A Phono Preamp question

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

  1. Night Rider

    Night Rider Well-Known Member Thread Starter

    United Kingdom

    After following the forum for a while I thought it was time to be more active and actually post something !

    I have been researching phono preamps as I am currently relying on a built-in stage in my Onkyo amplifier. My question concerns those preamps which offer a "subsonic filter" to reduce or eliminate rumble caused by vinyl imperfections. Is this a feature that is genuinely useful ? Not every manufacturer includes it. Apparently this can "protect speakers from excessive wear", and I wondered how many members have a preamp with this feature, and what are their opinions on it ?

    Thank you in advance.
  2. Manimal

    Manimal Forum Resident

    Southern US
    Yes it’s useful. Comes standard on most vintage integrated stereo components. Without it you stand th chance of having your cones pump away like crazed rabbits.
  3. Night Rider

    Night Rider Well-Known Member Thread Starter

    United Kingdom
    Thank you Manimal. You are the first person to reply to my first ever post !
    Kristofa and mike catucci like this.
  4. Strat-Mangler

    Strat-Mangler Forum Resident

    A subsonic filter is a useful feature but is not available on a lot of components. Nevertheless, you always have the option of buying an external one in the form of a KAB RF1 which is what I ended up doing as my first phono preamp didn't have a subsonic filter and my current one has one but it unfortunately also affects audible frequencies.

    KAB Electro Acoustics http://www.kabusa.com
  5. Just Walking

    Just Walking Forum Resident

    Abingdon UK
    There are two effects - warp or vertical ripple related, which is antiphase, and horizontal as a result of the hole being off-centre (surprisingly common) which is in phase.

    But a decent filter (third order seems usual) gets rid of both. But I do not, other than that observation, have any suggestions what phono stages might have that feature.
  6. Just Walking

    Just Walking Forum Resident

    Abingdon UK
    Crossed with Strat-Mangler's reply. Their system uses a technique that mono's low frequencies; because vertical warps are antiphase, if you mono that part of the audio spectrum the warp signals cancel without any reduction in bass music signals.

    In the UK the equivalent is the Devinyliser The Signal Transfer Company: The Devinyliser although you do have to build a small box and power supply for it.

    The advantage of the Devinyliser is that it cuts in at 50Hz (when directionality is irrelevant), whereas the KAB unit is passive, and therefore has to include inductors (never a sonic good idea) and cuts in at a very high and audible 140Hz.
    Last edited: Mar 12, 2018
  7. Rick Bartlett

    Rick Bartlett Forum Resident

    it's a pity so many modern amplifiers don't have a sub-sonic filter anymore, cos so many older amplifiers
    do! it's a useful switch and while you may not have to use it, in some setup scenario's,
    it can be like your best friend to eliminate those annoying low rumble, feedback frequencies, especially
    also if your not using any kind of equalizer. my amplifier I think has a 60 or 70 hz sub-sonic filter
    that I just mostly leave in particularly for a turntable.
  8. 33na3rd

    33na3rd Forum Resident

    SW Washington, USA
    That would be a great name for a band!
    SteelyNJ and Manimal like this.
  9. patient_ot

    patient_ot Forum Resident

    I find a built-in filter useful but it's not a make or break feature on a phono pre for me. Reason being is that for $20-30 you can add a set of in-line filters that will perform a similar function. I do that with one of my preamps.
  10. blakep

    blakep Forum Resident

    Purists will argue that a subsonic filter is a "band aid" solution and not necessary but especially (IMO) if one is making a significant commitment to vinyl and using, or ever going to be considering using, ported or vented speakers, I would consider it to be absolutely essential. Personally, I would not own a decent phono stage without a subsonic filter or, as a second choice, a good outboard like the KAB. But my preference would be for an on board.

    The further argument from the purists is that subsonic filters are not transparent and mess up the sound quality. No question that all subsonics are not created equal and, to a certain extent, this may be true with simpler subsonics. As in all things audio, you may get what you pay for ;).

