Amplifier Humm and hiss from speakers

[EshDes]

HI All

 

looking for some advice - noticed a humm from a power amplifier purchased recently and also while connected to speakers there is a low hiss sound from both speakers.

I have tried different speakers, different jumper cables and  switched amps. The hiss from the speakers is still there...however its the power amp that still has the humming noise.

I took the power amp away from all other items and plugged it in a different area and still hear the humming noise. Is this normal? Do I need to get it serviced? or is it result of poor current?

Would a DC blocker help? once I have heard distortion come through the speakers (very rare occurrence) (crackling noise). 

 

Or is there some generous person out there that would be willing to loan me a DC blocker for a day so I can check whether the problem goes away? and then eliminate the possibility of crappy power? 

 

Any advice would be appreciated.

 

Kind Regards

 

Eshan

Edited October 28 by EshDes

[muon*]

If the hum is a from the power transformer of the amp try and borrow a DC blocker and see if it helps.

[Hydrology]

As @muon* suggested check out a DC blocker - there should be plenty of Melbourne dealers who could loan you a unit for proof of concept. You haven't mentioned what amp you have (make/model) nor if you have reached out to the store (if bought new) or original owner (if bought secondhand). Also, what speakers you have.

[EshDes]

18 minutes ago, Hydrology said:

As @muon* suggested check out a DC blocker - there should be plenty of Melbourne dealers who could loan you a unit for proof of concept. You haven't mentioned what amp you have (make/model) nor if you have reached out to the store (if bought new) or original owner (if bought secondhand). Also, what speakers you have.

Hi - I recently bought a Vincent SP994 from Stereonet - my speakers Monitor Audio 100g V6, EPOS M22, Audiolab MDac+ (using as pre), Blusound Node N130, and my former integrated is a Rega Elex R and Rega P1 turntable. Yeah I am going to and see whether A2A and see whether they will loan a unit.

[andyr]

1 hour ago, EshDes said:

HI All

 

looking for some advice - noticed a humm from a power amplifier purchased recently and also while connected to speakers there is a low hiss sound from both speakers.

I have tried different speakers, different jumper cables and  switched amps. The hiss from the speakers is still there...however its the power amp that still has the humming noise.

I took the power amp away from all other items and plugged it in a different area and still hear the humming noise. Is this normal? Do I need to get it serviced? or is it result of poor current?

Would a DC blocker help? once I have heard distortion come through the speakers (very rare occurrence) (crackling noise). 

 

Or is there some generous person out there that would be willing to loan me a DC blocker for a day so I can check whether the problem goes away? and then eliminate the possibility of crappy power? 

 

As @muon* suggested, if it's the power amp's power transformer which is buzzing ... this could well be caused by DC on your mains.  (Do you - or a neighbour - have solar power installed?)

 

As you seem to be in Melbourne, I can lend you one of my 'DCbloks'.  (I live 500m from A2A in Richmond.)

 

Please PM me if you're interested.

 

Andy

 

[EshDes]

3 minutes ago, andyr said:

 

As @muon* suggested, if it's the power amp's power transformer which is buzzing ... this could well be caused by DC on your mains.  (Do you - or a neighbour - have solar power installed?)

 

As you seem to be in Melbourne, I can lend you one of my 'DCbloks'.  (I live 500m from A2A in Richmond.)

 

Please PM me if you're interested.

 

Andy

 

I just got solar installed.

[Benje]

If you want to determine if it is the solar, you could turn the solar off at both the unit and switchboard.  See if the buzz persists.

 

There should be detailed instructions with your install pack about how to turn the solar on and off, ie disconnecting/reconnecting the solar.  Follow this diligently.

 

Benje

[Ryehifi]

I had a similar problem with my last stereo and house.

 

I purchased one of these and it worked well.

 

https://addictedtoaudio.com.au/products/ifi-audio-gnd-defender?variant=39246916059270&utm_content=blend_feed&utm_medium=blend&utm_source=google&currency=AUD&utm_source=google&utm_medium=blend&utm_campaign=35709&gad_source=1&gbraid=0AAAAADmblwJjipCjwigntBgzQlxIIu91Q&gclid=Cj0KCQjw7Py4BhCbARIsAMMx-_K14BrnryNvAn5b2o4u34QIpGDFB0iH7mnhhWcFn3xSwWFAfPp3IzoaAoAWEALw_wcB 
 

[EshDes]

Hi All

 

Turned off the solar and then listened in again - dont know whether its my imagination but the humm had audibly decreased. So thanks for the tip!

