Drive NOS AD1865/62,PCM1704/02/63,TDA1541 from FIFO: Universal I2S-PCM driver board - Page 45 - diyAudio
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Old 9th June 2013, 03:15 PM   #441
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Quote:
Originally Posted by new2hifi View Post
Ok! Now I am confused. TI PCM1704 can do 24bit/768kHz as per datasheet (page 7) with 32-bit frame length, thus meeting the maximum BCLK rate of 24.576MHz (32 x 768).

I am confused that why this converter uses 64-bit frame length?
When I say 64Fs, I mean "64Fs I2S input". The PCM daughter board accepts I2S input from 32Fs to 64Fs which will cover most of I2S sources.

When you talk about the 32-bit frame length from the 1704 datasheet, it means the 32bit frame length of the PCM signal feeding to 1704. It's totally a different story than the I2S input. The PCM daughter board will generate exactly 24bit PCM signal in stopping clock mode or 32 bit in continue clock mode for 1704.

Actually, with the possible half-speed mode, the board can generate 786KHz PCM signal with CLK frequency running at 24.576MHz from a 786KHz I2S input.

Ian
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Old 9th June 2013, 07:34 PM   #442
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Originally Posted by qusp View Post
perhaps its because there is not a single interface that can output 768kHz i2s/PCM afaik (see edit, there are a couple), there is no native 768khz PCM content available and even if there was it would be upsampled and somewhat pointless? the inherent LPF in the vast majority of amplifiers and line stages, even if its just gate capacitance of devices used, renders this content as noise only. not really a possible feature that should impose changes on hardware or software IMO.

just because you can do something, does not mean that you should. THD, noise and other performance will in most cases be significantly worse at 768khz (somePWM and class D noise and harmonics are the same independent of frequency), most DACS perform at their best at 96-192khz. then of course there is the lack of a 768khz ADC. the 768khz ability is driven by marketing, there are probably companies selling $500-1000 firmware upgrades to supply such a possibility.

actually I lie, the Zodiac platinum will do it over USB, there is probably a couple of other proprietary very expensive products with custom drivers that can, just so they are able to justify an 'upgrade' to previous versions and have more exclusive buzzwords. the rest of my post stands.

Thanks qusp! for the information. Your points about performance and lack of content for 768khz are well taken. I don't have any music higher than 44.1kHz but I do intend to buy some 192kHz files when I'll have such DIY DAC. I was trying to understand the working of this converter, how it will work with PCM1704 and why 64 bit frame was used.
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Old 9th June 2013, 07:41 PM   #443
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Quote:
Originally Posted by iancanada View Post
When I say 64Fs, I mean "64Fs I2S input". The PCM daughter board accepts I2S input from 32Fs to 64Fs which will cover most of I2S sources.

When you talk about the 32-bit frame length from the 1704 datasheet, it means the 32bit frame length of the PCM signal feeding to 1704. It's totally a different story than the I2S input. The PCM daughter board will generate exactly 24bit PCM signal in stopping clock mode or 32 bit in continue clock mode for 1704.

Actually, with the possible half-speed mode, the board can generate 786KHz PCM signal with CLK frequency running at 24.576MHz from a 786KHz I2S input.

Ian
Thanks Ian! I am novice thus I really wanted to understand the frame length difference and the wisdom behind the 64-bit frame length. I used PCM1704 example as to my knowledge this is the highest spec true 24bit DAC.

Thanks for pointing out the difference between input and output frame length.
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Old 9th June 2013, 08:31 PM   #444
qusp is offline qusp  Australia
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Quote:
Originally Posted by new2hifi View Post
Thanks qusp! for the information. Your points about performance and lack of content for 768khz are well taken. I don't have any music higher than 44.1kHz but I do intend to buy some 192kHz files when I'll have such DIY DAC. I was trying to understand the working of this converter, how it will work with PCM1704 and why 64 bit frame was used.
no problem mate, all good, the push for higher speed starts to get a bit silly when its only upsampled from lower rates IMO, especially when many dacs will do this internally anyway. I havent been following this board closely so not sure of the full capabilities, but I do know that its fairly academic.

notice Ians proviso

Quote:
Actually, with the possible half-speed mode, the board can generate 786KHz PCM signal with CLK frequency running at 24.576MHz from a 786KHz I2S input.
there are a few interfaces that will allow output at this rate, perhaps after upsampling in puremusic or amarra, but I dont even think there are any proprietary ADCs that will sample this high, there is only a single ADC chip that i'm aware of that can even do 384khz PCM, the ES9102. this is not to be confused with 1bit DSD, which is at a much higher rate.

one thing the higher rates will do is take the pressure off the analogue stage low pass filter by pushing the images higher up in frequency. Air itself will roll off HF audio frequencies well before 100khz afaik, even if your speakers can produce it. so 384kHz is more than enough IMO

Last edited by qusp; 9th June 2013 at 08:35 PM.
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Old 20th June 2013, 04:17 AM   #445
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Default Half-speed mode passed simulation

I revised the verilog code to implement the half-speed mode. Now, it passed the simulation.