    I've used the KAB in the past and found it to be absolutely transparent and high quality. The switchable (which I simply leave on all the time) subsonic filter in my Aqvox phono preamp is -9 dB at 10 Hz, -18 @ 5 Hz and -48 dB @ 2 Hz and is also definitely transparent.
  11. Just Walking

    Just Walking Forum Resident

    Abingdon UK
  12. Thorensman

    Thorensman Forum Resident

    These days injected require such a filter.
    My old Leak preamp had one .
    It depend on your turntable really.
  13. mike catucci

    mike catucci Forum Resident

    Welcome to the forum! Not an expert on subsonic filters so I'll leave that to the experts and just say hello.
  14. Cosmo-D

    Cosmo-D Well-Known Member

    I've got one on my Pioneer SX-3800. I never remember to switch it on, because I haven't had any discs/turntables that seem to produce a significant amount of rumble. Maybe I just don't know what to look for. An A/B comparison turning it on and off yields no audible differences (which I suppose means it's pretty transparent) so I've always just left it off. I don't know if it is necessary, but it certainly doesn't hurt to have.
  15. Davey

    Davey very clever with maracas

    SF Bay Area, USA
    The KAB unit has a power supply, and while I haven't seen the schematic, I doubt it's a passive deign.
  16. Night Rider

    Night Rider Well-Known Member Thread Starter

    United Kingdom
    A big thank you to everyone who has replied. There is certainly food for thought there !
    I will definitely look into all suggestions made.
    Visiting forums really can be an education in itself.
  17. blakep

    blakep Forum Resident

    Yes, not too many of us out there! I've had the Aqvox for 10 years now and really can't justify "upgrading"-it would probably be pricey. But I think it's hard for a lot of vinylphiles to get their head around not having any ability to load the cartridge :), even though, in this case, it makes a lot of sense.

    I remember your description of your build from another thread-very impressive!
  18. Just Walking

    Just Walking Forum Resident

    Abingdon UK
    You're right. I've re-read the product pages a lot more carefully, and seen that it is active, and uses a Meanwell wall wart external supply.
  19. hesson11

    hesson11 Forum Resident

    Correct me if I'm wrong, but isn't this true of only ported speakers (which admittedly includes nearly all speakers these days) and not true for acoustic-suspension speakers (which are pretty rare these days).
  20. blakep

    blakep Forum Resident

    You are correct. The woofer pumping (and possibility of damage) will be significantly less with acoustic suspension or sealed units so it is much less of an issue.

    However, another thing to consider is the strain that you are placing on your amplifier by trying to reproduce those inaudible very low frequencies. And that is going to occur whether one is using a ported or sealed enclosure.

    So as well as being kind to your speakers, the subsonic filter is also being quite nice to your amplifier as well.

    They're just nice, those subsonic filters. ;)
    Manimal likes this.
  21. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Brooklyn, NY
    Pro-Ject phono's have rumble or "subsonic" filter. I have 3 different models: Tube Box S, Tube Box DS, and Phono Box DS+ - they all have it. So does Parasound Zphono/USB.
  22. John Moschella

    John Moschella Forum Resident

    Christiansburg, VA
    Wow, interesting thread. I really had no idea that so many people find this useful. Maybe it does depend on the turntable. Haven't had one for over 25 years, and not once have I felt any need. And I've never damaged my speakers.
    Dennis0675 likes this.
  23. Gibsonian

    Gibsonian Forum Resident

    Iowa, USA
    If your speakers dont go low it' like having a built in filter.
  24. Just Walking

    Just Walking Forum Resident

    Abingdon UK
    Or open baffle ones like mine. Absolutely need a rumble filter.
  25. Leonthepro

    Leonthepro Skeptically Optimistic Autodidact Debater

    Uppsala Sweden
    Anyone know if the Schiit Mani has a filter? Probably not I assume.

Share This Page