something like this can probably be used for high sample rates. I don't have personal experience with this particular model.
I built an isolator based on the TI ISOUSB211, which works fine. It is not a commercial product though. I built it for testing purposes.
 
One set of balanced cables to got from the DAC to preamp of whatever is too expensive?
I’m currently running 6 unbalanced 1/4” cables, 2 to DSP from DAC, and 4 out from DSP to subs and speakers. Would I need to replace all the cables? Or would just the 2 work between the DAC and DSP?
 
I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
Balanced cables are often very expensive in HiFi-shops. But you can buy balanced cables much cheaper in a music-shop or in a store selling gear for DJ:s.
 
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Going Balanced can still result in the same ground situation as the current USB situation - but any INDUCED noise along the way will be cancelled out (CMRR).

If all of the noise is indeed induced along the unbalanced line (via the shield), then going balanced alone will solve it. If not - lifting pin 1 might STILL be necessary to eliminate the USB ground contamination issue.

The $5-$20 USB adaptor is pretty sure to eliminate it - and in a case like my MiniDSP 2x4 with Unbalanced AVR input, I can't go balanced from the AVR - so the USB isolator is the ticket...
 
The DSD Tech SH-G01L has been recommended as an inexpensive 480Mbps USB2 isolator.
You're 100% sure this will stop a USB ground loop? I don't want another balanced cable situation where people say it'll fix my ground loop, and then for it to not work. Had to cancel my order of balanced cables earlier....
 
USB isolators can only prevent noise coming from the source to the DAC.
When there are groundloops between (active) monitors or connected amplifiers or other devices the isolator will do nothing.
You need to determine where the issue comes from. When removing the USB cable from the DAC results in a silent system then chances are an isolator will be the solution.
Which one depends on the used bitrates and amount of channels.
 
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Sorry for the 1000th post on ground loops, but after looking at how expensive regular USB isolators are, would something like this cheap aliexpress isolator work? Are there any other ways around a ground loop?

Powered USB hubs are off the table because some hubs only use the mains power for extra juice and will operate on just USB and won’t fix a ground loop.

I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
I bought one of these a while back to try and cure GPU and USB mouse noise from a PC with an SMSL SU-1;

USB2.0 high-speed isolator 480Mbps

pretty similar (was a bit cheaper then).

It worked but got very warm powering the DAC which implied it was pulling a lot of current from my PC's USB port which I didn't like so I dispensed with it. Ended up buying an ifi 'iDefender' which uses a separate 5V-in, but before it arrived I discovered that using 'Class 2' (two-pin AC inlet, 'floating-ground, double-insulated') PSU's for my amplifiers side-stepped the noise problems from the PC.

The 'iDefender', however, isn't that cheap, nor are other externally powered USB isolators.

ETA >> Bottom line is that USB DACs might be low power devices but they still need a couple of watts (unlike, say, a piece of lab kit that's purely receiving data), and while that might be well under the 1.0A/5W spec for a USB 3.0 port, if it's via a DC/DC convertor in one these 'isolators' the isolator itself may well be pulling a lot more than that (as I suspect the device above was) which feels like asking for trouble (new motherboard when the USB controller fails?).

ETA 2 >> The isolator I linked to above (and similar ones) provide high-voltage isolation which implies no direct electrical connection between any pins but it still provides power (specs say up to 800mA in and 400mA out) which is why I assume it uses a DC/DC convertor (and presumably some sort of buffer/repeater for data). Not sure how the really cheap ones listed on Amazon, AliExpress et al work but most of them are apparently for data/control only, not USB powered devices (which of course includes many DACs and headphone amps).

Generally I'm wary of anything which might draw power near the limit of USB and steer clear of them (the only failure I've ever experienced with a MB was with my old PC when I once plugged in a USB HDD which was apparently faulty and instantly fried the ASmedia USB 3.0 controller (F1 "USB over-current detected!" on boot from then on) - fortunately there was a 'native' Intel controller for four of the six USB 3.0 ports so I just disabled the ASmedia one in BIOS).
 
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I’m currently running 6 unbalanced 1/4” cables, 2 to DSP from DAC, and 4 out from DSP to subs and speakers. Would I need to replace all the cables? Or would just the 2 work between the DAC and DSP?
See @solderdude's post above. If the noise mainly materializes in the DAC to DSP connection then balanced cables here would help.

Quick check (after the check proposed by solderdude) is to pull the cables from the DSP input and see if the hum is still there. If it is, neither balanced cables nor an USB isloator would help.

If the noise is gone, I'd move on to balanced cables first (get these for little money from a music instruments store, not a HiFi store). In case you still have issues then please come back so we can help debug your situation better (we'd need more details about the involved devices, their power connections etc).
 
Hi,

Excuse me if I'm not in the same wagon as you (perhaps I'm missing something) but... the OP has not disclosed what kind of DAC outputs and preamp inputs he has in his system. Particularly if the preamp inputs are not balanced (i.e. differential), what would be the purpose of a balanced cable?
 
The purpose of balanced cables is to ensure any unwanted currents (ground loops or whatever) flows through the shield.
In 'normal cables' the signal flows through the inner wire AND the shield.
When the shield has some resistance (or the wires connected to its connectors) some voltage drop will occur across the shield.
That unwanted 'noise' will be added to the signal and that's what you can hear.
In balanced the signal is between 2 wires and the shield is not used for the audio.
Balanced signals also are immune to signals that are 'common' in nature (which means they have the same amplitude and phase) and these will simply 'cancel' while the wanted signal is differential (opposite in phase) and does not cancel.

So... when a source and DAC have a different 'potential' (read voltage difference such as noise or hum or other unwanted signals) these do no end up in the audio signal but are present but travel through the shield and not via the (wanted) signal path.

In such a case (when both input and output are differential (balanced) the signal remains clean. All relevant cables then must be balanced.

First... find out where the culprit is. Sometimes it is a simple matter of finding out where it comes from and using proper grounded mains supplies might be all that is needed.
In such a case no balanced cables nor isolators are needed.
Most audio systems work perfectly even with RCA cables if power supplies are properly connected, interlink wiring is at least decent and shielded.
 
Most audio systems work perfectly even with RCA cables if power supplies are properly connected, interlink wiring is at least decent and shielded.
This is very true. Parasitic shield currents are often generated by a protective earth (or common mode) voltage difference between two mains outlets which are used in the system. And this kind of problem is resolved by properly (i.e. without cheap "T" adapters) connecting the power cords on the same mains outlet or adjacent ones.

But still the system should be immune to this noise if the preamp(s) and the dac have differential inputs / outputs connected to each other with balanced cables (or when preamp at least has balanced inputs and the balanced cable is properly connected at the DAC side). I still don't get it
 
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JDS Synapse 3D Printed enclosure version is USD$49
 
Sorry for the 1000th post on ground loops, but after looking at how expensive regular USB isolators are, would something like this cheap aliexpress isolator work? Are there any other ways around a ground loop?

Powered USB hubs are off the table because some hubs only use the mains power for extra juice and will operate on just USB and won’t fix a ground loop.

I can’t go balanced because it’s way too much money, because even though my gear has balanced connections, the cables are like 5x the price. Any help is appreciated
I would advise you against these cheap USB isolators.
With a good USB isolator, a large part of the price is the development.

Adam Hall XLR cables work well and cost €5-10/$ each.

As @solderdude said, it is better to find the cause than to tinker with the symptoms and buy things blindly.
 
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