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Old 14th March 2008, 06:37 AM   #1
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Join Date: Apr 2002
Default PCM63 DAC mods

Not sure how many of you use this excellent DAC. I have 4 in my Theta Gen Va (2 per channel, running in balanced mode).

I have started the process of getting the most from the chip and yesterday linked up an Andy Weeks (ALW) super regulator to the +5V analog supply of the chip (obviously disconnected the old one).

Big difference in bass response, which has become cleaner and less bloated.
Also, the "space between the music", i.e. the silences are quieter.

My 2c
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Old 14th March 2008, 10:41 AM   #2
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Default PCM63


Thank you for this report! This looks very promising indeed.
I wonder how it will work & sound with any of the non balanced versions (I mean with the “common” 1x PCM63 per Channel).

What selection level of PCM63 you are having?
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Old 14th March 2008, 11:08 AM   #3
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What's the best DIY PCM-63 implementation ? Mine are waiting to be used !
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Old 14th March 2008, 01:00 PM   #4
euro21 is online now euro21  Hungary
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Join Date: Sep 2004
Location: Budapest
Mods of my Lite DAC-50 (PCM63P-K DAC, 6922 SRPP):

- HEXFRED diodes in rectifying stages;
- 5H choke in HV stage (C-L-C);
- Power supply bypass capacitors (MKP10);
- NOS Tesla E88CC in SRPP;
- ClarityCap coupling capacitors
- Coupling capacitor bypass by 0.1uF VCap (teflon);

and the best:
- I/V resistor change to Sowter 8347 transformer (1:18, 2K0 Caddock resistor in secondary).
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Old 14th March 2008, 01:27 PM   #5
eddylws is offline eddylws  Malaysia
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Hi euro21,

As i know the Lite DAC-50 is a upstampling.
can make it NOS?

Have you try change the DF1704u to DF1700p?


Eddy Lim
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Old 14th March 2008, 02:03 PM   #6
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Join Date: Dec 2007
Default DF1700 ??

Hi Eddy,

I don't get it: Would NOS + DF1700 become at the “end results” the better sounding configuration??

The DF1704 is such an excellent Digital Filter! The DF1700 is really nothing great; there is no any comparison between them.

"Going backwards" with the Digital Filter should have a very good reason for doing so.

Meanwhile, any news about your "K2" ?

Regards, IY.
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Old 14th March 2008, 03:34 PM   #7
eddylws is offline eddylws  Malaysia
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Join Date: Aug 2006
Hi irgendjemand,

thanks for you info.

You mean i should go for DF1704 instead of DF1700?
I am help my freind to build up a DAC, do you think Lite DAC50 is a goo idea? Appreciate your Advise.

That is some technical problem still need some time to figher out. I will post it once i have review on it, but i am very sure that the different is more then 70% if compare with PCM63P-K. It sound very dynamic, batter sound stage & background sound very detial.


Eddy Lim
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Old 14th March 2008, 03:59 PM   #8
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I think all 63's will benefit. I am using the 63K's
Will try the digital +5V soon and post results
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Old 14th March 2008, 06:22 PM   #9
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Join Date: Dec 2007

I don't know the Lite Dac50, I am sorry. May be Manfred Hiller (you know him I think) will be able to tell you more, also about the combination of NOS & DF. By the way, he is the one who gave me the information about using the DF1704 correctly (in SLOW mode!) instead of the 1700.

Meanwhile have success with the PCM63P-K2 & please keep us posted.


The steps between K and K2 (and Y) are so big that it might be hard to tell, what will be the actual impact; it would be interesting to try it however indeed by all 63’s categories.

As eddy just wrote above, his K2 sounds very dynamic, the sound stage is better & background sound is very detailed. I would add to this your remark – “the silences are quieter” by K2 and also – there is more body in the sound (the all performance of the K2 is somehow similar to the "Y").

My own impression: The higher the selection level goes, the bigger, cleaner and detailed (yes, all the phenomenon comes here together!) the sound becomes, also less aggressive.

What will be hard to tell is the exact “amount” in this combination of “more body” and “cleaner”. With the 63’s “Y” the sound is the biggest, but paradoxally, I don’t feel the necessity for a cleaner / less bloated sound. The Chip seemed to me to be in perfact balance.

But, as you enjoy such an improvement with the regulators – this is all what counts actually.
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Old 14th March 2008, 06:33 PM   #10
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Just tried a 150uF OSCON on pin3 -Distortion and closed! So, the usual trick on Vref does not work here. Also note that unlike 1 bit dac's, the Vref pin is not at Vcc/2.

Next to see what happens on pin 1 and 4.
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