On the Distortion of Cirrus Logic CS431xx-Based Devices: A Comparative Review

[Ahmonge]

It's not a matter if we want to upgrade D30pro's firmware or not. D30pro and other old models in that era are not capable of upgrading MCU firmware in the first place. Only XMOS firmware was upgradable.

On top of that, D30pro was discontinued for about/over two years now. (Which was only in production in less than a year)

I can't help but feel truly disappointed.

 

[jkim]

I can't help but feel truly disappointed.

Right. But at least there's the NOS option for the D30 Pro..

 

[Ahmonge]

Right. But at least there's the NOS option for the D30 Pro..

I see, but I don't feel comfortable sending ultrasonic trash to the HP amplifier.

 

[jkim]

I see, but I don't feel comfortable sending ultrasonic trash to the HP amplifier.

Not a problem if you upsample any signal to 384 kHz on your OS. Even 192 kHz Fs is alright.

 

[Ahmonge]

Not a problem if you upsample any signal to 384 kHz on your OS. Even 192 kHz Fs is alright.

Not possible in my case, as I use an iPad as source.

 

[L5730]

More testing to do (and my methodology might be a mess) but I don't see the same behaviour on Tempotec Sonata HD Pro.
This device does have some extra distortion if the volume is pushed to the maximum, but one button press down clears that up - I think this was documented in the review.

I have tested the same file and the dual tone signal and reducing playback level from Foobar2000 does not cause a sudden increase in distortion. Everything just gets lower until the ADC noise floor - kind of anticlimactically expected behaviour. Looked like an AKM DAC output in examples ...

I couldn't hear clicks playing the Song-of-the-Sisters test file.

Tempotec Sonata HD Pro
Foobar2000 in ASIO mode (ReplayGain pre-amp 0dB, manual output control)
Windows volume set to 100%
24 bit / 192 kHz recordings made by RME BF Pro FS

Included spectrogram of -15dB playback volume of CMaj.flac reference file.
Looks like typical non-CS DAC chip behaviour?
Ignore the multiple horizontal bars - harmonics of ground noise 50 Hz coming from somewhere....

 

[L5730]

Wondering about picking up a FiiO K11 at the moment.
I was thinking FiiO would likely solve the DRE issue with a FW update....however....

Oh dear

 

[jkim]

More testing to do (and my methodology might be a mess) but I don't see the same behaviour on Tempotec Sonata HD Pro.
This device does have some extra distortion if the volume is pushed to the maximum, but one button press down clears that up - I think this was documented in the review.

I have tested the same file and the dual tone signal and reducing playback level from Foobar2000 does not cause a sudden increase in distortion. Everything just gets lower until the ADC noise floor - kind of anticlimactically expected behaviour. Looked like an AKM DAC output in examples ...

I couldn't hear clicks playing the Song-of-the-Sisters test file.

Tempotec Sonata HD Pro
Foobar2000 in ASIO mode (ReplayGain pre-amp 0dB, manual output control)
Windows volume set to 100%
24 bit / 192 kHz recordings made by RME BF Pro FS

Included spectrogram of -15dB playback volume of CMaj.flac reference file.
Looks like typical non-CS DAC chip behaviour?
Ignore the multiple horizontal bars - harmonics of ground noise 50 Hz coming from somewhere....

Have you normalized the recording to -1 dBFS at its peak? And here's my spectrogram setting in Audacity:

 

[L5730]

Hmm....
Whilst I am not currently hearing clicks (apart from the abrupt one at the end of the sample audio) there would appear some vertical lines of distortion originating from somewhere - and they fit to be where they should be, as the material increases in volume.

Apologies that the image is so populated with noise - maybe that is masking what I can hear!

Cleared some mains noise, but am getting USB pollution (8kHz) - no surprises DAC and ADC on same PC...

 

[tccalvin]

Hmm....
Whilst I am not currently hearing clicks (apart from the abrupt one at the end of the sample audio) there would appear some vertical lines of distortion originating from somewhere - and they fit to be where they should be, as the material increases in volume.

Apologies that the image is so populated with noise - maybe that is masking what I can hear!

Cleared some mains noise, but am getting USB pollution (8kHz) - no surprises DAC and ADC on same PC...

Looks consistent with the non-hump DACs

 

[L5730]

Hooked up Tempotec Sonata HD Pro to Moto G55 mobile phone via USB-C OTG adaptor.
VLC playing, no ReplayGain, all volumes at maximum.
This cleared up the USB noise and other additional rubbish.

I hope this image shows more information (normalised recording to -1dBFS).

When I set the ReplayGain Preamp in VLC to -15dB, there isn't really any sign of these distortion spikes, so probably too low in amplitude and masked by other noise?

 

[tccalvin]

Hooked up Tempotec Sonata HD Pro to Moto G55 mobile phone via USB-C OTG adaptor.
VLC playing, no ReplayGain, all volumes at maximum.
This cleared up the USB noise and other additional rubbish.

I hope this image shows more information (normalised recording to -1dBFS).
View attachment 475490


When I set the ReplayGain Preamp in VLC to -15dB, there isn't really any sign of these distortion spikes, so probably too low in amplitude and masked by other noise?

