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Old 28th August 2011, 11:29 AM   #1
josha is offline josha  United Kingdom
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Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Default NAD T550 Missing Dac!

Hi all,

I opened up my NAD T550 DVD player today with a view to tweaking it.

This is from the NAD Datasheet for the T550.......

'....Unusual for DVD players, high quality Burr-Brown (OPA2134) op-amps are used instead of the much lower grade usually found........'

And

'.....A Burr-Brown PCM1716, normally associated with top of the range CD players. In combination with the 96/24 DAC this means you will get the best performance, regardless if you are playing back CD's, DVD's or VCD's'

here (Manuals and downloads - datasheet)

Great, I thought, not a bad place to start tweaking, I even read a thread on here where someone replaced that DAC with a Wolfson. It's i2s so maybe I could even tap it and replace it altogether.

Anyway - I got the top off and the main PCB out, imagine my surprise when I could find no trace of the PCM1716 OR the OPA2134's!!!!

It seems the DAC is actually a PCM1600 (for the 5:1) and there is a space for the PCM1716 (it's even marked on the PCB) but it isn't there!

NAD imply that, when playing a CD, the decoding is done by the PCM1716 but not in this case! I understand the various merits of the op-amps and DAC's and I wasn't expecting miracles from this exercise but I feel I've been 'had by NAD'

Anyone any thoughts / experience of this??

Cheers

Josh
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Old 28th August 2011, 06:50 PM   #2
josha is offline josha  United Kingdom
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Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Ok - I definitely don't have a pcm1716 on board, or any OPA2134's despite what the NAD marketing blurb says.....grrrrr.

I do have an SCLK, LRCLK, DATAO and GND labeled solder points on the board though so I thought I'd tap into these to see if I could get i2s out. I can! I then connected these up to my TDA1543 DAC (having checked with the scope first) and I get sound!

But.....it's crackly on both channels and low volume. So I think I'm getting 24bit and squeezing it into a 16bit DAC (this assumption from much googling!).

My question is, can I re-sample to 16bits or am I wasting my time on this one?

The goal was really to use the NAD as a transport coupled to the DAC via i2s, without having to go via spdif (I haven't got a receiver).

Again, any thoughts appreciated!

Cheers
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Old 10th June 2013, 07:43 PM   #3
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Is this a good transport for an external DAC?
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Old 11th June 2013, 05:26 AM   #4
josha is offline josha  United Kingdom
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Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Hi Calamaro,

I don't know I'm afraid, I never tried it with an external DAC. Mine is SLOW though, takes ages to read CD's and won't read CDR's at all (by design).

That said, it's quite well built, has a remote control and a nice, clear display.

Cheers
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