|
Computer Audio Asylum Music servers and other computer based digital audio technologies. |
|
|
|
Computer Audio Asylum Music servers and other computer based digital audio technologies. |
|
In Reply to: Musiland Monitor 01 USD - late to the party, but... posted by Thorsten on December 17, 2009 at 10:35:40:
Folks,
After the above experience with the digtal output only Musiland USB Gizmo I decided to take a second hard look at the one with the integrated DAC (the PCM 1793 is not the last word but not THAT bad and the OP275 analog stage ain't exceptional but should do okay) to see why I could not stand listening more than 10 to 15 minutes to the thing and then only at quiet volumes.
Well, first, there are two switched mode supplies on board, they create around +/-5V Supplies for the Op-Amp output stage and probably also for the DAC's analog supplies.
These switched supplies where not a total disaster, but left around 50mV peak-peak noise at the 100KHz+ switching frequency, as the reservoir capacitors had trouble handling this frequency well. A pair of big (220uF/10uF) Os-Cons fitted instead plus one each 10uF SMD ceramic cap squashed the switching noise to less than 1mV peak-peak though one switcher started to have maybe 2mV p-p of around 2KHz ripple, no idea where that came from, but one can live with that I think.
What was worse was that these two switchers threw over 200mV peak-peak noise at their switching frequency into the USB Power line which of course fed the rest of the device so this same noise was on each and every power supply node minimally attenuated!
Next stop was a SMD choke and big Os-Con separately for each switcher to kill this noise. After that what was left was the same USB Port supply noise I had noticed with the 01 USD, so I attacked it the same way. As I had already dropped five (!) expensive Os-Cons into the gizmo, I finished off replacing the remaining original (6pcs) local decoupling caps with Os-Cons as well.
Now poking the 'scope around the PCB reveals very little noise anywhere, again, surprisingly quiet for such a complex and high speed logic design.
Sound quality is much improved I would say, at least i can listen on 'cans quite loud and by now several hours without fatigue. I suspect the modification of the 01 US the way I did will beyond the abilities of most of the people here.
If you happen to buy a 01 US to pick off the I2S signal from the chip (in principle smart move) make sure to remobe the DAC IC, Op-Amp AND to turn off (cut the trace to each switcher) the switching supplies, plus power the whole PCB from a clean 5V supply instead of the USB bus and you might have something quite passable in return.
The Musiland platform should be capable of around 100pS or thereabouts jitter if fed a clean supply, which not a lot of DAC's and CD-Players equal. Just add your favourite DAC chip (make mine a TDA1541 please), analog stage (make mine a Tube, maybe the Universal Tube Stage diyhifisupply sells) and you have a nice DIY asynchronous USB DAC on a modest budget.
The result may not have Gordon or Charles quaking in their boots, but could be nice for "cheapo fun".
Maybe someone will pick up the OEM solution Musiland offer and incorporate it into an affordable kit or something? That way one might end up with an excellent solution that does mess up SPDIF signals and power supplies and has a better clock solution.
I hope this helps some of those of you who have been asking privately for info and where I lacked time to answer.
Ciao T
Thor
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Musiland Monitor 01 US - Thorsten 11:08:18 12/17/09 (2)
- RE: Musiland Monitor 01 US - fmak 22:21:23 12/17/09 (1)
- RE: Musiland Monitor 01 US - jkeny 04:24:10 12/18/09 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
