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

[mc.god]

Why not saying who so we can thank him too? My bet is on @mc.god...

No, the kind lender wasn't me, i don't own so many dongles and anyway would have been problematic send them to USA

 

[Roland68]

Introduction

View attachment 452324​

Since their release in fall 2017, Cirrus Logic's two digital-to-analog converter (DAC) chips, the CS43131 and CS43198, have gained traction in industry, being adopted in quite a few consumer hi-fi and professional audio devices. With the recent boom of hi-fi products designed and manufactured by Chinese companies, more and more products adopting these chips keep coming out these days. Attractive features that have led these manufacturers to use the chips are:

• Excellent, if not state-of-the-art, measured performance in SINAD/THD+N and dynamic range
• Relatively low cost
• Integrated, quite capable headphone driver (see below; even the CS43198 has a headphone driver)
• Small packaging for wide applications in portable devices
• Energy-efficient

Despite this popularity, some industry designers and DIY audio enthusiasts have criticized these DAC chips. One issue is about the technology called Dynamic Range Enhancement (DRE) implemented in the chips. This technique increases a DAC's low-level performance and achieves a higher measured dynamic range (DR) by adjusting the chip's gain structure, depending on the signal strength, to find a good trade-off between digital and analog gain settings. DRE is not a new technology but has also been employed by other DAC chip manufacturers. Setting aside the debatable point on whether the DR of a DRE-enabled device, measured by the AES17 standard procedure, is faithful to a theoretical definition of a dynamic range, criticism against these Cirrus Logic chips has been on the fact that the use of DRE is not officially documented by Cirrus Logic anywhere.

Another issue, relatively less known, is that some devices employing these chips exhibit substantially elevated distortion/noise responding to certain signals. This phenomenon was examined and reported in an article published at the Reference Audio Analyzer, a Russia-based audio gear review website founded by Roman Kuznetsov. What this article demonstrated is that this peculiar behavior is not just observed in artificial testing signals but also in real audio content. And it occurs to several CS431xx-based devices tested at the site, except for only a few others producing no such distortion. Based on these observations and the information on the chips' datasheets---i.e., based on what he can see---, he conjectures that the problem could be caused by a malfunction of the chips' Class H amplifier and would be resolved by proper firmware design.

The purpose of writing this review at ASR is multifold:

1. To test more CS431xx-based devices toward compiling a list of devices affected by this problematic distortion behavior;
2. To suggest an effective measurement method for detecting and characterizing the distortion;
3. To eventually (and hopefully) have audio manufacturers react and come up with a solution (if they are going to keep using these chips).

The purpose of this review is not to find the precise cause of the problem or suggest a solution, simply because it is not possible to achieve that based on measurements alone or the known information.

Measurement Setup​

• AD converter: E1DA Cosmos ADCiso Grade A in Mono Mode, and Cosmos Scaler as a buffer.
• Software: Room EQ Wizard (v5.4 beta 80).

The Peculiar Distortion: Cirrus Humps​

Some CS43131-based portable devices tested here at ASR showed excellent noise and distortion performance as well as very nice output power. To name a few: MEIZU Hifi Audio Pro, Tanchjim Space, TempoTec Sonata BHD Pro, JCALLY JM20, etc. In fact, many CS431xx-based devices are nearly indistinguishable when tested by a standard package of measurements, unless incorrectly designed (e.g., inadequate caps in power supply circuits). Problems occur when a complex signal (e.g., multitone) meets with somewhat low levels.

Let's take some multitone measurements from my recent review of the FiiO KA15:

These are the FFTs of a 32-tone signal at the maximum, unclipped level as well as at a 6 dB lower level. Normally, if we feed the same signal at a lower level, the ratio of the signal to distortion/noise deteriorates only slightly because of the weaker signal, just as shown above. However, the FIIO KA15 does not exhibit such an incremental trend but an abruptly high distortion when the signal further weakens:

And the response becomes normal when the signal reaches a much lower level:

The entire picture of level-dependent distortion can be seen in the sweeping measurements of Total Distortion + Noise (TD+N) using the same signal over varied strengths:

Notice a clear "hump" which indicates the rise of TD+N in a range of signal strengths. Let us dub this a "Cirrus hump." In comparison, the JCALLY JM20 and JM20 MAX do not show this behavior in the same measurements.

One may think this measurement signal, made of 32 equal-amplitude tones, is unrealistic which may never occur in real audio content. In fact, essentially the same phenomena can be found with any multitone signals, even with dual tones, as long as tone components are in similar amplitude. See below:

This dual-tone signal, called "TDFD Bass" in Room EQ Wizard, is simply composed of 41 Hz and 89 Hz sine tones. As with multitone signals, the KA15 distorts responding to these dual tones in a range of signal strengths. Again, a sweep of these tests across a range of signal strengths was performed:

A hump in this sweep test of TD+N versus output levels is unmistakably clear, too, compared to other CS43131-based devices (JCALLY JM20 and JM20 Max) which do not produce distortion.

