Hello!
I just finished a channel on my P3a amp and I get a loud hiss. Just to clarify, when I say hiss, I mean the sound of an FM tuner that is not on a station, or the sound of air between your teeth. The "sss" sound in the letter ess.
I only hear this when I take the input from my PC sound card. I don't hear it when I input something like a portable MP3 player. Knowing this, I thought there was a ground loop, so I disconnected the input shield from ground. This didn't help. I even tried disconnecting the star ground from the chassis (earthed). didn't work.
I'm using an Avel transformer: Parrallel input and Series output (Red and Orange as CT). Dual Power supply. I'm pretty sure I have the transformer wired right, but please make suggestions if you think otherwise.
I'm using ESP's Dual Power Supply design: http://sound.westhost.com/project04.htm
Please let me know if you have any suggestions as to what this might be. or how I can fix it.
Thanks!
I just finished a channel on my P3a amp and I get a loud hiss. Just to clarify, when I say hiss, I mean the sound of an FM tuner that is not on a station, or the sound of air between your teeth. The "sss" sound in the letter ess.
I only hear this when I take the input from my PC sound card. I don't hear it when I input something like a portable MP3 player. Knowing this, I thought there was a ground loop, so I disconnected the input shield from ground. This didn't help. I even tried disconnecting the star ground from the chassis (earthed). didn't work.
I'm using an Avel transformer: Parrallel input and Series output (Red and Orange as CT). Dual Power supply. I'm pretty sure I have the transformer wired right, but please make suggestions if you think otherwise.
I'm using ESP's Dual Power Supply design: http://sound.westhost.com/project04.htm
Please let me know if you have any suggestions as to what this might be. or how I can fix it.
Thanks!
/sreten.
Hi blap0220,
Each system has it's unique characteristics and susceptibilities. Most commercial products are engineered for maximum immunity to noise like this. It's entirely possible for another brand to make noise like crazy. Just accept the fact that computers are known to be noisy little fellas. They even came out with spread spectrum clocking to reduce the noise power at any one frequency to help get around noise emission codes(electrical emi).
If your amplifier has a high enough bandwidth, it may react easier to this type of noise. Why not try an RC network on your input right at the jack to limit the bandwidth of your input signal? That may cure it.
-Chris
'cause.
Each system has it's unique characteristics and susceptibilities. Most commercial products are engineered for maximum immunity to noise like this. It's entirely possible for another brand to make noise like crazy. Just accept the fact that computers are known to be noisy little fellas. They even came out with spread spectrum clocking to reduce the noise power at any one frequency to help get around noise emission codes(electrical emi).
If your amplifier has a high enough bandwidth, it may react easier to this type of noise. Why not try an RC network on your input right at the jack to limit the bandwidth of your input signal? That may cure it.
-Chris
The P3A does already have an ultrasonic filter formed with the 220pF capacitor on the input. It's -3dB down at about 360KHz.
I'd check the components on the input. The 220pF should ideally be a polypropylene and not a ceramic, although a monores ceramic might be ok here.
To try the steeper filter idea out, change it to 470pF for a cutoff at about 170KHz.
I'd check the components on the input. The 220pF should ideally be a polypropylene and not a ceramic, although a monores ceramic might be ok here.
To try the steeper filter idea out, change it to 470pF for a cutoff at about 170KHz.
Hi jaycee,
I'm thinking that the garbage coming out of the computer sound card may come in at 96 KHz, possibly lower. This is not a good situation. 44.1 KHz stuff would be much more difficult to get rid of. It may also be beating against power supply noise. $20 power supply, I wouldn't be surprised if this were to occur.
-Chris
I'm thinking that the garbage coming out of the computer sound card may come in at 96 KHz, possibly lower. This is not a good situation. 44.1 KHz stuff would be much more difficult to get rid of. It may also be beating against power supply noise. $20 power supply, I wouldn't be surprised if this were to occur.
-Chris
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