tomb
Member of the Trade: Beezar.com
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- Mar 1, 2006
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USB can be anything from 4.5v to 5.2v with a nominal of ~5v. In reality it fluctuates depending on supply load, for example plug in a USB memory key and copy some data to it while monitoring the voltage and it will jump all over the place.
One thing i have found the PupDAC susceptible to is dropouts due to spikes in the output ground. I can fairly consistently make it drop off by power up my valve amp connected to it, or even turning on my cheap Chinese eBay soldering station can cause it to drop off, though interestingly the USB connection to my UPS drops off too when i use it.
It doesn't seem to make any difference if i power it from the computers USB output, Doodlbug or a completely overkill power supply / Isolator box i previously built so it has to be small voltage spikes coming back into the RCA output grounds that is causing it, or a voltage differential between the input and output grounds.
Whatever amp you are connecting to the PupDAC, make sure its powered from the same power point as the computer, other than that i haven't really got any solutions to avoid it.
I've experienced some of this, but seems like with the DoodleBug it comes back online without a manual disconnect-reconnect. It sort of reminds me of why we went from BUF634's with headphone amps in the early days and went to discrete parts, instead. The OPA2836 may provide ample protection against frying the DAC - a serious problem with the Starving Student and Alien/BantamDACs and Gamma 1's. It's one reason I'm a whole lot more careful with any source when connecting/disconnecting to a powered-up amp (I simply do NOT do it anymore.). Yet, what we're describing might be attributed to less output protection circuitry in the opamp.
Of course, whenever comparisons were made - the less protection circuitry, the better something sounded. So, I would rather accept the hassle of it knocking offline sometimes with the understanding that it will sound better The BUF634 has a lot of protection circuitry on the output, but it always sounded kind of "tame."