Help with hiss

Hello Friends,

My speakers have developed an audible hiss that I am trying to chase down. The hiss can be heard from across the room and while music is being played. Sometimes, the hiss is pulsating and sometimes constant. It occurs at all hours, perhaps less so in the early morning. Sometimes there is no hiss at all and everything is silent. It is an intermittent issue that is unpredictable.

My speakers are powered by mono block amplifiers. Both speakers exhibit the exact same behavior. The monos are plugged directly into the wall outlet. I also plugged them into a PS Audio AV Power Center with no relief. I changed power cords with no relief. No other piece of gear is on, although all are plugged in and some are in standby. I turned one mono off of course stopping the hiss in that speaker. The other continued to hiss. In reverse, same result.

This is not a “hum” (like from a ground loop). It is the same hiss that you can hear with your ear next to the tweeter but much louder.

I’m happy to answer any questions at all to help me resolve this. Thank you in advance.



Was it always this way or did it happen recently? Did you add any new appliances or light dimmers, etc. in the house or change anything else in your system?  This is a head scratcher and any audiophile’s nightmare, so I hope someone here can help you solve this.

@soix Thank you. Excellent question and something I forgot to include.

I’ve owned this system in its current iteration for a few years now. This hiss started maybe 2 or 3 months ago, but I lose track. The only new “thing” I’ve added to my home is a conversion of a kitchen ceiling light from fluorescent tubes to LED. Fearing this may have cause it, I turned the light off but the hiss continued. It also does it in the bright of day when no lights are on. I’ve also studied if the hiss appears when the refrigerator cycles on. It does not coincide, and again, I’ve had all the same stuff for years.


Damn!  Does it still occur with listening at night?  Maybe it’s possible something outside your house but in your electrical grid has changed.  If it was me I’d try a balanced power conditioner (like Underwood Core Power or Equi=tech) or a power regenerator from PS Audio.  Other than that I got nuthin, but you’ve got my sincere sympathy and hope someone smarter than me here can help you figure it out. 

Assuming the hiss comes from both speakers, then it is not your speakers or your amplifiers.  It comes from further upstream, a component that processes both channels. 

I would guess your preamp.  

@soix Thank you so much. This is definitely a drag. It does happen at night, but my listening may start before the hiss starts. Once the hiss starts, it’s pretty obvious. Even my wife noticed it. I had feared that it might be something in the grid. My neighbor had recently built a wood shop. When I heard the hiss, I asked him if he was using any of his shop tools (sometimes the hiss sounds like a saw starting up). He denied using anything in the shop. It also occurs when he’s not even home.

@ditusa  Since you ask, I’ll assume it matters….Odyssey Audio Kismet Reference monos and Odyssey Audio Kismet monitors. Flawless performance for years. Thank you!

You said that your amps are plugged directly into the wall outlet.  What else is on that circuit? Have you tried unplugging everything else that's on that circuit.

I installed two dedicated circuits for my gear. One is used for the power amps and the other for the rest of the gear. Noise was reduced to virtually zero.

Good luck.

@carlsbad2  I had given that some thought, and I agree that it is likely upstream from the amps/speakers. Question: my preamp is a tube pre that is not on or in standby mode. It is plugged in, but fully “off”. Could it still create a problem? Thank you!

@nd1der  All the rest of my gear is plugged in to a Brick Wall, which is plugged into the same circuit. This includes the Mac laptop that I use for steaming. Knowing that computers can cause issues, I unplugged that from the Brick Wall with no relief. I’m not sure if it’s on the same circuit, but my internet modem is in the same room. Concern that might be an issue, I turned off and unplugged the modem with no relief. Thank you! Keep it coming!!

So, for the LED thing, dimmable LED lightbulbs seem to be OK but some LED strips and power supplies are not. If your LED lights have a wall wart, that may very well be a cause.

Another potential issue is if you've moved or introduced a Wifi router or device around your stereo recently. 