I will go down the path of testing out a DC blocker that's been kindly offered....and then make a decision around what DC blocker to get.

 

Audiolab DC blocker and IFI come to mind...still wondering which to get - but leaning towards the IFI as it means I dont have to get new cables compared to the Audiolab.

[muon*]

19 minutes ago, EshDes said:

Hi All

 

Turned off the solar and then listened in again - dont know whether its my imagination but the humm had audibly decreased. So thanks for the tip!

I will go down the path of testing out a DC blocker that's been kindly offered....and then make a decision around what DC blocker to get.

 

Audiolab DC blocker and IFI come to mind...still wondering which to get - but leaning towards the IFI as it means I dont have to get new cables compared to the Audiolab.

Also consider one of Andy's units.

[EshDes]

Hi All

 

A big thank you to AndyR for lending me a dc blocker. Didnt solve the issue - not the units problem. Noticed that the Amp running in Class AB rather than class A was quieter. But the hiss from the speakers is there. I think its a ground loop issue...wonder if there is anyone than can lend me a Grounding device to test that option out before I take the Amp for a service?

[mbz]

Did you actually measure the frequency of the hum, ie, mains 50Hz or rectified 100Hz, expect 50Hz since 100Hz is more of a buzzzz.. mobile phone ap like spectriod or pc freeware like audacity or ... can measure.

 

50Hz could be ground loop or...

100Hz is amp internal, like failed(short) voltage regulator or...

 

[EshDes]

Thanks. A stereoent member just lent me a ifi ground defender the hum is there and so is the white noise from the speakers. Also trying balanced cables to see whether that sorted it. But unfortunately not the case. So I will give this a go and see what it might be. Thanks all! Appreciate all the advise.

[EshDes]

Hi All

 

Does anyone know a good amplifier service person to reach out to? Cheers

[Robertoh]

On 02/11/2024 at 12:05 PM, mbz said:

Did you actually measure the frequency of the hum, ie, mains 50Hz or rectified 100Hz, expect 50Hz since 100Hz is more of a buzzzz.. mobile phone ap like spectriod or pc freeware like audacity or ... can measure.

 

50Hz could be ground loop or...

100Hz is amp internal, like failed(short) voltage regulator or...

 

Just out of ignorance and curiosity, how would one measure the audible frequency? Is this possible to do with a smartphone app or similar?

 

I have a hum on my stereo set-up that is much more audible when my amp is on its phono setting than when switched to the other inputs. The hum remains when the amp is on the other inputs, just a lot quieter.

 

I suspect interference either from the mains or from plug-in transformers for other devices nearby, such as the Nbnco modem, WiFi router, Fetch box, etc.  I think I have to just methodically work through unplugging the suspects one by one to identify the culprit(s), and/or check whether the problem occurs if the amp is in a different room.

 

Running the audio gear from the filtered and protected outlets of a Thor A12BF smart power board doesn't seem to have helped eliminate the problem.

 

No solar PV at my (rented) abode.

 

Thanks for any suggestions. Cheers

[Steff]

15 minutes ago, Robertoh said:

Is this possible to do with a smartphone app or similar?

Yes you can install a spectrum analyzer app --these are often free (with ads).

The degree of accuracy will not be 100% but you will get a ballpark sense of the wave length of the noise.

 

Isn't it the case that the phono preamp internal has a higher gain (sensitivity) than the other elements of your integrated thus likely amplifying the hum more strongly?

50hz might not be easy to hear, 100hz much more so.

Sounds like it's the amp itself--have you got another one to plug in?

And/or plug the amp into another house's electrical outlet.

Edited Friday at 06:06 AM by Steff

[Robertoh]

19 minutes ago, Steff said:

Yes you can install a spectrum analyzer app --these are often free (with ads).

