TAS6584-Q1: Continuation of the discussion regarding the Class H behavior in the TAS6584

Hi 

We have reproduced this problem on our EVM board, this should be a bug.

Let me check with our digital designers, will give you feedback later.

Additionally, most customers do some signal and tuning processing outside the amplifier and use the AMP only as a power amplifier. Do you have any concerns about fixing the analog gain and amp volume?

BR.

Wei Qiu.

Hi Wei Qiu, 

At a system level, there is quite a lot of processing in the "head unit" (i.e. the main control center for the EV) before it is sent to the amplifier module(s).  However, the volume control in any high-quality system should be placed at the output audio data path so that the full bit depth resolution can be used for all processing that comes in front of it. Additionally, it's location in the oversampled domain also provides less chance of zipper noise and rapid response to volume change requests to the user without audible artifacts.

So the volume control being located in the oversampled domain at the end of the data path offers the best solution for resolution (and makes for a quieter/smoother volume control.) With that said, if we use the volume control in the TAS6584 as it is today, the Class H does not work properly based upon the real signal and the real power supply rail voltage that is required in the system. So, the efficiency promised by the use of the Class H tracking supply architecture is unattainable- forcing a choice between optimum dynamic range and audio resolution OR efficient Class H operation.

Finally, the analog gain should be set to only what is necessary to produce the highest expected output amplitude of the source content being amplified. This is because any analog gain that is applied which higher than this requirement increases the noise floor of the system. Ideally- both the rails of the amplifier and the gain applied to the signal should be as low as possible to avoid wasting power and increasing idle channel noise.


Thanks for your response, and look forward to hearing back from you!

Hi.

Got it, thanks for your explanation.

In TAS6584, the digital gain(page 0) is in last stage after the Class-H. So the digital gain will not impact the Class-H output. See the process flow below:

Maybe you can use the volume control in audio process GUI page to change the volume.

Can you share your e-mail, we can send related register description to you for manual changing volume.

The process flow sequence is optimized In TAS6684. You can also try TAS6684, the share the same pin definition.

BR.

Wei Qiu.

Hi Wei Qiu, 

Yes- my email address is cody@upstreamaudio.com.

By the way, we did use the gain controls you have circled in red to attempt to see if they might have any impact on the Class-H control and it behaved in the same manner as the volume control. 

I have requested access to the TAS6684 data sheet (I am only able to see the product brief online.) Do you think that its controls would operated correctly?

Thanks!

Hi

Noted, I will have a try again, will give you feedback later.

BR.

Wei Qiu.

Thank you Wei Qiu- 

in the meantime can you please tell me if the 6684 device fixes this bug? Also can you please grant us access to the full data sheet for that device?

Hi.

According to the bench test, the volume of CH1&CH2 (CH3&CH4) needs to be changed together to make the output of Class-H track the input of CH1 or CH2. This seems to be another bug, is this solution acceptable to you?

• Test conditions: only CH1 play, the other 3 channels are set to Hi-Z.
• Default: -20dBFS input, 0dB volume (In audio process GUI page) -> 87.5% Class-H duty cycle
• Case1: -20dBFS input, 4dB volume CH1, the other 3 channels set to 0dB (In audio process GUI page) -> 50% Class-H duty cycle
• Case2: -20dBFS input, -110dB volume CH1, the other 3 channels set to 0dB (In audio process GUI page) -> 87.5% Class-H duty cycle 
• Case3: -20dBFS input, -110dB volume CH1&CH2, the other 2 channels set to 0dB (In audio process GUI page) -> 100% Class-H duty cycle 

There are no such bugs on TAS6684, and the Class-H function covers the impact of all types volumes.

UA&A_CodyDowling said:

Also can you please grant us access to the full data sheet for that device?

Have sent to your e-mail.

BR.

Wei Qiu.

Hi Wei Qui, 

I think that there may be some static offset in the left/right and front/rear speakers in the vehicle (think of the "balance" or "fader" function in an automotive head-unit.), but they could be adjusted together for an overall volume control. If that is the case, which does the volume control follow between Ch. 1 and Ch. 2? The channel with lesser attenuation?

I think perhaps that, if the TAS6684 has addressed all of these bugs, it may make be a better idea to use it instead of the TAS6584, correct? If so, where can we obtain the TAS6684 loose ICs, so that we can rework our EVMs to use the improved parts. Can you help us with a few samples of this device?

Hi.

UA&A_CodyDowling said:

I think that there may be some static offset in the left/right and front/rear speakers in the vehicle (think of the "balance" or "fader" function in an automotive head-unit.), but they could be adjusted together for an overall volume control. If that is the case, which does the volume control follow between Ch. 1 and Ch. 2? The channel with lesser attenuation?

