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Swissonic Converter AD 24/192 (ADC) Measurements

dominikz

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After the recent measurement I did for the unbranded ADC I got off eBay, to compare a friend borrowed me a relatively similar device by a thomann.de house brand - Swissonic Converter AD 24/192 that sells for about 40€:
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20210613_201720.jpg

Basic features are mostly the same, except this one comes with a power button, a dedicated 9V PSU and boasts 24bit/192kHz sample rate conversion support. Visually it is more appealing to me, albeit a bit bigger than the unbranded ADC I tested previously. Let's have a look at how it performs. :)

The measurements you'll see next were done with the RME Babyface soundcard, first generation - measured here. The ADC was connected to optical SPDIF input of RME Babyface, clock source was the optical input (i.e. ADC) and the sample rate was 192kHz (native sample rate of ADC), though I also did a few tests at 48kHz to see how it behaves after resampling in the receiving device. Unbalanced/headphone output of RME babyface was used as the signal generator.

NOTE: One thing I noticed right away is that the device seems to have flipped left and right channels :confused: - i.e. the analogue channel marked as 'R' is sent as left channel over digital, and vice-versa. So the measurements you're about to see were done with the analogue connection flipped, to get correct L/R channel mapping.

Again, I'll start with RMAA summary at 192kHz sample rate (MME driver, input level set to recommended -1 dBFS by reducing RME output level by ~2dB):
1623609194531.png

Although far from state of the art, we can see right away it performs much better than the unbranded, cheaper device: flatter FR, ~10 dB better noise and dynamic range (approximately hits 16 bit range), an order of magnitude lower THD and IMD, THD+N/SINAD better by more than 20dB, and crosstalk by more than 40dB!

It is interesting that the right channel shows a lot better noise performance than the left one:
1623610795745.png


At 48kHz the results are mostly comparable, main issue being that noise level goes up by about 10dB:
1623609627044.png



Here's the frequency response at 192kHz vs 48kHz:
Swissonic Converter AD 24-192 - frequency response 192kHz vs 48kHz.png

As we can see, the channels match each other nicely and the FR is flat and uneventful - as it should be :) There is no significant LF loss in audible band this ADC - it is actually even less than in my RME soundcard ADC:
FR compare.png

The one strange thing that shows up in both RMAA and REW measurement is different behaviour of the filter between channels at 48kHz sample rate - we see the left channel has a nice and sharp filter, while the right one seems to lack it and just shows a blip before the Fs/2 frequency - TBH I'm not sure why is that.

Next let's see the spectrum of a 1 kHz sine at -1 dBFS peak at Fs=192kHz:
Swissonic Converter AD 24-192 1kHz tone at -1 dBFS peak 192kHz sampling rate.png

Distortion is dominated by the 2nd harmonic, but the spectrum is reasonably clean otherwise. We see noise-shaping in the extreme HF.
48kHz shows slightly elevated noise level, but otherwise similar:
Swissonic Converter AD 24-192 1kHz tone at -1 dBFS peak 48kHz sampling rate.png


Let's look now at the THD vs level sweep at 1kHz:
Swissonic Converter AD 24-192 - THD vs level.png

As we see, compared to the unbranded ADC this one achieves lower absolute THD figures (minimum is around 0.002% / -94dB around 0,2Vrms / -17dBFS RMS input level), and can handle more input voltage - clipping onset is ~1,5Vrms / ~5,7 dBu. Again we can see a bit better performance in the right channel vs left.

Lastly let's look at the THD vs frequency at two input levels at 192kHz, first at 0,1 Vrms input (-26,4 dBFS RMS), left ch:
Swissonic Converter AD 24-192 - left ch THD at 0.1V input (192kHz).png

And then at 1 Vrms (-6,4dBFS RMS):
Swissonic Converter AD 24-192 - left ch THD at 1V input (192kHz).png
At 48kHz sample rate, 1Vrms input - not much surprise here:
Swissonic Converter AD 24-192 - left ch THD at 1V input (48kHz).png

As we can see from these and previous measurements (THD vs level), above 0,2-0,3 Vrms input the 2nd harmonic becomes the dominating factor of THD.

In summary, this ADC seems to perform much better, and though not state of the art, it should IMO be transparent when used to digitize low dynamic range sources like turntables and such - I quickly tested it with mine and thought it worked just fine :) Flipped channels are an issue, of course, but I don't know if all units have it - be sure to check if you have this device and connect the cables accordingly.
 
I'm looking to connect this to a Focusrite Scarlett, but I need to run at 44.1KHz. I contacted Thomann and they said it would only run at 48KHz, despite your review saying otherwise. Because that's all the Manual says.

Will this run at 44.1KHz?
Does it automatically pick up the rate from the host device?

