Adventures in USB isolation ...

[Mark S.]

Installed a USB isolater for my SMSL SU-1 yesterday;

'Inexpensive' Aliexpress USB Isolater

At ~£36 delivered (in about a week) it's much cheaper than the two offerings from Topping, HS01 and HS02 (£69 and £109).

and ... it works, sort of, so far.

Complete silence from speaker amp now (headphone amp is on an isolated SMPS and doesn't suffer from any induced noise).

Since Equalizer APO asks for a reboot every time a device is connected, I did so on plugging the SU-1 back in, and the first thing I noticed was a much longer delay between POST and the Windows login screen (Asus screen and spinny wheel).

The housing gets warm, IR reading is 43°C (26°C ambient) with the device in clear air at the back of my PC.

Since it only delivers 1/3 of the power (300mA) of a USB 3.0 port I wonder if it actually dissipates the other 2/3rds. If the SU-1 is pulling, say, 250mA / 1.25W then it may be dissipating fully 2.5W. which makes me wonder about longevity.

 

[Mark S.]

What I'm unsure of is if sound quality has been affected by this gizmo (jitter?). It's going to be difficult A/B-ing without uninstalling/reinstalling EQ APO multiple times (which I don't really want to do given how cantankerous it is).

Why hasn't this esteemed site tested these cheap devices?

 

[Keith_W]

Why hasn't this esteemed site tested these cheap devices?

Amir has not tested the device that you linked to as far as I am aware. But he has tested other USB isolators. Conclusion: they make a difference on the test bench, but not necessarily in a positive way - one of them reduced distortion spikes, the others added them! Whether they make an audible difference or not is extremely unlikely, even if you bought a poorly designed DAC that was sensitive to noise from USB. With a well designed DAC there would be no issues.

 

[Mark S.]

I can tell you now; this one (I don't know about others) is a piece of junk. Don't bother.

 

[Mark S.]

Amir has not tested the device that you linked to as far as I am aware. But he has tested other USB isolators. Conclusion: they make a difference on the test bench, but not necessarily in a positive way - one of them reduced distortion spikes, the others added them! Whether they make an audible difference or not is extremely unlikely, even if you bought a poorly designed DAC that was sensitive to noise from USB. With a well designed DAC there would be no issues.

A "well designed DAC" is all very well, but in my experience you don't want a ground anywhere downstream of a USB DAC from a PC.

 

[Mark S.]

Anyway, I listened to music for a day with this piece-of-sh!t between the PC and the SU-1 and was frequently confronted with 'staticky' distortion and generally Not Very Good Sound. You have been warned.

 

[Mark S.]

And as I type I'm listening to Stanley Clarke's Journey To Love, back to the SU-1 straight out from the PC to my headphone amp and what can I say (ETA >> but that it's REALLY good) ......

 

[Mark S.]

... except that I'm going to listen to it via the Cayin RU6 and see how that grabs me (when I'm in the mood).

 

[Mark S.]

I managed to find an isolated (i.e. with a two-pin, figure-of-eight mains lead) 24V 4A SMPS for my TPA3118 amplifier (or is it TPA3116? Can't remember) which has made it silent, wish I'd made a more concerted effort to find one before wasting money on the isolater. I suppose I might find a use for the latter in future.

 

[Sal1950]

I solved a stubborn USB ground loop hum with a cheap $25 USB to Toslink optical converter
off Amazon. The offers 100% total isolation.

 

[Ken Tajalli]

Amir has not tested the device that you linked to as far as I am aware. But he has tested other USB isolators. Conclusion: they make a difference on the test bench, but not necessarily in a positive way - one of them reduced distortion spikes, the others added them! Whether they make an audible difference or not is extremely unlikely, even if you bought a poorly designed DAC that was sensitive to noise from USB. With a well designed DAC there would be no issues.

Only the very cheapest of desktop DACs, and portable ones don't have usb isolation builtin.
Portable ones don't need them, that's why.
But with desktop ones, a ground loop (if it occurs) is audible!
If there is a ground loop issue, then a proper isolator fixes it, otherwise, it won't do anything.

 

[Mark S.]

I solved a stubborn USB ground loop hum with a cheap $25 USB to Toslink optical converter
off Amazon. The offers 100% total isolation.

It wasn't just ground-loop noise (or even really ground-loop as such), most of the time there was very little noise but it would get really bad when the GPU was working hard (i.e. gaming) and also with other random stuff, like streamed video in a browser window. No ground downstream of the USB DAC, no problem. I also wanted to be able to use USB for native DSD with Foobar, and it just generally seems the more solid interface now.

 

[Mark S.]

