RD30 Quad multibit d/a converter - Page 2 - diyAudio
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Musicaltech Musicaltech specialize in top digital audio concepts using powerful programmable logic devices. Original designs include total replacement of off-the-shelf chips - seen by the Musicaltech team as a limitation in performance and flexibility. Information about one of the the most sophisticated dacs avaialable for DIYers, either multibit or delta-sigma, are available in the dedicated forum.

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Old 23rd September 2012, 05:56 PM   #11
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Quote:
Originally Posted by eplpwr View Post
Some technical questions on the RD-30:

- Are you generating the clock in the FPGA (soft PLL), or are you using crystal(s)?
- Is the Bytemorph DF oversampling to 768kHz or 384 kHz?
- Are you doing oversampling in integer multiples, or ASRC? I see only 384/768 kHz mentioned - for n x 44.1 kHz input I'd like to see 352.8 or 705.6 kHz.
There are 2 main clocks involved, and both are external XO's. One is a high-frequency clock involved in sampling the input signal; second - and key of the reclocking system, combined with fpga internal ram buffer - is the Si570 DCO. This allows the creation of a PLL entirely in the digital domain (all-digital-pll). The performance of the ADPLL is essentially given by the performance of the Si570, which offers a remarkably low phase noise for a DCO.
The Bytemorph DF is actually a collection of 3 independent filters; they are indeed integers (no ASRC). There is a 8x filter for 44.1k and 48k; a 4x filter for 88.2 or 96k input; and a 2x filter for 176 and 192k. The filters are switched on-the-fly when sample rate changes. I will come back with detailed DF performance in the next posts.
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Last edited by Lupulroz; 23rd September 2012 at 06:08 PM.
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Old 24th September 2012, 01:49 PM   #12
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As promised, digital filter performance graphs in detail.
DF1 data:
Filter type : Parks McClellan linear phase equiripple
Taps : 1510
Input sample rate : 44.1k. 48k
Output sample rate : 352.8k, 384k
Stopband attenuation : -144 dB
Passband ripple : +/-0.00008 dB
Attached Images
File Type: jpg fs_overall.jpg (65.5 KB, 483 views)
File Type: jpg fs_step.jpg (49.5 KB, 475 views)
File Type: jpg fs_transition.jpg (71.1 KB, 469 views)
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Old 24th September 2012, 01:52 PM   #13
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DF2 data:
Filter type : Parks McClellan linear phase equiripple
Taps : 1510
Input sample rate : 88.2k , 96k
Output sample rate : 352.8k, 384k
Stopband attenuation : -145 dB
Passband ripple : +/-0.00007 dB
Attached Images
File Type: jpg 4x_overall.jpg (64.3 KB, 462 views)
File Type: jpg 4x_step.jpg (49.8 KB, 446 views)
File Type: jpg 4x_transition.jpg (63.8 KB, 79 views)
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Old 24th September 2012, 01:53 PM   #14
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DF3 performance:
Filter type : Parks McClellan linear phase equiripple
Taps : 1510
Input sample rate : 176.4k , 192k
Output sample rate : 352.8k, 384k
Stopband attenuation : -145 dB
Passband ripple : +/-0.00008 dB
Attached Images
File Type: jpg 2x_overall.jpg (67.8 KB, 68 views)
File Type: jpg 2x_step.jpg (49.2 KB, 57 views)
File Type: jpg 2x_transition.jpg (73.1 KB, 58 views)
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Old 27th September 2012, 08:19 PM   #15
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Hi Lupulroz
I'll be happy to receive it as soon as possible; I have a lot of HD Tracks at 24/192 kHz to listen. For the moment I can`t use my old DAC with CS4398 for 24/192kHz sample rates I play them from my Dune HD Max media player.

Maybe you will help me to take from this player via HDMI I2S signal for this DAC.

Look forward for more information and opinion about this DAC if someone already have it.
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Old 28th September 2012, 01:42 AM   #16
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Impressive set of features, well done!
I notice that the graphs in posts 13, 14 have switched places.
Any room left for different types of digital filters...minimum phase apodizing and the likes? Accesible via remote of course
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Old 28th September 2012, 10:48 AM   #17
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Originally Posted by gabrielbecheanu View Post
Hi Lupulroz
I'll be happy to receive it as soon as possible; I have a lot of HD Tracks at 24/192 kHz to listen. For the moment I can`t use my old DAC with CS4398 for 24/192kHz sample rates I play them from my Dune HD Max media player.

Maybe you will help me to take from this player via HDMI I2S signal for this DAC.

Look forward for more information and opinion about this DAC if someone already have it.
Hi Gabriel,
a HDMI receiver core is possible to implement in a future release of software. However this require lots of testing and there is also the problem of HDCP (digital content protection) which usually applies to HDMI.
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Old 28th September 2012, 11:13 AM   #18
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Originally Posted by sidiy View Post
Impressive set of features, well done!
I notice that the graphs in posts 13, 14 have switched places.
Any room left for different types of digital filters...minimum phase apodizing and the likes? Accesible via remote of course
Thank you Sidiy! You are right, I switched graphs, my bad
About different digital filters : that's the idea! There are enough hardware resources ,in short time a variety of filters will be available, via remote. We are working now on system to upgrade the firmware via usb input, to make the board easy upgradable in the field.
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Old 28th September 2012, 09:29 PM   #19
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Lupulroz hi, what sort of prices are we looking at for the DAC and the I/V

Cheers George
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Old 29th September 2012, 06:32 AM   #20
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Lupulroz hi, what sort of prices are we looking at for the DAC and the I/V

Cheers George
Hi George,
you have PM.
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