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ODAC - European and Worldwide pre-orders

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forgot to mention when I first plugged it in, the pcb emitted a high pitch squeal for about a minute... I was quite annoyed and was relieved when it stopped. Hope that doesn't come back... wonder what it was from?

It was around 15khz range. I've done tests and I can't really hear anything over 18khz, especially my left ear.

This was on a netbook, acer aspire one d250 running windows xp. USB port on the Left hand side, opposite of the power adapter.
 
forgot to mention when I first plugged it in, the pcb emitted a high pitch squeal for about a minute... I was quite annoyed and was relieved when it stopped. Hope that doesn't come back... wonder what it was from?

I have no explanation for that and have never heard it myself. There is a charge pump built into the ESS DAC that operates at a very high frequency. It's possible, but very unlikely, it was "unhappy" for some reason and running at an audible frequency. In my experience audible noise from tiny SMT components requires relatively high currents and there simply are no high currents anywhere in the ODAC. It's especially odd it lasted for a minute and then stopped.
 
Disclaimer: This brief ODAC review is based on my own limited listening sessions to date with the ODAC + O2 combo during last weekend. The opinion is my own and based on my own impressions.

Setup: I started by soldering the supplied 3.5mm stereo jack onto the ODAC board and bridging the two pads, which connect the stereo jack to the DAC chip output. I then connected the ODAC to a Windows 7 64 notebook with the enclosed mini USB cable. The device was immediately recognized as a sound device and I enabled 96KHz with 24 bit resolution in device settings. I connected the ODAC output via a short, shielded, self-made connector cable to the O2 input and the O2 output to AKG K550 headphones.

Sound: What immediately struck me, when I listened to selection of tracks from itunes, which were either lossless or compressed, is how much “more” of the music you can hear i.e. my brain focused on clarity of the sound and additional details that have been veiled before. Needless to say, all compressed music is pretty much unlistenable. I could easily hear distortions in AAC compressed music content purchased from Apple (256kbit) which was a new and unexpected thing for me. Since this clarity is amazing, what seems to happen, is that it initially kind of overshadows the lower frequencies (the brain focuses on the things in the sound that were not hearable before) and seems to let you think that they are somehow missing from the content. At one point I was afraid, thinking to myself, where the bass has gone, however, after a while, the brain re-adjusted and then all I heard was music, perfectly balanced and clear. The ODAC has dead silent background on my AKG K550 headphones, which are quite sensitive. I have not tried listening with other headphones or earphones yet since now my son is the happy owner of the ODAC (I also built an O2 amplifier before for him) and he confirmed the amazing clarity (I have not warned him) and that he could also hear compression distortion (that has not made him very happy), even on his Koss Porta Pros, although these headphones are not best known for analytical or discerning sound.

I also briefly connected the ODAC to the iPad 2 through the Apple USB connector accessory and a generic USB 2.0 hub, which allowed me to get (finally) the sound off the ipad 2 in digital format and listen to it through the O2 + ODAC. No configuration changes whatsoever were necessary. Apparently, it is also possible to play back 24bit 96KHz content from the ipad using 3rd party software, however I have not tried this yet. I tried the apple USB accessory with iPhone 4, however it was not recognized by the iPhone so I did not try to connect ODAC to it. Maybe it is worth another try?

Next steps: Once I obtain the next ODAC unit from Stefan, I will spend some more time with it, also comparing the sound to the Behringer SRC2496 Ultra Match Pro output ( Behringer: ULTRAMATCH PRO SRC2496 ) output. The Behringer contains a DAC chip with roughly similar specs. It also contains the ASRC sample rate converter chip, which usually helps to reduce jitter to a large extent, although I have no ways of measuring this :).
 
Yes, I was surprised it was the PCB... I checked my laptop, and surrounding devices before I put my ear up to the PCB and sure enough, it was coming from the top side of the board.

The sound can be described like the squeal of solid state switching, like PWM dimming circuits for LED flashlights.

Is there a special mode the ESS chip goes into during power up / USB discovery mode?
 
Yes, I was surprised it was the PCB... I checked my laptop, and surrounding devices before I put my ear up to the PCB and sure enough, it was coming from the top side of the board.

The sound can be described like the squeal of solid state switching, like PWM dimming circuits for LED flashlights.

Is there a special mode the ESS chip goes into during power up / USB discovery mode?

Hum as you've described can be emitted from inductors, such as L100 found on the ODAC. I haven't had a chance to look at the IC datasheets, but startup sequences could certainly put different loads on the inductor than normal.
 
well.. i'm in trouble getting sound from odac..
i soldered 3.5 mm plug to the board and connected between thinkpad T500 notebook and meta42 headamp.. device recognized as a sound device but i get no sound. today connected it to a mac at work and mac recognized it odac but no sound either..
what can be the problem, what should i do? thanks..
 
well.. i'm in trouble getting sound from odac..
i soldered 3.5 mm plug to the board and connected between thinkpad T500 notebook and meta42 headamp.. device recognized as a sound device but i get no sound. today connected it to a mac at work and mac recognized it odac but no sound either..
what can be the problem, what should i do? thanks..

hi, did you solder in the bridges J1 and J2?

An externally hosted image should be here but it was not working when we last tested it.


they are necessary to enable the 3.5mm output

Stefan
 
All that have paid their order till yesterday afternoon find the tracking numbers of their orders on the sheet in google docs (#77).
Had to spend some time with my wife yesterday evening so updated it only today... erm... now...

Next post run will be on Wednesday, would be nice if the outstanding, billed orders are paid till then ;)


Stefan
 
Yes I'd really appreciate a replacement cable, I will send you back the actual one if you want to. I tried to test it with a multimeter on "ring" mode but the probes are too big and don't fit into the connector without touching the metal surrounding.

No worries about the old cable, maybe you can use it as wire for some DIY ;) Will send you a new one tomorrow.

Stefan
 
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