One experiment you might find is to literally turn off everything else in the house from the panel. 

If turning all of that off does not improve your issue then it's definitely in your audio chain.

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Wait.  You’re using a Mac laptop as your streaming source???  That’s awful.  Let’s do this — share your WHOLE system from soup to nuts and let’s attack this piece by piece.  The more we know, the more we can possibly help.  Now I’m thinking your streaming source could be part of the problem.  Tell us as much as you can about your system.  The more we know, the more your chances of getting help and finding a solution.  Pretty sure I speak for all here that we’d love to help you solve this infuriating problem, and there are a whole bunch of us here who’d like nothing more than to help you overcome this because we all feel your pain.  Help us help you. 

Unplug the interconnects from your preamp.  that will rule it out.  is there anything else plugged into your amps (besides power)?

If it is still there, then it is likely a power or interference issue as Erik has described.  It can't really be any of your equipment since the likelihood of the same problem happening in both channels at the same time is astronomically small.  Or would that be particle physics small?


I had a weird noise coming from my mono amps a few years ago.   Took a while to figure it out.   It was  plug in air freshener,  every time it cycled to dispense the scent my speakers would make a weird crackling noise.    

Man, I am so appreciative for all these suggestions and help! I knew I came to the right place!

@erik_squires As far as the LED thing, this is a large kitchen ceiling light that I converted from 2x4’ fluorescent bulbs to 2 LED bulbs. I didn’t replace the fixture, but bought the LED’s that have the built in ballast to be able to operate them in the same fixture. I’ll replace the entire fixture when I find one I like. So, no strips, wall warts, etc. And they are not dimmable. Like I said, the hiss occurs whether or not that light is on.

The WiFi modem/router is in the same place it has been for years (20+). It’s also the same one I’ve had for years. I did eliminate it on the off chance that it was creating a problem, but the hiss continued. 
I may have to shut down the whole house to find this. I am not opposed. Thank you!

@soix I can’t argue that the Mac is less than ideal. I was an early adapter of Roon and, at the time, the options were pretty thin. The Mac was something that could run Roon and I was familiar with them. My next upgrade is a real streamer, so the MacBook’s days are numbered. Even so, I’ve had this configuration for years. The only thing this Mac does is run Roon. It is the only thing it has ever done. I have never used it for any other purpose. I did unplug it from the Brick Wall ( those wall warts can be problematic), but the hiss continued.

@carlsbad2 I will unplug the outputs from the preamp. Good idea. Power and one input (from the preamp) are the only things plugged into the amps. I, too, fear that this is less system related and more power grid or power supply problem (from outside). That makes it beyond my control which I don’t want to think about right now.

@oddiofyl I don’t have anything like that. I’m hard pressed to remember that last “new thing” I introduced to this house. I’m not a big change person. I research the life out of something, make a decision and then live with that decision until it breaks or becomes so outdated that it no longer serves a useful purpose. That’s why this is a little baffling….nothing has changed, but the system suddenly began to exhibit this annoying feature. Thank you!


Assuming it's NOT your equipment, did you replace interconnects in that period of time? If you went from unshielded to shielded that would explain general noise pick-up but weird if it's hiss specifically.

@erik_squires I had that thought as well. I didn’t so much change any cables, but I did add a cable around Christmas time. I got a Schiit Loki for Christmas, so I broke out a pair of Raven Audio cables to use to put the Loki in the system. Unfortunately, right now, I have a hodgepodge of cables and not a full loom from one manufacturer. I have mostly Audioquest, but a couple of Zu Missions (I think), and the Raven. My turntable is a Rega, so the cables are captive. 



Well, I don't mean to suggest any cable brand is particularly good or bad, I was just wondering if you'd made a change that could account for it.

Right now it looks like you have to go up the food chain, but keep en eye out for any wall warts.  They still generate noise even when the load is off.

