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Quiet Stereo Amp Suggestions
PhantmShado
post Apr 12 2012, 08:40
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My HK 3490 I use on my desk with bookshelves about 2 feet away from me always seems to have a low hiss noise (slightly louder on right channel then on left) that is always present at some volume regardless of chosen input. The noise at times bothers me more than other times just listening to the speakers, but if I plug in audio technica headphones (which I've found to be easy to drive) the hiss becomes unbearable.

To this end I was wondering if there are any stereo amps I might look at that eliminate this hiss? I currently use the optical in and so would like a replacement that also has that. The speakers are Linn Majik 109s and they are pointed in at me each at about 2 feet from my ear.

Thanks.
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soulsearchingsun
post Apr 12 2012, 13:13
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Reasons for this:
- do you happen to control the volume on your source (e.g. computer) rather than on your receiver? For best performance, set your sources to full (or near full) volume and control loudness with your receiver. Otherwise you'll unnecessarily amplify noise.

- your receiver has a defect

- you're super sensitive

I don't think build quality should be a problem with this amp. It has a claimed SNR of 95dB which is good imho.

edit: Be sure to disable all DSP or headphone enhancement, somtimes they add a notable amount of noise.

This post has been edited by db1989: Apr 12 2012, 14:30
Reason for edit: removing pointless full quote of first post
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Speedskater
post Apr 12 2012, 13:53
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Some equipment information:
The HK 3490 is rated at 120 Watts per channel.

In the Stereophile magazine test of the Linn Majik 109s:
My estimate of the Linn's B-weighted sensitivity was significantly lower than the specification, at 85dB(B)/2.83V/m.


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Arnold B. Kruege...
post Apr 12 2012, 14:20
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There are two possible sources in the receiver of the noise that is bothering you. It is either coming from the power amps, or it is coming from the peamps or pehaps a little bit of both. Don't dismiss the possibility that the noise is environmental, like HVAC noise or a lamp or something like that.

(1) Turn the receiver off. Still hear the noise?

(2) If the noise follows the setting of the power switch, then to determine where in the receiver it comes from:

(3) Disable the connection between the receiver's preamp and power amp. There seem to external jacks and switches that relate to this. Do you still have noise with the power amp inputs shorted? If so, you need less efficient speakers, or to move them further away from you, or some such.

(4) If the amp is sufficiently quiet by itself but you get noise when it is connected to the preamp, then you need to reduce the sensitivity of the power amp. This can be accomplished with the external in/out jacks and in-line attenuators Part Express's line of in-line attenuators

This post has been edited by db1989: Apr 12 2012, 14:30
Reason for edit: as in post #2
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Nessuno
post Apr 12 2012, 14:36
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QUOTE (PhantmShado @ Apr 12 2012, 09:40) *
The noise at times bothers me more than other times just listening to the speakers, but if I plug in audio technica headphones (which I've found to be easy to drive) the hiss becomes unbearable.


Bypassing the amplifier and plugging the headphone directly into the soundcard output socket mutes the hiss?


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mixminus1
post Apr 12 2012, 15:35
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@OP: Are you sure this isn't tinnitus, i.e. "ringing" in your ears? Serious question, as I have very high-frequency tinnitus myself, and it occasionally changes into a sort of hissing sound. Your comment about the hiss becoming worse when you put on headphones (which will block out some degree of external sound, depending on the 'phones) - and also about being slightly louder in the right channel - brought this to mind.

If you don't hear the hissing anywhere else, and it is especially noticeable through headphones, then it does indeed sound like the HK has a rather high noise floor *and* you're particularly sensitive to it.

I had a Kenwood receiver back in the early 90's that I bought brand new (which likely had published noise specs similar to the HK), and even with the volume all the way down, I could easily hear hiss from the tweeters of my Boston Acoustics bookshelf speakers from about 18" away.

My Marantz NR1601 receiver that I bought a couple years ago, OTOH, is essentially dead silent - even with the volume at a normal playback level (~-26 dB through speakers or -20 dB through headphones), there is no audible hiss whatsoever through headphones (also Audio-Technicas, FWIW), and I have to have my ear nearly on the faceplates of my Dynaudio Audience 52's tweeters to hear any hiss from them.