Akai MPCs are now allowing USB class complaint devices, so I won't have access to any of the software interfaces that Focusrite provides, to make changes.

Thanks
.
 
I'm looking to connect this to a Focusrite Scarlett, but I need to run at 44.1KHz. I contacted Thomann and they said it would only run at 48KHz, despite your review saying otherwise. Because that's all the Manual says.

Will this run at 44.1KHz?
Does it automatically pick up the rate from the host device?

Akai MPCs are now allowing USB class complaint devices, so I won't have access to any of the software interfaces that Focusrite provides, to make changes.

Thanks
.
In my tests above I only tested 192kHz and 48kHz sample rates, and unfortunately I don't have the device anymore to test 44,1kHz as well.
But in my understanding (which might be wrong) this ADC always outputs at 192kHz, so it would be up to the receiving device to resample to some other sample rate if needed.
Probably the safest way would be to test in your system - Thomann offer a 30-day return window so it may be feasible to do so.
 
In my tests above I only tested 192kHz and 48kHz sample rates, and unfortunately I don't have the device anymore to test 44,1kHz as well.
But in my understanding (which might be wrong) this ADC always outputs at 192kHz, so it would be up to the receiving device to resample to some other sample rate if needed.
Probably the safest way would be to test in your system - Thomann offer a 30-day return window so it may be feasible to do so.
Thanks man for the reply. I'm in Vietnam, so I can't really test. Maybe I should try Focusrite support.
 
@dominikz are you still using it with turntable? Have you found a better solution?
Actually I'm using the unbranded ADC from eBay with my turntable. It performs worse than the Swissonic objectively, but IMHO sounds fine so I haven't bothered to look for a replacement - at least not yet. :)
 
@tsoltan you can also use sound blaster X-fi HD.
Has both line and phono in. The phono in is noisy, but if you already have a phono stage, you can use the line in and in this case the results are very good IMO (depending on your phono stage, of course)
Edit: you might be looking for an analog to toslink converter. The X-fi would be analog to usb. Sorry for misunderstanding
 
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How do you set the sample rate on this ADC?
 
Thanks for these adc reviews @dominikz.

The Swissonic's 192kHz sample rate was unfortunately not compatible with my system so I went on the hunt for another option. I came across this one:
20230626_135353.jpg


Which is unbranded on its casing but I believe is the "Vedindust Analog to Digital Audio Converter", on Amazon UK currently for £16.99 (I got mine used from eBay for £10).
It seems like a well made item, with an aluminium case and gold plated connectors.

I ran some measurements in RMAA for comparison to the other ADCs measured here. Results below... All at 24/48kHz which I believe is the output sample rate of the Vedindust adc. M-audio analog out --> Vedindust --> M-audio optical in.

The first measurement is a loopback showing the dac/adc performance of the M-audio USB Transit (the old type) as a benchmark.
The other measurements are with different USB power supplies. You can see the performance varies quite a bit depending on the supply.

The performance with the battery power bank is looking really good, but in reality i'll run it off one of the power supplies. Its likely to be fine for cassette/vinyl duty anyway.

Vedindust.JPG


First time using RMAA so take measurements with a pinch of salt, but it looks like a usable bit of kit in any case.
 
I would want to take a look at a few graphs, notably:
* find out what the +/- 0.11 dB FR variation is all about
* determine the cause for the large differences in THD and IMD+N despite little change in noise / DR

Also, I doubt I could resist the urge to take a look inside and identify the chips used, looks like a few Phillips screws is all you need to undo...
 
Here's what's inside...
20230626_141116.jpg

No markings on the main chip. PCB has the web address for the company - vpfet.com

Some graphs... battery power bank vs phone charger.

ADC FS.JPG


ADC N.JPG

ADC THD.JPG

ADC IMD.JPG
 
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I'm not sure if it counts as audiophile, but this USB power supply performs a lot better than any others.
Phihong PSB05R-050Q.

20230707_140006.jpg


This one is from a TomTom, but its an OEM that Harmon Kardon and many others have used. £6 new from eBay.

Graphs below for the VPfet ADC running on battery vs the Phihong supply:

1688735033586.png

1688735064669.png

1688735088930.png

1688735115333.png


Obviously not as good as battery power, but way better than other USB power supplies tested.
I bet I could spend a lot more money and get worse performance.
 
Is it possible that this unit can be used to improve the performance of a Minidsp 2x4HD? The ADC on that is pretty poor, with a high noise floor. So i'm considering using an external ADC between the reciever and optical input on the Minidsp, instead of using the analog inputs.

When i switch between digital and analog inputs on the Minidsp, the noise goes from inaudible to clearly audible, regardless of anything being connected. I would estimate +10db.
 
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