A couple of things to try.. first, re-route all cables making sure that the low level cables (interconnects) are at 90deg to any power cable they need to cross. Make sure speaker cables are kept away from power cables.


If that doesn't help, turn everything off, disconnect any interconnect to the mono blocks and then turn them on. If you still hear the hiss, then it's from the amps. If you don't, then connect the interconnects but do not turn on the preamp. If hiss, then it's the connection (interconnects or the input of the amp). If no hiss, then connect the preamp (test first without it on and then with it on). And so on, work your way backwards until you identify the source.

I went through this exercise only to find that if I plugged in my integrated amp to a different outlet on my PS Audio PowerPlant, any and all hiss went away.

@erik_squires Oh, I did not take it that way at all!🙏🏻 I think I was trying to address the very real issue of shielded vs. unshielded. I’m not sure which of the cables are which, but it will be very easy to get that information. I’m afraid my Brick Wall is loaded with wall warts, but there has been no recent addition, unless one is beginning to fail (which is possible). I’ll end up systematically unplugging each one and seeing if that has an effect.

I don’t want to jinx it, but since I got up on this quiet Sunday morning, the system is absolutely silent. I’m thinking you guys may have scared away the gremlin!! He knew I called in the big guns!

@audiojan Thank you so much for that! I do what I can to route the cables that way. It’s quite a mess back there without a lot of room to spread things out like they should be. I am cognizant of it, though. I will also do as you suggest and disconnect the interconnect to the amp. I agree that isolating the amp from the rest of the system may provide some answers or direction. 

@forestg Wrote:

 I didn’t so much change any cables, but I did add a cable around Christmas time. I got a Schiit Loki for Christmas, so I broke out a pair of Raven Audio cables to use to put the Loki in the system.

Just a thought, the Loki does have a wall wart style power supply. The two most common reasons for hiss is either a grounding issue or a gain staging issue.

I know this may sound silly but my guess is check the amplifier bias, maybe it's drifting, causing the hiss. Wish I could be of more help. See Odyssey Audio below:



@ditusa Hi Mike, The Loki does have a wall wart. I’ll unplug it to see if that helps. I have several components that use wall wart style power supplies. I’ll check them all while I’m at it.

I had thought of the bias issue. I’ve read several discussions, especially pertaining to Odyssey, about adjusting bias to change the sound. The only thing perplexing about the bias drifting is that both amps exhibit the identical behavior at the identical time. Can drift in one effect the other so directly? I understand that bias exists and that it is a “thing”, but that is the extent of my knowledge. It is not anything I would attempt myself. You’ve been very helpful. Thank you so much.

This is a natural phenomenon. You can spend the rest of your life trying to figure this out. Based on the writings of Stereophile and others, this hiss is originating from your components. The noise floor is poor and this hiss is symptomatic of poorly measuring components. 

if your amp has gain adjustments try lowering the gain. Stereophile has written about this before.


good luck. 


Try a cheater plugs on the Amps and Preamp. 

Cheater = 3 prong to 2 prong adapter. 

Hiss is random noise generated by active electronic components. It is not induced nor due to grounding issues like a 60Hz hum. Nor is it impacted by cables, AC power or external electrical components. Are you familiar with ’gain staging’? Basically, your amps are running at max gain and your preamp isn’t required to run at a level very far above its noise floor. Solution: Reduce the input sensitivity on your monoblocks and drive your preamp harder.

As well if you are using a low-gain MC phono cart the signal to noise ratio of the MC preamp may be 10-20 dB noisier than a MM input. You can check this by switching to an unused line input, and if the hiss drops, that’s the contributor. The solution is the same - gain stage your preamp and monoblocks, and now your MC preamp as well, to raise the signal (variable) to noise (fixed) ratio.

Gain staging is a basic survival skill in live sound and recording studios, (it was one of the first things I was taught, along with grounding theory) but is rarely mentioned in HiFi. Here’s are two good good tutorials:

From Sweetwater Music:

Ghosts in the machine…


Such an annoying problem to have.