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PhantmShado
post Apr 12 2012, 18:50
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QUOTE (soulsearchingsun @ Apr 12 2012, 05:13) *
Reasons for this:
- do you happen to control the volume on your source (e.g. computer) rather than on your receiver? For best performance, set your sources to full (or near full) volume and control loudness with your receiver. Otherwise you'll unnecessarily amplify noise.

- your receiver has a defect

- you're super sensitive

I don't think build quality should be a problem with this amp. It has a claimed SNR of 95dB which is good imho.

edit: Be sure to disable all DSP or headphone enhancement, somtimes they add a notable amount of noise.

The volume has always remained at full on my computer and media applications. The noise I refer to is present regardless of selected input though.

I have not ruled out a receiver defect, especially as I have a second HK 3490 unit in the living room that also has hiss through my ATH's. That unit's left channel has the louder hiss though, again regardless of input. I fear, perhaps unreasonably, that it is related to the base design of the product. I only listen to the one in the living area from a distance though and so didn't know about that one also having hiss until I plugged in the headphones.

My caring about the hiss from speakers may just be me being too sensitive to it, but I maintain the sound through my ATH's is simply intolerable.


QUOTE (Speedskater @ Apr 12 2012, 05:53) *
Some equipment information:
The HK 3490 is rated at 120 Watts per channel.

In the Stereophile magazine test of the Linn Majik 109s:
My estimate of the Linn's B-weighted sensitivity was significantly lower than the specification, at 85dB(B)/2.83V/m.

Does this mean a component mismatch or is it just some information?


QUOTE (Arnold B. Krueger @ Apr 12 2012, 06:20) *
There are two possible sources in the receiver of the noise that is bothering you. It is either coming from the power amps, or it is coming from the peamps or pehaps a little bit of both. Don't dismiss the possibility that the noise is environmental, like HVAC noise or a lamp or something like that.

(1) Turn the receiver off. Still hear the noise?

(2) If the noise follows the setting of the power switch, then to determine where in the receiver it comes from:

(3) Disable the connection between the receiver's preamp and power amp. There seem to external jacks and switches that relate to this. Do you still have noise with the power amp inputs shorted? If so, you need less efficient speakers, or to move them further away from you, or some such.

(4) If the amp is sufficiently quiet by itself but you get noise when it is connected to the preamp, then you need to reduce the sensitivity of the power amp. This can be accomplished with the external in/out jacks and in-line attenuators Part Express's line of in-line attenuators

(1) Nope, the sound was coming from the speakers and they don't do it with the receiver off.

(3) I honestly have no idea how to do this from looking at the unit. Are you able to offer more input? Also, I imagine replacing the amp is more likely to make me happy than replacing the speakers.

EDIT: never mind, I think I get it now. I'll try it when I get home.


QUOTE (Nessuno @ Apr 12 2012, 06:36) *
QUOTE (PhantmShado @ Apr 12 2012, 09:40) *
The noise at times bothers me more than other times just listening to the speakers, but if I plug in audio technica headphones (which I've found to be easy to drive) the hiss becomes unbearable.


Bypassing the amplifier and plugging the headphone directly into the soundcard output socket mutes the hiss?

I don't have a sound card, I have an optical spdif connection from motherboard to amp. Also, the hiss is present in every input I hit.


QUOTE (mixminus1 @ Apr 12 2012, 07:35) *
@OP: Are you sure this isn't tinnitus, i.e. "ringing" in your ears? Serious question, as I have very high-frequency tinnitus myself, and it occasionally changes into a sort of hissing sound. Your comment about the hiss becoming worse when you put on headphones (which will block out some degree of external sound, depending on the 'phones) - and also about being slightly louder in the right channel - brought this to mind.

If you don't hear the hissing anywhere else, and it is especially noticeable through headphones, then it does indeed sound like the HK has a rather high noise floor *and* you're particularly sensitive to it.