Distortion Measurements of CS431xx-based Devices​

An ASR member kindly sent quite a few CS431xx-based devices for testing. And I also own a couple. Here is a list of tested devices:
View attachment 452324
(From left to right)

• FiiO BTR13 - QCC5125, dual CS43131, no op-amps
• FiiO KA15 - SPV5048-Pro, dual CS43198, dual SGM8262-2
• HiBy FC5 (w/ display) - Airoha AB1565, dual CS43198, dual SGM8261-5
• JCally JM20 - SA9312, single CS43131, no op-amps
• JCally JM20 Max - SA9312, single CS43131, SGM8262-2
• JCally JM20 Pro - CB5100-Pro, single CS43131, no op-amps
• JCally JM28 - SA9312, single CS43198, no op-amps
• Shanling UA1 Plus - CT7601, dual CS43131, no op-amps
• Tanchjim Stargate II - CB5100-Pro, single CS43131, no op-amps
• TRN Black Pearl - CB5100-Pro, dual CS43131, no op-amps
• TTGK TT39518F01-Pro module - CB5100-Pro, dual CS43198, no op-amps

These were measured exactly in the same condition. The following devices were found exhibit the distortion behavior:

• FiiO BTR13
• FiiO KA15
• HiBy FC5 w/ display
• JCally JM20 Pro
• Tanchjim Stargate II
• TRN Black Pearl
• TTGK TT39518F01-Pro

And the following did not produce distortion:

• JCally JM20
• JCally JM20 Max
• JCally JM28
• Shanling UA1 Plus

See their multitone sweep tests:
View attachment 452227

Across the affected devices (thick solid lines) distortion profiles over the multitone signal level, i.e., Cirrus humps, are consistent with each other. The TD+N results of unaffected devices, shown in dashed lines, are just as expected, being dominated by each device's power of noise components.

Below are the sweep results of dual-tone TDFD Bass IMD test signals:
View attachment 452228

Again, the elevated TD+N in a range of signal levels is an unmistakable character of the affected devices (thick solid lines), whereas the unaffected devices' measurements mainly indicate their noise components (dashed lines).

Other Characteristics​

The devices affected by the above measured distortion respond even to a single tone in a similar manner if the tone frequency is 8 Hz or below. This was first observed by an ASR member and reported here. All the affected devices reported above were found produce the same distortion in response to this subsonic sine tone whereas unaffected devices do not (like this). Another interesting characteristic discriminating the affected devices from unaffected ones is their noise level. For all CS431xx-based devices, their noise level depends on the test signal level in a distinctive manner due to the adopted DRE (dynamic range enhancement) technique.

See below for the effect of DRE in action on the noise level:
View attachment 452223

What is interesting is that, for all the devices showing the distortion behavior, this noise level is a simple function of the test tone level as shown above. It does not depend on the previous signal levels. This is not the case of the devices not producing distortion. See below:

That is, the noise level depends on not only what test tone level a sweep test starts from but also in which direction the test goes from there. If the signal weakens incrementally, the noise level stays the same as at the starting point, meaning that the DRE logic does not increase its effect, until the signal finally reaches below -50 dBFS. But if the signal strengthens, the noise level adapts to it meaning that DRE decreases its effect (by trading digital gain for analog gain). This implies that DRE in unaffected devices makes less aggressive adjustments of its gain structure (combination of digital & analog gain). Less active DRE, on whatever logic it operates, is not a problem at all, because the noise performance of CS431xx-based devices would by no means be poor even without DRE.

Of course, based on these observations alone, we cannot draw a conclusion on why the unaffected devices do not produce distortion. But we may conjecture that this different operation of DRE may be related to the occurrence (or absence) of the distortion.

Audibility of the Distortion​

It is difficult to tell how clearly audible these measured distortions would be in real audio content. But given the fact that the problem is observed even in a simple dual-tone test reported above, it is no wonder Roman at RAA was able to easily spot a movie soundtrack to demonstrate the distortion. Note that the website provides multiple recordings of the same track played at different levels, which are level-matched for the higher % distortion to be heard easily. Other than the most audible cases, it takes trained ears familiar with distorting sound to hear it. It is not clear "clicking" or severe clipping distortion. And the original track already contains quite high background noise. The distortion sounds like occasional crunch in the midst of fluctuating noise floors. In comparison, through an unaffected device, the background noise is not much fluctuating without crunch.

But we are talking about 0.06% distortion in the worst case. And human ears are easily deceived in this case. That is one big reason why the issue of subjective audibility is difficult to resolve. Also, there must be infinite possibilities of this distortion occurring in audio content. That is another reason why this issue should not be considered based on subjective listening of a few samples, and why systematic measurements---even a simple sweep of test tones over varied signal levels---are important.