Agreed, this will add a lot of restrictions to the customer's application.

Our digital designers give a new solution to fix this bug, you can have a try again by follow below steps:

1. Don't connect to the board, set the Class-H parameters.

2. Dump the Class-H setting.

3. Merge the Class-H control code in the RAM change part.

w c0 00 00
w c0 3e 30 # Enable RAM
w c0 7f 64
w c0 00 01
w c0 04 00 fe 00 40
w c0 08 00 fc 00 00
w c0 0c 00 fc 00 00
w c0 10 00 fc 00 00
w c0 14 00 fc 00 00
w c0 18 00 fc 00 00
w c0 1c 00 fc 00 00
w c0 20 00 fc 00 00
w c0 24 00 fc 50 00
w c0 28 00 fc 00 00
w c0 64 00 82 00 93
w c0 68 00 fc 00 00
w c0 6c 84 c9 01 bc
w c0 70 08 00 30 20
w c0 74 8f 00 ff ff
w c0 78 85 5b 00 df
w c0 7c 00 26 20 25
w c0 80 85 5a 00 81
w c0 84 84 c1 07 55
w c0 88 08 fc 20 11
w c0 8c 08 fc 29 d9
w c0 90 00 fe 20 2a
w c0 94 84 cb 00 df
w c0 98 00 fc 00 00
w c0 9c 02 c2 0f e0
w c0 a0 08 fc 20 11
w c0 a4 08 fc 2a b9
w c0 a8 84 cb 00 df
w c0 ac 84 c9 00 a5
w c0 b0 08 e0 01 20
w c0 b4 08 1e 00 21
w c0 b8 08 fc 28 99
w c0 bc e2 44 00 80
w c0 c0 84 d1 00 a6
w c0 c4 08 ff 0d 21
w c0 c8 08 1e 00 40
w c0 cc 08 fc 08 98
w c0 d0 02 0b 00 19
w c0 d4 08 ff 0d 01
w c0 d8 86 c1 00 0a
w c0 dc 08 e0 01 42
w c0 e0 08 00 10 00
w c0 e4 88 0e 17 59
w c0 e8 e2 44 20 82
w c0 ec 02 0b 00 19
w c0 f0 00 26 20 60
w c0 f4 88 0e 17 5a
w c0 f8 02 48 00 0d
w c0 fc 02 40 00 71
w c0 00 02
w c0 04 84 02 04 00
w c0 08 84 c9 07 5a
w c0 0c 84 c1 07 59
w c0 10 00 ff 20 63
w c0 14 00 fc 00 00
w c0 18 86 c9 00 82
w c0 1c 08 00 10 20
w c0 20 84 c3 00 04
w c0 24 00 fc 00 00
w c0 28 00 26 20 4f
w c0 2c 84 c2 00 4c
w c0 30 02 40 07 57
w c0 34 84 c1 02 20
w c0 38 00 ff 21 29
w c0 3c 00 fc 00 00
w c0 40 84 c3 02 20
w c0 44 86 c9 00 83
w c0 48 08 00 10 20
w c0 4c 00 fc 00 00
w c0 50 00 fc 00 00
w c0 54 00 26 20 5a
w c0 58 00 fc 00 00
w c0 5c 02 40 07 58
w c0 60 84 c1 02 21
w c0 64 00 ff 21 29
w c0 68 00 fc 00 00
w c0 6c 84 c3 02 21
w c0 70 85 62 00 81
w c0 74 8c ff 00 04
w c0 78 04 20 00 25
w c0 7c 84 00 04 00
w c0 80 86 cb 00 0b
w c0 84 84 cb 00 05
w c0 88 02 c0 00 00
w c0 8c 00 fc 50 00
w c0 90 8f 00 00 01
w c0 94 04 20 2b 82
w c0 98 08 00 0a 21
w c0 9c 04 20 51 48
w c0 a0 08 44 0a 11
w c0 a4 0c 20 10 6c
w c0 a8 08 44 66 71
w c0 ac 06 60 30 44
w c0 b0 84 ca 01 01
w c0 b4 00 fc 00 00
w c0 b8 00 66 20 70
w c0 bc 02 c0 00 01
w c0 c0 00 fe 20 75
w c0 c4 0c 20 4c 11
w c0 c8 84 c8 01 01
w c0 cc 84 ca 01 03
w c0 d0 02 c8 00 00
w c0 d4 84 ca 01 02
w c0 d8 84 ca 01 01
w c0 dc e0 20 c3 03
w c0 e0 84 c8 01 03
w c0 e4 80 07 00 82
w c0 e8 0d 00 10 30
w c0 ec 00 fc 00 00
w c0 f0 00 fc 00 00
w c0 f4 00 66 20 8e
w c0 f8 00 fc 00 00
w c0 fc 84 d0 01 04
w c0 00 03
w c0 04 06 60 50 5c
w c0 08 00 fc 00 00
w c0 0c 00 fc 00 00
w c0 10 00 46 20 85
w c0 14 00 fc 00 00
w c0 18 00 fe 20 91
w c0 1c 0c 20 8c 11
w c0 20 86 d0 21 04
w c0 24 00 fc 00 00
w c0 28 e0 00 00 82
w c0 2c 80 07 00 82
w c0 30 0d 00 10 30
w c0 34 08 44 26 32
w c0 38 84 d2 01 05
w c0 3c 00 fe 20 91
w c0 40 00 fc 00 00
w c0 44 02 d0 00 00
w c0 48 84 ca 01 05
w c0 4c 84 d2 01 04
w c0 50 e0 20 a3 05
w c0 54 84 82 01 06
w c0 58 e8 21 00 00
w c0 5c 88 07 00 82
w c0 60 86 c8 21 06
w c0 64 8f 30 00 0c
w c0 68 02 db 00 10
w c0 6c 0c 21 08 72
w c0 70 0c 20 f1 4c
w c0 74 02 c8 00 00
w c0 78 02 60 00 06
w c0 7c 8f 78 00 00
w c0 80 00 46 21 1b
w c0 84 86 ca 29 00
w c0 88 06 60 30 5c
w c0 8c 00 fc 00 00