I had a Kenwood receiver back in the early 90's that I bought brand new (which likely had published noise specs similar to the HK), and even with the volume all the way down, I could easily hear hiss from the tweeters of my Boston Acoustics bookshelf speakers from about 18" away.

My Marantz NR1601 receiver that I bought a couple years ago, OTOH, is essentially dead silent - even with the volume at a normal playback level (~-26 dB through speakers or -20 dB through headphones), there is no audible hiss whatsoever through headphones (also Audio-Technicas, FWIW), and I have to have my ear nearly on the faceplates of my Dynaudio Audience 52's tweeters to hear any hiss from them.

I'm sure it isn't tinnitus, it is clearly coming from the speakers. It seems to get louder as I put my ear closer and all that.

I will see if I can find a similar marantz product (not buy before discussion is done, I do want to know how to short out the preamp to do that test, but I'm curious if they have one).

This post has been edited by PhantmShado: Apr 12 2012, 19:42
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PhantmShado
post Apr 13 2012, 03:01
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Ok, I pulled the jumpers connecting preamp and amp and on both my living room and desk unit as I was curious. The hiss situation remained unchanged on the living room amp. However, listening to the desk speakers, the hiss rose to a regular music volume on removal of the jumpers. It was also still just the right channel though while the left remained very quiet.

Any other ideas besides just getting a new amp? As it's predominantly on one channel for each of the amps, I assume it doesn't relate to the speaker load as both left and right should be the same.
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PhantmShado
post Apr 13 2012, 06:17
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Ok, after a search the only other stereo amp I could find with optical in was this:
http://www.amazon.com/Onkyo-TX-8050-Networ...2180&sr=1-1

Can anyone speak to whether this is a good product?
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Arnold B. Kruege...
post Apr 13 2012, 13:22
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QUOTE (PhantmShado @ Apr 12 2012, 22:01) *
Ok, I pulled the jumpers connecting preamp and amp and on both my living room and desk unit as I was curious. The hiss situation remained unchanged on the living room amp. However, listening to the desk speakers, the hiss rose to a regular music volume on removal of the jumpers. It was also still just the right channel though while the left remained very quiet.


If I get this right, your receiver's background noise was unchanged but still objectionable after you pulled the input to its power amp, but the noise was only objectionable in the right channel?

It's axiomatic that the channels of a stereo power amp should be audibly identical.

What happens if you switch the channels in the speaker wiring?

It is possible that the difference you hear is either due to the speaker or its acoustical environment.

If I am understanding what you wrote, when you pulled the inputs to your desk speakers, their noise level increased greatly, but again the channels were different, and again only the right channel was objectionable or was most objectionable.

What happens if you swap the locations of the speakers, L & R?

Is there a possibiliity that the high frequency response of your L & R ears varies?

This post has been edited by Arnold B. Krueger: Apr 13 2012, 13:22
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PhantmShado
post Apr 13 2012, 19:17
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QUOTE (Arnold B. Krueger @ Apr 13 2012, 05:22) *
QUOTE (PhantmShado @ Apr 12 2012, 22:01) *
Ok, I pulled the jumpers connecting preamp and amp and on both my living room and desk unit as I was curious. The hiss situation remained unchanged on the living room amp. However, listening to the desk speakers, the hiss rose to a regular music volume on removal of the jumpers. It was also still just the right channel though while the left remained very quiet.


If I get this right, your receiver's background noise was unchanged but still objectionable after you pulled the input to its power amp, but the noise was only objectionable in the right channel?

It's axiomatic that the channels of a stereo power amp should be audibly identical.

What happens if you switch the channels in the speaker wiring?

It is possible that the difference you hear is either due to the speaker or its acoustical environment.

If I am understanding what you wrote, when you pulled the inputs to your desk speakers, their noise level increased greatly, but again the channels were different, and again only the right channel was objectionable or was most objectionable.

What happens if you swap the locations of the speakers, L & R?

Is there a possibiliity that the high frequency response of your L & R ears varies?


