I recently acquired a Parasound Zamp V1 used, and it has a constant loud hum at what sounds like 120 Hz to me. The hum is in both channels and is there even when only a speaker(s) on either or both channels is connected in addition to AC power (no input is required for the hum). The hum is reduced when I connect an input via the pre-out on my NAD C372 (which I've never had this issue through and still don't using its amplifier stage instead of the Zamp), and I can increase/decrease the volume of the hum by adjusting the level for each channel with the knob on the back of the unit. I tried plugging it in in a totally different room that is on a different circuit as well, but that did not make any difference.
I noticed that immediately when I plug the amp in with speakers connected, the hum starts quiet and then gets louder over the course of a few seconds -- this leads me to wonder if this might be caused by bad capacitors since this is about the same time period that, based on labs in the physics class I had a few years ago, a larger capacitor seems to take to reach capacity/equilibrium.
Any thoughts on how I could fix this? Does my theory about the caps make sense, or are there any other ideas anyone has?
Thanks!
I noticed that immediately when I plug the amp in with speakers connected, the hum starts quiet and then gets louder over the course of a few seconds -- this leads me to wonder if this might be caused by bad capacitors since this is about the same time period that, based on labs in the physics class I had a few years ago, a larger capacitor seems to take to reach capacity/equilibrium.
Any thoughts on how I could fix this? Does my theory about the caps make sense, or are there any other ideas anyone has?
Thanks!
Check the input sockets and level controls carefully, because the ground connection(s) may be loose,
have a bad solder joint, etc. If these are good, then the main filter capacitors may be bad.
Main filter cap could be bad, or simply cracked free of its solder.
120Hz points to power supply ripple. grounding hum and induced hum tends to be 60Hz.
120Hz points to power supply ripple. grounding hum and induced hum tends to be 60Hz.
The ground connections and all solder joints look good, so I've ordered Nichicon replacement caps for all of the electrolytics on the board. Thank you guys for the suggestions, I'll let you know how it goes when they get here in a few days!
It's fixed. The culprit ended up being a 100 uF 50V cap right next to the power input on the circuit board.
Anyone have any thoughts on whether to replace the rest of them or not? I bought all high quality Nichicon caps, but I would think Parasound would use good high quality ones stock anyway given the typical quality of their products.
Thank you all for the help!
Anyone have any thoughts on whether to replace the rest of them or not? I bought all high quality Nichicon caps, but I would think Parasound would use good high quality ones stock anyway given the typical quality of their products.
Thank you all for the help!
Update: I listened for about 15 minutes during which things sounded great, went to switch over to a different set of speakers (turned everything off for safety first), and after that the right channel had very distorted sound, or no sound when playing at low level, as if there was a bad RCA connection that was barely making connection or something. Checked everything over and tested to isolate the issue to the amp, and sure enough the right channel now always is incredibly distorted after I had the amp working perfectly for about 15 minutes.
Tried replacing the rest of the electrolytic caps on the board since I had them on hand anyway, but no improvement. When I was switching speakers, I did adjust the R/L levels slightly with the two knobs that were on the back of the unit (looked like transistors), so not sure if that might've caused an issue.
Anyone have any ideas why the right channel would suddenly get all distorted like that?
Tried replacing the rest of the electrolytic caps on the board since I had them on hand anyway, but no improvement. When I was switching speakers, I did adjust the R/L levels slightly with the two knobs that were on the back of the unit (looked like transistors), so not sure if that might've caused an issue.
Anyone have any ideas why the right channel would suddenly get all distorted like that?
Very old post but I got one of this one eBay, you know the typical I found it in my father's attic and I don't know anything about it, I don't have a power cord so I cannot test it, blah, blah blah...
So the first thing I noticed is that there was no fuse installed in it but the fuse holder had signs of melting so I decided to install a bigger fuse than the recommended one and I noticed smoke coming from the outputs even with the switch turned OFF, any ideas what could be causing this behavior?
So the first thing I noticed is that there was no fuse installed in it but the fuse holder had signs of melting so I decided to install a bigger fuse than the recommended one and I noticed smoke coming from the outputs even with the switch turned OFF, any ideas what could be causing this behavior?
Just picked one of these up, recently. The owner warned me that the Auto-on-off no longer functions, and the unit must be unplugged to turn it on and off. Hooked the thing up, and it has massive hum in both channels. The owner swears he's been using it, and it must be a ground loop issue, which is wholey possible as I use my PC to a USB audio interface to my headphone amp, which is all powered on the same power strip.
Either way, I opened the chassis up and whatta ya know, the only visibly bad cap happens to be tied to the trigger circuit for power up. However, TEAPO are notorious for showing no signs of failure despite failing. So off to Digi-Key I go!
Either way, I opened the chassis up and whatta ya know, the only visibly bad cap happens to be tied to the trigger circuit for power up. However, TEAPO are notorious for showing no signs of failure despite failing. So off to Digi-Key I go!
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It's just that glue they sling at the bigger radials, but its gone brittle now, and could be conductive. Best believe I'll clean the PCB up while the caps are out.
Well, I replaced all the electrolytics and it didn't blow up. However, it still has a constant hum in the left channel (I'm only hooking headphones up to it) that is not affected by volume nor whether any audio cables are hooked up or sound is playing. Also, there is no audio output in the left channel while playing music, only the hum remains. I do get audio on the right channel.
The only puzzling part of this whole process was a single capacitor, which had a silkscreen for a bipolar electrolytic, but I took a polarized electrolytic out, and put one back in the way it was oriented before the replacement.
Next, I will try hooking up a pair of speakers to see if I still get hum. I'm unclear how the amp deals with the headphone jack being TRS, while the speaker output has separate positives and negatives. Perhaps, the relay on the PCB is bad, causing my problem?
The only puzzling part of this whole process was a single capacitor, which had a silkscreen for a bipolar electrolytic, but I took a polarized electrolytic out, and put one back in the way it was oriented before the replacement.
Next, I will try hooking up a pair of speakers to see if I still get hum. I'm unclear how the amp deals with the headphone jack being TRS, while the speaker output has separate positives and negatives. Perhaps, the relay on the PCB is bad, causing my problem?