How much hiss from power amplifier is too much?

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Dear hi fi fanatics,

{Epos M22 Speakers / Creek Evolution 2 Integrated Amp / Dennon CD Player}

Two things:

I got hiss coming out of my integrated amp. It's ok when I listen through speakers - ie, you have to have your ear right up against the speakers to notice it (and when you pull back a metre or so you don't hear anything). Is this "pretty normal" in your experience? When I listen to my brother's £50 Matzuki stereo system I can't hear anything with my ear pressed to the speaker.

When does one become over-sensitive to a little bit of hiss - and when is hiss too loud?

Second thing:

I like to listen to music pretty quietly at night through my headphones. Here, I can certainly discern the noise floor hiss "in front" of the music I'm listening to.

Again, is this just par for the course in high end hi fi gear? Do I need a proper headphone amp for such daring listening?

This is my first hi fi set up so I don't have much experience to gauge where my neurosis on the matter ends and the limits of acousitcal physics begin. Sorry for the rambling - I look forward to any of your thoughts very very much. :).PS My systemsounds really great - I am very happy!
 

hoopsontoast

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To the first problem, I would have thought it would be odd for a new SS amplifier to generate hiss, maybe some interference from other appliances in the house, or power cables etc. If you cant hear it from your seating position I would not worry though.
 
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Anonymous

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Clearly any kind of hiss is less than desireable, but I keep getting the same answer that hiss is inevitable from any power amplifier. Is this the experience of other users?

It is reassuring that the Classe system mentioned above also produces hiss - afterall this is a top end system.
 

bluebrazil

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only thing i could suggest is to maybe try it in your brothers house, this might identify if you have a noisy mains or if you are picking up some other sort of interference. have you tried a variety of sources and is the hiss just as noticable whatever you are using?
 

BenLaw

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stee_doc said:
Clearly any kind of hiss is less than desireable, but I keep getting the same answer that hiss is inevitable from any power amplifier. Is this the experience of other users?

It is reassuring that the Classe system mentioned above also produces hiss - afterall this is a top end system.

I have no hiss through my systems.
 

bluebrazil

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yes ben, thats why i think its a fault somewhere. if he has the hiss on all sources its either a faulty amp or interference. i wouldnt bother trying a mains conditioner or shielded cables etc, (for possible mains or rfi issues), till it was taken back to the dealers and heard there.
 

oldric_naubhoff

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my speakers are Magnepan MG12, they have very good high frequency response.

amps:

Teac AGH 600 produces quite a lot of hiss. you can easily hear it from 1m when volume is set to "normal" listening levels.

Pathos Classic One is so quiet that when the volume is set to "normal" listening levels I need to put my ear right up against the tweeter ribbon to hear something. when I crank up the volume to the max I hear mains interference hum and still no hiss...

looks like there are quieter and noisier amps out there. don't settle for second best. but question is why some amps that measure like -100dB SNR still hiss?
 

Covenanter

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All electronic circuits produce some noise, it is inherent in all materials, and this will get amplified. This might be heard as hiss and if you are relatively young you are more likely to hear it than old fogeys like me whose hearing is going. This evening I tried my Marantz MP6004 with the volume control at 3 o'clock and I could hear nothing from 6" away from the speaker. I think if I had an amplifier that produced hiss that I could hear from any distance at normal listening levels I'd be taking it back.

Chris
 

Hi-FiOutlaw

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I would go step by step:

1) go to you mains bord and switch everything of, exept the room you have your hi-fi, and see if the hiss is still ther, if it is go to your dealer, if not step 2.

2) switch on, one by one of your circuit breaker to see if you have any appliance in other room that is Contributing to the hiss.

3) leave the kitchen to last.

if this help to find the source of hiss, better, if not visit your dealer.
 

Inter_Voice

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My system has no hiss at all. Any hissing sound means it is not normal. Most probably you have a bad power source. Try plugging the power chord onto different wall sockets, or use line filtering devices.
 

shooter

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Its quite normal for an amp to hiss, my current system does and so did my last, cant remember further back then the last one.

If your not hearing any hiss from a meter away then that is perfectly nornal but if you are concearned drop Creek an email i'm sure they will bet back to you:

technical@creekaudio.com
 

busb

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I've just put an ear up to my speaker drivers - slight hiss from the tweeter & slight hum from the bass unit (the same for both sides). A metre away - nothing. This is with the volume control wound right up due to my DAC controlling volume. Try this in a dealer's showroom: it will be the same to a lesser or greater extent. I'd perhaps worry if I could hear music or speach that would indicate interference from radio signals.

Considering that most of us hear some high frequency noise in our ears as mild Tinitus anyway, I'd not be worried at all. The last time I heard hum from normal listening distance was when my TT earth wire came off 25yrs ago.
 

Covenanter

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I think maybe we need to be clear what you mean by "hiss"! Mains interference tends to be either a hum arising from the alternating nature of the mains (which is low frequency) or intermittent pops and squeaks from high current devices, like motors, switching on and off. However it can't hurt to buy a mains conditioner, they are not expensive and it would eliminate potential problems. High frequency noise from the mains, if there were any, is unlikely to get past the power supply element in your amp (which will have a massive capacitor in it which effectively dumps high frequency signals to earth).