I have two HK 3490s. The one I use in the living room where I am far away enough from the speakers I don't detect the hiss mainly has noise on left channel. When I disconnected the jumpers that noise was unchanged. For the one on my desk where the speakers are close enough the hiss bothers me, the noise is mainly on the right channel. Upon removal of the jumpers that right channel noise got much louder, while left remained nearly silent.

I agree both channels SHOULD be identical, but they are not. I question whether it somehow relates to poor wiring within the product.

If I switch the wiring the noise now comes out of the left speaker as expected. When I plug headphones in the noise is very clearly on the right channel.

It is not possible the noise is due to the speakers, the noise carries on to headphones.

I have not swapped the speaker locations, but I don't think this matters as both amps carry over their noise imbalances to the headphones jack.

The hiss honestly does not seem to be that high frequency. Also I can use just right ear to both and observe the same thing.
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Nessuno
post Apr 13 2012, 19:35
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QUOTE (PhantmShado @ Apr 13 2012, 20:17) *
I have two HK 3490s. The one I use in the living room where I am far away enough from the speakers I don't detect the hiss mainly has noise on left channel. When I disconnected the jumpers that noise was unchanged. For the one on my desk where the speakers are close enough the hiss bothers me, the noise is mainly on the right channel. Upon removal of the jumpers that right channel noise got much louder, while left remained nearly silent.


It seems like a defective unit. Have you tried to swap just the two of them?


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Ferongr
post Apr 13 2012, 19:54
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In my experience, even equipment from reputable manufacturers can have problems. A Marantz SR4300 surround receiver I own has audible hiss in both channels driving a pair of relatively insensitive (87dBspl/w/m) speakers. Furthermore, the right channel has a very faint (almost inaudible) 50Hz mains buzz that's a lot more audible when using the headphone output.I attribute the noise floor to the ADC part of the ADC-DAC chain (even analog stereo sources get converted to digital for volume control, EQ and mixing and back to analog) because when feeding the amplifier through SP-DIF there's no hiss. There's a Source Direct mode but it's probably just a placebo switch since it doesn't bypass the ADC-DAC chain (you can still control volume). When lowering the (digital) volume control to 0 the hiss cuts out (probably because the ADC-DAC chain mutes) and only the mains buzz remains.

Sadly, without proper 3rd-party measurements (or listening before purchase for obvious flaws like these) you can't be sure that even a modern amplifier can be transparent.

This post has been edited by Ferongr: Apr 13 2012, 19:55
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DonP
post Apr 13 2012, 21:02
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FWIW, an Adcom AV preamp I bought in the mid 90's had a lot of hiss in the earphone jack. My best guess is they reused a headphone amp circuit that was just fine in prior models of preamp, but this was the first one with a lot of digital circuitry in the cabinet and the noise got in. I sent it back under warrantee and they fixed it up just fine by adding shielding around that circuit board.
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PhantmShado
post Apr 14 2012, 22:16
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Well, I went ahead and took a trip to Frys where plugging my phones into the Onkyo TX-8050 sure enough resulted in hiss free sound. After they agreed to price match amazon, I went ahead and brought it home. I didn't even know how much the hiss was bothering me (maybe more than that had gone bad?), but listening to my Linns without it it's like having them new again, and I am quite appreciative of being able to use my ATH headphones out of it. So, I guess I'm good here. Thanks for the tips all!

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stephan_g
post Apr 17 2012, 20:55
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HKs are notorious for bad solder quality, so possibly that was at work here. Besides, AVRs can be quite noisy. Our old Kenwood KRF-V8090D (I don't remember what its US counterpart was called) makes a nice hiss bomb. Most of that seems to come from the PGA, as with electronic muting active, the speakers are dead quiet. The HK3490 is spec'd at a 95 dB(A) SNR, which should be much the same.

The TX-8050 seems to use a far less noisy PGA, at a 106 dB(A) SNR for line inputs. Note that it, just like the HK, uses simple dropper resistors on the headphone output, i.e. that one isn't exactly a 0-ohm job. Oh, and I suggest going to the Onkyo website with the serial number of your unit at hand, as they currently have a recall of several models from a specific batch going on and you want to make sure yours is not affected.
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