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SE84C Power Supply Hum (Read 1712 times)
BWR
Ex Member



SE84C Power Supply Hum
05/12/06 at 22:57:22
 
Over the last 6 months the hum seems to have increased. I use the amp with M&K nearfield monitors at my PC at work. I'm about an arm's length away from the speakers.

Initially the amp seemed to be very quiet. After a couple of months I started noticing the hum after shutting down my PC at the end of the day. Now the hum can easily be heard above the sound of the running PC.

Anyone else experiencing this and any solutions?

Thanks,

Bob
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Hotsauce
Ex Member



Re: SE84C Power Supply Hum
Reply #1 - 05/13/06 at 00:29:44
 
Have you tried new tubes?  Especially the rectifier.  I've had several chinese rectifiers hum after a few months use.

John C.

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selmerdave
Ex Member



Re: SE84C Power Supply Hum
Reply #2 - 05/13/06 at 02:36:26
 
I have the same problem with my PC, but I'm not using my Zen with them.  I use a set of Bose Roommates with the computer, and they have a high gain setting and a low gain setting.  Especially on the high gain setting, when I shut down the computer I get a pretty nasty buzz/hum that remains until I turn it on again (or more often disconnect them).  So my guess is it's a computer thing and has nothing to do with your Zen, the easy way would be to disconnect the computer from the amp and see if it's still making the same sound.

Dave
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BWR
Ex Member



Re: SE84C Power Supply Hum
Reply #3 - 05/13/06 at 04:30:44
 
No, I haven't swapped out any tubes. Hoping I wouldn't have to.

+++++++++

I should have been more clear... I don't have the amp sourced from the PC. I use a standalone Cambridge Audio CD player as the source. So it's not related to the PC and it's not related to the source at all. With nothing else in the system powered up except the amp I get a steady hum. I'm assuming its coming from the power supply, since it's not gain related.
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ado420
Ex Member



Re: SE84C Power Supply Hum
Reply #4 - 05/13/06 at 17:21:06
 
[quote author=selmerdave  link=1147474642/0#2 date=1147484186]I have the same problem with my PC, but I'm not using my Zen with them.  I use a set of Bose Roommates with the computer, and they have a high gain setting and a low gain setting.  Especially on the high gain setting, when I shut down the computer I get a pretty nasty buzz/hum that remains until I turn it on again (or more often disconnect them).  So my guess is it's a computer thing and has nothing to do with your Zen, the easy way would be to disconnect the computer from the amp and see if it's still making the same sound.

Dave [/quote]
Acutally Dave, it sounds like it has EVERYTHING to do with your speakers and nothing to do with your computer, other than maybe the chassis ground of your computer. I used to have a similar problem with my T-Amp after turning off my pre-amp, and then I remembered something I learned in school about FET's with unconnected inputs oscillating wildly. If it increases in intensity and pitch after the PC has been turned off, you might need to revise your grounding scheme in that case, as that is how I got rid of it.

Or turn the speakers off beforehand, but I'm sure you already knew that.


Unconnected hum eh? Could be a ground loop, more likely noisy ground in your house/area. Maybe an Isolation Transformer could help you, or some kind of line conditioner.

Hope that helped,
Ado
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Sam in CR
Ex Member



Re: SE84C Power Supply Hum
Reply #5 - 05/13/06 at 18:20:02
 
[quote author=Hotsauce  link=1147474642/0#1 date=1147476584]Have you tried new tubes?  Especially the rectifier.  I've had several chinese rectifiers hum after a few months use.

John C.

[/quote]

Ditto.
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selmerdave
Ex Member



Re: SE84C Power Supply Hum
Reply #6 - 05/13/06 at 23:05:59
 
[quote author=ado420  link=1147474642/0#4 date=1147537266]
Or turn the speakers off beforehand, but I'm sure you already knew that. [/quote]

Well, they don't have a power switch, I think they're meant to be "on" at all times.  I just don't use the high gain setting unless I need to, that's about as much as I care to do with this problem.  But thanks for the suggestions Ado, if I have more problems or feel motivated I'll try to fix it.

Dave
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