CS43131 versus CS43198​

Now the topic is not about these two Cirrus Logic DAC chips' distortion but about their difference, if any. The block diagrams on Cirrus Logic's corresponding product pages indicate that the CS43131 integrates a stereo headphone amplifier whereas the CS43198 does not. The current drive capability of many CS43131-based devices with no additional op-amps has been shown to be very nice. How about a device employing only one CS43198 or two with no headphone driver added? We may think it will serve only as a line-level DAC source. However, if you search AliExpress, you will see some headphone dongles described as having a CS43198 or two with no op-amps. A headphone dongle with no amplifier? It actually makes sense ... because the CS43198 shows no difference from the CS43131 in measurements! Let's consider two pairs of devices that are believed to be clones of each other:

• The JCALLY JM28 is believed to be a clone of the JCALLY JM20 except that the former is with a CS43198 and the latter with a CS43131.
• The TTGK TT39518F01-Pro is believed to be a clone of the TRN Black Pearl except that the former is with dual CS43198's in a bare module and the latter is with dual CS43131's and housed in a nice black case.

View attachment 452319View attachment 452320View attachment 452321View attachment 452326

It was confirmed that the two DAC chips on the TT39518F01-Pro module have letter markings "CS43198."

The measurements of THD+N versus output voltage under 300 Ohm and 32 Ohm loads for these clone pairs were found identical to each other:
View attachment 452318
View attachment 452317


If headphone drive capability is identical between the two chips, then what tells them apart? I cannot think of a reason other than a marketing scheme.

Conclusion​

Tests of eleven DAC/headphone amplifier combo devices that adopt either Cirrus Logic CS43131 or CS43198 were performed, and seven of them were found exhibit the same distinctive distortion behavior as reported in an article published at the RAA website. It was also demonstrated that level sweep tests with multitone signals can be used to detect and characterize this distortion behavior. Also found was the unique operation of DRE (dynamic range enhancement) in unaffected devices different than in affected devices. Lastly, the CS43198, known to be with no integrated headphone amplifier, was found not just capable of driving headphone loads but also produce the same measured performance as the CS43131.

Setting aside the issue of subjective audibility, this measured distortion is obviously an engineering flaw that should not occur in DA converter products targeted at Hi-Fi markets and consumers. It is really bothersome that any device employing CS43131 or CS43198, whether it is a headphone dongle, desktop DAC/HP amp, digital audio player, or a music streamer, should be suspected to potentially produce this distortion. Based on the fact that some devices are not affected by this problem, like Roman at RAA I also believe it can be resolved by firmware design. But the problem is that there is no clear register in the chips' datasheets that must be related to this behavior. No one knows for certain, perhaps except for Cirrus Logic engineers---or even worse, former Wolfson engineers. For the reasons listed earlier, we will see more and more products with CS431xx will keep coming out. We hope audio gear manufacturers will react to this issue and find a solution, and better yet, it will become common knowledge.

Lastly, based on the measurements by RAA, myself and others, a spreadsheet of CS431xx-based devices has been compiled to show devices known to and not to produce distortion, and other information. This list will be updated as more devices are tested.

Really great report and great work, exactly what I was looking for, all in one place.
Thank you very much for going to such an effort.

 

[Roland68]

Introduction

View attachment 452324​

Since their release in fall 2017, Cirrus Logic's two digital-to-analog converter (DAC) chips, the CS43131 and CS43198, have gained traction in industry, being adopted in quite a few consumer hi-fi and professional audio devices. With the recent boom of hi-fi products designed and manufactured by Chinese companies, more and more products adopting these chips keep coming out these days. Attractive features that have led these manufacturers to use the chips are:

• Excellent, if not state-of-the-art, measured performance in SINAD/THD+N and dynamic range
• Relatively low cost
• Integrated, quite capable headphone driver (see below; even the CS43198 has a headphone driver)
• Small packaging for wide applications in portable devices
• Energy-efficient

Despite this popularity, some industry designers and DIY audio enthusiasts have criticized these DAC chips. One issue is about the technology called Dynamic Range Enhancement (DRE) implemented in the chips. This technique increases a DAC's low-level performance and achieves a higher measured dynamic range (DR) by adjusting the chip's gain structure, depending on the signal strength, to find a good trade-off between digital and analog gain settings. DRE is not a new technology but has also been employed by other DAC chip manufacturers. Setting aside the debatable point on whether the DR of a DRE-enabled device, measured by the AES17 standard procedure, is faithful to a theoretical definition of a dynamic range, criticism against these Cirrus Logic chips has been on the fact that the use of DRE is not officially documented by Cirrus Logic anywhere.

