Quote:
Originally Posted by synaesthetic
That looks suspicious--HiFiMAN products always seem to be focused more on the boutique audiophile folks, and they end up having bad design and lots of measurable problems. Also, that DAC has an NJM4556 to start with, and you replaced it with an op-amp that's designed for extremely high-frequency tasks. Yeah, you could use an AD797 for a preamp stage in a speaker rig, but even Analog Devices claims it's been mostly used in non-audio applications.
People like to replace the NJM4556 because it costs 60 cents and they think that means it's crappy, but it's dumb. That opamp is specifically designed to drive headphones--it's one of the few opamps that measures well into loads below 150 ohms, and it's extremely high-current (70mA). The AD797 manages 50mA but not into headphone loads I'm sure.
These days, I pretty much don't trust a DAC or amp to be decent unless it's made by me... or Violectric, Benchmark or Centrance. Working on putting together an Objective2 and ODAC combo.
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i'm well aware people can't randomly drop in the AD797 onto a circuit board, and hope everything will work well. i had the op amp in my closet and decided to see what would happen. so far i don't hear any oscillation occuring and it is way better than what i heard from the stock op amp (4556AD JRC). if oscillation does occur, it's no problem on my end. i can roll more op amps i intended to try out in the first place. particularly the AD8597, LT1028, and AD8599 i have laying around.
i've already talked to dsnuts and kiteki on head-fi (i know head-fi isn't what it used to be 4 years ago, but there ARE members who have valuable knowledge and you have to seek them out) and they know fully well about these kind of things, and both agree it wouldn't hurt to try the AD797 and see how it goes since it has a nice internal layout.
did i take a gamble on this DAC/AMP made in china? i sure did! but for 105 shipped with usb/optical/coaxial input, the ability to roll op amps, a headphone amp, and to use it as a DAC with the CS4398 chip if i chose to try another external amp sits well with me.