Why would upgrading a preamp cause more tweeter hiss?

I guess I should add ... this is when the volume is at 0. 

With volume at zero, it would seem likely the hiss originates in your power amp.  Curious that it is louder after preamp change - perhaps something else was inadvertently changed such as cable dressing.  I have never owned a system where hiss was audible from listening seat.  So I don't think this is normal.  Talk to your dealer.

CharlieP posted:

With volume at zero, it would seem likely the hiss originates in your power amp.  Curious that it is louder after preamp change - perhaps something else was inadvertently changed such as cable dressing.  I have never owned a system where hiss was audible from listening seat.  So I don't think this is normal.  Talk to your dealer.

+1; i can only hear hiss if i put my ear close to the tweeter, although fair to say my 252 has less hiss than my 282

Same; have to be (too) close to speaker to hear hiss.  I do find that the mute button on my 82 makes a difference though.

It is a normal level of hiss, nothing to contact my dealer for. I do sit closer to my speakers than most as it is all my set up will allow. So that is probably why I can hear it from there. My question wasn't about that, it was about why changing a preamp would add more hiss, especially when going up a model. Same power amp, same cables, same everything. Only the preamp changed. I just wouldn't have figured that upgrading a pre would introduce more hiss. Kind of odd. 

You'll probably find that if you mute the pre, the hiss will vanish. If so, the likely cause is simply the fact that pre-amps like the 202 and 282 and fairly high input sensitivity so you get hiss from the nominal current (is what I have been told elsewhere - no need to bash me if wrong). If the hiss remains when you mute, then is more likely to be RF picked up by the power amp.

As I recently discovered, unplugging the power amp from the pre will get rid of the hiss but doesn't actually confirm where the problem lies. If it comes from RF to the power amp, you need a full circuit for that to be heard. Muting the pre however, leaves that cuicuit open. So if muting resolves the issue, then the pre is the source of the hiss. If not, the power amp.

But bringing it down to earth, the 282 (for example) like the 82 before it, gives a fair amount of hiss which is surprising at first but should not be audible more than 1m from the speakers.

RF contamination will most likely not cause hiss... Hiss is usually from the inherent background noise from the components in the audio path.

I experience this with the addition of the 282.  I had the 282 checked out by Naim and there was no fault.

Simon-in-Suffolk posted:

Hiss is usually from the inherent background noise from the components in the audio path.

Simon, other system components being equal is it fair to say that hiss will be proportional to speaker efficiency?

I won't deign to asnwer on anyone's behalf except to say hiss is fairly noticable (within the 1m bubble) on my system and at 86db my speakers are not terribly efficient.

But I hear where you are coming from and it seems like it should follow except that efficience is measured at just 1w 1m which is pretty close and pretty low energy so I don't think it takes much to make a hiss either way.

Jude2012 posted:

I experience this with the addition of the 282.  I had the 282 checked out by Naim and there was no fault.

Yeah, I am sure there is no fault with mine either. Certain levels of hiss are normal. My speakers are 85db so also not the most efficient, but I do have Jet tweeters, So that is probably making my hiss noticeable at 5 - 6 feet away. 

feeling_zen posted:

You'll probably find that if you mute the pre, the hiss will vanish. If so, the likely cause is simply the fact that pre-amps like the 202 and 282 and fairly high input sensitivity so you get hiss from the nominal current (is what I have been told elsewhere - no need to bash me if wrong). If the hiss remains when you mute, then is more likely to be RF picked up by the power amp.

 

Yep, it does go away when I mute. Input sensitivity are quite different on the 2 preamps.

202
Input Sensitivity
75mV

152
Input Sensitivity
130mV

Do you think this would contribute to higher hiss on the 202, even when nothing is connected to it?

awn posted:

feeling_zen posted:

You'll probably find that if you mute the pre, the hiss will vanish. If so, the likely cause is simply the fact that pre-amps like the 202 and 282 and fairly high input sensitivity so you get hiss from the nominal current (is what I have been told elsewhere - no need to bash me if wrong). If the hiss remains when you mute, then is more likely to be RF picked up by the power amp.

 

Yep, it does go away when I mute. Input sensitivity are quite different on the 2 preamps.

202
Input Sensitivity
75mV

152
Input Sensitivity
130mV

Do you think this would contribute to higher hiss on the 202, even when nothing is connected to it?

Yes. But one of the more quaiified engineers on the forum can qualify or refute that.