Another issue, relatively less known, is that some devices employing these chips exhibit substantially elevated distortion/noise responding to certain signals. This phenomenon was examined and reported in an article published at the Reference Audio Analyzer, a Russia-based audio gear review website founded by Roman Kuznetsov. What this article demonstrated is that this peculiar behavior is not just observed in artificial testing signals but also in real audio content. And it occurs to several CS431xx-based devices tested at the site, except for only a few others producing no such distortion. Based on these observations and the information on the chips' datasheets---i.e., based on what he can see---, he conjectures that the problem could be caused by a malfunction of the chips' Class H amplifier and would be resolved by proper firmware design.

The purpose of writing this review at ASR is multifold:

1. To test more CS431xx-based devices toward compiling a list of devices affected by this problematic distortion behavior;
2. To suggest an effective measurement method for detecting and characterizing the distortion;
3. To eventually (and hopefully) have audio manufacturers react and come up with a solution (if they are going to keep using these chips).

The purpose of this review is not to find the precise cause of the problem or suggest a solution, simply because it is not possible to achieve that based on measurements alone or the known information.

Measurement Setup​

• AD converter: E1DA Cosmos ADCiso Grade A in Mono Mode, and Cosmos Scaler as a buffer.
• Software: Room EQ Wizard (v5.4 beta 80).

The Peculiar Distortion: Cirrus Humps​

Some CS43131-based portable devices tested here at ASR showed excellent noise and distortion performance as well as very nice output power. To name a few: MEIZU Hifi Audio Pro, Tanchjim Space, TempoTec Sonata BHD Pro, JCALLY JM20, etc. In fact, many CS431xx-based devices are nearly indistinguishable when tested by a standard package of measurements, unless incorrectly designed (e.g., inadequate caps in power supply circuits). Problems occur when a complex signal (e.g., multitone) meets with somewhat low levels.

Let's take some multitone measurements from my recent review of the FiiO KA15:

These are the FFTs of a 32-tone signal at the maximum, unclipped level as well as at a 6 dB lower level. Normally, if we feed the same signal at a lower level, the ratio of the signal to distortion/noise deteriorates only slightly because of the weaker signal, just as shown above. However, the FIIO KA15 does not exhibit such an incremental trend but an abruptly high distortion when the signal further weakens:

And the response becomes normal when the signal reaches a much lower level:

The entire picture of level-dependent distortion can be seen in the sweeping measurements of Total Distortion + Noise (TD+N) using the same signal over varied strengths:

Notice a clear "hump" which indicates the rise of TD+N in a range of signal strengths. Let us dub this a "Cirrus hump." In comparison, the JCALLY JM20 and JM20 MAX do not show this behavior in the same measurements.

One may think this measurement signal, made of 32 equal-amplitude tones, is unrealistic which may never occur in real audio content. In fact, essentially the same phenomena can be found with any multitone signals, even with dual tones, as long as tone components are in similar amplitude. See below:

This dual-tone signal, called "TDFD Bass" in Room EQ Wizard, is simply composed of 41 Hz and 89 Hz sine tones. As with multitone signals, the KA15 distorts responding to these dual tones in a range of signal strengths. Again, a sweep of these tests across a range of signal strengths was performed:

A hump in this sweep test of TD+N versus output levels is unmistakably clear, too, compared to other CS43131-based devices (JCALLY JM20 and JM20 Max) which do not produce distortion.

Distortion Measurements of CS431xx-based Devices​

An ASR member kindly sent quite a few CS431xx-based devices for testing. And I also own a couple. Here is a list of tested devices:
View attachment 452324
(From left to right)

• FiiO BTR13 - QCC5125, dual CS43131, no op-amps
• FiiO KA15 - SPV5048-Pro, dual CS43198, dual SGM8262-2
• HiBy FC5 (w/ display) - Airoha AB1565, dual CS43198, dual SGM8261-5
• JCally JM20 - SA9312, single CS43131, no op-amps
• JCally JM20 Max - SA9312, single CS43131, SGM8262-2
• JCally JM20 Pro - CB5100-Pro, single CS43131, no op-amps
• JCally JM28 - SA9312, single CS43198, no op-amps
• Shanling UA1 Plus - CT7601, dual CS43131, no op-amps
• Tanchjim Stargate II - CB5100-Pro, single CS43131, no op-amps
• TRN Black Pearl - CB5100-Pro, dual CS43131, no op-amps
• TTGK TT39518F01-Pro module - CB5100-Pro, dual CS43198, no op-amps

These were measured exactly in the same condition. The following devices were found exhibit the distortion behavior:

• FiiO BTR13
• FiiO KA15
• HiBy FC5 w/ display
• JCally JM20 Pro
• Tanchjim Stargate II
• TRN Black Pearl
• TTGK TT39518F01-Pro

And the following did not produce distortion:

• JCally JM20
• JCally JM20 Max
• JCally JM28
• Shanling UA1 Plus

See their multitone sweep tests:
View attachment 452227

Across the affected devices (thick solid lines) distortion profiles over the multitone signal level, i.e., Cirrus humps, are consistent with each other. The TD+N results of unaffected devices, shown in dashed lines, are just as expected, being dominated by each device's power of noise components.

