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amb: Is there a noticable improvement when the AlienDAC is powered by external power compared to usb power?
I did some noise floor measurements via RMAA looped back into my M-Audio Firewire Audiophile, and at 16b/44.1k, there is practically no difference between USB power or an external 9V battery (both regulated to a measured 4.77V by the REG101UA onboard). At 16b/48k, however, the battery gives approximately 2dB lower noise floor through most of the audio band. Not a huge difference, and since these are all well below -100dB it's not going to be audible.
One thing I did observe, is that the noise floor is about 6dB worse when the board is uncased. Since I have very little RFI where I did the measurements, I think the extra noise is probably self-induced. Since the PCM2702 has the DAC and the analog output section built-in, and no provision for separate digital and analog grounds or other isolation between the two, there is probably noise crosstalk from the digital section into the analog section. By having the PCB encased in a grounded aluminum extrusion, the amount of radiated noise is partially absorbed.
As an added incentive to having it cased... I shocked mine to death the other day.
Back to using my onboard sound. Oh well, it's only for gaming anyways.
__________________ "For a list of all the ways technology has failed to improve the quality of life, please press three."
Moon Audio modded Original CD-2008MK-II / de Almeida Signature Shadow XLR / McAlister Audio Massive Attack / Headphile modded BlackGold recabled AKG K340 OR APureSound V3 recabled Grado RS-1
So, here is what I build last - oh, I don't even know any more how long it took. I am not very skilled with any of these things so let's say that it took quite a while. It isn't completely finished yet, but I am getting there.
The amp is a Porta Corda USB originally so that part I didn't build. I've got Sir Meier to thank for that. I just made the wooden casing. On the back of the amp I also made a connection for a 24V adapter.
I started out with this:
After that I ended up with this:
And right now I've got this:
The drawing on the top has been burned in there. You might not be able to see it that well on the picture.
I still want to get some kind of power supply in there, but I have no idea how I should get it in there or what kind of things are available. Suggestions are welcome.
Edit: You are going to have to do with a crappy picture of the result until there is a better camera available here.
Here is my newest....Retro stylee...
Size: 8.5 inches x 5 inches x 6 inches deep.
Weight: about 15 - 20 lbs.
Contains: +15v (78/7915) regulated PSU.
Walt Jung's AD823/AD815 based Low Distortion Line Driver.
50k dual step attenuator.
Preamp out jacks (w/optional output caps, via a switch) connected to switching headphone jack (w/out caps).
Switchcraft patchbay TRS jack.
Relay based on/off muting circuit.
Ground loop isolation.
Exterior ground tap.
I found this box at a junk yard, made of 1/2 inch thick aluminium...and went to work...
How about a tube shield used as a jack shield ????
Sounds: neutral, not emphasized in any one area but still very detailed.
I have not compared it to my other Hamps, yet.
Offset around 1.7mv both channels.
Completely silent at full volume.
The look of it sorta reminds me of a Geiger meter of sorts... If only you had a large meter at the front (perhaps make it show the sound levels)
__________________ [ S O U R C E ] Lenovo ThinkPad T61p | Creative SBLive! w. kX Project Mod| iPod Colour 60GB [ W I R I N G ] TARA Labs Prism RCA | Monster XP Speaker | DIY iPod-RCA | DIY Mini-Mini | DIY iPod-Mini [ A M P L I F I C A T I O N ] Yamaha R-95 Stereo Receiver | Cmoy w. TLE2426 Railsplitter [ H E A D P H O N E S ] Sennheiser HD-477 | JVC HA-D990 | Westone UM1 [ L O U D S P E A K E R S ] Energy C-300 Floorstanders | KLH ASW12-120 12" Subwoofer [ W A N T S ] Grado SR-325i | Mini3 Parts
Here is my newest....Retro stylee...
Size: 8.5 inches x 5 inches x 6 inches deep.
Weight: about 15 - 20 lbs.
Contains: +15v (78/7915) regulated PSU.
Walt Jung's AD823/AD815 based Low Distortion Line Driver.
50k dual step attenuator.
Preamp out jacks (w/optional output caps, via a switch) connected to switching headphone jack (w/out caps).
Switchcraft patchbay TRS jack.
Relay based on/off muting circuit.
Ground loop isolation.
Exterior ground tap.
Holly Cr*p! That is built for 40,000 ft drop!
I was going for simple small case for my Desktop CMoy...
)
Linear Mode
