Big Fat Moderator
Ghost Notes (AKA Cone Cry)
How do I get rid of that @#$%^ ghost note problem in by Bad Cat TremCat 30 1X12 combo? The only way I can play the amp without hearing ghost notes is in 15 watt mode with a 1X12 extension cab added and the amp set at 4 ohms.
When I am running the amp with the single 12" speaker (no extension) at 8 ohms, the ghost notes are absolutely intolerable.
What am I calling a ghost note? The deliberate note I'm playing comes through loud and clear along with another "ghost" note at around 50% of the deliberate note's volume. The ghost note is a sour discord in a different key than the deliberate note - not at all similar or complimentary.
Big Fat Moderator
More info on this topic... this info was passed to me by a fellow member. Em7, you out there? What's your take on this?
Many amplifiers are prone to "ghost notes." It helps to know what kind of amp we're talking about.
Certain capacitor brands, like F+T, LCR have high leakage current. Other capacitors for coupling have ESR problems, sometimes caused by the physical construction, and lead type. Pure copper leads reduce this, and tubular capacitors are less prone. This is because they do not have any flat sides for the signal to bounce off of.
Some amplifiers like F-type Black/Silverface models that have the ghost note issue can be reduced by cutting the phase inverter "output" coupling capacitor values in half.
Others generally are just suffering from old, or leaky filters. Vintage amplifiers like V-type AC30s have very low filtering, I believe this was not because of design, but more as an economical approach to save money. The same is true with many amplifiers designed in the 1950s. Increasing the filtering can cure the ghost note problem.
With M-type amps there are two ways to help cancel this out:
1) Install a luf 600-1000V non-polar plastic capacitor across the last decoupling electrolytic in the line. This is the last filter, which filters the supply for the preamp. The capacitor will be wired to "by-pass" this filter, one lead to ground, the other to the capacitor lead.
2) Increase the filtering. On 50 watt models, it seems to take another 50mf across the main B+, and another 50mf for the screen supply.
For 100 watt M amps, expect to add another 100-150mf across the main B+, and at least another 100mf for the screen supply. Now, the amp will be stiffer on bass notes, if not acceptable, you can add anywhere from a 100-200 ohm 209 watt resistor in series with the output transformer center tap, this will give back a looser feel.
That's a really interesting read but points to an inherent flaw in component call-out. Ultimately, it's a design flaw, regardless of manufacture. Ouch!
In a probably unrelated note, I've had a bit of ghosting or possibly post note resonance on my old Boogie recently. It drove me nuts. After tearing that amp apart and contemplated swapping what I thought was a bad EL34, I turned my screw driver toward the cabinet grill. Since I had recently swapped the old C90s for WGS stuff, the grill could have been over/under torqued back into place. Sure enough, after releasing and retightening all screws, the resonance disappeared. :s It cost me two fists-full of ripped out hair, but no $$.