Any one with experience of MQA CD

I don't think that is how it works. On high res they:
Take a band limited filtered 96khz sampling rate file;
High/low pass it to separate the high frequencies greater than 22khz into one container (file) and the frequencies lower than 22khz into another container;
Dither the lower frequencies down to 17-ish bits with the dither noise spread around;
Use an algorithm to encode and compress higher frequencies, greater than 22khz;
Finally store that data encoded higher frequency information in the least significant bits to recreate a "24 bit" container holding 17-ish bits of data.

It has been a while since I've looked at the patent documents. I may be confusing when the dither happens. It may happen before the high/low pass filter.

For the CD, shrink it down even more.
Dither to 14 or 15 bits;
Store a bit or two of encoded high frequency information in the least significant bit within a 16 bit container.

I wouldn't be surprised if the 15 bit "CD" versions didn't really have any extra high frequency information encoded because MQA requires one bit to operate itself, light the blue light, display the encoding rate of the original file that has nothing to do with what you are hearing, encode encryption that to date is not used as DRM, and tell the player which filter to use.

 

I purchased the 4 different samplers from CDjapan. Only as a curiosity, really. I believe there is a utility that you can run against an MQA encoded track to see exactly what kind of metadata is stored in them and the technical specifications of the audio itself, but I haven’t run it against any of them.

 

That's the way PCM digital audio works. For clean, distortion-free sound, you need an anti-aliasing lowpass filter on both the input of the ADC used to make the digital recording and on the output of the DAC that converts it back to analog for playback.

In the '80s and '90s there were some cheap CD players which lacked any kind of anti-aliasing filter on the output of the DAC, with the theory being that with the cheap amplifier and speakers you'd likely have them connected to, you'd probably never notice the difference. (Just like all the FM tuners that don't filter out the 19 kHz MPX pilot tone!) But if you connected one to a good amplifier and played it at a high enough volume, the aliasing products above 22 kHz could damage your tweeters.

 

Here is the result of mqascan of the tracks ripped from Various Artists - Jazz Hi-Res CD Sampler [MQA-CD] (UCCU-40126):

Code:

===== [01] Autumn Leaves.flac =====
0000c210: MQA signature at bit 8
0000c210: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x00021a8b
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x00010eb
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x06473a63
          checksum                   4: 0xd
===== [02] Say It (Over And Over Again).flac =====
0000d3f2: MQA signature at bit 8
0000d3f2: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x01bf1a75
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x00df900
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x080efa63
          checksum                   4: 0x9
===== [03] The Girl From Ipanema.flac =====
0000d9ce: MQA signature at bit 8
0000d9ce: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x026e17ad
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x01370ea
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x043f3a63
          checksum                   4: 0xc
===== [04] Moanin'.flac =====
0000288f: MQA signature at bit 8
0000288f: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x03481d5a
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x01a4100
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x080ffa63
          checksum                   4: 0xf
===== [05] Days Of Wine & Roses.flac =====
0000483d: MQA signature at bit 8
0000483d: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x04cc1d3c
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x0266100
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x080f2a63
          checksum                   4: 0xc
===== [06] Old Devil Moon.flac =====
0000c731: MQA signature at bit 8
0000c731: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x053c1dc0
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x029e100
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x080e7a63
          checksum                   4: 0xb
===== [07] Cleopatra's Dream.flac =====
0000cd67: MQA signature at bit 8
0000cd67: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x05b315a2
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x02d9900
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x080f3263
          checksum                   4: 0xd
===== [08] The Cat.flac =====
0000ac60: MQA signature at bit 8
0000ac60: [5] datasync
          magic                     36: 0x11319207d
          stream_pos_flag            1: 1
          pad                        1: 1
          orig_rate                  5: 0x03 [352.8 kHz]
          src_rate                   5: 0x00 [44.1 kHz]
          render_filter              5: 8
          unknown_1                  5: 0x04
          unknown_2                  1: 0
          pad                        2: 0
          mqa_level                  8: 0x90
          items                      7: 2
          size                       8: 0xc2
          size                       8: 0x20
          type                       8: 0x00
          type                       8: 0x01
          stream_position           32: 0x0666111f
          [type 0]
          unknown_3                  2: 2
          unknown_4                  4: 0
          unknown_5                  7: 15
          unknown_6                  7: 127
          start_offset              27: 0x03330ed
          pad                        1: 0
          data                     146: [skipped]
          [type 1]
          unknown_7                 32: 0x030eaa63
          checksum                   4: 0x8

 

Hah. Thank you for this. I love how there’s a parameter literally called “magic”

 

But my question is why filter frequencies over 22.05Khz if they have been filtered by the anti-aliasing filter on the A/D stage? Maybe allthe switching done at 44.1 Khz inside the D/A is what creates those ultrasonic frquencies that need to be filtered?

 

The most simple answer is that the "stairsteps" (that some might inaccurately show you in a picture of digital signals) need to be removed, to reconstruct the original signal that was encoded. Otherwise, the digital output contain an "alias", a mirror image of the signal at intervals above 1/2 the sampling rate that causes distortion.

TNT-Convertus: a minimalist DAC

 

This video does a good job of explaining it:

 

After watching "Bohemian Rhapsody" i got the urge to try the Queen: Greatests Hits (coming out soon) but i just wonder if the regular CD portion of the MQA disc sounds at least as good as a SHM version of it.

 

Note that there is only 1 version of any album on MQA-CD: the MQA-encoded one.