To me "hiss" is relatively high frequency and is like the sound of the word itself. In circuits it tends to be thermal noise, all materials produce some random noise and the hotter they are the more they produce. Individual components can be noisier than others just because of their individual physical structure. It is perfectly possible to have, for example, resistors in your circuits which are noisy.

It might be worth plugging and unplugging your various bits of kit to see if the noise changes. For example do you get the hiss with the CD player switched on and when it is off? Is it the same on both speakers? Does it vary as you change the source selector on your amp? By playing with these things you may be able to identify the source of the hiss.

Chris
 
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Anonymous

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Clarifications:

I hear the "hissing" sound when the unit is plugged in on it's own in a random location in the house (through the headphone out). When plugging in the speakers (and no other separates) I hear exactly the same sound. I spoke to Creek and their knowledgable and friendly technical guy explained I was listening to the sound of the power amp. By switching to the "direct a/v" input (ie turning off the pre-amp part of this integrated amp) I was able to hear again the same sound - implying again that it is simply the sound the power amp makes.

The quality is of a hiss - not a hum - and is a very gentle sound. It remains constant regardless of the position of the volumn knob. It was suggested that depending on the sensitivity of the speakers (and my ears I supose), the hiss might be more noticeable.

Having very little experience of hi end gear like this I am keen to check with you all that I have not drawn the short straw with this kit I have chosen. And thanks to these varied responses I have a much better picture of what I should expect.

PS. This is the second Evo 2 I have tried. The first one was a pre-owned unit and the hiss also had a strong crackling sound - so I sent it back and bought a new one. If the unit develops to also include the crackle I will certainly send it back - but for now I think this doesn't seem too irregular - and given the amazing quality of this amp I am going stick with it - I think.
 

Covenanter

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stee_doc said:
The quality is of a hiss - not a hum - and is a very gentle sound. It remains constant regardless of the position of the volumn knob.

Well in that case it must be coming from the output stage of the amp because if it were coming from anywhere else the amp would amplify it and it would go up and down with the volume control. Seems to me that it's the old "if we can't explain it we call it a feature".

I wouldn't be happy!

Chris
 

MajorFubar

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Covenanter said:
stee_doc said:
The quality is of a hiss - not a hum - and is a very gentle sound. It remains constant regardless of the position of the volumn knob.

Well in that case it must be coming from the output stage of the amp because if it were coming from anywhere else the amp would amplify it and it would go up and down with the volume control. Seems to me that it's the old "if we can't explain it we call it a feature".

I wouldn't be happy!

Chris
Yeah that's why I asked whether in varied with the volume pot. Back in the day nearly all amps hissed a bit when you cranked up the volume because they often had an active pre-amp on every input. That's quite unusual these days for anything except the phono input.
 
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Anonymous

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Covenanter, if it's not an impertinant question - what are your hi fi components? I am intrigued by your hiss-less set up. Are you really telling me if you squash you ear next to your tweeter there is no sound at all? You must have good signal to noise ratio? 0-100db?
 

MajorFubar

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None on my system either unless I crank the volume past three o'clock. And by then the sound would be loud enough to cause structural damage so it's of no concern. Obviously this doesn't apply to the phono input; just the line-level inputs.
 

Covenanter

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stee_doc said:
Covenanter, if it's not an impertinant question - what are your hi fi components? I am intrigued by your hiss-less set up. Are you really telling me if you squash you ear next to your tweeter there is no sound at all? You must have good signal to noise ratio? 0-100db?

Not impertinent at all, indeed I said on an earlier post my amp is a Marantz PM6004 (the speakers are KEF Q500s). I've just tried it again and no I can't hear any hiss from 6" or indeed if I put my ear so its almost touching the tweeter cone. Turning the volume up to 3 o'clock makes no difference either.

It may be that my speakers aren't sufficiently sensitive to reproduce any hiss, although they would be classed as medium sensitivity I think. Or it may be that I am old enough so that the hiss is too high frequency for me to hear. This is an interesting link on the subject:

http://www.gcaudio.com/resources/howtos/systemnoise.html

Chris

PS I've just looked up the sensitivity of the speakers in the OP, EPOS M22, and they are the same as my KEFs - 87dB.
 
I think there are two issues here:-

1. The slight hiss you may hear when placing your ear close to the tweeter is normal (though some amps are queiter than others), and will be inaudible from a few inches away as you report. This is nothing to worry about.

2. The background hiss you say overlays the headphone experience is possibly because the headphone stage is not very good, or there is too much gain (if you are listening just above zero volume compared with speakers), or the phones are revealing an inherent 'trait', perhaps being too sensitive themselves (by which I mean loud for a given setting).

I suspect too much gain, which might be improved if the source was attentuated - but this is only a guess. Even checking at a dealer can be tricky because most have noisy shops, compared with your living room.

Alternatively, a dedicated headphone amp might be the way to go, as long as you can get a home trial with option to return.
 

Covenanter

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Picking up on the headphone aspect of your problem, I was listening to Vaughan Williams 6th Symphony this afternoon and this has passages which are effectively silent except for a soprano singing very quietly. I mean very quietly, with my amp volume control at 10 o'clock they are very quiet. If I could hear hiss in the silent bits it would completely spoil the experience.

I would try a headphone amp.

Chris
 

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