During the AliExpress Sale, I've ordered another Zishan DSD (AK4497) - so that I'll have one as a reference, while modding the other.
Hello, I'm scratching my head and searching everywhere to find out the most "elegant" way to get a near 0 output impedance to drive my BAs in the best possible way, and read a hint at replacing the opamp with one that has shorts protection and removing the output resistors, sounds like the best idea to me so far, apart from plugging a ifi ematch between the player and the IEM, which I find too expensive for what it is/does.
Has anyone done this mod IRL and can validate it's working? What model of opamp would suit? Thanks in advance!
The easy output to achieve 0Ω on, is the Balanced (2.5mm TRRS) jack - since the outputs of the two soldered-on OP275 op-amps are connected directly to the 22Ω series resistors.
So, installing 0Ω resistors in-place of the 22Ω resistors, would mean low impedance output on the Balanced jack.
But you'd probably want to replace the OP275 op-amps, with higher current models, that have short-circuit protection.
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The Single-Ended (3.5mm TRS) jack is driven by a set of transistors that follow the socketed op-amp, so the op-amp is isolated - but the transistors may need the 22Ω series resistors.
If the circuitry between the socketed op-amp and the jack is removed, including replacing the 22Ω resistors with 0Ω resistors, then there'd be a low impedance Single-Ended output.
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According to several posts in this thread, replacing the 3.3V & 5.0V Low Dropout Voltage Regulators for the Digital circuitry makes a noticeable difference in the audio performance.
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For maximum performance from all three op-amps driving the output jacks, the high voltage Analog power supply circuitry may need to be upgraded - I'm not sure what its V+ & V- output current rating is.