Getting more from my DAC


I need some advice. I've put together a mid-fi office system over the last few months:

Sony XE500 CDP acting as a transport
MSB Link DAC III with 24/96 upsampling
McCormack Micro Integrated Drive amp with upgraded PS
Tannoy System 600 nearfield monitors

Toslink cable between transport and DAC. Ratshack gold series interconnect between DAC and amp. Audioquest Type 6+ wire between amp and speakers.

I was fairly happy with this system until I tried connecting the Sony CDP directly to aux posts on the amp and switching back and forth between the CDP/DAC combination and the stand-alone CDP. On a straight A/B comparison, using the selector switch on the front of the amp, I hear almost no difference, even with well recorded piano music/female vocal/jazz.

This is disappointing. The amp is low powered but pretty transparent, I believe - as are the speakers, which were designed as pro monitors and have a reputation for being revealing. So why aren't I hearing a more perceptible improvement - change, even - in the sound when the DAC is introduced into the system?

Are my crappy cables strangling the DAC? Is the transport too cheapo to let the DAC do its work? Do I need to follow the MSB/Modwright upgrade path before the DAC will really shine in my system? Or is the whole system a bit too bargain-basement to benefit from a decent DAC?

Words of wisdom gratefully received.
spartane5c
I think I'd start by looking at the cd drive/transport. I had been using a Cambridge cd4se player as a transport for an Sonic Frontiers/Assemblage 2.7 Platinum dac. When, on the advice of a dealer, I tried the new Cambridge Azur 640c as a transport, I was floored by the difference. Far more improvement than I would have expected. I tried using a glass toslink interface and found it was lacking a little musicality. Very clear and great treble extension, but not as fully fleshed out in the midrange as the Aural Symphonics cable I use. I am getting a Sterevox digital cable today to try as well.
Try the Stereovox HDXV like Photon46 suggested. It's a great digital cable. It's only $100.00 and may be purchased (or just auditioned first) from The Cable Company. Ask for John Pharo, he's a nice and knowledgeable guy who can really help. The Cable Company's phone number is 1-800-fat-wyre. The website is www.fatwyre.com.
The transport is the primary problem. It can definitely benefit from mods, but you will probably need to put a Superclock2 in it at considerable expense. A digital cable is also recommended, and a good one. You can come really close to the digital cable performance with a glass toslink such as this one:
http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?category=220&item=SP-TOC-99HQ&type=store

You can also get the MSB modded. I recently modded a Gold version and it turned-out really spectacular.

Select your modifier carefully. A digital engineer will have more knowledge about transports and S/PDIF interface.
Heresy here....but, could it be that there isn't as much difference between DACs/Players as is touted? I've had similar experiences over the years in a roughly equivalent system switching between Rotel/Theta Theta/Sony Rotel/MSB and Pioneer/MSB. I still keep upgrading and I think my system sounds better each time, but on that A/B test, I don't know and it makes me wonder....