Below are the sweep results of dual-tone TDFD Bass IMD test signals:
View attachment 452228

Again, the elevated TD+N in a range of signal levels is an unmistakable character of the affected devices (thick solid lines), whereas the unaffected devices' measurements mainly indicate their noise components (dashed lines).

Other Characteristics​

The devices affected by the above measured distortion respond even to a single tone in a similar manner if the tone frequency is 8 Hz or below. This was first observed by an ASR member and reported here. All the affected devices reported above were found produce the same distortion in response to this subsonic sine tone whereas unaffected devices do not (like this). Another interesting characteristic discriminating the affected devices from unaffected ones is their noise level. For all CS431xx-based devices, their noise level depends on the test signal level in a distinctive manner due to the adopted DRE (dynamic range enhancement) technique.

See below for the effect of DRE in action on the noise level:
View attachment 452223

What is interesting is that, for all the devices showing the distortion behavior, this noise level is a simple function of the test tone level as shown above. It does not depend on the previous signal levels. This is not the case of the devices not producing distortion. See below:

That is, the noise level depends on not only what test tone level a sweep test starts from but also in which direction the test goes from there. If the signal weakens incrementally, the noise level stays the same as at the starting point, meaning that the DRE logic does not increase its effect, until the signal finally reaches below -50 dBFS. But if the signal strengthens, the noise level adapts to it meaning that DRE decreases its effect (by trading digital gain for analog gain). This implies that DRE in unaffected devices makes less aggressive adjustments of its gain structure (combination of digital & analog gain). Less active DRE, on whatever logic it operates, is not a problem at all, because the noise performance of CS431xx-based devices would by no means be poor even without DRE.

Of course, based on these observations alone, we cannot draw a conclusion on why the unaffected devices do not produce distortion. But we may conjecture that this different operation of DRE may be related to the occurrence (or absence) of the distortion.

Audibility of the Distortion​

It is difficult to tell how clearly audible these measured distortions would be in real audio content. But given the fact that the problem is observed even in a simple dual-tone test reported above, it is no wonder Roman at RAA was able to easily spot a movie soundtrack to demonstrate the distortion. Note that the website provides multiple recordings of the same track played at different levels, which are level-matched for the higher % distortion to be heard easily. Other than the most audible cases, it takes trained ears familiar with distorting sound to hear it. It is not clear "clicking" or severe clipping distortion. And the original track already contains quite high background noise. The distortion sounds like occasional crunch in the midst of fluctuating noise floors. In comparison, through an unaffected device, the background noise is not much fluctuating without crunch.

But we are talking about 0.06% distortion in the worst case. And human ears are easily deceived in this case. That is one big reason why the issue of subjective audibility is difficult to resolve. Also, there must be infinite possibilities of this distortion occurring in audio content. That is another reason why this issue should not be considered based on subjective listening of a few samples, and why systematic measurements---even a simple sweep of test tones over varied signal levels---are important.

CS43131 versus CS43198​

Now the topic is not about these two Cirrus Logic DAC chips' distortion but about their difference, if any. The block diagrams on Cirrus Logic's corresponding product pages indicate that the CS43131 integrates a stereo headphone amplifier whereas the CS43198 does not. The current drive capability of many CS43131-based devices with no additional op-amps has been shown to be very nice. How about a device employing only one CS43198 or two with no headphone driver added? We may think it will serve only as a line-level DAC source. However, if you search AliExpress, you will see some headphone dongles described as having a CS43198 or two with no op-amps. A headphone dongle with no amplifier? It actually makes sense ... because the CS43198 shows no difference from the CS43131 in measurements! Let's consider two pairs of devices that are believed to be clones of each other:

• The JCALLY JM28 is believed to be a clone of the JCALLY JM20 except that the former is with a CS43198 and the latter with a CS43131.
• The TTGK TT39518F01-Pro is believed to be a clone of the TRN Black Pearl except that the former is with dual CS43198's in a bare module and the latter is with dual CS43131's and housed in a nice black case.

View attachment 452319View attachment 452320View attachment 452321View attachment 452326

It was confirmed that the two DAC chips on the TT39518F01-Pro module have letter markings "CS43198."

The measurements of THD+N versus output voltage under 300 Ohm and 32 Ohm loads for these clone pairs were found identical to each other:
View attachment 452318
View attachment 452317


If headphone drive capability is identical between the two chips, then what tells them apart? I cannot think of a reason other than a marketing scheme.

