Hiss and Hum

Discussion in 'General Audio Discussion' started by dsavitsk, Dec 14, 2021.

  1. dsavitsk

    dsavitsk Friend

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    I've had the opportunity to audition some audio gear lately. Most of it would fit comfortably in a speaker system costing in the $5K-$15K range. Not super esoteric, but also not budget gear. I've been surprised to hear a considerable amount of background noise from it. Hiss, high frequency noise, hum, etc.

    In some cases, reviewers have noted "slight hiss", but it has always been followed by a note that it is only audible right at the speaker, not from a listening chair, and that it is certainly not audible while music is playing. My experience has been the opposite. I am surprised at how loud it is, how little it is mentioned, and how obtrusive it is - even while music is on. (I'm working on acquiring a calibrated sound level meter, and I'll post actual numbers when I do.)

    So I am curious, how much hiss do you tolerate?
     
  2. fastfwd

    fastfwd Friend

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    None.

    I mean, if I could hear it only by pressing my ear against a tweeter, I guess I'd tolerate that -- especially if it were present in both channels. But my speaker system doesn't even have that much hiss.

    Do you really hear hiss over the music? Is its amplitude volume-control dependent?
     
  3. Gazny

    Gazny MOT: ETA Audio

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    Absolutely none! well maybe a little, but I always feel it comes in. The noise pollution near me is pretty low so anything above 25db ambient is noticeable. The hum, buzz, Johnson, thermal noise bother me. Some more than others, but prolonged exposure really gets my tinnitus to act up. Not that I believe this noise is part of SINAD, but I do seek quiet amplifiers while still maintaining musicality and not destroying the music.
     
  4. Lyander

    Lyander Official SBAF Equitable Empathizer

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    I don't feel particularly bothered by Hiss unless it's the kind you shoot up in Control (video game reference). I recently got ears on a Massdrop CTH thanks to a very generous member of the forum and there's a significant amount that comes through once the amp is done initialising; it serves to let me know that I can start playing music at worst.

    It should also be noted that this is almost solely an issue with the Klipsch HP-3 (semi-open and very sensitive); it's not nearly as noticeable with the Senn HD600, which requires that my room be reasonably quiet and the knob well past 3 o'clock before I notice any hissing.

    Perhaps if it actually interfered with the music I'd be concerned, but it appears to not be much higher than the noise floor on most of my "audiophile" recordings so I just shrug it off.
     
    Last edited: Dec 14, 2021
  5. Beefy

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    Speaking in the context of headphones.....

    Solid state gear, I do not tolerate *any* hiss or hum. I grab my most sensitive phones, max volume, connected to source, no music playing, it should be dead silent. There is just no excuse for noise in SS gear.

    Tube gear, I'll tolerate a little bit of tube background noise. But if I can hear noise in quiet sections of the music at normal listening volumes, that is unacceptable.

    I have far less experience with speakers, but I'd probably keep the same standards. My modestly specced and priced NAD integrated amp has zero hiss and hum - a super duper expensive audiophile amp should be able to manage the same.
     
  6. ColdsnapBry

    ColdsnapBry Almost "Made"

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    I don't tolerate any his or hum on solid state.

    Tubes, well it depends. My Mogwai SE had background noise and that got sold because at that price range I can't tollerate that.. My SW51+ has background noise, but it's very light and the amp sounds good enough to enjoy it. Both have been reported to have background noise, so I don't really go chasing it.
     
  7. Tachikoma

    Tachikoma Almost "Made"

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    I would say none but now that I have a baby monitor running 24/7 in the background, a little.

    I have been thinking about tube amps a bit - would a speaker-level autoformer + interstage/cap (instead of a traditional output transformer with fixed taps) work for headphones? It feels like a neat way to simultaneously get a good load for the tube and attenuate noise.
     
  8. dsavitsk

    dsavitsk Friend

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    An old project. The website is long gone, but a 71a parafeed that used an autoformer output.
     
  9. Tachikoma

    Tachikoma Almost "Made"

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    Hmm... would it be possible to use this https://jandkaudiodesign.blogspot.com/2016/10/optvc.html (5k:600 at the highest volume setting, attenuation range of -60 dB, primary dc 10 mA) instead of an autoformer and skip the parafeed cap? For a 71A, plate current at 90V is only 10 mA.

    The result is probably useless for anything but super efficient headphones, but DHT for IEMs lol.
     
    Last edited: Dec 15, 2021
  10. dBel84

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    so many factors play into this and I view hiss and hum differently

    Circuit design whether tube or solid state , if you use enough feedback, hiss should drop to negligible levels, but this is not always conducive to "best" sound. As an aside, noisy tubes tend to sound the best - this is an observation that has been anecdotally supported by several members here.

    Speaker sensitivity - very big difference between 85dB/spl and 120dB/spl

    Hiss = transistors and tubes are noisy , optimal design can reduce this to a large degree and especially focusing on the power supply - i don't think I have ever had an amp / preamp that did not have some level of hiss at full volume. ( probably an exaggeration - there are chip amps that are inaudible ) My tolerance comes in at how intrusive it is - if at zero volume , it can be heard at listening position ( headphones or speakers ) , then I would try and reduce it.

    Hum - in theory you should be able to reduce hum in any application but the extremes have to be questioned at times ( separating psu from amplifier circuit ) - if it is truly low level background, I can ignore it. If it is at all intrusive, it is not acceptable. I have spent hours addressing hum and not being able to get rid of it all in some of the builds, despite pulling out most of the tricks.
     
  11. scblock

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    Considering how much hiss and hum is inherently in so many recordings the "absolutely zero" thing doesn't make sense to me. If I can't hear it at normal listening volume, then practically speaking it doesn't exist. If I can hear it at that volume then it needs to be addressed. The most challenging thing for me is the turntable setup, where the amplification level is enough that audible hiss can sneak in, or when I had some power transformers too close to the RCA cables which induced distracting levels of hum before I solved it.
     
  12. ColdsnapBry

    ColdsnapBry Almost "Made"

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    I feel like though if there's a noise floor of his/hum with nothing playing, then this prevents the amp from having a black background when music is playing. Maybe it's just a coincidence but the tube amps I have that have a good feedback implementation, Hagerman Tuba, has a much blacker background than my amps that have some noise floor.
     
  13. Philimon

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  14. atomicbob

    atomicbob dScope Yoda

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    2 or more channel speaker listening: Hum or hiss below the perceptual threshold after accounting for room ambient residual noise. This varies depending on room noise criteria measurements. Very slight hum and hiss when ear is positioned at less than 25 cm from each speaker.

    Headphones: -85 dBu for HD800 or HD6x0.
    -75 dBu is the typical threshold of perception for those headphones when room ambient is below approximately NC25.
     

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