The degree of accuracy will not be 100% but you will get a ballpark sense of the wave length of the noise.

 

Isn't it the case that the phono preamp internal has a higher gain (sensitivity) than the other elements of your integrated thus likely amplifying the hum more strongly?

50hz might not be easy to hear, 100hz much more so.

Sounds like it's the amp itself--have you got another one to plug in?

And/or plug the amp into another house's electrical outlet.

Thanks for super-rapid and helpful reply @Steff. I have another amp I can try, just too lazy to get down to do the unplug/replug/fight with the speaker cables task yet. I seem to recall a similar issue with the other amp in that location, but it's not been used for nearly two years and my memory is definitely fallible. 

 

Yes, I suspected the underlying problem may be amplified more by the gain in the phono pre-amp, rather than the amp itself. If there was an issue with turntable grounding, would that be audible with the turntable motor not running?

 

In short term, the treatment is just to get another record on, asap, and get on with listening to music, not listening "out" for hums without music .....

Edited Friday at 06:20 AM by Robertoh

[Steff]

It's a labour of love, for sure. I would proceed the other way, unplug everything but the amp, and then add things one by one. Including your RCA cables, etc.

Yes, I think an issue can arise from the tone arm cables also, this might not require its motor running - if you work out it's indeed the turntable side of things...there are plenty of knowledgeable folks here who can advise with clarity and experience (of whom I am not one)! But since you hear the hum for the other inputs, too, it points away from the phono side.

Edited Friday at 06:32 AM by Steff

[andyr]

55 minutes ago, Robertoh said:

I have a hum on my stereo set-up that is much more audible when my amp is on its phono setting than when switched to the other inputs. The hum remains when the amp is on the other inputs, just a lot quieter.

 

That's standard.

 

Although if you can still hear some 'hum' when you select other (non-phono) inputs ... that's a bit concerning.  In my setup - with my ears right up against tweeter & mid-bass drivers:

• I hear absolutely nothing ... when non-phono inputs are selected
• and a slight bit of hiss from the tweeter & hum from the mid/bass drivers ... when phono is selected.

 

55 minutes ago, Robertoh said:

I suspect interference either from the mains or from plug-in transformers for other devices nearby, such as the Nbnco modem, WiFi router, Fetch box, etc.  I think I have to just methodically work through unplugging the suspects one by one to identify the culprit(s), and/or check whether the problem occurs if the amp is in a different room.

 

I would agree with Steff's methodology:

 

28 minutes ago, Steff said:

I would proceed the other way, unplug everything but the amp, and then add things one by one. Including your RCA cables, etc.

 

 

[mbz]

2 hours ago, Robertoh said:

mobile phone ap like spectriod or pc freeware like audacity or ... can measure.

Suggest measure the frequency, rectified/100Hz would point to amp internals so disconnecting external noise sources would be a waste of time, Candidates would be tired voltage regulator(s), caps,,,

 

50Hz hum could be environmental so yeah power "everything" off.

 

Often helpful if you mention make/model of the amp, ie, knowing if valve/SS/new-ish/vintage... and also spkrs/sensitivity...

[Robertoh]

First up, thanks folks for your suggestions.  I kinda tried each of them in turn.

I installed the freeware Spectroid app on my Android phone and ran a few tests last night.

Firstly, just to mention in case there is some interaction of response curves happening, my amp is a restored Sansui AU-555A (it's had the "LeeStereo mods"); the speakers are Yamaha NS-670 (with upgraded crossovers); the turntable is a restored Dual 1219; CDP is a Marantz CD-63SE. 

With all transformers for the nearby gear still connected (NBNCo HFC access modem; Telstra modem/wifi router; cordless phone; Fetch box), and no source input playing,  the amp demonstrated very little noise at the speakers (both audible to me with my ear near a speaker and as shown on Spectroid) on all sources except Phono 1 and Phono 2.  Phono 1 is connected to the TT; Phono 2 is not in use.  Phono 2, with no RCA plugs or blanks inserted, seems to be picking up general background white noise hiss, but this is only audible on that input setting, which is normally not used. Phono 1 demonstrated a distinct hum-hiss, becoming audible increasing as the volume was increased, especially upwards from about "3" on the Sansui's volume knob.  Spectroid showed a fair bandwidth of frequencies involved, with the main peak between 96-104Hz , a lower peak at around 50 Hz (which was more pronounced if I turned up the Bass tone control, unsuprisingly), and a top-end tail up to 15+KHz.  This reading did not change significantly with the turntable motor engaged but the stylus off a record.

