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Author Topic: DSP output format, noise and bit perfect info needed  (Read 1792 times)

jacqlan111

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DSP output format, noise and bit perfect info needed
« on: June 28, 2012, 08:08:45 pm »

Hi
I'm getting closer to my ultimate setup which include 4 independent DACs on an activ multiamp setup.  Some will be astonished to see that configuration but I put great emphasis on the DAC issue for HiFi achievement.

My concern is about the MC's DSP output settings for smooth track changes and bit perfect results.
I was getting "jitter" (noise-cracks) at the track changes when keeping silences between them.  If I use an aggressive cross-fade, It's OK. I've been trying all possible settings to avoid crossfading without success. Here I am worry about using MC's tracks modification options for bit perfect results.  Do I have to be worry?Later I discovered that the noises disappeared if all sample rates are fixed to the same number (either 44-48-88-96...Khz) then the clock seams to be synchronised without jitter (if jitter there is).

I use a RME HDSP AES 32 sound card with 8 digital output channels to feed 2 Bel Canto DAC3 and 1 PS Audio dacIII . The missing one is temporally fixed by a Linn ativ card system.  My 3rd Bel Canto (DAC 3.5 VSB) will be here next Friday.  I use MC's PEQ to create activ crossovers and flat curve frequency response.  This is an other topic, but MC does not need any help from any VST software to do so.
The RME card is folowing every sample rate changes and feeds the dacs automatically with internal word clock adjustments.
What is the MC's upsampling implication on the bit perfect issue?
The clocks synchronisation is quite hazardous for my knowledge state.  Some advises will be greatly appreciated.
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Matt

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Re: DSP output format, noise and bit perfect info needed
« Reply #1 on: June 28, 2012, 08:19:15 pm »

Changing hardware sample rates requires reopening the output hardware.  It may make a little hardware-level noise, varying based on the hardware.

Media Center has an audiophile-grade resampler, which as you found, removes the need to reopen the hardware since the output sample rate doesn't change.

It's personal preference if you want to upsample or live with the hardware reopens when switching sample rates.
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Matt Ashland, JRiver Media Center

jacqlan111

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Re: DSP output format, noise and bit perfect info needed
« Reply #2 on: June 28, 2012, 09:11:51 pm »

Changing hardware sample rates requires reopening the output hardware.  It may make a little hardware-level noise, varying based on the hardware.

Media Center has an audiophile-grade resampler, which as you found, removes the need to reopen the hardware since the output sample rate doesn't change.

It's personal preference if you want to upsample or live with the hardware reopens when switching sample rates.
Thanks Matt, it make sense to me. 
I don't understand why the aggressive crossfade option over two different sample rate tracks is noise free, when a gaped change should give more time for hardware adjustment.
Whatever if MC has an audiophile-grade resampler then I prefer the upsampling solution that keeps other track options opened. 
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Matt

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Re: DSP output format, noise and bit perfect info needed
« Reply #3 on: June 28, 2012, 09:25:38 pm »

I don't understand why the aggressive crossfade option over two different sample rate tracks is noise free, when a gaped change should give more time for hardware adjustment.

I don't either, because the program can't (so won't) crossfade between different output sample rates.  It's possible having music right up the the gap (gapless or crossfade mode) masks any little hardware reopen noise.
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Matt Ashland, JRiver Media Center

Monteverdi

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Re: DSP output format, noise and bit perfect info needed
« Reply #4 on: July 03, 2012, 10:49:14 pm »

Hi Matt,

I am also experiencing crack noise in track changes when using Mytek to bitstream dsf files by DoP. It seems to be Mytek's hardware problem. Mytek has addressed the crack noise issue associated with changing tracks with different sampling rates by its latest firmware 1.6.0. They may need to deal with the noise brought in by DoP in the next upgrade. Grateful if you could draw their attention to this matter. Thanks.
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