The best DAC for the money

S23chang, I don't think it's that bad :) I just say that I'm doubt that opamps and crystal oscillator upgarde may significantly improve sound quality (if I'm wrong I'd appreciate some more detailed explanation) for budget level device, such as NAD. If you're talking about upgrade of digital filters and all the stuff around the internal DAC - I think it would be easier and cheaper to buy a new CDP. Or, an external DAC :)

Dmitrydr, You'll be surprise how much difference the opamps and the clock circuit ( not just the crystal oscillator) can do for you.
First of all, I leave the digital filter along. Like you said, if I have to change DAC then might as well buy a new player.

I was pretty skeptical about op-amps and clock mod as you since I didn't know much about digital source before until I tried this for myself.

On the analog stage, there are op-amps that amplifies the output signals from the DAC to the right level. Think of them as pre-preamps for the CD player.
Some designer decided to use tubes instead of op-amps to make it more analog sound.
In any case, choosing a different op-amp can give you a different sound. Better or worst is your judgement.
Most of stock op-amps used in the CD players are in $1 to $3 range each. You can always get a better spec op-amps (from $4 to $30 each) to replace the current one in your CD player. The two major op-amp makers are Analog Device and Burr Brown from Texas Instruments. There are at least 5 more manufactures out there but these two companies are the most popular ones. In general, with the better spec, better op-amp should improve the resolution and sonic characteristic. That's pretty much sums up for the op-amp.
As far as clock circuitry vs the crystal oscillator goes, there is only one word to describe it: Stability.
The clock circuitry is at least 100 times more stable than just the crystal itself. What oscillator does in the digital circuitry is to help stablize the timing in the circuitry. The accuracy will improve the noise, imaging and pace. The combination will make the CD sound more analog while keeping the sweetness of its original sound.

I'm not affiliate with Audiocomm superclock II or the LC Audio XO-3 clock but you can always read more about them from their website. Also, I'm not using their product.

Capacitor and resistor mods on power supply maybe will do something good but I felt that I'm happy with the sound already and I don't see the performance per dollar gain.
In my opinion, of course it will help somewhat but not as much improvement as the op-amp and clock mod.

If this is not what you're looking to improve from your current CD sound then I don't know what else to tell you except switch to a different "Hi-End" CD player.

Just my 2 cents thought on CD player

Where do you get CDP modified ? Did you do it by yourself ?

Thanks, -TT

The dAck! battery powered dac is a nice sounding unit at $400. You can demo one with a $50 deposit, although the waiting line is a bit long for demo models. I took a chance and purchased one outright and am very glad I did.

Hey Bob,

I was on the waiting list for a demo of the dAck! but think they forgot about me. So far, what is your experience with the DAC? My biggest reservation regarding a battery powered DAC is that I leave my system on 24/7. Do you think it as an inconveniece?

I am using the Nixon, and it also has a lot of the attributes that some people who own the dAck! has described on AudioAsylum and AudioCircle. So, I wonder how much of the dAck!'s magic is due to the lack of digital filters or the lack of AC added pollutants.

The dAck! certainly is prettier. I heard Dusty at CI Audio is making a variety of a nonOS DAC too.