You probably just need to adjust the spectrogram range in Audacity to display quieter signals. As far as I understand, "Range (dB): 100" means that you're only displaying content ranging from 0dBFS to -100dBFS. If you lower the input volume, some stuff is going to fall outside that range (say, at -101dBFS) and it won't get displayed.

If you keep lowering the input gain, at some point the clicks will be masked by the noise, however the spikes should still be visible past 24kHz until they get buried in ADC noise.

 

[Luciferium]

Any info (dose it have a hump) on Jcally JM98MAX?

 

[HissingFree]

Any info (dose it have a hump) on Jcally JM98MAX?

Interesting device, but ultimately doesn't do much to me compared to JM20 Max, because it only supports 3 EQ modes and no EQ frequency tuning is possible.
I think it will have the same hump.

 

[Njoy]

=== Important Findings ===

Out of curiosity, I measured the TRN Black Pearl again in its NOS (Non-Oversampling) mode. A 32-tone signal @ -20 dBFS---at which the Cirrus hump is at its largest---was used. In fact, I did this test and reported results a few posts earlier here and also here. But at THOSE times, the signal chain was:

• A 32-tone signal was generated at the sample rate of either 96 kHz or 44.1 kHz.
• AND the Black Pearl played it at the same sample rate as the signal was created.

This assumes a true NOS playback situation, i.e., the DAC plays originally recorded (i.e., sampled) digital content with no resampling or filtering.

However, I asked myself, "what if CD audio (sampled at 44.1 kHz Fs) is played by this DAC w/ NOS selected but at a much higher sample rate?" In fact, Windows should upsample the signal, and its upsampling quality must be good (see here).

It turns out that such playback achieves what we want: neither a Cirrus hump and nor NOS artifacts!

Below are FFT captures of a 32-tone signal @-20 dBFS generated at 16 bit / 44.1 kHz Fs (i.e., CD audio), played by the Black Pearl (NOS) in various sample rate settings in Windows 11.

First up is 44.1 kHz playback sample rate:
View attachment 461867
No Cirrus hump distortion, but as expected, huge NOS distortion from broken waves. Also notice some high frequency roll-off b/w 10 k - 20 kHz which is typically observed from NOS D/A conversion.

Next, 96 kHz playback sample rate:
View attachment 461868
Still quite large NOS artifacts but this clearly indicates that the signal is being resampled.

192 kHz playback sample rate:
View attachment 461869
Upsampled to 192 kHz, NOS distortion is much lower. No high-frequency roll-off, either. At this resampling rate, I won't worry about the NOS distortion---it is no longer NOS, anyway.

How about 384 kHz playback sample rate:
View attachment 461870
Upsampled to 384 kHz, there is just the CS431xx's regular noise shaping effect alone. There's a hint of distortion at 384 kHz, but it is lower than the noise shaping peak.

Now that the absence of a Cirrus hump has been confirmed, how about the Part II tests described in the review?
The C Major clip first. Played with NOS at Fs = 192 kHz:
View attachment 462301
No clicks.

The Dune soundtrack clip:
View attachment 462302
Clean.

Then, we want to ask an important question, why do we not have a Cirrus hump nor the distortion observed in Part II tests when NOS is selected? In the review we conjectured the distortion could be due to improperly implemented dynamic range enhancement (DRE) in the CS431xx chips. Actually, in the NOS mode DRE is turned off! See below:
View attachment 462306
In the NOS mode, noise stays the same regardless of the signal level (red solid line). The full noise reduction from DRE, when it is turned on, is 24 dB (green solid line) just as observed here.

These data provide convincing evidence that the distortion we're dealing with is caused by DRE, because the distortion is gone when DRE is not in action.

One may ask if the DAC's noise performance becomes horrible with DRE not engaged, since DRE contributes whopping 24 dBs to noise reduction according to the above measurements. In fact, the DRE effect in reality is not 24 dBs. The reason is that the noise level measured above covers wide bandwidth (20 Hz - 90 kHz) and hence is dominated by the noise shaping peak in the ultrasonic region (> 50 kHz). This setting was intended to accurately measure the 'DRE gain' which is solely digital gain and reflected well in the noise shaping. But the noise level in the audio band (20 Hz to 20 kHz) is dominated by analog (i.e., thermal) noise. With DRE, analog noise in this passband is very low but still there's a limit. The dynamic range (DR) of the TRN Black Pearl's balanced output with DRE turned on is
Left: View attachment 462353, Right: View attachment 462354
whopping 132.7 dB! Actually this performance challenges the noise limit of my measurement setup (E1DA Cosmos ADCiso and Scaler). I have never seen this high DR in Amir's AP measurements of any DAC. No doubt the Black Pearl's power supply circuits must have a very nice design. But the real reason how it achieves this astonishingly high DR is simply because of DRE.

