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batee 7th March 2004 06:45 AM

Help with Zen Headphone Amp - hiss...
Built Marcello's headphone amp last evening. Sounds great except for a faint hiss (sounds like white noise).


Measures about 5mVPP at the output terminals when connected to paused source (a Sony DVD player) measuring 0mVPP.

Sony 75 Ohm headphones.

Don't have it in an enclosure yet - part's on the truck. Did connect ckt ground to line ground via 100 Ohm resistor.

Noise disappears when I short the input terminals of the amp boards.

Amplitude is constant regardless of bias settings or source level.

Used a few cheap (RS) carbon comp resistors in non-power situations (I live in a small town).

FETs matched to 300uV.

Thanks in advance for any assistance,

Bryan A. Thompson

Nat Riscica 8th March 2004 08:14 AM

Hello Batee,

I have had the same problem. I solve it by adding a o.oo1 ceramic capacitor across the base-collector of the ztx 450 like the original Zen schematic.:D

Nat Riscica

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