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Cause of sibilance?

Discussion in 'audio' started by mjhill1234, Aug 5, 2022.

  1. mjhill1234

    mjhill1234 pfm Member

    Thanks Mike P, you are correct although the loading specifies 47K is sounds better to my ear at 19K.
  2. mjhill1234

    mjhill1234 pfm Member

    Additionally now I have just received a nice accurate force gauge from a fellow PFM'er, I have discovered my Amazon special was reporting +0.2g more than it was actually set at so was originally tracking at the lower end of the recommended range. Have now set this to the upper limit and will give this a go along with my 19K loading and hopefully its sorted.....
    a.palfreyman likes this.
  3. mjhill1234

    mjhill1234 pfm Member

    I think I’ve got it! 2.0g VTF with a very slightly tail down VTA and a 100K shunt (32K loading). The higher VTF has eliminated the sibilance and the 100K has just taken the edge off the brightness. If I go anymore on the VTF it starts to sound a bit muddled and lifeless and any further tail down on the VTA and the bass looses its punch. Tried a variety of records and this seems like the best balance.
    a.palfreyman likes this.
  4. G T Audio

    G T Audio Trade: Manufacturer and Distributor

    What ever you do, do not put anything between the cartridge and the phono stage!!! If your phono stage is being overloaded, then there is something either wrong with the phono stage, or you need to get a better one that has plenty of headroom for a good MM cartridge.

    Avantgarde horns are very sensitive to partnering equipment and cabling, although I don't think this is the problem you are experiencing, as every source would be sounding the same...

    You should never introduce any resistance, either in series or in parallel, between the cartridge and the phono stage.
  5. a.palfreyman

    a.palfreyman pfm Member

    First of all, the resistances I suggested were selected to maintain 47k loading on the cartridge, but reduce the input to the phono stage by roughly half. This was purely a test to determine if this cured the sibilance problem which would thus indicate that the phono stage was being overdriven. As it made no difference to the perceived sibilance whilst providing an input level similar to a different cartridge that didn't suffer sibilance, this showed that it wasn't the phono stage and must therefore be related to the cartridge. I also provided information on how to screen it to avoid hum pick-up, a method that works, as I used it when I built an experimental board for an MM phono stage.
    I'll also refer you to this thread on the WAM: Matching sound levels from an MM and MC inputs of a phono stage | HiFi Wigwam
    If you read posts 9 and 10 in particular, it appears that member 'Rothwell Audio' provided (or certainly offered to provide) an attenuator to allow the use of a HOMC into an MC input to a phono stage...a lot more extreme than this instance here.
    However, if there is a technical explanation why this shouldn't be done, please let us know.
  6. Neiro

    Neiro pfm Member

    Audionote will tell you that the IQ3 takes quite a while to run in (100+ hours) your occasional use is probably not doing it any favours. Also it does prefer 2g and a slight taildown. Sounds like you are there mechanically. Maybe get some more hours on it and then see if you really do need the additional resistance.
  7. mjhill1234

    mjhill1234 pfm Member

    The description of the phono stage says "The MM phono stage is an active class A stage using a transformer less design, which means matching is very easy. It is far less critical of capacitance, resistance, impedance, inductance or reactance matching that transformer couple RIAA stages normally need." and while its not the most expensive of units (and price doesn't necessarily mean good), I would say £1000+ for a phono stage should perform well enough. I am also assuming its a good match for my amplifier as its made by the same company (although that is an assumption on my part). While I am aware that putting anything at all in the audio chain is not desirable and usually less is more, I can say that adding a 100K resistor in parallel with the cartridge sounds great to my ears, and unless that is a bad idea in that its going to damage something I guess thats what matters? As @Neiro said maybe I just need to use it more and it will soften up when its run in. Maybe the IQ3 is not a good match for my tastes/system, but I am reluctant to throw more money at another cartridge unless there is a dealer friendly enough to lend me something to audition!
  8. G T Audio

    G T Audio Trade: Manufacturer and Distributor

    As I said in an earlier post, you should never introduce any component between an MM cartridge and the input of the phono stage, least of all any high resistance! Adding a resistance in a sensitive circuit like the input of a phono stage could easily introduce a noise issue which could mask any result you are looking to achieve. Also, it is very likely it will degrade the audio signal and probably mask the main problem.

    It's quite simple. The phono stage manufacturer will have designed the phono stage to cope with an MM input voltage from the cartridge of around 10mV. Sometimes it's more than that depending on the design, especially if it is a valve/tube design where there is generally a lot of headroom. So if the sonic result is sibilance then it will either be a faulty cartridge, a faulty phono stage or possibly if the cartridge is new, then it might need running in. Check the capacitance of the phono lead to make sure it is compatible with the cartridge. I suspect if the problem still exists after 50 hours then speak to your dealer where you purchased the items from and get them to assist in identifying the problem, especially if the cartridge is new.

    @mjhill1234 - Note what I said earlier about the Avantgarde Duos being sensitive to partnering equipment and cabling. Being very efficient, they can magnify issues in partnering equipment. Also, to replace those speakers today will cost you around £50K, so bear that in mind when matching to partnering equipment.

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