w c0 90 00 fc 00 00
w c0 94 00 46 21 18
w c0 98 00 fc 00 00
w c0 9c 06 60 50 5c
w c0 a0 00 fc 00 00
w c0 a4 00 fc 00 00
w c0 a8 00 46 21 15
w c0 ac 00 fc 00 00
w c0 b0 06 60 70 5c
w c0 b4 00 fc 00 00
w c0 b8 00 fc 00 00
w c0 bc 00 46 21 12
w c0 c0 00 fc 00 00
w c0 c4 06 60 90 5c
w c0 c8 00 fc 00 00
w c0 cc 00 fc 00 00
w c0 d0 00 46 21 0f
w c0 d4 00 fc 00 00
w c0 d8 06 60 b0 5c
w c0 dc 00 fc 00 00
w c0 e0 00 fc 00 00
w c0 e4 00 46 21 0c
w c0 e8 00 fc 00 00
w c0 ec 06 60 d0 5c
w c0 f0 00 fc 00 00
w c0 f4 00 fc 00 00
w c0 f8 00 46 21 09
w c0 fc 00 fc 00 00
w c0 00 04
w c0 04 06 60 f0 5c
w c0 08 00 fc 00 00
w c0 0c 00 fc 00 00
w c0 10 00 46 21 06
w c0 14 00 fc 00 00
w c0 18 06 61 10 5c
w c0 1c 00 fc 00 00
w c0 20 00 fc 00 00
w c0 24 00 46 21 03
w c0 28 00 fc 00 00
w c0 2c 06 61 30 5c
w c0 30 00 fc 00 00
w c0 34 00 fc 00 00
w c0 38 00 46 21 00
w c0 3c 00 fc 00 00
w c0 40 06 61 50 5c
w c0 44 00 fc 00 00
w c0 48 00 fc 00 00
w c0 4c 00 46 20 fd
w c0 50 00 fc 00 00
w c0 54 06 61 70 5c
w c0 58 00 fc 00 00
w c0 5c 00 fc 00 00
w c0 60 00 46 20 fa
w c0 64 00 fc 00 00
w c0 68 06 61 90 5c
w c0 6c 00 fc 00 00
w c0 70 00 fc 00 00
w c0 74 00 46 20 f7
w c0 78 00 fc 00 00
w c0 7c 06 61 b0 5c
w c0 80 00 fc 00 00
w c0 84 00 fc 00 00
w c0 88 00 46 20 f4
w c0 8c 00 fc 00 00
w c0 90 06 61 d0 5c
w c0 94 00 fc 00 00
w c0 98 00 fc 00 00
w c0 9c 00 46 20 f1
w c0 a0 00 fc 00 00
w c0 a4 06 61 f0 54
w c0 a8 00 fc 00 00
w c0 ac 00 fc 00 00
w c0 b0 00 46 20 ee
w c0 b4 00 fc 00 00
w c0 b8 84 d0 41 10
w c0 bc 86 c2 61 00
w c0 c0 00 fe 21 1d
w c0 c4 84 d2 01 09
w c0 c8 84 c0 41 0f
w c0 cc 00 fe 21 1d
w c0 d0 84 c2 01 09
w c0 d4 84 c0 41 0e
w c0 d8 00 fe 21 1d
w c0 dc 84 c2 01 09
w c0 e0 84 c0 41 0d
w c0 e4 00 fe 21 1d
w c0 e8 84 c2 01 09
w c0 ec 84 c0 41 0c
w c0 f0 00 fe 21 1d
w c0 f4 84 c2 01 09
w c0 f8 84 c0 41 0b
w c0 fc 00 fe 21 1d
w c0 00 05
w c0 04 84 c2 01 09
w c0 08 84 c0 41 0a
w c0 0c 00 fe 21 1d
w c0 10 84 c2 01 09
w c0 14 84 c0 41 09
w c0 18 00 fe 21 1d
w c0 1c 84 c2 01 09
w c0 20 84 c0 41 08
w c0 24 00 fe 21 1d
w c0 28 84 c2 01 09
w c0 2c 84 c0 41 07
w c0 30 00 fe 21 1d
w c0 34 84 c2 01 09
w c0 38 84 c0 41 06
w c0 3c 00 fe 21 1d
w c0 40 84 c2 01 09
w c0 44 84 c0 41 05
w c0 48 00 fe 21 1d
w c0 4c 84 c2 01 09
w c0 50 84 c0 41 04
w c0 54 00 fe 21 1d
w c0 58 84 c2 01 09
w c0 5c 84 c0 41 03
w c0 60 00 fe 21 1d
w c0 64 84 c2 01 09
w c0 68 84 c0 41 02
w c0 6c 00 fe 21 1d
w c0 70 84 c2 01 09
w c0 74 84 c0 41 01
w c0 78 00 fe 21 1d
w c0 7c 84 c2 01 09
w c0 80 84 c0 01 0c
w c0 84 84 c2 01 09
w c0 88 06 e0 11 0c
w c0 8c 00 fc 00 00
w c0 90 00 fc 00 00
w c0 94 00 22 21 24
w c0 98 00 fc 00 00
w c0 9c 00 fe 21 26
w c0 a0 84 cb 07 56
w c0 a4 02 c2 7e 00
w c0 a8 84 c3 07 56
w c0 ac 84 c0 01 09
w c0 b0 00 fc 50 00
w c0 b4 00 fc 00 00
w c0 b8 84 48 01 00
w c0 bc 86 a1 01 9c
w c0 c0 02 73 00 19
w c0 c4 00 fc 00 00
w c0 c8 84 c2 30 01
w c0 cc e0 60 00 00
w c0 d0 84 4a 01 00
w c0 d4 80 07 00 80
w c0 d8 00 fc 50 00
w c0 dc 00 fc 00 00
w c0 00 00
w c0 7f 78
w c0 00 09
w c0 a4 00 00 00 00
w c0 a8 00 00 00 00
w c0 00 1e
w c0 cc 00 1f c0 00
w c0 d4 00 00 05 00
w c0 d8 00 00 06 00
w c0 dc 00 00 00 00
w c0 e0 00 00 00 00
w c0 00 00
w c0 7f 8c
w c0 00 01
w c0 2c 00 00 00 01 #enable classh
w c0 30 ff ff ff ff
w c0 00 02
w c0 44 00 00 00 01 #disable AUX
w c0 00 04
w c0 98 00 00 00 01 #add on ram
w c0 00 07
w c0 8c 7f ff ff ff

