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Luxman Class A Integrated Slight Buzzing Noise

Hello--

I just purchased my first class A amp--a Luxman 550ax--from an AG member recently. I noticed this morning that when I get close to the amp while it is turned on there is a slight buzzing noise coming from the unit. If looking directly at the top of the unit it seems to be coming from the right middle of the unit. Doesn't seem to affect anything with my Harbeth speakers and I only hear it from a couple feet away. I was wondering if this is normal for a class A amp. Anyone with a 550 or 590 have this issue? Any ideas what could be causing it? I have it plugged into a Richard Gray 400 Power Center using the stock Luxman two prong JPA1000 polarized power cord.

Sources are a PC connected USB to a Fostex HPA8C DAC connected to the Luxman with Transparent Audio Link 100 RCA cables.

Thanks,

Dave
ddinkel
erik_squires
16,839 posts
 
Well, this is a 3 year old thread, but usually excess mechanical hum is caused by DC on the line.

DC can be caused by dimmer switches, and a variety of digital power supplies, including PC's and fluorescent light supplies.

Removing the cause, or using a balanced power conditioner (including regenerators) will work. Sometimes you may have to go to your AC panel and turn off every single circuit that isn't your stereo to find this.

Best,
E
twoleftears's avatar
twoleftears
5,326 posts
 
Well, yes and no.  *Some* hum is caused by a ground loop, and *some* hum is caused by DC on the line, and both of these are cured fairly easily.  Check out this guide.

https://www.psaudio.com/ps_how/how-to-find-and-fix-hum/ 

However, there are *plenty* of instances where these fixes and others will not touch the hum.  Usually it has to do with the design or quality of manufacture of the transformer, or some strange interaction between the transformer and your AC.

There were a number of reports on the net of Luxman integrateds humming; if it weren't for this I would probably own one right now.  It you get this far, it's usually not fixable.  Live with it or move on.

See also the discussion somewhere in the thread "ask Ramtubes a question".
erik_squires
16,839 posts
 
Well, yes and no. *Some* hum is caused by a ground loop, and *some* hum is caused by DC on the line, and both of these are cured fairly easily.

You missed the key adjective. "Mechanical". This means that something in the equipment is physically vibrating. This can be heard even with no speakers in the room. I know of no instance when this is caused by ground loops. If you do, this will be a novel situation for me.



Best,
Erik

builder3
776 posts
 
I'll chime in, but can't offer any help. My L-590AX is dead quiet. It's also the same piece that greginnh owned above, in August, 2015.
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