Computer Audio Asylum

RE: cMP� update

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cics

A

In Reply to: RE: cMP� update posted by theob on November 16, 2014 at 09:19:50

It's a wrap from my side.

I haven't changed anything since 2.0b39 as the results remain tremendous (especially when upsampling to 192k).

I recall you prefer native rate at 44.1k or as per source. That means the DAC is doing upsampling and for me it's a bad choice. Even the latest DACs can't deliver the accuracy of computers using Secret Rabbit Code (as the sheer horsepower needed is lacking). Interpolation and phase errors will have audible impacts.

Follow Ups:

RE: cMP� update - GStew 20:09:37 11/18/14 (1)
cics,

Great to hear from you again. I really hope you're doing well.

There's been some interesting developments on the digital filtering side. First, there's the product Bibo01 mentioned above. I've seen some good comments on it in the Computer Audiophile site.

Then there has been a lot posted in various places by John Swenson, who used to post a lot of very informative and technical information on this board.

He had done research on digital filters and found that on-chip digital filters are implemented in ways that produce great specs, but don't sound good. If one uses a DAC chip where the on-chip filter can bypassed (available on chips such as the PCM5142, AK4399 and later AKM chips, and any NOS chip that was designed to be used with a separate digital filter chip such as the TDA1541, TDA1543, and PCM1704, but NOT the ESS chips) and provides a custom filter tuned to sound good (but not produce as good of specs as the ones used in the chips), the sound can be MUCH better.

Here are several threads and posts where he talks about that:

http://forums.slimdevices.com/showthread.php?99088-Upsampling-Impressions&p=751349&highlight

http://bottlehead.com/smf/index.php?topic=6898.msg67124#msg67124

http://bottlehead.com/smf/index.php?topic=4086.msg50467#msg50467

http://bottlehead.com/smf/index.php?topic=4086.msg46950#msg46950

http://bottlehead.com/smf/index.php?topic=4086.msg54324#msg54324

http://bottlehead.com/smf/index.php?topic=4086.msg64940#msg64940

http://www.computeraudiophile.com/f8-general-forum/are-we-just-kidding-ourselves-21163-post337374/#post337374

Then of course, the ESS chips are the current hottest flavor. This can also have benefits for them (which will make this of interest to people using either the Twisted Pear and/or Acko DACs). Even though their final digital filtering can't be bypassed, the initial OSF filtering can (using settings via I2C... and according to poster Barrows, doing that can have significant benefits IF one does that upsampling upstream and is running the DAC in sync mode... See comments on these threads:

http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/buffalo-iiise-new-digital-analogue-converter-build-chassis-17980/

http://www.diyaudio.com/forums/vendors-bazaar/259996-sonore-async-usb-i2s-interface-onboard-osf.html

http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/ethernet-universal-serial-bus-industry-standard-cables-connectors-and-communications-protocols-between-computers-and-electronic-devices-optical-or-coax-my-digital-analogue-converter-17582/#post334712

I, for one, would love to see all filter options of SRC and SOX exposed to allow more experimenting with filters. For example, allowing entry of the SOX command line parameters in the cPlay.ini file and passing that to SOX could be a possibly easy way to implement this.

I know we had talked about this back in 2008 or so. At the time, I didn't have the technical prowess to implement that in my system, but now can do.

We also now have some evidence of the power of using alternative filtering techniques. I, for one, would love to play with them more on my cMP/cPlay machine.

If we could get some updates to enable this (and maybe even upsampling to 352/384, which is needed for alternative filter work with the PCM5142), that could open a whole new world for cMP/cPlay setups.

Then we'd only need a good PCI/PCI-E alternative to the 192-max rate Juli@!

Again, great to hear from you!

Greg in Mississippi
Everything matters!
- RE: cMP� update - cics 04:20:34 11/19/14 (0)
  Thanks Greg.
  
  Yes I'm very aware of on-chip filters which produce nice specs at the expense of interpolation accuracy. Correct interpolation will create both pre- & post-ringing yet DAC chip specs show very little. An obvious flaw.
  
  I'm not familiar with the player Bibo01 mentioned but seems interesting. To beat SRC at 145db SNR will be a major achievement. Its all in the math. Bibo01 - please supply a link to the filter being used.
  
  For me I found upgrading the amp from 33H's to 1.2KW yielded significant gains. SNR improved from below 100db to a very good 124db SNR. Everything is portrayed with unbelievable detail and liquidity. I haven't found any need to upgrade cPlay any further. With source code on the site, anyone with good C/C++ skills can make the changes you desire.
  
  Intel is doing 14nm processors which would bring more gains... and lends itself to an ultimate player streaming 32/192k I2S to a Buffalo/ESS setup. Tempting! Nice to see their recommendation for NOT using an external clock. Instead keep that oscillator very near the chip.
  
  As to 354k/392k upsampling, this can be achieved at the expense of more processing power. Years ago I did sums to determine theoretical max upsampling needed based on sound travelling through air at room temp. The max upsampling number was approx 350k. Air consists of molecules a few Angstroms apart and it's nature's way of delivering sampled music:) You see there's no such thing as pure analogue (in our quest for SQ, its a string of molecules). This means any further upsampling is a complete waste. I often find talk of things going into MHz which has no bearing on SQ. Yes it may sound different but not necessarily better.
RE: cMP� update - theob 02:33:24 11/17/14 (0)
It's interesting on why I switched. It was because I wanted dsd capability. I never tired of cplay sonic excellence. I also found kernel streaming was better than asio (in jRiver and Foobar). Upsampling to me is a mixed bag, sometimes better sometimes not. This is all by subjective judgment. Anyway it is really nice to see you post again. I hope you engage in the continuous improvement process. It would be great if you do.
RE: cMP� update - olegpolitaev@gmail.com 00:06:10 11/17/14 (0)
CMP is great project! cPlay_2_0b36 best version. Cics, you can eliminate the need for libraries ole32,olepro....and other?
Jack Wong's micro shell32.dll is great!!!
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