I bought the amp used from USAM and received it today then proceeded to set it up.
Set up consists of:
Parasound A21+
Rogue RH-5 preamp
Yamaha CD-S1000
NAD C658 DAC/pre
Mirage M760 speakers
A mix of AQ Water and Acoustic Zen Matrix Reference interconnects
Zu Audio speaker cables
As soon as I powered it up there was a very apparent and loud hiss coming from the right speaker. Left speaker is quiet.
I replaced the speaker cables and checked all connections. Hiss still present.
I used both balanced and unbalanced cconnections. Hiss still present.
I used multiple sets of balanced and unbalanced cables. Hiss still present.
I put in place a new set of speakers. Hiss is still present.
I swapped out the preamp. The hissing is still present.
I replaced the A21+ with my Pass Labs XA-25. Hissing sound is gone.
It is loud enough my wife could hear it in the next room, she has very sensitive ears. Unless you are aware of something I am not I cannot fathom where the problem lies.
I know enough to be dangerous about working on these electronic devices so I don't want to accidentlly blow something up.
Any insight from the significantly more experienced will be greatly appreciated.
Jay
Set up consists of:
Parasound A21+
Rogue RH-5 preamp
Yamaha CD-S1000
NAD C658 DAC/pre
Mirage M760 speakers
A mix of AQ Water and Acoustic Zen Matrix Reference interconnects
Zu Audio speaker cables
As soon as I powered it up there was a very apparent and loud hiss coming from the right speaker. Left speaker is quiet.
I replaced the speaker cables and checked all connections. Hiss still present.
I used both balanced and unbalanced cconnections. Hiss still present.
I used multiple sets of balanced and unbalanced cables. Hiss still present.
I put in place a new set of speakers. Hiss is still present.
I swapped out the preamp. The hissing is still present.
I replaced the A21+ with my Pass Labs XA-25. Hissing sound is gone.
It is loud enough my wife could hear it in the next room, she has very sensitive ears. Unless you are aware of something I am not I cannot fathom where the problem lies.
I know enough to be dangerous about working on these electronic devices so I don't want to accidentlly blow something up.
Any insight from the significantly more experienced will be greatly appreciated.
Jay
If you unplug the inputs, power up the Parasound A21+ only with speakers connected, does hiss still present?
Try swapping left and right on the input. If the issue moves from one channel to the other, the issue is with the source. If the hiss remains in the right channel the amp is the issue.
This doesn't sound like a cable issue. If the issue is with the amp - and it probably is as you tried another amp already - the issue is with the electronics. I'd let the seller know and explore options for returning the amp. You can get the schematics from Parasound and try to fix it, but I doubt it'll be a simple fix.
I had a Parasound A23 for a while. It was dead quiet. Well... Except for a crackle every now and then but that was due to water damage. I was give the amp and tried my best to fix it. I managed to get it running ... except for that darn crackle. I never got that crackle resolved and ended up gutting the chassis and reusing the power supply and other sundry items. Your A21 should be quiet.
Tom
This doesn't sound like a cable issue. If the issue is with the amp - and it probably is as you tried another amp already - the issue is with the electronics. I'd let the seller know and explore options for returning the amp. You can get the schematics from Parasound and try to fix it, but I doubt it'll be a simple fix.
I had a Parasound A23 for a while. It was dead quiet. Well... Except for a crackle every now and then but that was due to water damage. I was give the amp and tried my best to fix it. I managed to get it running ... except for that darn crackle. I never got that crackle resolved and ended up gutting the chassis and reusing the power supply and other sundry items. Your A21 should be quiet.
Tom
Yes. Without any inputs the hissing still exists. Thanks for your input.
Last edited:
Try if turn the "Gain" knob from Min. to Max. and the "Turn On Options" Audio or Manual setting make any difference?
I bid on a Parasound, lost auction at $180 for 80 w/ch. You did better than that you got a discount for a problem.
Hiss repair is time consuming. You have to have a sound probe or oscilloscope. You go through the channel from the back forwards, looking at each output pin to see if the hiss is still there. Where the hiss disappears, the stage after that is the problem. Then you replace parts at the bad stage. Most likely a resistor, although transistors diodes & least likely capacitors are all possible. Not a good problem to start learning to repair amps. Plus if you use a regular 3/4" metal probe, amateurs often cross two pieces of metal and blow up something. I use pamona grabbers myself, scope probes are $50 if I step on it.
Warning to newbies, use only one hand at a time with the power on. >24 v across your heart can stop it. No jewelry on hands wrists or neck. 1 v at high amps through a ring can burn your flesh to charcoal. Wear safety glasses, parts sometimes explode. An incandescent bulb series the AC input (60 w typically) can limit the energy of mistakes.
Hiss repair is time consuming. You have to have a sound probe or oscilloscope. You go through the channel from the back forwards, looking at each output pin to see if the hiss is still there. Where the hiss disappears, the stage after that is the problem. Then you replace parts at the bad stage. Most likely a resistor, although transistors diodes & least likely capacitors are all possible. Not a good problem to start learning to repair amps. Plus if you use a regular 3/4" metal probe, amateurs often cross two pieces of metal and blow up something. I use pamona grabbers myself, scope probes are $50 if I step on it.
Warning to newbies, use only one hand at a time with the power on. >24 v across your heart can stop it. No jewelry on hands wrists or neck. 1 v at high amps through a ring can burn your flesh to charcoal. Wear safety glasses, parts sometimes explode. An incandescent bulb series the AC input (60 w typically) can limit the energy of mistakes.