As I understand it a lower sensitivity value makes the input stages all the more sensitive to current down to that voltage level. Some of the newer gear has lower sensitivity in the 270mv range. The 202 and 282 herald from older Naim legacy designs before high voltage output digital sources so they are very sensitive.

joerand posted:

Simon-in-Suffolk posted:

Hiss is usually from the inherent background noise from the components in the audio path.

Simon, other system components being equal is it fair to say that hiss will be proportional to speaker efficiency?

Joerand - i think that is a fair assertion...

If the hiss is with volume at 0, it shouldn't be anything to do with input sensitivity, however is the hiss the same on each different input? With an external source connected and not?

Every piece of electronic sound equipment generates electronic noise, heard as hiss, and every different circuit - which means every different pre-amp - is likely to have diffent level of electronic noise (hiss), which is amplified by the power amp and played through the speakers, so one could indeed sound different from another. The odd thing is that you can hear it from either pre-amp: Normally one would expect hiss to be inaudible at the listening position in a normal domestic hifi set up - I can only normally hear mine with my ear about 2 inches from the tweeter, and have never heard hiss at the listening position except with the volume turned up high. You say you're abnormally close to the speakers - is it only a foot or two? Otherwise do you have a high gain system - high gain power amp, and/or horn speakers, for example, whose high efficiencies are known to reveal electronic noise all too easily?

On my 82, with 91dB speakers there is the same volume of hiss from all inputs both connected and not.  The mute button stops all hiss.

Innocent Bystander posted:

If the hiss is with volume at 0, it shouldn't be anything to do with input sensitivity, however is the hiss the same on each different input? With an external source connected and not?

Every piece of electronic sound equipment generates electronic noise, heard as hiss, and every different circuit - which means every different pre-amp - is likely to have diffent level of electronic noise (hiss), which is amplified by the power amp and played through the speakers, so one could indeed sound different from another. The odd thing is that you can hear it from either pre-amp: Normally one would expect hiss to be inaudible at the listening position in a normal domestic hifi set up - I can only normally hear mine with my ear about 2 inches from the tweeter, and have never heard hiss at the listening position except with the volume turned up high. You say you're abnormally close to the speakers - is it only a foot or two? Otherwise do you have a high gain system - high gain power amp, and/or horn speakers, for example, whose high efficiencies are known to reveal electronic noise all too easily?

It is the same on all inputs, weather anything is connected or not. Also, mute does not stop it.  I posted earlier that it did as when I first fire up the pre-amp and it does its 30 second mute thing, there is no hiss, as soon as it un mutes itself, there is hiss. If I manually press the mute button after that, the hiss does not change.

By close, I am about 6 feet from my speakers, at that distance, I can hear the hiss, but just barely. I do have Jet tweeters, which I am sure are partly to blame. I am running a 150X for a power amp, but with my 152 pre on the same amp, I had no hiss. 

Sometimes a small change can trigger these things. If you hear hiss even when muted I would suspect other causes that were merely triggered by the minor job of inserting the new preamp.

Do you have speaker cables coiled or bunched within proximity to the power amp? Does the hiss vary in volume at certain times of the day? Is it equal on both channels?

I recently had a truly awful RF problem which I incorrectly blamed on the 282 since nothing had changed in the system component wise other than a rack rebuild with all the components in the same stacking order. Something in that task just managed to set off the problem which was RF picked up from the speaker cables manifesting as a hiss with a radio station carried on it. The normal 282 hiss could be stopped by muting but the RF related noise remained. As mentioned, it needs a full cuicuit so the preamp still needs to be connected to hear it but the cause was still the speaker cables being bunched under the rack within 10cm of the 250.

feeling_zen posted:

Sometimes a small change can trigger these things. If you hear hiss even when muted I would suspect other causes that were merely triggered by the minor job of inserting the new preamp.

Do you have speaker cables coiled or bunched within proximity to the power amp? Does the hiss vary in volume at certain times of the day? Is it equal on both channels?

I recently had a truly awful RF problem which I incorrectly blamed on the 282 since nothing had changed in the system component wise other than a rack rebuild with all the components in the same stacking order. Something in that task just managed to set off the problem which was RF picked up from the speaker cables manifesting as a hiss with a radio station carried on it. The normal 282 hiss could be stopped by muting but the RF related noise remained. As mentioned, it needs a full cuicuit so the preamp still needs to be connected to hear it but the cause was still the speaker cables being bunched under the rack within 10cm of the 250.

 

 

My cables are all pulled away from everything, I made a habit of that on previous systems. I also changed my cable to NACA5 .. and have it spread out nicely, not coiled. The hiss is equal on both channels, and from what I have noticed at least, it does not vary at certain times of day. It is always the same. 