The question is, do we really need this high DR? Absolutely not. We cannot hear the difference between two DACs with this high DR and much lower DR. Let's see the DR of the same Black Pearl's balanced output with DRE turned off (i.e., with NOS):
Left: View attachment 462355, Right: View attachment 462356
Its DR with no DRE is decent at 120.5 dB. Sure, the difference b/w DRE being on and off is somewhat large (12 dB), but a DR of 120.5 dB is still very nice.

What about 50 mV SNR with DRE turned on?
View attachment 462357 (left ch. shown; right ch. is 0.1 dB lower)
With DRE turned on, the Black Pearl's SNR at 50 mV into its unbalanced output is amazingly high 96.5 dB! This number would actually be at the very top of Amir's headphone amp 50 mV SNR chart:
View attachment 462360

Now, 50 mV SNR with DRE turned off:
View attachment 462358 (left ch. shown; right ch. is 0.1 dB lower)
With no DRE (i.e., with NOS), the SNR decreases to 85.3 dB. Is this bad noise performance? Not at all. I cannot hear any hiss from my 7Hz x Crinacle Zero:2 when hearing -120 dBFS white noise (not supposed to be heard) with the device volume set to max. In fact, an SNR of 85.3 dB at 50 mV is very similar to (just 2 dB worse than) what I measured from the Qudelix 5K.

Would I choose DRE in order to have unnecessary 96.5 dB SNR @ 50 mV and swallow the Cirrus hump distortion? Definitely not.

I was curious of other CS431xx-based DACs that support selection of filters. Tried the Tanchjim Stargate II and JCally JM20-ProFiiO KA15. Observed exactly the same behavior as above.

Key Takeaways:

• When a CS431xx-based DAC can be set to 'NOS' mode the DAC no longer applies DRE (dynamic range enhancement) and does not exhibit Cirrus hump distortion---to make sure, all the DACs supporting filter selection need to be checked but this seems to be the CS431xx chips' default behavior when NOS is selected.
• Playback at a sample rate of 192 kHz or higher, if a good upsampling algorithm is supported by the operating system, will mitigate NOS artifacts. Whether upsampling is supported, and how good it is, will depend on the operating system, though.
• Some may wonder if the DAC's noise performance is still good with DRE not engaged. I can assure that it is still decent. You won't hear hiss even from sensitive IEMs.

Using SMSL M300 SE with Samsung mobile phone.Android driver in Samsung literally up samples everything to 192khz, sounded not so good.Now, after going through your post, I chose NOS filter. It sounds great, or is it just my mind playing games?

 

[tccalvin]

Using SMSL M300 SE with Samsung mobile phone.Android driver in Samsung literally up samples everything to 192khz, sounded not so good.Now, after going through your post, I chose NOS filter. It sounds great, or is it just my mind playing games?

I believe that Android defaults to 48kHz as its sample rate. Without upsampling, a NOS filter is going to sound bad (high end roll-off plus added distortion, easily noticeable). If you upsample your audio files offline, the NOS filter is going to sound right. If you use a system-level, real-time upsampler you're potentially going to get worse results (but likely very hard to notice) because the system is going to optimize for low latency and power efficiency.

 

[Njoy]

Samsung phone re samples to 192kHz
MI phone does it 48kHz
Oppo ( wife's) does it 96kHz
Used wav files ripped from CD.Using UAPP with exclusive mode, all play at 44.1khz.

 

[CedarX]

Interesting device, but ultimately doesn't do much to me compared to JM20 Max, because it only supports 3 EQ modes and no EQ frequency tuning is possible.
I think it will have the same hump.

The JCally JM98MAX is built around a TTGK module, identified as TT39518F01-Pro, VID/PID 0x661/0x881 (although I’m not sure it’s actually a TT39518F01-Pro: 3.5mn SE only). It is WalkPlay-enabled ... kinda: you can set and save Custom PEQs (combination of up to 8x filters, PK/HS/LS/HP/LP type). The custom PEQ seems to overwrite the default PEQ slot. The problem is it doesn't "stick": you can switch between your Custom PEQ, Bass, and Highs PEQ presets with a short press of the side button, but as soon as you disconnect/reconnect the dongle, it reverts to the default PEQ (flat) setting. You have to re-enable your Custom PEQ through the WalkPlay app. It is a similar behavior as the Kiwi Allegro Pro (KT02H20+ dual ES9603Q).
The other WalkPlay features—Low/High gain, Class AB/H, DAC filters, L/R balance— although visible in WalkPlay, don't appear to do anything.

So, if one is ok with re-enabling Custom PEQ in WalkPlay each time the dongle is connected, the JM98Max could be used as a high-power dongle (~JM20Max) with PEQ (~JM20Pro).

 

[Rantapossu]

I tested my new Focusrite Scarlett 2i2 (4th Gen) too and sure enough, there it was! The famous and feared Cirrus Hump:

This was measured from the line level outputs, but I suspect that the hump also exists on the headphone output...

 

[Carlo2AC]

Are these values from the E1DA 9039S real?

Output power:
>400mW@32ohm@1kHz@THD=1% each channel
Output power:
>680mW@16ohm@1kHz@THD=1% each channel

Nothing about 300ohms but what its there is already impressive

Anything portable with more power and no issues than the E1DA 9039S?