Jump to content
IGNORED

Looking for advice on mechanical hum


Recommended Posts

I'm looking for some advice. I have what I am assuming is transformer hum coming from my audio components. It's most prominently heard from my DAC (Lampizator Atlantic) though can also be heard from my amp (Classe CAP-2100) as well as a linear PSU (HDPlex).

I would describe the noise as a low pitched buzz or hum. It emanates from the components and is not heard through the speakers. The hum is present in the components even if everything is disconnected apart from the power cord. No hum when powered off. It's noticeable from the listening spot which is around 3-4 metres away. It doesn't seem to vary. It is present in the middle of the night also. I have tried different sockets in my house with no changes to the hum. I have not yet tried sockets outside my house but I will in a day or two.

I recently returned the DAC for testing and was assured that when tested there was no audible hum at all.

I have read into this to some degree but electronics is not my field. I have tried 2 different DC blockers (MCRU and ATL Hifi) and neither produced an audible difference. I also use a power conditioner (Audience AR4) but this has no effect on this noise.

Any insights or help here would be greatly appreciated.

There are 2 types of people in this world - those who understand binary and those who don't.

Link to comment
Share on other sites

The hum then is not through the speakers , so it is not a signal problem. 

 

I would attach a power scope to the AC and analyse the voltage waveform with intent on a harmonics up to the 31st should be enough.

 

if you have a ups even if it is small one to power up the amp and Dac separately and see what the hum does.

AS Profile Equipment List        Say NO to MQA

Link to comment
Share on other sites

I have exactly the same problem, although in my case it only affects one component.  But absolutely quiet when checked out (by me) at my dealer.  I'm told it's caused by "DC offset", but I have no idea what that is or how to remedy it.

Link to comment
Share on other sites

9 minutes ago, One and a half said:

The hum then is not through the speakers , so it is not a signal problem. 

 

I would attach a power scope to the AC and analyse the voltage waveform with intent on a harmonics up to the 31st should be enough.

 

if you have a ups even if it is small one to power up the amp and Dac separately and see what the hum does.

 

 Probably a little difficult for the average member to do though..

 Even the steel top/lid of the case which is a little too close to the top of the transformer can cause this.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

Link to comment
Share on other sites

3 hours ago, sandyk said:

 

 Probably a little difficult for the average member to do though..

 Even the steel top/lid of the case which is a little too close to the top of the transformer can cause this.

The hum affects three different components, all with transformers. When it's all three, there's got to be more than a mechanical resonance. Now if the hum had a different pitch and changed there maybe a clue as to what, but it hasn't.

 

For all three to hum and buzz, there are a few possibilities, without looking at the waveform, one can only make a smart guess. DC offset kits are just as dangerous to apply than the cause itself, so not recommended. Remove the source.

 

Can be anything from a lamp dimmer, flourescent, heater controller, or a really large SMPS, but not RF.

 

AS Profile Equipment List        Say NO to MQA

Link to comment
Share on other sites

Thanks for these replies.

 

5 hours ago, One and a half said:

The hum then is not through the speakers , so it is not a signal problem. 

 

I would attach a power scope to the AC and analyse the voltage waveform with intent on a harmonics up to the 31st should be enough.

 

if you have a ups even if it is small one to power up the amp and Dac separately and see what the hum does.

 

I agree that it is not likely a signal problem. I do not have a power scope, and as sandyk mentions, I fear that doing this would be beyond my level of expertise. I also do not have a UPS.

 

5 hours ago, Norton said:

I have exactly the same problem, although in my case it only affects one component.  But absolutely quiet when checked out (by me) at my dealer.  I'm told it's caused by "DC offset", but I have no idea what that is or how to remedy it.

 

It has been suggested to me also that it may well be DC on the mains, or DC offset. I have however tried at separate times 2 DC blockers, both feeding the power block and direct to the DAC - though neither made any difference in either configuration. Have you tried a DC blocker yourself?

 

5 hours ago, sandyk said:

 Even the steel top/lid of the case which is a little too close to the top of the transformer can cause this.

 

The same noise persists with the lid completely removed.

 

1 hour ago, One and a half said:

Remove the source.

 

Can be anything from a lamp dimmer, flourescent, heater controller, or a really large SMPS, but not RF.

 

 

Well, my understanding is that the sockets that my audio equipment is connected to is part of a ring circuit that does not include the large appliances - though I could be wrong. We do not have any dimmer switches or fluorescent bulbs. The noise was present in the middle of the night also. 

