ZEN-like headphones amp

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#21
Hi, tschrama. I found that the hum was present with a power supply that had fairly high ripple, but not with my lab supply. The voltage supply to the amp board itself had no ripple because of the cap multiplier. My conclusion was that the ripple current coming into the cap multiplier was inducing a voltage somewhere in the amp circuit, or more likely in the ground wires connecting the two (no, not a ground loop - separate ground wires for each channel, and for their bypass caps). Smoothing the ripple before it got inside the box solved the problem.
 
#30
Hello John-China,
your idea is not at all new, you can find other threads about Bal-Zen (what is, in point of facts, the same conceptual thing) by the DIYAudio search engine.
The problem here is the headphones "common-grond", to achieve best results probably you should re-wire all your headphones: I'm not willing to do this.
Marcello
 
#33
Here are two photos of my headphone preamp.
The two "additional" PCBs are the power supply board, and the muting - equalizer board: this one provides a two-seconds delay to avoid the power-on bump, and the "hi-frequency equalizer" slightly shaves the upper frequency behaviour: the effect can be tuned by four dip-switch, in the bottom of the chassis.

Marcello
 

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