It’s been a long time since I wrote about guitars on this site. After a hiatus of almost four years, I started taking lessons again half a year ago and play almost every day. This also meant dusting off my amp, a Peavy Valveking Royal 8, a 5W all-tube amp with 8″ speaker. I had never really liked the sound of it, even though I had the stock speaker replaced with a Celestion Super 8 right from the go. The sound was still blatty and muffled, chords on the neck pickup were a muddy mess with too much mid-range.
My solution a couple of year ago (found while playing with my Wah pedal) was a Treble Booster that improved things a lot, but I always had plans for trying some modifications that I read about. While some people recommend replacing the output transformer, I wanted to go a simpler route and simply replace a few parts. This is what I did (schematic):
- Replace R8 with a 220 Ohm resistor to run the power tube a bit cooler.
- Replace C1 with a 2.2uF capacitor.
- Replace C9 with a 22nF Mallory capacitor.
Caution: Tube amplifiers run at very high voltages, and may hold those voltages even after powering down. Only attempt these modifications yourself if you know what you are doing!
I ordered all parts from Musikding. I opened up the amp (remove the four bolts on top and three wood screws on the rear of the chassis, unplug the speaker, and pull out the chassis) and simply clipped of the parts to be replaced as close to the body as possible. This makes it possible to solder in the new parts without having to remove the circuit board.
The result is a considerable improvement. Don’t expect Fender cleans, but the muddiness is gone. The neck pickup is now usable. I would definitely recommend these simple modifications should you be dissatisfied with the sound of your Royal 8.
There are also some other modifications I read about and have the parts for, but not installed yet:
- Replacing C6 with a 5nF cap and C12 with a 0.5nF cap
- Replacing C3 with a 47nF cap
Finally, should you play the amp exclusively clean and get overdrive from pedals, it might be worth trying a 12AY7 or 12AT7 as preamp tube.
Edit: I have now replaced C3 as well. I have decided not to replace C6 and C12 at this point, since one of them sits directly on the circuit board, making it impossible to clip it off and easily solder in a replacement. The sound is pretty good at this point. Low notes are still an issue – an E5 powerchord is a muddy mess. I guess this is due to the 8″ speaker and maybe the output transformer, and not easily resolved. An EQ up front or a Treble Booster (I built mine from this kit) helps here.