I read through above but could not tell if the problem persists with only a power cord being attached to the power amps, and the amps being connected to the speakers. From what I gathered, the RCA’s were disconnected at the preamp, but still connected to the amps?

Does the hiss stay constant, or does it increase in volume as you turn it up?


Do other people hear it ? I'm only asking do to the fact I thought I had an issue with my home theater system but finally realized  have a slight case of intermittent Tinitis that comes and goes, so at times I'll hear hissing and other times it's fine.

@forestg just wanted to chime in when I saw your post.  I noticed the same "hiss' coming from my Rega Elex~R integrated.  I thought it was for certain my tube dac, but after disconnecting everything, moving the amp, and trying different speakers I can still hear a hiss but at normal mild listenting levels it's inaudible; you can only hear it at that level if you happen to be right next to the speaker.  If I crank it, then you can hear it from across the room, especially if you listen for it.
Fully agree with others on checking the bias. 
Hope it's nothing harmful and you figure it out.

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@tee_dee I may have to spend the rest of my life figuring this out! It can’t stay like this!

@wturkey Thanks! I may have one left over when I had to chase a ground loop hum in my (home theater) subwoofer.

@panzrwagn Thank you so much for this! Very informative. I’ll read those articles if for no other reason than to learn more about our crazy hobby! I can’t rule this out, either. These amps have pretty high input sensitivity and, I believe, are a high gain design.

@perkri I did not disconnect the RCA’s from the amp..from either end. I did swap out power cables and I did plug them in directly to the wall outlet and into a PS Audio Power Center. Nothing changed in any scenario. Unplugging the inputs at the amp is what I will try next, based on a previous recommendation 🙏🏻. The hiss stays constant. No change with volume adjustment, nor input selection on the preamp. It does it with nothing but the amps turned on. Thank you!

@rbull11 Great thought! Alas, everyone hears it. It is real. But I, too, suffer from Tinitus and have often made sure it was the speakers hissing and not my head! Thanks!

@amtprod I’m definitely going to look into the issue of bias. I hear a lot about it, so it clearly has great impact. This is a “on or off” kind of hiss. It’s either doing it or not. And it does not change with volume or input changes at the preamp. And you can hear it quite noticeably “under” the music when it’s playing. Like a lot of background noise. Quiet passages aren’t quiet. It’s very annoying not to have the clarity I’m used to. These are pretty “crisp” speakers (Scanspeak beryllium tweeters). Thanks!

@serjio I will have to look in to that. Sounds intense. I was concerned that something else from someone else was shitting into my system, but hey, you never know! Thanks!



I have an Odyssey Audio Stratos. For 20 yrs it was dead quiet. In 2021, I sent it to Odyssey for a Kismit upgrade. It came back with a hiss in the speakers and transformer hum. I sent it back (almost $300 in shipping by now). They said that they replaced everything. When it came back, it still had hum and hiss problems albeit at a lower volume but hiss nonetheless. I gave up on it an bought new amps from a different manufacturer and I’m hum and hiss free again. Now the Odyssey just sits on the floor at the back of my room…just sitting there…mocking me every time I walk by :_

BTW, it always had bias issues. It was always a crap shoot as which side the center image would be leaning.

Here’s another thing to try. 

when amp in, connected to speakers with nothing else connected, try holing into the rca connectors and see if the noise subsides 


other thing to check, is the DC on the speaker outputs if you have a multi meter.  

Assuming you have backup equipment, take the amp and preamp out and try your backup amp setup.  One other thing, I had a tube phono pre amp that after 30 min. or so, began to hum until it was unplugged.  And yes, it was well grounded.

@forestg Wrote:

I’ve owned this system in its current iteration for a few years now. This hiss started maybe 2 or 3 months ago, but I lose track.

How old are the two amps?


Speakers do not hiss. Amps, preamps and source components do. Especially tubed ones. Disconnect your preamp from your amp and turn the amp on. If you still hear hiss thru your speakers. your amp is the culprit.