 

I will take the DAC to my work (which is around 4 miles away) and try there to see if a different power supply affects anything, and will report back.

 

There are 2 types of people in this world - those who understand binary and those who don't.

Link to comment
Share on other sites

I have the same issue and it seems to affect some transformers more than others. I assume it to be DC on my lines as it occurs in different locations in my home and on various audio devices to a varying extent. I cannot hear it from my listening position, or from my speakers, or headphones so I stopped pursuing it.


"Don't Believe Everything You Think"

System

Link to comment
Share on other sites

Interesting to hear mourip. Did you try plugging the devices in anywhere outside of your own property? Good you cannot hear it from the listening position - I can hear it, as long as the room is completely silent. It's one of those noises that a newcomer might not hear, though when you've heard it, you keep noticing it. 

There are 2 types of people in this world - those who understand binary and those who don't.

Link to comment
Share on other sites

 

My experience with this issue was primarily with Toroidal power transformers when they are connected to an AC line that has a DC imbalance due to other devices on the AC line that have uneven current usage... they use only the positive (or negative) side of the AC line thus the current draw is not equal on both sides of the AC signal.  Bryston for example on many of their power amps in the past used a "DC Block" circuit built in.  The issue being worse with non-iron core based transformers. 

 

It's been many years now since I've run across this issue.  I believe at the time I was involved, a few companies made external devices to eliminate it, 'not sure but no doubt someone still does.

 

I kept this old pix of two slightly different approaches in dealing with this.

DCblock.gif

Link to comment
Share on other sites

STC - interesting that your Classe amp had hum when voltage was more than 248V for a 230V rated device. When being tested at the manufacturer, they used up to 250V and still no hum was heard. 

 

rayooo - yes a few others have mentioned that DC on the AC line may be a potential cause. As mentioned above, I tried 2 different DC blockers (from MCRU and ATL Hifi) with no discernible benefit. 

 

one and a half - I think I have a standard multimeter in the garage - would this be suitable for measuring mains voltage from the plug? How do I do that? Yes, the problem was there before I got the AR4. I had wondered if the AR4 might have helped - it did deliver some sonic benefits, but did not affect the hum!

There are 2 types of people in this world - those who understand binary and those who don't.

Link to comment
Share on other sites

1 hour ago, zoltan said:

I had similar issues with one particular transformer. The only thing that helped was a PS AUDIO HUMBUSTER II. 'Nomen est omen' I guess. 

 

The Humbuster is effective indeed!

Triangle Magellan Concerto 2 < AQ Everest < Vitus Audio SS-010 Mk2 < AQ Dragon High Current < AQ WEL XLR < Chord Qutest DAC w UpTone JS-2 & AQ Dragon Source < AQ Diamond USB < Innuos Phoenix USB w AQ Dragon Source < Aurender N100H & AQ Dragon Source < NetGear GS105GE Switch w UpTone LPS1.2 < Supra CAT8 Ethernet < Gryphon PowerZone w AQ NRG-Wild < Stillpoints UltraSS, Ansuz Darkz D-TC & D2, Omicron Harmonic Stabilizer, Gold Evolution SE & Classic < Furutech FT-SWS (R) < Synergistic Research Orange Quantum Fuse < Solid Tech Hybrid < GigaWatt G-16A 2P Circuit Breaker

Link to comment
Share on other sites

@extracampine the meter should be capable of 300V or better, it is a digital type?

For UK sockets the orientation of the earth , neutral and active are:

top earth, clockwise next is active, clockwise next is neutral. 

 

Use the black probe and plug it into the earth. Take the red probe and connect to active.

this should read 230V. 

 

Move the red probe and connect it to neutral. This should read very low, less than 2V, mV is even better.

 

take both probes out and measure across active and neutral, the value should be the same as active to earth, 230V.

 

This is measured at the wall. Some outlets have a shutter that will prevent you sticking probes in and you won’t be able to make contact. In that case, a flying lead with bare ends needs to be fitted to a set of terminals to measure, a standard IEC 320 kettle lead would work as they have the inscription on the plug to tell you which is active, neutral and earth.

 

there is no need ever to touch the metal ends of the probes, always keep fingers at the other end of the probe!!!!

AS Profile Equipment List        Say NO to MQA

Link to comment
Share on other sites

21 minutes ago, One and a half said:

@extracampine the meter should be capable of 300V or better, it is a digital type?

