A litlle follow up. Since my first post I have gotten in contact with John from Basic Audio, who has been very willing to help me out. But shipping 1 knop to Europe will cost $40, so I thought it was better to cool down on my OCD and leave the pedal as it is. Another possibility...
Guitar Player Magazine once published a small article about the way Johnny Smith tuned his guitar.
As I remember by using harmonics, open strings and fretted notes all over the fretboard.
I like to revisit this interesting method.
Does anyone know in which issue of GP this article...