Only the very cheapest of desktop DACs, and portable ones don't have usb isolation builtin.
Portable ones don't need them, that's why.
But with desktop ones, a ground loop (if it occurs) is audible!
If there is a ground loop issue, then a proper isolator fixes it, otherwise, it won't do anything.

Whatever the issue, all DAC's I've tried are noisy via USB from a PC. The SMSL SU-1 improved on the cheapo Sound Blaster PLay!3 (ETA > as did the RU6) but it still wasn't silent. It is, now that I have an isolated PSU powering the amp.

It may be that this only affects class-D/switching amps, but that's all I've used for several years now (even my faithful and much-loved Rotel RA820BX4 went to pastures new a few years back).

 

[Ashimaru]

I solved a stubborn USB ground loop hum with a cheap $25 USB to Toslink optical converter
off Amazon. The offers 100% total isolation.

Can you provide the purchase link?

 

[Snoopy]

Just use a raspberry pi.. or a Streamer with LAN instead of a pc

 

[gino1961]

Very interesting thread indeed
Speaking of usb isolator i would look at those that allow to use and external power supply maybe low noise and linear

AUDIOPHONICS USB Isolator Module ADUM 4160 Raspberry Pi - Audiophonics

audiophonics module isolator usb adum 4160

www.audiophonics.fr

From what i understand different dacs using usb power have different rejection of power supply noise
Maybe with some the effect of a cleaner power supply could be more evident

 

[Ken Tajalli]

Very interesting thread indeed
Speaking of usb isolator i would look at those that allow to use and external power supply maybe low noise and linear

AUDIOPHONICS USB Isolator Module ADUM 4160 Raspberry Pi - Audiophonics

audiophonics module isolator usb adum 4160

www.audiophonics.fr

From what i understand different dacs using usb power have different rejection of power supply noise
Maybe with some the effect of a cleaner power supply could be more evident

Most DACs (AFAIK) only use the USB +5V as a switching signal, of course dongles depend on it.
So the noise doesn't go anywhere.
For isolation, you need not go any further than Topping HS01 or 02. They are both very effective, and can take external power.
If you do use an external PSU, make sure it is a standard good quality phone charger, no linear PSU.

 

[gino1961]

Hi thank you for the very helpful advice
At present I am listening through a SMSL SU-1 using a generic USB charger
I have no particular noise
But with another dac the ps100 I can hear noise with the volume on my headphone amp at max
I opened the cheaper dac and I can't see any filtering on the power supply input
Clearly the usb charger is very noisy but the better dac doesn't seem to suffer
I would try a good linear supply anyway
Smps have noise around 100mV and more
Good linear ones show very low ripple of just some mV
They are less practical I agree

 

[Ken Tajalli]

Hi thank you for the very helpful advice
At present I am listening through a SMSL SU-1 using a generic USB charger
I have no particular noise
But with another dac the ps100 I can hear noise with the volume on my headphone amp at max
I opened the cheaper dac and I can't see any filtering on the power supply input
Clearly the usb charger is very noisy but the better dac doesn't seem to suffer
I would try a good linear supply anyway
Smps have noise around 100mV and more
Good linear ones show very low ripple of just some mV
They are less practical I agree

Linear PSUs have more inband noise than SMPS.
Also, linear ones, can create ground loop noise situation, because they are grounded. SMPS, by default, are not.
A good SMPS is less noisy (where it matters) than a linear one.

 

[DVDdoug]

But with another dac the ps100 I can hear noise with the volume on my headphone amp at max
I opened the cheaper dac and I can't see any filtering on the power supply input
Clearly the usb charger is very noisy but the better dac doesn't seem to suffer

Typically, noise gets into the analog-side through the USB power. USB power (form a computer) is usually noisy (no problem for the digital audio data) and some computers are worse than others, and some interfaces are better filtered than others.... So you don't know which to blame. It's usually a high-pitch whine. It tends to be more of a problem on the ADC side of audio interfaces because the high-gain mic preamps amplify any noise.

It's not usually "ground loop noise" but it can be.

An interface with its own power supply should eliminate this possibility.

I would try a good linear supply anyway
Smps have noise around 100mV and more
Good linear ones show very low ripple of just some mV

The problem is - You can't simply "use a different power supply" with a USB-powered device because you need the data and power connections.

But, linear or switching can be good.
The noise ("ripple") from a switching supply is high frequency and that makes it easier to filter-out. (You want to pass DC, which is zero-Hz, so the higher the frequency the better.) Plus it's usually above the audio range, whereas 50 or 60Hz (or the 100/120Hz harmonics) is obviously in the audio range.

A linear voltage regulator (purely DC) can help in either case and I've seen a circuit that was "double regulated" with a 2nd (lower voltage) linear regulator in series for the preamp or other "sensitive" circuitry.