For UK sockets the orientation of the earth , neutral and active are:

top earth, clockwise next is active, clockwise next is neutral. 

 

Use the black probe and plug it into the earth. Take the red probe and connect to active.

this should read 230V. 

 

Move the red probe and connect it to neutral. This should read very low, less than 2V, mV is even better.

 

take both probes out and measure across active and neutral, the value should be the same as active to earth, 230V.

Nominal voltage in the UK is 240 V.

 

21 minutes ago, One and a half said:

This is measured at the wall. Some outlets have a shutter that will prevent you sticking probes in and you won’t be able to make contact. In that case, a flying lead with bare ends needs to be fitted to a set of terminals to measure, a standard IEC 320 kettle lead would work as they have the inscription on the plug to tell you which is active, neutral and earth.

The shutter is released by inserting something in the ground (top) terminal. No need for dangerous flying leads. The kettle lead is a good option though.

 

Link to comment
Share on other sites

9 hours ago, extracampine said:

Interesting to hear mourip. Did you try plugging the devices in anywhere outside of your own property? Good you cannot hear it from the listening position - I can hear it, as long as the room is completely silent. It's one of those noises that a newcomer might not hear, though when you've heard it, you keep noticing it. 

 

Sorry. I have not tested at another location.


"Don't Believe Everything You Think"

System

Link to comment
Share on other sites

7 minutes ago, One and a half said:

240V must be due to Brexit then 

It has always been 240 V. There was an EU-wide "harmonisation" back in the 90s, but the tolerances were set such that nobody actually had to change anything. Replacing all the affected grid equipment would have been far too costly.

Link to comment
Share on other sites

Despite the DC blockers not helping, I still reckon it is DC offset. And mind you, the SMPS of a PC can easily cause the problem. So my idea : switch off all the PCs you have around and see what happens.

In the end it can be any power supply, even one in your audio chain. Thus, start out with switching all off and then switch on your DAC only. Next switch off your DAC and then switch on your amp as the only one. If by this means all from your audio chain stays quiet, you are assured that at least it's not in the audio chain itself. Now switch on all of the audio chain to be sure it's not a reactance to each other. Still quiet ? now start switching on all else in the house and better start with the fridge. x-D

 

Assumed you could get it quiet with the above procedure, also take care that you listen carefully and closely per device switched on. I mean, each device will change the potential somewhat (the ground reference of the mains) which in the end is DC offset when you use two mains rings for the audio (with separate earth). So it can well happen that each device contributes a little until it gets too much for the transformers and they saturate (which causes the mechanical hum).

 

If you find it is in the audio chain itself, remove your USB isolator(s) for a test (assumed you have that).

Lush^3-e      Lush^2      Blaxius^2      Ethernet^2     HDMI^2     XLR^2

XXHighEnd (developer)

Phasure NOS1 24/768 Async USB DAC (manufacturer)

Phasure Mach III Audio PC with Linear PSU (manufacturer)

Orelino & Orelo MKII Speakers (designer/supplier)

Link to comment
Share on other sites

zoltan - I have seen the PS Audio Humbuster mentioned. I beleive that it is out of production and hard to find. If it worked, then surely there should be an equivalent product elsewhere?

 

As I mentioned, I have already tried 2 DC blockers, neither of which seemed to affect the hum very much.

 

One and a half/mansr - I will test the mains voltage and report back

 

Peter - interesting that you still reckon that it is DC offset, despite my 2 DC blockers not working. Do you think they were ineffective? The MCRU one was not cheap - around £350 or so I think. I do not have any PCs that run off SMPSs. The audio PC has a linear PSU from HDPLEX (which I have switched off, but this made no difference).

 

Regarding switching things off around the house - I can open the circuit breaker for all circuits in the house except the ring circuit that the hifi is on, and disconnect everything from that circuit apart from the DAC, to make sure that it is only the DAC that is drawing power in the house - is that what you mean? If I get it quiet with this procedure I would be overjoyed! What do you mean by USB isolator? Don't think I have one of those. My music is in another room on a NAS which connects to the audio PC in the listening room via ethernet; that then connects to the DAC via USB.

 

The only thing is, I could switch everything off in the house, but couln't it be a neighbours appliance that is affecting our mains? Can't really ask them to switch all their appliances off every time I want to listen to music :D

There are 2 types of people in this world - those who understand binary and those who don't.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share



×
×
  • Create New...