Simulation was running at 384KHz with 49.xxx MHz MCLK. You can see at full-speed mode (default), the CLK frequency was 24.xxxMHz, exactly as same as SCK. With half-speed mode jumper JHALFn jumped to low level, it goes half-speed mode. All data was exactly as same as full-speed mode, but CLK frequency was just as half as SCK, now becomes 12.xxx MHz.

Next step, Iíll do some real test with logic analyzer on the fixture. This project will be ready for launch if everything is OK.

Ian
Attached Images
File Type: png FullSpeedMode384KHz.png (33.9 KB, 363 views)
File Type: png HalfSpeedMode384KHz.png (35.1 KB, 358 views)
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Old 20th June 2013, 09:08 AM   #446
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Looks promising Ian!

Taking into account that most NOS DACs are home-brewed, many of them without (a proper) ground plane, running at lower speeds can only do good.

Zsolt
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Old 20th June 2013, 03:28 PM   #447
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Feeding the PCM1704 with +-5V 300mA my driver NOS only reads maximum 96KHz
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Old 2nd July 2013, 12:18 AM   #448
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Default I2S to PCM board half-speed mode passed real world test

New upgraded firmware has been programmed, the daughter board passed the real world test without any suspecting.

Four waveforms were captured from screen of logic analyzer, they are:
192KHz 18bit half-speed mode
192KHz 18bit full-speed mode
384KHz 18bit half-speed mode
384KHz 18bit full-speed mode
From those waveform, it’s very clear the difference between half and full speed mode.

Bit perfect confirmed for both half-speed and full-speed mode up to 384KHz by loop test fixture as well. The MCLK frequency can go up to 98.xxx MHz from Si570 clock board without any problem. It also works for other MCLK frequency options, such as 49.xxx/45.xxx, 24.xxx/22.xxx and 12.xxx/11.xxx.

Real listening test did on PCM1704 and TDA1541A DAC. Half-speed mode sounds as good as full-speed mode. Both of them have no problem running at 192KHz. I didn't do the 384KHz listening test. I don't have a 384KHz music source.

Half-speed mode makes it possible running your NOS DAC at higher Fs. But, theoretically, full-speed mode comes with lower noise. The reason is obvious. There is more silence time on signals than the half-speed mode.

I got the final PCB, I’ll post some pictures soon.

Ian
Attached Images
File Type: png HalfSpeed192KHz18Bit.png (20.7 KB, 248 views)
File Type: png FullSpeed192KHz18Bit.png (18.8 KB, 246 views)
File Type: png HalfSpeed384KHz18Bit.png (21.9 KB, 242 views)
File Type: png FullSpeed384KHz18Bit.png (17.9 KB, 38 views)
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Last edited by iancanada; 2nd July 2013 at 12:42 AM.
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Old 2nd July 2013, 01:02 AM   #449
PET-240 is offline PET-240  Australia
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Gday Ian,

Havent been following along with any diligence here, Ill believe you when you say its good. Havent even gotten to the fifo as yet with child and another on the way....the silliness of life methinks.
Look forward to getting this and throwing in the stash "to do" pile, really glad Chris has done the wiki for the fifo as well. Much appreciation for your efforts!
Thanks,
Drew
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Old 6th July 2013, 03:58 PM   #450
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TOTAL 102

TV Man x 2
merlin el mago
rtd
jameshillj
erin x1 (or 2)
Nikola Krivorov x1
Rupor54
vitalica
analog_sa
andrea_mori x 5
dsavitsk
tagheuer
hirez69 x 2
ccliu x 2
BDL
cddumat
regal x 2
zoran
Jogi
Zen(zenelectro) x 2
Buzzforb
SPWON
crobbins5421 X 2
marcus1 x1 (or 2)
casshan x 2
Dweeb99 X 2
jackw X 2
kazap X 2
danzup x 3
Giordano x2
Tony_T
Tubo x1
clivem x2
noizas x4
JoeyDD x2
skullaudio
dinos8746 x2
dvb-projekt
bisesik x2
guglielmope x1
Valeriano x1
mhgawel x1
av-trouvaille x 1 (or 2)
iloveswan x1
dtses
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Lil' Knight x1 (or 2)
skippyboy x1
acccruz x1 (or 2)
WhiteBull x1
hksidney x 1
vts2006 x 3
JustBuildLspkAS.x3 &1 fifo kit finished for pcm1704 (ihave AD1862 ,pcm63,pcm1704)
54: PET-240 2 * TDA1541
TonyB
damohpi x1
iloveswan x 1
Joseph K x 2
mefistofelez x2 (pcm63P)
JLOP x1 (WaveIO, AD1865 NOS SRPP)
sceglar x1
4me2ctv x 1
tubesguy x 1
ctrange x 1
spm x 1
Joonas x1
Loboone x 1
flowerpot x 1
pavelal x 1
Steve Ha x 1
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Superdad x 1 (WaveIO, PCM1704K, discrete I/V)
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