Conclusion​

Tests of eleven DAC/headphone amplifier combo devices that adopt either Cirrus Logic CS43131 or CS43198 were performed, and seven of them were found exhibit the same distinctive distortion behavior as reported in an article published at the RAA website. It was also demonstrated that level sweep tests with multitone signals can be used to detect and characterize this distortion behavior. Also found was the unique operation of DRE (dynamic range enhancement) in unaffected devices different than in affected devices. Lastly, the CS43198, known to be with no integrated headphone amplifier, was found not just capable of driving headphone loads but also produce the same measured performance as the CS43131.

Setting aside the issue of subjective audibility, this measured distortion is obviously an engineering flaw that should not occur in DA converter products targeted at Hi-Fi markets and consumers. It is really bothersome that any device employing CS43131 or CS43198, whether it is a headphone dongle, desktop DAC/HP amp, digital audio player, or a music streamer, should be suspected to potentially produce this distortion. Based on the fact that some devices are not affected by this problem, like Roman at RAA I also believe it can be resolved by firmware design. But the problem is that there is no clear register in the chips' datasheets that must be related to this behavior. No one knows for certain, perhaps except for Cirrus Logic engineers---or even worse, former Wolfson engineers. For the reasons listed earlier, we will see more and more products with CS431xx will keep coming out. We hope audio gear manufacturers will react to this issue and find a solution, and better yet, it will become common knowledge.

Lastly, based on the measurements by RAA, myself and others, a spreadsheet of CS431xx-based devices has been compiled to show devices known to and not to produce distortion, and other information. This list will be updated as more devices are tested.

Could it be that the distortion is a component problem in the CS431xx's circuitry?

The datasheet emphasizes the importance of capacitors, such as low ESR, X7R/X5R types, especially in the VCP_FILT, FILT+/-, FLYP_VA, and FLYN_VA ranges.
On the one hand, it often happens that parts purchased for production do not meet the specifications or are functional counterfeits; on the other hand, manufacturers deliberately cut costs.
Likewise, there are now known problems in the industry with SMD resistors of smaller sizes that are too cheap.
Such components could lead to noise, oscillations, and feedback in such locations, especially in the often very sensitive DAC chips.

 

[myy0222]

I found a post on a Chinese forum: Link
It also mentions that the CS43131 commonly has multi-tone issues, with test charts included. Here's a translation of some key parts of the post:
— (the test was done at 0dB) "So, is it okay as long as you don’t turn it up to maximum volume?" — "In some cases yes, in others no. It’s quite troublesome."
— "Update: Cirrus Logic's own engineers arrived on-site and confirmed the problem exists, but it’s not a hardware issue and can be fixed. A solution is expected next week."
— "China couldn’t fix it, so they handed it over to U.S. engineers, but then came Christmas and New Year... and now no one knows what’s going on."
— "— Months have passed, and still no news?" — "Unfixable, it’s a chip issue." — "2022 now, is it completely hopeless?" — "Looks like it’s hopeless."

At the end of 2021, Luxury&Precision released the W2-131, mentioning that it “eliminates persistent BUG issues” and, "relying on Luxury&Precision’s strong FPGA expertise, the first one offers a portable DAC/amp that avoids the multi-tone problem found in most CS43131-based chips".[1][2][3]

Interestingly, in the shared List of CS431xx-Based Devices spreadsheet linked in our post, this particular model is marked as “
known to produce "Cirrus Hump" distortion”. Strange.

 

[CedarX]

— "Update: Cirrus Logic's own engineers arrived on-site and confirmed the problem exists, but it’s not a hardware issue and can be fixed. A solution is expected next week."
— "China couldn’t fix it, so they handed it over to U.S. engineers, but then came Christmas and New Year... and now no one knows what’s going on."
— "— Months have passed, and still no news?" — "Unfixable, it’s a chip issue." — "2022 now, is it completely hopeless?" — "Looks like it’s hopeless."

This is… interesting
These dongles are cheap thingies, but these issues are chip-related, now I wonder if the DAPs, desktop DACs, using CS431xx chips have the exact same issues?
What about the SMSL DO200 Pro reviewed by Amir—12x CS43131? … twelve times???

 

[MCH]

This is… interesting
These dongles are cheap thingies, but these issues are chip-related, now I wonder if the DAPs, desktop DACs, using CS431xx chips have the exact same issues?
What about the SMSL DO200 Pro reviewed by Amir—12x CS43131? … twelve times???

Topping d30 pro was measured by amir and L7, and remained up the list in terms of low noise, and I don't remember anyone reporting any of these issues.

