First and foremost…super thx for everyone's high-quality & results-producing feedback. I'm glad I switched forums on this project!
… I worked on a Sony SCD-333ES.
That thing had PCM1738 dacs inside.
The mags gave it good reviews, the internal pics impressed the audiofools, but really, it sounded dreadful.
I've put a good clock, with S/PDIF reclocking (Tent XO3), solved lots of problems of improper decoupling (huge Silmic caps miles away from the chips... typical Sony), analog stage, PSU, etc.
It certainly improved vastly but the end result was that it was much better as a transport, connected to a (very modified) Audio Alchemy DDE v3.0 dac.
My conclusions back then were that the PCM1738, although used in some high(er) end players, is no much different, sonically, from most delta-sigmas.
Then again, a 6 channel player (like the SCD-333ES) is always too compromized for high end stereo, 2 channel playback.
Carlosfm: If I may be so bold… what are you using currently
for a DAC and xport/player?
BTW: I'm new to this forum so it's archive's treasure troves are, for me, mostly unexplored. Some of my queries may, hence, be redundant … but that's the learning curve, I suppose. Anyway…
If I do ditch modding this DAC, what DIY DAC projects do you (anyone) recommend as being especially noteworthy? (Please filter out NOS and vacuum-tube designs, if possible ;) -- I've gone that route a number of different ways and never found the sound to my liking).
I've got a Tent clock on order for this unit, and will most likely (ultimately) integrate that with a Kwak Clock.
Joseph K wrote:
Just wanted to point out that the 1738 is an early advanced segment dac, exactly like the pcm1794, the cs4396-97-98-122, the WM8740 the AD1955 etc.. That is, like all the modern good sounding dacs?
You may want to scope out this thread...http://www.diyaudio.com/forums/showthre ... adid=94695
…and this message…http://www.diyaudio.com/forums/showthre ... ost1114753
… at the other site for some more comparisons/contrasts between "popular", "modern" DAC chips.
As far as the A324, I believe the model up from (or the model that came after) the A324 used another TI/BB PCM17xx chip (1792??) Unfortunately, and all else being equal (i.e., if the rest of this unit's topology is decent and continuing to mod is efficacious) there is no easy way to pop in a better DAC chip -- say a 1796 -- into this circuit.
First you'll need to replace the RCA with a BNC 75 ohm and use a piece of 75 ohm coax down to the input transformer. In case you don't really need the digital output and the optical input then you can bypass those two ICs, reuse the output transformer as an input TX and go directly to CS8420 input(s)....
The image I posted earlier is several mos. old. I ditched the output circuit some time ago. But I haven't gone so far as to directly inputting SPDIF IN into CS8420, bypassing all that other junk, so thx for the push here!
)....and then of course ask Jocko a lot of questions.
Glad you brought up SPDIF and asking "Jocko a lot of questions" because…
… my transport (and SACD/DVD-Audio/-Video playback) unit is a Pioneer DV-59AVi. Potentially, as stock, a "6 channel player compromised design" as Carlosfm noted above.
Here is the Digital Out section of the Pioneer:
I want to upgrade its S/PDIF out. Opting for BNC, as many of you have suggested, is an obvious choice. But, what else
? And especially
with respect to my Pioneer. Scanning this circuit from a 2005 diyaudio thread…
… I *think* the best route for re-constructing the Pioneer's S/PDIF out is to integrate the pulse-transformer-based output Katapum/JH worked out
a while back on diyhifi
as well as diyaudio.
But I'm in the learning-curved/newbie-dark about elements of the circuit above.
First, what are the values for the two "2R???", just before the BNC jack for, say, my Pioneer's output.
Perhaps the answer lies in JH's response (below) but I can't "decode" it…
Specifically, in that late-2005 thread JH wrote:
… I did not calculate the pad values, but it can be a little bit high without having to worry about blowing the protecton diodes in the RX front end, or worse, creating tons of EMI.
Pad values…are these the "2R???" I queried about above?
Also, I'm going to *assume* -- correct me if I'm wrong -- that Katapum's SPDIF INPUT circuit is *generic* enough to be used in most DACs:
There was some further modifications to this input circuit here…
http://www.diyhifi.org/forums/viewtopic ... ight=#7196
…but I'm not sure what the final
SPDIF INPUT circuit looked like?