am i experiencing the vox 'ghost note', cone cry, or something else?

Discussion in 'Amps and Cabs' started by sabbath90, Mar 7, 2006.

  1. sabbath90

    sabbath90 Member

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    my ac30cc is acting kind of weird lately. whenever i play up high theres a quite noticeable undetone. it's distorted and about an octave lower than the original note. it starts on about the 7th fret on the high e and the 12th on the g and b and continues the rest of the way up the fretboard. that leads me to believe it's not cone cry, right? could this be the famous vox ghost note? it's really quite annoying and makes soloing pretty unpleasant. i'm thinking that this is either the ghost note or a fault in the amplifier. has anyone experience anything like this? i've changed tubes and messed with the smoothing and bias settings on the back and nothing has helped. this is very frustrating. please help me.
     
  2. Macaroni

    Macaroni Member

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    I just read something re the same question...

    "Ghost notes can quite often be caused by the amps power supply, especially in an amp with small or relatively small value filter capacitors. The sag that occurs when an amp is pushed (which manifests itself as a sort of compression - which we like!) causes a 120Hz signal from the power supply to modulate the actual guitar signal, resulting in ghost notes. Volume always makes it worse. While adding larger filter caps can help reduce it or eliminate it, you may not want to do this to an amp or may not be able to. If the amp uses a tube rectifier, the size of the first filter cap has to be kept under a maximum value that the rectifier can handle. Also, adding more capacitance has an impact on the sound of the amp. While it can increase an amps ability to produce low frequencies, it will make the amp have less sag and may also make the amp sound more sterile. Having a tube rectifier increases sag also.

    A lot of amps will exhibit this to a greater or lesser extent. Old AC30s had very small value first capacitors and can really have this problem a lot, as do other class AB amps with tube rectifiers and small filter caps. You could use a solid state rectifier, which would allow you add more capacitance, although it would be an experiment, as obviously the sound would be affected."
     
  3. Tone Disciple

    Tone Disciple Gold Supporting Member

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    Try plugging into a different speaker cab and see if you still hear the problem. I have experienced the same thing you are talking about in the past and have been unable to get a definitive answer to what is causing it. In the absence of that info you end up trying a process of elimination. If you get it through another speaker cab, you may want to check out new tubes. One of the techs I use for amp work says that just a slight movement in the speaker can cause this issue. He also says that some paper cones are less hardy than others. Reconing speakers, replacing the speaker, etc may be possible solutions, but I agree that it is very annoying.
     
  4. SamN

    SamN Member

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    Here is something from Mitch Colby in the Plexi Palace forum where he is addressing the issue, from some rather vocal detractors of the cc series.

    "Unreasonable isn't the word. The guys won't listen to reason or reality and his account of what we said isn't factual. We received an email from a worried customer who owns an AC30CC2X after reading that post. Here was our reply:

    I apologize for the delay, thank you for hanging in there. In spite of what you've read or may have been told, the undertone you're hearing is not the result of a "design flaw". Rather it is a characteristic of the AC30CC circuit, and in a sense, part of the overall voicing of the amp. It's not uncommon to hear various levels of undertones and overtones on many amp designs. In order to refresh our memories, earlier today we compared an AC30CC to a circa 63' vintage AC30 Top Boost and found the vintage model to have a very similar and equally present undertone. The setting of the Treble control has a lot to do with emphasizing or de-emphasizing the amount of underertone.


    Regardless, should you want to lessen it somewhat, try the Modern Smoothing setting (44uf), and the Warm Bias setting (82 Ohm). The different speaker compliments can also make the undertone more or less apparent. As the Wharfdales place more emphasis on mids, the undertone will be more present than with the Alnico Blues (though I believe you already own the AC30CC2X). I also want to note that contrary to what has been mentioned, we never qualified the undertone in the AC30CC as a "design flaw" which we did not intend to address "because the amp is on the market and it is too late to deal with design issues". Rather, the undertone is again characteristic of a design that ultimately adds up to be a great sounding amp.

    I hope this clears up the confusion, please feel free to let me know if you have any further inquiries."

    Mitch
     
  5. riffmeister

    riffmeister Gold Supporting Member

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    octave lower pitch on the high notes? that describes cone cry.
     
  6. Macaroni

    Macaroni Member

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    I thought cone cry was a screeching, yowling tone, usually when playing notes around the upper frets on the higher strings? That's where I've experienced it with a number of lower wattage speakers (eg: 30W), and usually when using OD with the neck pickup.
     
  7. sabbath90

    sabbath90 Member

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    ok thanks guys. i guess i can live with this. i don't notice much live. it's mainly when i'm playing by myself. it's only REALLY noticeable when playing something like half notes and then bending. i can work around this though. thanks.
     
  8. riffmeister

    riffmeister Gold Supporting Member

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    that's a voice coil rub
     
  9. sabbath90

    sabbath90 Member

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    ok i just went and messed with the smoothing again. i used a tiny screwdriver to slide the selector switch this time. before i used the tip of my car keys, and i must've not moved it the whole way because the ghost note totally 100% went away in modern setting even in the hot bias mode. it doesn't sound quite as magical to my ears as the vintage setting when playing chords but it sounds good enough. i can solo now! excellent.
     
  10. electronpirate

    electronpirate Member

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    Do the cap mod like Mitch sais. That's a great amp and you should have it exactly the way you like it.

    EP
     
  11. radialaced

    radialaced Member

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    Hmmm, I just bought a G12H 30 that's doing that. Do you think Celestion with fix it for me?
     
  12. smallcrap

    smallcrap Member

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    Old thread but I think I have this going on with a G12H30 as well. It's kind of a lower rumble that seems to get worse with more gain or volume. I'm using it in a Tophat Club Royale 1x12 combo.

    Anyone else experience this with their's?
     
  13. sundaypunch

    sundaypunch Member

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    That is how AC30's typically sound. They are under-filtered and you get the ghost note. Most people don't notice it. The fact that the "modern filtering" switch took care of it should confirm this for you.
     
  14. RevelationAmps

    RevelationAmps Member

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    Yeah originally this sounded like cone cry to me (octave under the pitch only on high notes, especially bending, on the high E string). However, given that changes in the amp made it go away, it makes me wonder.

    Voice coil rub can be caused by many things but when I have seen it, it's been from overheated voice coil that deforms and rubs. In that case I don't think the speaker mfg. would likely cover it unless it did it right out of the box, in which case the VC is probably misaligned in the gap.

    BTW whatever the fix for cone cry ends up being, it probably will be a different speaker with more dope and you may lose some of that shimmer and sensitivity on lower-volume stuff. It's a trade-off. As long as it's in tune, I usually prefer the more detailed speaker and live with the cone cry.
     

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