 

[AnalogSteph]

I won't be surprised if there are some examples, as the Class H operation that causes these issues is on by default. A desktop DAC can easily afford to switch to AB mode if the manufacturer is aware of the problem, it's more of an issue for portable devices.

Here is an analysis:

CS43198 and CS43131 DAC sound defects

reference-audio-analyzer.pro

Interestingly enough, the less high-strung but broadly similar AKM devices are completely clean.

 

[jkim]

I found a post on a Chinese forum: Link
It also mentions that the CS43131 commonly has multi-tone issues, with test charts included. Here's a translation of some key parts of the post:
— (the test was done at 0dB) "So, is it okay as long as you don’t turn it up to maximum volume?" — "In some cases yes, in others no. It’s quite troublesome."
— "Update: Cirrus Logic's own engineers arrived on-site and confirmed the problem exists, but it’s not a hardware issue and can be fixed. A solution is expected next week."
— "China couldn’t fix it, so they handed it over to U.S. engineers, but then came Christmas and New Year... and now no one knows what’s going on."
— "— Months have passed, and still no news?" — "Unfixable, it’s a chip issue." — "2022 now, is it completely hopeless?" — "Looks like it’s hopeless."

At the end of 2021, Luxury&Precision released the W2-131, mentioning that it “eliminates persistent BUG issues” and, "relying on Luxury&Precision’s strong FPGA expertise, the first one offers a portable DAC/amp that avoids the multi-tone problem found in most CS43131-based chips".[1][2][3]
View attachment 453136
View attachment 453135
Interestingly, in the shared List of CS431xx-Based Devices spreadsheet linked in our post, this particular model is marked as “
known to produce "Cirrus Hump" distortion”. Strange.

Thanks for the information!

The problem that was discussed on the Chinese forum and measured at L7audiolab is limited to a restricted situation in which a multitone test signal is given at its maximum (digitally) unclipped level. The problem is gone when the signal is 0.5 dB lower. This issue in itself is not a big thing since such a case will not occur in real audio content. However, the "Cirrus Hump" that the RAA article indicated and my review established means that essentially the same thing---most likely digital inter-sample overs---occurs even when the signal is in a range of substantially lower levels.

And the reason why I listed the Luxury & Precision W2-131 under "devices producing distortion" is because it was tested at RAA and found indicate the Cirrus hump behavior.

Would you please keep monitoring audio forums in China and update us if there's anything new related to this issue?

 

[jkim]

I won't be surprised if there are some examples, as the Class H operation that causes these issues is on by default. A desktop DAC can easily afford to switch to AB mode if the manufacturer is aware of the problem, it's more of an issue for portable devices.

Here is an analysis:

CS43198 and CS43131 DAC sound defects

reference-audio-analyzer.pro

Interestingly enough, the less high-strung but broadly similar AKM devices are completely clean.

Thanks for the comment.

Malfunction of the chip's Class H amplifier was my initial conjecture based on:

• The description at the RAA website AND
• The fact that there are some CS431xx-based devices that do not show this distortion behavior AND
• The Cirrus Logic datasheet saying that the Class H mode can be defeated by the "Class H Control" registers.

However, I ruled out this possibility after testing devices whose firmware supports switching between Class H/AB modes. The behavior persisted whatever mode the device was set to.

 

[CedarX]

However, I ruled out this possibility after testing devices whose firmware supports switching between Class H/AB modes. The behavior persisted whatever mode the device was set to.

If this issue is firmware dependent—not setting the CS431xx chip with the “right” register values—I think we should not rule out that the OEMs may have screwed the Class H/AB switching as well…

 

[jkim]

If this issue is firmware dependent—not setting the CS431xx chip with the “right” register values—I think we should not rule out that the OEMs may have screwed the Class H/AB switching as well…

Right. Especially when the mode switching does not affect power consumption which I also looked at.

 

[Roland68]

Thanks for the comment.

Malfunction of the chip's Class H amplifier was my initial conjecture based on:

• The description at the RAA website AND
• The fact that there are some CS431xx-based devices that do not show this distortion behavior AND
• The Cirrus Logic datasheet saying that the Class H mode can be defeated by the "Class H Control" registers.

However, I ruled out this possibility after testing devices whose firmware supports switching between Class H/AB modes. The behavior persisted whatever mode the device was set to.

The CS43131 evaluation board might be of interest to you for your analysis. Unfortunately, it's exceptionally expensive; you might think it's for a premium DAC chip.

Alternatively, the SMSL DS100 offers extremely good access to the CS43131 chip and external circuitry, if that helps you.
#9 Board DS100

 

[mc.god]

Thanks for the information!

The problem that was discussed on the Chinese forum and measured at L7audiolab is limited to a restricted situation in which a multitone test signal is given at its maximum (digitally) unclipped level. The problem is gone when the signal is even 0.5 dB lower. This issue in itself is not a big thing since such a case will not occur in real audio content. However, the "Cirrus Hump" that the RAA article indicated and my review established means that essentially the same thing---most likely digital inter-sample overs---occurs even when the signal is in a range of substantially lower levels.