I think you've taken most of the sensible self-diagnosis steps then. I would, as has been suggested by others, see if your dealer can pop over one evening to take a look and perhaps bring another Naim preamp (another 202 or preferably a 282) just for comparitive troubleshooting. Failing that, a friend with a compatible preamp.

One final check my dealer always recommends is to remove the SNAIC from the pre (and if a seperate PS is used, the interconnect between that and th epower amp) and use a multimeter in continuity mode to just check all the pins on the DIN cables for continuity.

The mute not impacting the hiss is an important clue here though more testing needs to be done. You've maid several references to your jet tweeters and I see not much response to that - probably as not many are familiar with them but also because it seems unlikely that this would be a factor for this specific problem. Though I would not rule anything out until eliminated by test.

feeling_zen posted:

I think you've taken most of the sensible self-diagnosis steps then. I would, as has been suggested by others, see if your dealer can pop over one evening to take a look and perhaps bring another Naim preamp (another 202 or preferably a 282) just for comparitive troubleshooting. Failing that, a friend with a compatible preamp.

One final check my dealer always recommends is to remove the SNAIC from the pre (and if a seperate PS is used, the interconnect between that and th epower amp) and use a multimeter in continuity mode to just check all the pins on the DIN cables for continuity.

The mute not impacting the hiss is an important clue here though more testing needs to be done. You've maid several references to your jet tweeters and I see not much response to that - probably as not many are familiar with them but also because it seems unlikely that this would be a factor for this specific problem. Though I would not rule anything out until eliminated by test.

unfortunately my dealer is way to far to do that, and I don't know anyone with naim gear that I could borrow from.  As for the tweeters ... they are very 'in your face" as is naim gear. This is why I mention them as a possible cause.  I will put a pair of speakers with normal tweeters in place when I get time for that comparison, probably this weekend. I am sure the preamp is fine and another 202 would more than likely have the same results. The hissing is not bad enough to be annoying, I just found it odd that a more expensive pre would be noisier than my 152. 

Well put it this way, I get almost zero hiss from my Uniti Qute2, absoletely zero from my Denon AV amp, but quite a bit from the 282. It's just the way it is. Hiss and cost don't have much relationship. 

Keep us posted on how you get on.

feeling_zen posted:

Well put it this way, I get almost zero hiss from my Uniti Qute2, absoletely zero from my Denon AV amp, but quite a bit from the 282. It's just the way it is. Hiss and cost don't have much relationship. 

Keep us posted on how you get on.

exactly! .. this naim stuff sounds way to good to let a little hiss put me off from it! .... and thank you for all the replys

It seems to me that if you're hearing the hiss that should be inaudible, and if it is very much a trebly hiss, rather than full spectrum white noise coming equally from the other speaker driver(s), which is the inference of you saying it is coming from the tweeters, then your system may be rather unbalanced spectrally, with over-emphasised treble compared to the rest of the system.

Regardless of that, do you  have to run your system with the volume control set very low? If so, to sit only 6ft from the speakers the solution would be to either change the speakers for something less efficient - maybe around 85 dB/W/1m would make a significant difference - alternatively change the power amp for one with lower gain.

Otherwise an L-pad speaker attenuator would have the same effect...

Innocent Bystander posted:

It seems to me that if you're hearing the hiss that should be inaudible, and if it is very much a trebly hiss, rather than full spectrum white noise coming equally from the other speaker driver(s), which is the inference of you saying it is coming from the tweeters, then your system may be rather unbalanced spectrally, with over-emphasised treble compared to the rest of the system.

Regardless of that, do you  have to run your system with the volume control set very low? If so, to sit only 6ft from the speakers the solution would be to either change the speakers for something less efficient - maybe around 85 dB/W/1m would make a significant difference - alternatively change the power amp for one with lower gain.

Otherwise an L-pad speaker attenuator would have the same effect...

I can hear a bit of white noise from the driver as well, but I have to plant my face into it to hear it, so its not an issue. Your comment about the system being unbalanced is why I mentioned my tweeters a few times, as having "in your face" tweeters with "in your face" electronics may not be such a good idea for a well balanced system. My tweeters also came with foam pads that fit into these little metal brackets around the tweeter, in the case that they are too forward. However, it sounds beautiful none the less, and I cannot hear any hiss when the music plays.  My speakers do have a sensitivity of 85db already, but, I am considering switching to a Totem floorstander any ways, which I know are more difficult to drive.