If the hiss stops, power it all down, connect your preamp to amp but don’t connect sources to preamp. Turn on the preamp, then amp. If it hisses now, it’s your preamp. Repeat this for each link in the signal chain. 

Also, you stated the hiss is constant no change in hiss loudness with volume variations, that says it’s the amp. If the source for the hiss was upstream, the amplifier would amplify it, as it does with any incoming signal. So your amplifier is most likely the culprit unless your speakers work like antennas and pick up static from some unknown source which is extremely unlikely.

+1 @audphile1 

Also, with the amp off and interconnects unplugged, insert RCA shorting plugs so that no signal is possible as an input.  Turn amps on.  Hiss OR no hiss its the amps.




I experienced an issue exactly like this. Turned out that a capacitor (or two) were leaking in my CD player. Could be a capacitor somewhere in your chain. Maybe even in your speaker crossover. Good luck!!

@campoly Similar story. These monos started life as Stratos and later upgraded to Kismet status. I think. I brought them to Klaus and said “do something”. He did. They sound great. 

@boxcarman Thank you for that. I do have a couple of pieces I could swap out and I had thought of that. But I don’t have another pair of monos and I have a passive preamp. So, not apples to apples.

@ditusa These were upgraded to Kismet status in August of 2021, same time as my Candela preamp was made.

@audphile1 I agree that the hiss is a symptom of a problem and not a problem with the speaker. I will do a systematic elimination of components as you (and others) have suggested. I appreciate it. I also can’t eliminate a power problem as they are monoblock amps exhibiting identical behavior. The amps themselves are silent (no buzzing, humming, hissing) coming from the amps. I agree that the most likely suspect at this point is something with the amps, as no other component is on. Some are in standby (Oppo BDP 105D), but I shut everything down if I’m not playing music (except the amps). Thank you so much for your valuable input!

@barts Thanks for that! An easy thing to overlook!

@rockadanny Thanks! I’m humbled. If there were a problem with, say, my CD player but the player wasn’t on could it still cause the symptoms I’m suffering? Or any other component, for that matter? I might suspect a capacitor in the crossover (good call), but it’s doing it in both speakers identically. I’m really not leaning towards the speaker(s) being the culprit, just a victim of whatever the real problem is.


Sorry to say this. I hope it's not your problem but I had a very, very similar experience that campoly had. I had a Stratos and Tempest, then later a Candela. After having very low level buzz, static and noise from the amp and preamps I sent them back to Klaus and he kept them 2 months and sent them back with the same issue. He claimed I had noisy electric. It took 2 years, really bad customer service and he bought the equipment back.... to this day we have issues. Lost a fair amount of cash.... with Odyssey Audio. I am hoping you can fix your issue...

One thing you might want to try is unplugging everything from the wall outlet and plugging your mono block amplifiers into a different outlet to see if that makes a difference. If the issue persists, it could be something to do with the amplifiers themselves. You might want to have them checked out by a professional to ensure they're functioning properly.

@forestg sorry, didn’t realize was both channels. yikes! cap leaking was assuming just one channel. would not expect hiss from unpowered gear.

@2psyop, Yep. Similar experience. For the year I had the upgrade, it was there longer than it was at my place. Straight answers were hard to come by but excuses and non-answers were easy to come by. I hope this isn’t the same for OP. I chalked it up to experience. Lesson learned. I’ve moved on.

@2psyop Thanks for sharing. I’m really sorry to hear of your experience. Mine has been the complete opposite. I’m sure there’s stories of great successes and not so great in every manufacturer’s history. I’m glad you found your resolve and are back to digging’ the tunes!

@audphile1 👍🏻 I’m with you!

@tempostarship Thank you for that. I had given some thought to doing that, but I wanted to isolate components first. It would be a lot of moving, as there are no other outlets in close proximity. I don’t want to use an extension cord because that could create problems of its own. So, I’d have to move the amps and speakers to another location. That would be the easy part. Putting them back where I had them would be the hard part!

