Congrats on the build.
Not much feedback regarding Ghost Notes for the 18 watt amps. But I found this on the gearpage.
"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. 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.
In your amp the power supply is very much part and parcel of the sound of the amp and an unfortunate by-product of this is ghost notes."
http://www.thegearpage.net/board/archiv ... 49895.html