### Class-H Control

#Add here

###

#Ram combine, must be written under sleep mode. Can’t be changed.
w c0 00 00
w c0 7f 00
w c0 3a 04 #disable original class-h & enable ram
w c0 00 00
w c0 7F 00
w c0 00 00

4. Restart the GUI and set the status to Sleep mode, then execute the RAM change code.

5. Set the status to play, then you can change the volume (in audio process GUI page) to control the Class-H output PWM 

This solution fixes the TDM format and individual channel volume control issues in Class-H applications.

We will later merge these changes into the PPC3 GUI in next version.

Also, I can send the detailed slides to your e-mail.

UA&A_CodyDowling said:

I think perhaps that, if the TAS6684 has addressed all of these bugs, it may make be a better idea to use it instead of the TAS6584, correct? If so, where can we obtain the TAS6684 loose ICs, so that we can rework our EVMs to use the improved parts. Can you help us with a few samples of this device?

Yes, compared with TAS658, TAS6684 is easier for customers to use because of fixing some bugs.

You can also apply for the samples to do the test by connecting with local FAE.

Tips: Some registers of TAS6684 have been modified, and the software needs to be redone.

BR.

Wei Qiu.

Hi Wei Qiu, 

This is *great* information, thank you so much for your help!

We are digging into the details now and will follow-up as soon as possible.