koladd
Head-Fier
- Joined
- Jul 4, 2004
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I'm a newbie in Headphone Amp DIY. I just soldered two Amplifiers according to the projects in Headwize. One is A Pocket Headphone Amplifier (by Chu Moy) using OPA134 Op-Amp. The other one is "A class A MOSFET Headphone Driver" by Szekeres.
The Op-Amp based amplifier is grouded to Virtual Ground as in my case 6 V (I use 12 V power supply). The MOSFET driver ground is 0V, on the other hand. The Op-Amp amplifier and MOSFET driver use seperate power supplies.
The input/output of the Op-Amp amplifier are grounded to the virtual ground. While the input the MOSFET driver is grounded to 0 V. Since the MOSFET driver has a gain smaller than one, I use the Op-Amp amplifier to pre-amplify the signal.
I'm not quite sure if the grounding in this case is all right, although everything works when I connect them together.
The problem I have is that when there's nothing plugged into the input jacket of the Op-amp amplifier, there's a relatively high pitch noise. When I plug my laptop audio output into the Op-amp amplifier input, the noise disappears. The strange thing is that if I plug my Panasonic portable CD-player into the amplifier, the noise doesn't dissapear at all.
Could anyone explain me why this is happening and how to solve the problem.
Thanks!
The Op-Amp based amplifier is grouded to Virtual Ground as in my case 6 V (I use 12 V power supply). The MOSFET driver ground is 0V, on the other hand. The Op-Amp amplifier and MOSFET driver use seperate power supplies.
The input/output of the Op-Amp amplifier are grounded to the virtual ground. While the input the MOSFET driver is grounded to 0 V. Since the MOSFET driver has a gain smaller than one, I use the Op-Amp amplifier to pre-amplify the signal.
I'm not quite sure if the grounding in this case is all right, although everything works when I connect them together.
The problem I have is that when there's nothing plugged into the input jacket of the Op-amp amplifier, there's a relatively high pitch noise. When I plug my laptop audio output into the Op-amp amplifier input, the noise disappears. The strange thing is that if I plug my Panasonic portable CD-player into the amplifier, the noise doesn't dissapear at all.
Could anyone explain me why this is happening and how to solve the problem.
Thanks!