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-   -   Help with Zen Headphone Amp - hiss... (http://www.diyaudio.com/forums/headphone-systems/29677-help-zen-headphone-amp-hiss.html)

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).

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

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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