@rockadanny Thanks. I wouldn’t expect it from static gear either, but I’m glad for some confirmation.

There have been some magnificent suggestions here, which is exactly what I was looking for. I had thought this thing to death and I was running myself in circles. I remain open to any ideas or thoughts people may have. I am not quick to fault the amps themselves, primarily because the hiss level, frequency, constant vs. pulsing, silence etc. is identical in both channels. It seems that if it were an issue with one of the amps, some of which were suggested here, I would expect one channel to have an issue but not both. In fact, while troubleshooting, I turned off and unplugged one amp but the other continued to hiss. I turned off and unplugged the other amp and the other one continued to hiss. 
Maybe coincidental, maybe wishful thinking, maybe an Audiogon forum exorcism, but since I got up Sunday morning I have not heard them hiss. I also have not played any music yet. And my neighbor hasn’t been home🤷‍♂️🤔

OK..have some answers here....


first off,  apologies for the delays,  but I also have always been upfront with the timing...we are hammered !!!and no,  of course I'm not sending back units with the exact same problem,  that's bs.  however,  when I change or upgrade amplifiers and put them both,  in my own system and on the bench,  and they a behave perfectly,  then they'll go out.  However,  when you get the same units in your system and then they misbehave then obviously something somewhere makes them go off the,  there is a simple way to check what kind of hiss or hum is going on:  if it stays the same volume regardless of volume then it is AC  related (and approaching the proverbial needle in a haystack situation) and not inter-system problematic...also,  if there's something wrong with an amp...or a pre for that matter then the hum would be there constantly...there's no "muscle-memory"  that kicks in,  and thus a dead give-away for some environmental problems...on the  flip side,  yes,  some units,  i.e. power supplies are more susceptible to environs (halogen lamps,  fridges,  outside lights,  anything that neighbors have and do before you in the grid,  etc.)  than others,  and  oxymoronically,  bigger and higher grade power supplies act up easier...that's what I found on our and on other brands gear (on which I worked on for friends) as well.....go figure.

But then again,  there  are devices (humbusters etc.)  that will take care of situational problems....all I can say on my side is that if there is a problem,  stay on my way or the other I'll make it right............and I do take exception about the "excuses" thing...taking a lot of time, (sometimes my schedule,  other times parts availability, especially the past 2 years)    unfortunately possible,  but I'll never lie to this point of writing,  I have 65 amps here for Kismet upgrades,  and more than half for the hyper power supply upgrades.  In addition to regular orders.....and we hand made over 7500 amps over the last 20 + years.  99 + %  of them without any never hear about them...and yup,  I mess up from time to time as well...sorry.


Hope that helps,  and just  get back with me,




OK so it sure sounds like its a power problem coming into your house. Your last post about plugging/unplugging each amp amp in turn and they exhibit the same symptom individually. Next step for me would be to purchase an isolation transformer and locate it in another area. I’m not talking about power conditioner here, but a real medical grade isolation transformer. A little pricey, but it will stop you from pulling your hair out. Good luck.




If it can’t be heard while music is playing, then why worry....there is some degree of hiss or noise in ever system. It depends how sensitive you are too it. My tubed phono preamp is noisier than my solid State. However, once the music is playing, I'll take the tubed phono any day...

What power issue would cause an audio component to hiss? We are still talking about hiss are we? Hiss as in ssssssss type sound. Not the hmmmmmmm sound. Correct? 

Amplifier or preamplifier hiss can go unnoticed or may not be as noticeable if you have inefficient speakers. Once you move to a pair of speakers that are above 91 or so db efficiency from an 85db speaker the hiss will be more apparent. 

There’s something fishy going on here that sounds like some sort of a user error or a faulty piece of electronic equipment in the signal chain or a pair of new very efficient speakers is revealing this hiss. Very curios now….