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Old 7th March 2004, 05:45 AM   #1
batee is offline batee  United States
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Join Date: Mar 2004
Location: Rolla, MO
Default Help with Zen Headphone Amp - hiss...

Built Marcello's headphone amp last evening. Sounds great except for a faint hiss (sounds like white noise).

Details:

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
batee@roadslessphotographed.com
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Old 8th March 2004, 07:14 AM   #2
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Join Date: Jan 2004
Location: Sicily
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.

Nat Riscica
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