 

I then progressively unplugged each of the mains transformers for the nearby comms gear.  Both the audible hiss/hum and the Spectroid frequency plot did not change significantly.   Similar results when plugging each of the comms gear in separately while the others were disconnected.

 

I have another amplifier that I will try in the same setup later tonight as comparison.

Edited yesterday at 01:12 AM by Robertoh

[Steff]

So on the amp side you have isolated it to the phono inputs, esp. the in-use phono 1, is that correct?

[Robertoh]

1 hour ago, Steff said:

So on the amp side you have isolated it to the phono inputs, esp. the in-use phono 1, is that correct?

Yes, that seems to be the case.

Not sure if this is relevant, but here goes.  When I unplug the turntable from the Phono 1 RCAs, I get the same "white noise" hiss that I get from the when Phono 2 is selected without anything plugged into its RCAs.  And when I plug the TT into the Phono 2 RCAs and select Phono 2 (without a record playing), I get the same distinct hum as described above on Phono 1 when the TT is plugged into it.

Wondering if I actually have an issue with the turntable, or the RCA cable to the turntable, rather the amp.   Hmm.  I have Technics SL-7 tucked away that I could try instead of the Dual. 

 

<edit>  Not sure if this makes any difference: I run the Dual TT on the switched mains outlet at the back of the amp.  To check whether this may be a factor, I just unplugged the turntable from this power source (i.e. TT completely unpowered).  No difference: still getting the dreaded hum.

Edited yesterday at 01:18 AM by Robertoh

[Robertoh]

1 hour ago, Robertoh said:

Yes, that seems to be the case.

Not sure if this is relevant, but here goes.  When I unplug the turntable from the Phono 1 RCAs, I get the same "white noise" hiss that I get from the when Phono 2 is selected without anything plugged into its RCAs.  And when I plug the TT into the Phono 2 RCAs and select Phono 2 (without a record playing), I get the same distinct hum as described above on Phono 1 when the TT is plugged into it.

Wondering if I actually have an issue with the turntable, or the RCA cable to the turntable, rather the amp.   Hmm.  I have Technics SL-7 tucked away that I could try instead of the Dual. 

 

<edit>  Not sure if this makes any difference: I run the Dual TT on the switched mains outlet at the back of the amp.  To check whether this may be a factor, I just unplugged the turntable from this power source (i.e. TT completely unpowered).  No difference: still getting the dreaded hum.

So, trying another turntable seems to point to the Dual TT or its cabling as the culprit.  Plugged in my Technics SL-7 and tried it on both the Phono 1 and Phone 2 RCAs, and it was much quieter than the Dual on either of those inputs, with hiss only audible at very high volume setting and not the characteristic buss I hear and measure when the Dual is plugged in.  This was apparent also with the Dual plugged into one Phono input, and the Technics the other, at the same time, and then swapping them. 

 

The very slightly hiss heard through the amp from the Technics turntable at very high volume was consistent with the Technics powered on, leaving it off, and disconnecting it from mains entirely. 

 

I am puzzled as to why I get the buzz from the Dual through the Phono inputs even when the TT is disconnected from the mains power, which I would expected would leave it "inert".

 

Next step will be to try the Dual vs the Technics on my second amplifier, but that is more fiddly due to needing to attach speakers, etc., so will have to wait until later...

Edited yesterday at 02:16 AM by Robertoh

[Steff]

7 minutes ago, Robertoh said:

I am puzzled as to why I get the buzz from the Dual through the Phono inputs even when the TT is disconnected from the mains power, which I would think would leave it "inert".

@SonicArt @andyr @bob_m_54 - any idea? Is it possible that the TT isn't "inert" because of current stored in a PSU copper spool or the like (as it was with old TVs being high current when disconnected from mains)?

Edited yesterday at 02:18 AM by Steff