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Old 2nd May 2012, 08:09 PM   #451
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Default questions

Hello,

I'm thinking of a DAC solution for long time. First idea was AD1862 (for same good sound of a former CD player) + AD1893 (for up to 192ks/s 24 bits support) + 25.576 MHz NDK xtal oscillator (NZ2520SD for low jitter). looking forward they can't be plugged together !

It sound FIFO can be used with AD1862, instead of AD1893 without ability to change sampling rate. but can't sampling rate be adjust by player ?

reading thread some questions raised :
-Are AD1862 and PCM1704 sounds very close ? noise & linearity spec. are similar. 2R2, BiCMOS technology for both. Main difference is analog supply voltage +/-12V for AD vs +/-5V. it may easy analog part. Also Sabre specifications are impressive but it's sigma-delta with very low voltage. did you have change to hear them? what do you think?

-Also why is there oversampling in most CD player ? an extra chip is needed for. we don't have superman hearing. is it only to improve jitter (with shaper clock edge) ? or is it so that a deemphasis filter is needed for CD player. btw add analog filter pre correction like in philips SAA720 sounds good ... is it so that some FPGA have built in programmable digital filter (:-)?

thanks guys for this very informative thread (:-) !
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Old 3rd May 2012, 12:52 AM   #452
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Quote:
Originally Posted by anaeroben View Post
-Also why is there oversampling in most CD player ? an extra chip is needed for. we don't have superman hearing. is it only to improve jitter (with shaper clock edge) ? or is it so that a deemphasis filter is needed for CD player. btw add analog filter pre correction like in philips SAA720 sounds good ... is it so that some FPGA have built in programmable digital filter (:-)? thanks guys for this very informative thread (:-) !
Oversampling moves the ultrasonic image replications higher in frequency by a factor equal to the oversampling ratio. The greatly eases the demands on the analog output filter. It does not increase resolution, nor extend the high frequency response, nor reduce jitter, nor does it have anything to do with de-emphasis.

Programmable digital filters, whether in FPGA, DSP, or application specific chips enable CD-player/DAC designers to implement proprietary filter responses rather than be limited to the few choices available in most DAC chips.
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Last edited by Ken Newton; 3rd May 2012 at 12:56 AM.
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Old 3rd May 2012, 01:29 PM   #453
PET-240 is offline PET-240  Australia
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Default Just Looking

Hey All,

Looking to integrate this on a TDA1541 and a Buff III.

waiting to hear integration as both are to be completed as yet. Have waveIO on way too, so hopefully qusp, we can get together and hear the differences between Titan and wave.

Looking forward to your results!

Cheers,

Drew.
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Old 4th May 2012, 10:06 AM   #454
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Hi all,

Thank you for up sampling explanations. but ??? isn't it so that ultrasonic images can't be hear ? are they harmful ones in amplifiers due to linearity issues (intermodulations makes ultrasonic alias to signal) ?
Also i wonder about 24 to 20 bit conversion, removing LSB sound OK. But is there some signal processing trick, because dither is used in some chips ?

have a nice week end !!
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Old 4th May 2012, 11:30 AM   #455
regal is offline regal  United States
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Quote:
Originally Posted by anaeroben View Post
Hello,

reading thread some questions raised :
-Are AD1862 and PCM1704 sounds very close ? noise & linearity spec. are similar. 2R2, BiCMOS technology for both. Main difference is analog supply voltage +/-12V for AD vs +/-5V. it may easy analog part. !
IMHO and many others the AD1862 and the PMC1704 represent the pinnacle of digital audio technology, all audio models following have used a very different cheaper to manufacture technology which just plain sound different.

I think this latest revision of the fifo allows one to "plug directly into a left and right PCM1704 or AD1862, which in the past has involved sound degrading glue logic or a hard coded oversampling chip prior to the dac chip. The silicon in wire oversampling chips never made it to the level needed to go beyond rbcd (DF1704/6 have a terrible impulse response and frankly sound wrong), then the proprietary blackfin/sharc dsp that followed aren't DIY pieces.

So this will be a major shift in ability to use these BB and AD crowning achievement DAC chips, some creative computer oversampling (we do need to find a modern apodizing 8x oversampling VST for foobar)
and/or analog filter will be needed but this is all DIY attainable.

This latest fifo has the potential to compete with the worlds best D/AC's without spending 5 figures.
If you are interested read up on the Phasure, similiar concept except not DIY and very expensive.

Then also for the NOS folks this also opens up possibilities to use good chips like the PCM56k or AD1865K without the dreaded channel mismatch. These chips are unique over the standard TDA1541 in that they allow very elagent analog stages due to the ability to deal with high voltage compliance on the output.

Last most important it allows the DAC to have a true masterclock without crazy jitter inducing isolators or being tied to a SDtransport.

