Sechtdamon

Continuation of R2R DAC Discussion From Stax Thread

89 posts in this topic

I completely agree that a chip, or hybrid solution would be best. In fact the concept of using a laser trimmed metal foil R2R network, where the foil network was layed down by photolith ought to be superb, hermetically sealed and dry nitrogen filled. Cheap it would not be...

 

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Although DF1704 TI paired with PCM1704 has been outdated and surpassed by FPGA based digital filter, PCM1704 is still a very good chip even after over 10 years of production. Sad to be obsoleted. As I know, TI stopped all audio R2R chip production. So we have to look into discrete design or use AD chip sth like Schiit used. Even for AD5791, it is only 20bit so when playing 24bit data, some calculation must have to be done.

Edited by joehpj

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I have a DAC based on AD1862 (20 bit) and I like it better than a same DAC based on PCM 1704, by a lot. Actually I don't really understand why people treat PCM 1704 as it is the best R2R dac chip ever. Engineered better? Sound wise better?

All Sigma-Delta Chips are using that calculations to decode PCM, the highest bit of a hybrid Sigma-Delta chip has as I know 6 bits. So if you do not have any problem with it, why do you think about 20 bit R2R dacs has problems with decoding 24 bit? cuz they are already outdated, cuz you care about the remaining 4 bits is left behind? If a dac can decode 20 bits perfectly, IF, I do not hecking care about the remaining 4 bits.

 

Anyway, what I extremely curious about is this:

http://www.transient-audio.nl/DAC_TWO.html

Are they using on shelf dac chips in it with a simple closure? WTF is in that closure? Anyone got some info abou it?

Edited by Sechtdamon

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my guess is that the transient part is all discrete, and very similar to the soekris with fewer bits. and like the soekris, opamps to do the se to balanced, and more opamps to do the filter.

there are no off the shelf 24 bit dac chips. if there was, things would be much easier regardless of their price

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9 hours ago, Craig Sawyers said:

I completely agree that a chip, or hybrid solution would be best. In fact the concept of using a laser trimmed metal foil R2R network, where the foil network was layed down by photolith ought to be superb, hermetically sealed and dry nitrogen filled. Cheap it would not be...

 

... and encased in a crystal controlled oven to negate any temp drift....

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9 hours ago, kevin gilmore said:

my guess is that the transient part is all discrete, and very similar to the soekris with fewer bits. and like the soekris, opamps to do the se to balanced, and more opamps to do the filter.

there are no off the shelf 24 bit dac chips. if there was, things would be much easier regardless of their price

PCM1704 was a 24bit dac. But the ENOB was less than AD5791. Why is that different? 

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15 hours ago, kevin gilmore said:

my guess is that the transient part is all discrete, and very similar to the soekris with fewer bits. and like the soekris, opamps to do the se to balanced, and more opamps to do the filter.

there are no off the shelf 24 bit dac chips. if there was, things would be much easier regardless of their price

That was the point I wanted to reach Dr. Gilmore, thanks.

 

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Interesting thread guys. The Chip type (in R-2R) as we are talking here does seem to have an effect on the sound. And I guess discrete different again, quite possibly surpassing a chip? But the effect of the filtering used and the quality of the power supply and output stage after the chip also has a big impact IMO. Having trawled through various R-2R DACs in the past it seems that has a marked effect on the sound you will get.

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Posted (edited)

so the 2 piece version will be capacitor coupled output, the 4 piece version will be dc coupled output, the newest version of cast and cascode fet buffer.

for balanced you will need 8 pieces. i'm sure a version of this is coming.

as far as I know, no dsd  but it should be capable of that.

pricing is finally rational

Edited by kevin gilmore
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Been going through some of the old threads on old multi bit dacs. Is Filburt's favorite opamp THS4032 (with the fancy decoupling) still the one to go for if you have to settle for an opamp i/v? Or are there other opamps that are better now? I haven't been able to get Filby's modded Assemblage sound out of my head, ever since I listened to it.

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That is what I used on my Rotel 991 (still haven't gotten around to discrete in it yet) along with 8xxx for the buffer/SE ->bal. It was touchy for decoupling. I used the Aries DIP adapters with on pin decoupling and no sockets for the 4032s.


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Awesome! How does it sound? And what discrete i/v were you planning on using? You wouldn't happen to have some of the borbely stuffed saved up would you? 

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It sounds good, probably not as good as my 855 with an rbroer (diyaudio) discrete, but much better than the stock opamps.
I have one of Colin Toole's discrete stages partly built for the 991. Still haven't decided whether to leave the ad8599 (IIRC) in as the SE to bal converter or to use something discrete there.


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