Ghost Notes

Well you can't knock it 'til you've tried it as they say

Better to book an outside table at the restaurant and, although flowers are tasty enough, you'd be better bringing 'Jenny' a couple of apples and a few sugar lumps as a welcome gift.

I'd say getting to second base on a first date is certainly possible - even for you Rex :p

;)
 
maxdown said:
Well you can't knock it 'til you've tried it as they say

Better to book an outside table at the restaurant and, although flowers are tasty enough, you'd be better bringing 'Jenny' a couple of apples and a few sugar lumps as a welcome gift.

I'd say getting to second base on a first date is certainly possible - even for you Rex :p

;)
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It's good to get advice from the voice of experience. ;)
 
Wow... I've decreased B+ to a small value to test this and as expected by the explanation, sounded like a weird pitch shifter.

In the test I was using a Recto, now I'm wondering if that intermodulation would be the part of the sound that I don't like about my Plexi patch...

Time to play with B+ in the Plexi and see what happens :)
 
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It is a beautiful thing!

Kind of confirms how many of the famous simple guitar tones recorded, have a sound of just amp & cab. My ears always heard ghost notes in isolated tracks, thinking it was a tad of chorus, phaser, doubling or fx.
 
FractalAudio said:
A phenomenon present in some vintage amps is an artifact known as "ghost notes".

Ghost notes are the result of intermodulation distortion between the note being played and ripple on the power supply. The ripple is at 120 Hz because the AC voltage is full-wave rectified. So there are frequency components of 120 Hz and its harmonics in the power supply.

These frequency components mix with the note being played and create new tones that are not harmonically related to the note being played. Since it is intermodulation distortion, tones are created at the sum and difference frequencies. For example, if you play a D at the seventh fret on the G string this is 294 Hz. The intermodulation will create new tones at 294 - 120 = 174 Hz and 294 + 120 = 414 Hz. The harmonics of the note being played also factor in. The aforementioned D will also produce tones at multiples of 294 Hz and these mix with the 120 Hz and its harmonics.

The G string above the 5th fret is most prone to this because of the harmonic spectrum of those notes.

The amount of ripple on the supply is a function of the supply impedance. More capacitance and less resistance will reduce the ripple. Conversely less capacitance and/or more resistance will increase the ripple. You can adjust these values in the Axe-Fx using the Supply Sag and B+ Time Constant parameters. Supply Sag adjusts the virtual resistance of the power supply. B+ Time Constant adjusts the resulting time constant of the supply resistance and capacitance, i.e. as you increase the sag the time constant stays constant (capacitance decreases). To counter this increase B+ Time Constant.

Old 100W Plexis exhibit this the most of any amp I've seen due to the high resistance of the power supply transformer. Our reference 100W Plexi has so much power supply resistance that the power supply sags up to 120V! This along with only 50 uF of power supply capacitance leads to prominent ghost notes.
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is there any chance of an audio A/B added to the post so we can hear a "Ghost" note.
 
Years ago, when I bought an AX8, it drove me crazy when I heard the ghost notes. I'd never noticed them on any other product, and hearing them was primarily responsible for selling the unit and switching back to only using tube amps, until the day I noticed my tube amps did it too. Sigh….

So, that was my introduction to the actual accuracy of Fractal's products, and soon afterwards I bought either an FX3 or the FM3, I don't remember which came first, and now I celebrate the ghost notes.
 
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