[kentajalli]

I recently picked up one of these from eBay for cheap, since I also got the higher model UD-501 that I am very happy with.
I just wanted to know, how the two compared, I was disappointed.
The UD-H01 sounded bland, without much resolution, with a certain tizz on high treble. So I said "the hell with it" and openned it up, to see what makes it tick (or not!).
Amazingly it uses good powersupply components, BurrBrown DAC chips same as the ones used in its brother the 501. But it was cheaply put together, in a plastic box, no shielding of any kind between sections, and uses that dreaded NE5532 opamp chip, the beloved of all manufacturers, because it is cheap!
It actually uses Muses 8902 Jfet opamps in the I/V section but then it all goes to 4 surface mount NE5532's for phono and balanced output buffering.
So I decided to have a go at it.
here is what it looked in virgin state:




I wanted to try different opamps for output, so I needed to put sockets in, but it proved difficult, since although there are special sockets for surface mount to DIL, but I could not find one to buy, so first I took the NE5532's out




Then I soldered a messy set of four sockets in place by hand and glued them in




Messy I know, how it actually worked was a very pleasant surprise for me, but it did.
So I started plugging stuff in, and listen.

Muses 8920
Sounded good.
Plenty of clean bass, but there was something wrong, not easy on my ears, so I quickly moved on.

Muses 8820
Sounded softer and better than 8920. 8820 is a bipolar chip. Again something was not right, bass was a bit loose, but treble (specially high treble) cleaned up, and became more airy, but also that "Tizz" became more in your face.

LM4562
This is more like it!
Clean bass, not as powerfull as 8920, but hey much better than NE5532's. Treble was also good, but not as good as 8820's, but less Tizz.
Getting some where now.

LME49860
Clearly the best of the lot. Sound just cleaned up, very similar to 4562's, just a tad cleaner sounding, so I chose these to remain in.
Overall great improvement over factory 5532's.

Next I tried to add some shielding between sections.
I used a thin cardboard and tape  to make a housing for the power section, then I stuck copper tape on it, and insulated the bottom part with ducktape, and grounded this housing in place.




I then made a similar housing for the digital section ( right side of the exposed board ending at edge of the rightmost relay) and then another for the analogue section, grounding each one. So it has three shielded compartments now.
You know something, The Tizz went away!
Upper treble is clean and airy, but not forced.
In this format it compares very well with it's brother the 501, although 501 is still a bit better.
At £110 (the original winning ebay bid) plus possibly another £20 for mods, it is one hell of a DAC.
I also had purchased a PS Audio Digital Link III DAC which I did not like at all , it went back to ebay.
I also got an AudioLab M-Dac, which is a beast of construction (never seen better in a DAC including my 501). It does sound better than my modified DAC (I admit), but the margin is so small, I am putting the M-DaC back on ebay, I probably get £400 for it - at over three times the price of modded Teac, I can not justify it.
Besides neither the PS audio nor the M-dac accept anything beyond 96KHz on USB.
The Teac on the other hand accepts up to 192KHz, which incidentally I have set my mediaplayer (JRiver) to output at 24bit 176KHz for material encoded at 44 and 88 KHz. 192KHZ output for 96KHz encoded material, I think it sounds smoother this way.
DSD gets converted on-the-fly to 192KHz too.