Quant Asylum QA403 with ESS DAC and ADC

[capslock]

https://forum.quantasylum.com/uploads/short-url/e9EUxkUod8AstX3q4DM5uLsmMNL.pdf

That didn't take long for them to replace the QA402. THD measurements in loopback and from external source look okish but those converters are capable of much more as demonstrated by several DACs tested here and of course IVX's Cosmos ADC.

How did they manage to loose about 10 dB harmonic performance in each? Poor layout? Wrong kind of resistors?

Then again, I am surprised that intermodulation performance, both multitone and two-tone, looks quite good. Is this maybe due to their analysis software?

 

[Ralf Stocker]

I asked myself the same. The chip is world class, just not in the device. Something must be wrong with the design. Probably the amplifier or the attenuator stages.

 

[radix]

They had a parts shortage and cannot produce the 402 any more.

 

[Ralf Stocker]

And the parts shortage continues with the QA403.

 

[radix]

I received a QA403 today. Here's the self noise (inputs terminated with 50R) and the loopback measurements w/ 6" BNC on the + phase.

I'm on the 1.142 and updated the firmware to v58 that comes with 1.142.

EDIT: I noticed QuantAsylum has a noise measurement on their website. I re-did my measurement using their settings, and it is here below.

Comparison

Measurement	QuantAsylum	My unit
THD	-129.47	-120.82
THD+N	-109.81	-104.98
N-D dBV	-110.4	-105.8

 

[Blumlein 88]

So that looks like the noise floor is about -100 db or so? Taking into account fft gain.

 

[radix]

So that looks like the noise floor is about -100 db or so? Taking into account fft gain.

The previous measurement I did was at -10 dBV. QuantAsylum measured the device at 0 dBV. I edited the post with a redone measurement.

 

[capslock]

In the -10 dB measurement:

HD2: in the noise
HD3: -135 dB + 10 dB = -125 dB

In the 0 db measurement
HD2: -135 dB
HD3: -121 dB

Good but not quite what these converters are capable of.

PS: When did you order your QA403?

 

[radix]

PS: When did you order your QA403?

QuantAsylum asked to exchange my QA402 for a 403 so they could refurb and sell to a customer who needed more 402s. That was OK with me, so I did the exchange. They likely shipped out my replacement pretty early in the availability, but I'm just guessing at that.

 

[restorer-john]

DIT: I noticed QuantAsylum has a noise measurement on their website. I re-did my measurement using their settings, and it is here below.

Comparison

Measurement	QuantAsylum	My unit
THD	-129.47	-120.82
THD+N	-109.81	-104.98
N-D dBV	-110.4	-105.8

That's a pretty serious deviation from their specs. If anything, yours should be better, not significantly worse...

 

[Ralf Stocker]

I suspect this is mass production and not lab tweaking with selected components.

 

[capslock]

That's a pretty serious deviation from their specs. If anything, yours should be better, not significantly worse...

As I understand it, that is an example, not a spec. Still, it is annoying that a random unit seems to perform much worse.

 

[capslock]

I suspect this is mass production and not lab tweaking with selected components.

I think Ivan (IVR) went through this with his 9038S3 DAC. In the end, he found that he gets consistently good performance with Susumo resistors. Not sure if is the resistance matching or the low voltage coefficient of these resistors that does it.

Do we know if QA calibrate HD2 and HD3 in their DACs and ADCs?

 

[restorer-john]

Do we know if QA calibrate HD2 and HD3 in their DACs and ADCs?

I have no idea.

Do they have individual calibration files tied in the firmware for each unit and/or can it be customized?

Calibration: default?

 

[radix]

QuantAsylum does advertise a dBV vs THD graph. This was driven by their QA480, which has a high quality notch filter.

My unit measured THD at -120.82 @ 0 dBV and -117 (rounding a little) @ -10 dBV. That looks about 3 dB under the THD measured with the QA480, which could be due to using the QA480.

Spoiler: dBV vs THD graph

The spec sheet claims noise floor -115 dBV, THD -115 dB and THD+N -105 dB. These are both measured with different settings than I used (I hadn't seen the spec sheet on the web site until now).

 

[pizzigri]

Hi Radix, your measurements make me a bit antsy- i purchased a qa203 and hoped for something not far off the published “specs”.
As of today, I still have not received mine, when I do I will do the same test you did and post results here.
franco

Ps- no more qa403 for the next several months, maybe even for all of 2022... maybe a 204 is due?

 

[HornJunkie]

Hey guys,

actually I'm searching a good (not great) audio measurement device and sound cart for measurements. Is the Q403 a recommondation? Don't like to spend thousands for an audio measurement tool.

Best regards,

Florian

 

[AnalogSteph]

Well, what kind of devices are you intending to measure the performance of, and how many?