All in all my opinion is to get on the bus before this thing goes commercial integrated into a $5k D/AC.
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Old 4th May 2012, 04:19 PM   #456
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Quote:
Originally Posted by anaeroben View Post
Hi all,

Thank you for up sampling explanations. but ??? isn't it so that ultrasonic images can't be hear ? are they harmful ones in amplifiers due to linearity issues (intermodulations makes ultrasonic alias to signal) ?
Also i wonder about 24 to 20 bit conversion, removing LSB sound OK. But is there some signal processing trick, because dither is used in some chips ?

have a nice week end !!
Correct, the ultrasonic images cannot be heard directly. Whether or not they can be heard indirectly as a product of amplifier intermodulation distortion depends on your amplifier. All discrete amplitude level D/A converter chips produce ultrasonic images of the desired signal, whether they use oversampling or not. Oversampling simply enables a more effective suppression of ultrasonic noise/image energy by moving such images greatly higher in frequency.

Aliasing is only a concern if the digital filtering is inadequately sharp, which means that non-oversampling (no digital filter) DACs are far more susceptable to aliasing then are oversampling DACs.

Regarding bit-length reduction, spectrally shaped dither is commonly utilized to randomize distortion resulting from simple truncation (chopping off) of the LSBs. The DAC noise floor is increased in exchange for a reduced THD, an engineering trade-off which is particulalry apparent as the signal level falls.

I hope that I correctly understood and addressed your questions.
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Last edited by Ken Newton; 4th May 2012 at 04:28 PM.
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Old 8th May 2012, 03:56 AM   #457
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Default Finish upgrading FIFO board from V3.33 to V3.80

Upgrading job finished finally. Two weekends were killedJ. New version will include the following features:

1. Optional 32bit left-justified output format support
Reason of this feature: To integrate FIFO with some DSPs or DACs which do not accept I2S input, for example, PMD100, SM5842, SM5843…

2. Optional 16-32bit left-justified input format support
Optional 16bit right-justified input format support
Optional 24bit right-justified input format support
Reason of these features: To interface FIFO with some digital audio frontend which do not output I2S. For example, interfacing with some DIRs from Japanese manufacturers, tapping signals form CDROM…

3. New optional default 512*Fs MCLK support
Only Single XO clock board user will benefit from this feature. Dual XO clock board will take over all the default *Fs settings.
Reason of this feature: Single XO clock board users will have more options to select frequencies. For examples, use 22.5792MHz oscillator for 44.1KHz Fs or 24.5760Mhz for 48Khz, and so on. And same XO will work for 88.2Khz or 96Khz either, just a jumper! .

All new features are jumper selectable. Only FPGA/CPLD firmware is involved in this upgrading. Hardware keeps no change. If you are happy with I2S and don’t need these new features, then you don’t need making any upgrading. Performance didn’t change any.

Testing FPGA board was upgraded at same time to perform loop test.

I attached the waveform of new support formats just for reference.

Have a good night.
Attached Images
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Old 8th May 2012, 04:02 AM   #458
PET-240 is offline PET-240  Australia
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Default Amazing!

Ian,

I'm still getting my head around the first setup, let us know how you go with B III!
How far off is the GB quantity?
Thanks again!
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Old 8th May 2012, 04:16 AM   #459
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Quote:
Originally Posted by PET-240 View Post
Ian,

I'm still getting my head around the first setup, let us know how you go with B III!
How far off is the GB quantity?
Thanks again!
Hi PET-240

Wktk_smile hooked up FIFO with BII :
http://www.diyaudio.com/forums/digital-line-level/192465-asynchronous-i2s-fifo-project-ultimate-weapon-fight-jitter-42.html#post2993060

And, Qusp is working with another ESS9018 DAC
http://www.diyaudio.com/forums/digital-line-level/192465-asynchronous-i2s-fifo-project-ultimate-weapon-fight-jitter-44.html#post2998719

I’ll start BIII hookup next week. Will post the result.

The upgrading was promised for the GB II. So it should be very soon.
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Last edited by iancanada; 8th May 2012 at 04:20 AM.
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Old 8th May 2012, 08:33 AM   #460
vzs is offline vzs  Europe
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Hi Ian,

Nice work and thank you for sacrificing two weekends (at least) for hobby - with a full time job and family I know this is hard

I plan to try different digital filters before my AD1865 and will start with DF1704 as that is the easiest to interface with my current setup and FIFO as it supports LVTTL and has I2S input. I would also like to try SM5842(7) and/or PMD100 so I will need the Left Justified output support as well.

Others might have asked: can existing FIFOs be upgraded with your new firmware? You are probably using JTAG for this, for ~15$ there are plenty of AVR JTAG programmers on ebay.

Thank you,
Zsolt
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