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Old 22nd October 2002, 02:36 AM   #11
jwb is offline jwb  United States
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Quote:
Originally posted by alvaius
EEProm yes, but why would you need a microcontroller?
Perhaps I don't. As soon as you mentioned DSPs, I assumed I would need a microcontroller to boot one up and so forth. But looking at the data for the SHARC, it looks like it can boot itself from an EEPROM.

Anyway I'm not interested unless someone has some software laying around already.
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Old 22nd October 2002, 02:39 AM   #12
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If one plans to make use of all the options available on the DF1704 a microcontroller will be necessary. In order to provide the oversampling bypass a CPLD or a FPGA will be needed if the pcb is to reasonably compact. From there it is relatively small step to rolling your own digital filter in the FPGA. This also opens up the option of PLL or FIFO based retiming.

ray.

p.s. $160 for output caps?????
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Old 22nd October 2002, 03:30 AM   #13
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Quote:
Originally posted by maczrool
Why not use the DF1706? It has 192kHz input. You can let the AD1896 do 4x OS and leave the other 4x to the filter.

Also, how do you get the DIF1703 to work properly with only one crystal? If you use a 24.576 mHz crystal, it's not a supported multiple of 44.1 kHz. Wouldn't you also need to employ a second crystal to handle 44.1 and 88.2 kHz sample rates? 11.2896 would work nicely at 256 and 128 fs respectively. How would one even implement a multclock system? Sorry, I'm kind of new to this.

Stu
I was under the impression that the DF1703 generates the required system clock based on its interal PLL and VCO, nevermind the rate of the master clock input. I believe the master clock input is used only to drive the SpAct when the 1703 is in PLL mode. The datasheet claims that the SCKO will be 256f<sub>s</sub> (or 128, 384, 512) regardless of the crystal frequency. If not, I am a dunce. The DIR1703 datasheet is extremely vague.
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Old 22nd October 2002, 03:49 AM   #14
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Quote:
Originally posted by rfbrw
If one plans to make use of all the options available on the DF1704 a microcontroller will be necessary. In order to provide the oversampling bypass a CPLD or a FPGA will be needed if the pcb is to reasonably compact. From there it is relatively small step to rolling your own digital filter in the FPGA. This also opens up the option of PLL or FIFO based retiming.
If all I want is a FIR filter, I hardly see why I need to implement it myself in a DSP or FPGA. A million other people, nearly all of them smarter than myself, have already done that. I can even buy them in hardware: the AD1896 implements a 64-tap FIR filter for 8:1 interpolation.

I'm inclined to use the AD1896 for interpolation and disregard the DF1704 altogether. The Analog part has much better specifications. So the incoming signal would be reinterpolated to 96kHz, which for CD audio would be 2.2x oversampling and 2x for DAT and friends. And the Analog datasheet seems to imply very low jitter on the output.

Then I would need some logic to split the left and right word into the different DACs. Is there a canonical way to do that?

The chipset would then be changed to DIR1703->AD1896->(logic)->PCM1704.
If it was AD1896->DF1704->PCM1704, that would be way too much like my previous DAC, except without the CS8420.

I can't seem to quickly locate a supplier of AD1896. Anyone know?
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Old 22nd October 2002, 04:32 AM   #15
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Pioneer-standard apparently stocks them when they feel like it. They run around $20.00. Here's the link http://MyPioneer.com/onestop/partdet...834763&rnd=801

About the DIR1703, that's not at all how I took it to work. From other posts I have read I would be inclined to think differently. I'll ahve to go back and read the doc on it. I hope you are right though. I have a few and would like to use them as you suggest. I have a couple PCM1704s and DF1706s on order.

Stu
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Old 22nd October 2002, 05:29 AM   #16
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Quote:
Originally posted by maczrool
About the DIR1703, that's not at all how I took it to work. From other posts I have read I would be inclined to think differently. I'll ahve to go back and read the doc on it. I hope you are right though. I have a few and would like to use them as you suggest. I have a couple PCM1704s and DF1706s on order.
If you needed a different crystal for 44.1 and 48kHz, it wouldn't be a very useful chip. I can't imagine it works that way. And from a careful reading of the datasheet, I believe it can do any frequency up to 96kHz with a 24.576MHz clock input.
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Old 22nd October 2002, 06:39 AM   #17
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Quote:
Originally posted by jwb

I'm inclined to use the AD1896 for interpolation and disregard the DF1704 altogether.

snip snap snip

Then I would need some logic to split the left and right word into the different DACs. Is there a canonical way to do that?
Well, I would ditch the AD1896 as well as the DF1704/6 and go with something along the lines of the Meitner IDAT but tastes differ as they say.
I do not know whether it was canonical or not but I have connected a CS8412 in I2S to two PCM1702 with no interchannel delay. In its most compact form using the "stopped clock method" it fit in a 44-pin XC9536 CPLD and would require only minor mods to work with the PCM1704.

ray.
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Old 3rd December 2002, 09:00 PM   #18
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Default Your DAC ?

Hello, Peter

are You happy with this DAC (PCM 1704; DF1704 )?
I understand that it is from broadhurst project.
How much costs the parts today, what you think about it?
You know my interst for to make a good level DAC-may be this is alternative to TDA 1541 superdac ?
What plans do you have for the future--new DIY DAC ?
What is for you by this DAC a problem ? or more important is to find all time better and better ideas. ( I myself made all the time upgrades for my tube amplifier: PP EL34 triode mode class A )

best regards

hifiwolf

Quote:
Originally posted by Peter Daniel
Here is a pic. The trafos on left are stacked one on top the other, so there are 6 of them. I also use split bobbin type, because they are better. Right beside trafos there are 20 Sprague Extralytic caps under the PCB (so no see). Rectifier diodes are directly attached to the small trafos so no see either. On the right side under another PCB there are 8 more big filter caps.
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Old 3rd December 2002, 09:11 PM   #19
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This is the finest DAC I had and heard, period. The TT doesn't even come close (and I had Maple Noll air bearing, Sumico Blue Point Special and Ono as preamp). I replaced my Technics X1000 (which was CAD 8,000) and it's like day and night.

Lot's of tweaking and mods went into this design, but the key elements are separate supplies (including transformers) for everything, good oscillator and parallel PCM 1704K chips (also with separate digital and analog supply).

I started from an oversampling DAC and my next move is to try NOS designs. I will mod my marantz CD94, then built TDA 1543 and then try AD1865K. Last two DACs will be fed direct I2S from my CD Pro 2 transport, because some people claim that SPDIF is the root of all evil.

As for I/V conversion I will definitely try Pass D1 stage. I'm surprised nobody's experimenting with it yet (or at least nobody's talking about it)
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Old 3rd December 2002, 09:34 PM   #20
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Actually my PCM1704 DAC uses an I/V stage inspired by the Pass D1. My version uses BJTs instead of MOSFETs. I posted the schematics here several times.

It sounds simply great, although I cannot measure distortion and so forth.
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