NAD T550 Missing Dac!

josha · 28th August 2011, 11:29 AM

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

josha · 28th August 2011, 06:50 PM

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

28th August 2011, 11:29 AM	#1
josha diyAudio Member Join Date: Apr 2005 Location: Holmfirth, West Yorkshire	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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28th August 2011, 06:50 PM	#2
josha diyAudio Member 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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