A Phono Preamp question

Discussion in 'Audio Hardware' started by Night Rider, Mar 11, 2018.

  1. Strat-Mangler

    Strat-Mangler Forum Resident

    Location:
    Toronto
    You're correct. It doesn't have one.
     
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  2. John Moschella

    John Moschella Forum Resident

    Location:
    Christiansburg, VA
    What do you mean go low, the specs on mine say they go to 35 Hz.
     
  3. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    I'm sure you can find that out on their website.
     
  4. blakep

    blakep Forum Resident

    As I mentioned above, all subsonic filters are not created equal.

    For example, I had David Hadaway at DB Systems install a very basic (internal and non-switchable) subsonic filter (-3 dB at 28 Hz) into a DB 8 phono preamp I use in a secondary system here for about $15 (I will almost certainly never use speakers in that system that go lower than 45-50 Hz). That is very unlikely to be as effective or transparent as his stand alone, which is probably similar in quality to the KAB, and sells at $185.

    But I have always wondered: how many phono preamps are out there with non-switchable subsonic filters simply pre-built into the circuit without identifying them in specs? Wouldn't be surprised if there are in fact many (varying in quality at different price points) that manufacturers have utilized and consumers are unaware of.
     
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  5. Strat-Mangler

    Strat-Mangler Forum Resident

    Location:
    Toronto
    In the case of my Lehmann Decade, the subsonic filter actually also affects some aurally heard frequencies so I have it off. The difference is not drastic but I'd rather get the full sonic picture rather than sacrificing some of the musical information, so I still use a KAB RF1 and disable the subsonic filter onboard my phono stage.
     
  6. blakep

    blakep Forum Resident

    Interesting. I did find the KAB to be very good when I used it. The subsonic in my Aqvox is even less intrusive, for lack of a better word, cutting in at lower frequencies. As such, it does allow (I think-I could be imagining it haha!) just a teeny bit more woofer pumping than the KAB.

    In the end, though, I couldn't distinguish any negatives with the KAB and can't with the Aqvox with the subsonic engaged. I actually think both very slightly improve the sound quality while drastically reducing the woofer pumping-I have ported speakers which are very susceptible to subsonics and do not like them.

    Harry Weisfeld of VPI is on record as saying that any decent preamp or phono preamp should absolutely be fitted with a subsonic filter. He thinks it is a bit of rude joke on the record playing public that there are preamps and phono preamps out there without them.
     
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  7. Mike from NYC

    Mike from NYC Forum Resident

    Location:
    Surprise, AZ
    Every phono preamp should have a defeatable subsonic/rumble filter. Every TT I've ever owned has some rumble as do records caused by a variety of factors including warped records.

    My new Musical Fidelity Nuvista Vinyl has one installed and I keep it on.
     
  8. Gibsonian

    Gibsonian Forum Resident

    Location:
    Iowa, USA
    Which likely means down somewhere between 3 and 10 dB down at 35 Hz. Yes, you dont need a subsonic filter.
     
  9. Just Walking

    Just Walking Forum Resident

    Location:
    Abingdon UK
    Equally important is the effect of arm/cartridge resonance.

    1. It effects the trackability of the cartridge. A large amplitude warp signal uses up tracking, and leaves less tracking available for the music.
    2. It modulates the tracking force, so at the peak of the warp the tracking force is increased and at the bottom of the warp it is reduced. Even with a well matched cartridge and tonearm, and a nominally flat record, a 20% tracking weight change is typical. If badly matched and a warped record the tracking force can go to zero, and the cartridge starts skipping.
    3. Warps introduce distortion via intermodulation between the warp frequency and the music signal, largely as a result of "stylus scrubbing"

    So although you can get rid of the effect on your speakers of a warp or vinyl ripples using a warp filter in the electronics, it does nothing for the three real effects above. The only way to dramatically reduce them is viscous (or eddy current) damping, which some arms have. Or use one of the old Shure cartridges (V15/IV and V, or the currently manufactured M97XE) which have a damping system at the cartridge. Or both.

    There is nothing new there - it was all well-known in the 60's and 70's.
     
  10. Chris Schoen

    Chris Schoen Forum Resident

    Location:
    Maryland, U.S.A.
    Never had one, never used one, maybe never needed one?
     
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  11. Dennis0675

    Dennis0675 District Champ

    Location:
    Ohio
    I’m shocked by the support of a filter. I must need to gain some more experience, every filter I’ve heard takes away as much (if not more) good as it does bad. It’s like throwing a blanket over your speakers to eliminate a buzz.
     
  12. myles

    myles Forum Resident

    Location:
    Near Marlow, UK

    Like any filter, it does depend what band it is allowing to pass or is stopping. I'd imagine that a subsonic filter is working at such low frequencies that it wouldn't effect the required output.
     
  13. Chris Schoen

    Chris Schoen Forum Resident

    Location:
    Maryland, U.S.A.
    You are right. That's what a "filter" does. It does not differentiate "noise" from "music".
     
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  14. myles

    myles Forum Resident

    Location:
    Near Marlow, UK
    But a filter that rolls off at 15-20Hz wont affect the music...it'll just remove the subsonic unwanted freqs. If it was higher up the spectrum, into the audible frequencies (those that make up the music) then I would agree it would be a problem.
     
  15. Dennis0675

    Dennis0675 District Champ

    Location:
    Ohio
    I believe in addition through subtraction. Trying to improve sound by adding anything to the signal path can be problematic. There is a reason this feature isn’t commonly available on new equipment and it’s not because it costs too much.
     
  16. G B Kuipers

    G B Kuipers Forum Resident

    Location:
    Netherlands
    I have never felt the need for a subsonic filter to be honest.
     
  17. Strat-Mangler

    Strat-Mangler Forum Resident

    Location:
    Toronto
    Try a KAB RF1, which is what I use. I've never used any other except for the Lehmann Decade's internal subsonic filter which I felt took away some aural frequencies (later confirmed by an article I read where it was tested) but the KAB RF1 is entirely transparent. No difference whatsoever whether it's in the chain or not.

    And my woofers stopped freely pumping away.
     
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  18. myles

    myles Forum Resident

    Location:
    Near Marlow, UK
    [​IMG]

    Adding a couple of caps and inductors to defeat rumble at sub 20Hz is not going to affect the wanted signal in any serious manner.

    *I don't know if the image above worked but it was a frequency response plot of a subsonic filter.
     
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  19. I prefer no to use my subsonic filter on my Sansui 717, I can hear the difference, but maybe it's the filter itself that is not good. Same happens with the high filter. Off is the best for me
     
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  20. Dennis0675

    Dennis0675 District Champ

    Location:
    Ohio
    Worth a shot. I think my first post on this form was a thread I started because my subwoofer was "pumping" when I added a turntable source. In true SHF fashion I had twenty guys telling me I had a ground loop. My solution ended up being new speakers that didn't need a sub and later I blew up the sub connecting it to the center channel out on a Fisher 400.

    I have a Sansui 9090 and the filters on that are enjoyable. I don't run them for very long but they are fun to play with.
     
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  21. Strat-Mangler

    Strat-Mangler Forum Resident

    Location:
    Toronto
    Yeah, pretty typical. :D

    The KAB RF1 is inexpensive and transparent. Although the pumping I had wasn't extreme, it definitely lowered whatever amount it was throbbing by at least 2/3 and heard no difference in my system. So definitely worth a try.
     

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