And the reason why I listed the Luxury & Precision W2-131 under "devices producing distortion" is because it was tested at RAA and found indicate the Cirrus hump behavior.

Would you please keep monitoring audio forums in China and update us if there's anything new related to this issue?

L7audiolab is a great forum, source of valuable information, but unfortunately it's not updated for a long time now, the admin was also an ASR member (WolfX-700) but it is no more registered here either, I hope everything is ok for him.

 

[jkim]

The CS43131 evaluation board might be of interest to you for your analysis. Unfortunately, it's exceptionally expensive; you might think it's for a premium DAC chip.

Alternatively, the SMSL DS100 offers extremely good access to the CS43131 chip and external circuitry, if that helps you.
#9 Board DS100

Good suggestion. But I would put that much effort only if there's a guarantee that manufacturers would incorporate the investigation's outcome. Or if I wanted to develope a product. Otherwise, not interested..

 

[Audionaut]

Thank you, @jkim
This is the work of an audio enthusiast

 

[Roland68]

Good suggestion. But I would put that much effort only if there's a guarantee that manufacturers would incorporate the investigation's outcome. Or if I wanted to develope a product. Otherwise, not interested..

Just ask Cirrus if they'd be happy to provide you with a demo board. There's a lot of discussion and testing of Cirrus Logic on this site, both by Amir and dedicated users like you.
They should actually be interested in supporting it.

 

[danadam]

And the following did not produce distortion:

• JCally JM20

My JM 20 produces some distortion when playing the file in attachment.

The dongle identifies itself as:

262a:18c8    Shenzhen CBHT Technology Co., Ltd    CS4131 HIFI Audio

The file has a chord with 32.7, 40.9, 49.1 Hz components (CMaj in just intonation):


I played the file at volumes 0 dB, -10 dB and -20 dB, and captured the output with ADI-2 Pro at 96 kHz. I normalized the files to -1 dBFS and here are the spectrograms:
, ,

Here's one place in the waveform when the distortion happens:

For comparison, Samsung dongle at 0 dB and -10 dB:
,

 

[jkim]

My JM 20 produces some distortion when playing the file in attachment.

The dongle identifies itself as:

262a:18c8    Shenzhen CBHT Technology Co., Ltd    CS4131 HIFI Audio

View attachment 453341

The file has a chord with 32.7, 40.9, 49.1 Hz components (CMaj in just intonation):
View attachment 453342

I played the file at volumes 0 dB, -10 dB and -20 dB, and captured the output with ADI-2 Pro at 96 kHz. I normalized the files to -1 dBFS and here are the spectrograms:
View attachment 453343, View attachment 453344, View attachment 453345

Here's one place in the waveform when the distortion happens:
View attachment 453347

For comparison, Samsung dongle at 0 dB and -10 dB:
View attachment 453348, View attachment 453349

Thanks for performing these tests. Since you have the ADI-2 Pro, I believe it's easy to run one of the multitone sweep tests that I suggested in my review. Would you run it with your JM20?

Also, you may want to do essentially the same tests as you did, using the movie soundtrack FLAC file at the RAA website.

In the meantime, I will test the JM20 and JM20 Max that I have using your file.

I am beginning to suspect that there may have been some revision changes in the JM20 (and/or JM20 MAX) production...

 

[multiformous]

It's funny... whenever I try these test clips on my various dongles, the Samsung is always the cleanest sounding (to my ear). That goes for Apple dongle, CX-based dongles (e.g. JM6), Jcally JM12 (TinHiFi or Fiio JA11 firmware), and Meizu HiFi. And my JM20 Max doesn't play the above test clean perfectly cleanly. And there's no fade in / ramp up when starting playback with my Samsung dongle.

 

[danadam]

Since you have the ADI-2 Pro, I believe it's easy to run one of the multitone sweep tests that I suggested in my review. Would you run it with your JM20?

Looks clean:

I suspect it has something to do with changing the amplitude of the signal, the fade-in. In attachment there is a similar file, but this time there's 2 second steady state:


The distortion happens only at the beginning of each segment. Here's JM20 at 0 dB, -10 dB and -20 dB:
, ,

and Samsung dongle at 0 dB and -10 dB:
,

Also, you may want to do essentially the same tests as you did, using the movie soundtrack FLAC file at the RAA website.

Done already half a year ago :

JCALLY JM20 Headphone Dongle Review

CB5100 certainly yields interesting results if you want to build your own dongle or make a custom USB-C DSP cable for headphones. The tinkerer in me has awak.. oh, 40 bucks, nevermind.

www.audiosciencereview.com