Jump to content

Is mild hum normal?


Klipschguy

Recommended Posts

My Mac 2105 has a very quiet hum (maybe 20dB) when I put my ear near the amp in a quiet room.  Is this small hum normal, or an indication I may have a leaky cap and need to have the unit serviced?  It is not audible in the speakers and does not change with volume.  Maybe somebody has a Mac they could put their ear close to?

  • Like 1
Link to comment
Share on other sites

All 60 Hz transformers hum. Some louder than others. Also the dimensions of the listening room can exacerbate the mechanical hum, you know standing waves and all that. Whether it bothers you is a matter of personal preference. It is the reason all my power amps are remoted to a utility room.

  • Like 2
Link to comment
Share on other sites

Okay, I feel better; thanks for the replies.  My new listening room is exceptionally quiet (less than 20dB) which is probably why I never noticed the transformer hum before. Fortunately the hum is not audible if you are more than about 2 feet way, even in a dead silent room. Fantastic amp, BTW.

  • Like 2
Link to comment
Share on other sites

Hi @Klipschguy

 

I have a MC 2125: there has been a very very slight buzzing in the speaker woofers for 15 years, but it has not changed: so I am monitoring. However, I have no noise from the MC2125 amplifier itself, no noise or hum in the shelf.

 

You can check if no screw or nut is loosened on your transformer itself or at its fixing on the frame.

  • Like 1
Link to comment
Share on other sites

6 hours ago, Klipschguy said:

My Mac 2105 has a very quiet hum (maybe 20dB) when I put my ear near the amp in a quiet room.  Is this small hum normal, or an indication I may have a leaky cap and need to have the unit serviced?  It is not audible in the speakers and does not change with volume.  Maybe somebody has a Mac they could put their ear close to?

Hum or buzz through the speakers can be a sign of bad or aging caps hum from the transformer is not too uncommon I'm not familiar with the Mac amps but sometimes on amps I have owned its the thin metal top cover that is actually amplifying the hum and in that situation a small piece of dynomat installed on the underside will take care of it.

  • Like 4
Link to comment
Share on other sites

Ok, I did a little more investigation. I think it may be something in the line. All of my components, except my turntable, have the same quiet, transformer hum (amp, pre-amp, tuner, sub).  I tried to turn everything off in the house with no change. I read about DC offset, but it’s role in transformer hum seems debatable.  
 

Since the hum is inaudible from any reasonable listening position and not present in the speakers, it should be fine. 
 

Andy

 

BTW Jjptkd, I suspect you have heard of McIntosh amplifiers; I just refer to their equipment as “Mac” - my apologies for the confusion. 

  • Like 1
Link to comment
Share on other sites

Well, just down here we have line surges at times from thunder storms, outages, etc.

I just use a $50 Belkin nothing too special.

Just as long I suppose that it does offer some some suge protection. Some conditioners are able to regulate, clean up some noise from electricity.

Have you tried a cheater plug on your Mac gear, just as a test...

  • Thanks 1
Link to comment
Share on other sites

Tripp/Lite make good surge protectors/noise filters.  I’ve been using two Isobar Ultras, a 6 (6-outlet) and an 8 (8-outlet).  As soon as I turned on the old CRT TV I was using at the time, I could see that the blacks were noticeably blacker, so that indicated something good was happening.  Wth the four Class D amplifiers I’m using (2 for the main front speakers and 2 for the subwoofers), I thought it would be a good idea to filter out any line noise they produced, and the Isobar Ultras seem to do that.   They’re designed to filter out line noise from printers in office applications in commercial use, and they serve me well.

 

They’re not that expensive, around $100 each.  They have steel housings and are compact.

 

As for hum, I ran into that when settling up the system.  The cause was having the system plugged into more than one circuit, since I wanted to spread out the load.  The cure was to run a ground wire from the turntable to the receiver (a good idea anytime) to the one power amp and then to the other power amp, but NOT TO GROUND!  You want to ground the components to each other, to compensate for the slight voltage difference between the wall circuits.  That’s all.  They should not be connected to building ground, other than through their 3-pronged power plugs.

  • Thanks 2
Link to comment
Share on other sites

5 hours ago, Klipschguy said:

I read about DC offset, but it’s role in transformer hum seems debatable.  

Toroids do not like DC offset at all. Your Mac is not a toroid. Its this one, right? I had one of these back in the day until it got stolen. Sumabitches.

 

2105.jpg

Have you recently changed abodes? I mean is your ambient environment quieter now? When i moved to my house out here in the sticks it was much quieter. The hum from equipment transformers drove me nuts. Unbeknownest to me i built a 2 channel room with perfect dimensions to  accentuate 60Hz hum. That's why i remoted all my amps. Many thanks to Bill Whitlock of Jensen Transformers helping me to figure out WTF was going on.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...