I'm not sure what version skylark you're talking about, but I've got a '61 Gibson GA-5 skylark. it uses a 6V6 power tube, 5Y7? rectifier tube, and a 12AX7 pre-amp tube. I switched out the power tube for a cooler grade 6V6 so I can crank it a little more before it starts to break up and I also changed out the pre-amp tube for uhm....I can't remember right now, but it has a lower gain rating that the 12AX7 which interprets ot more headroom....12AU7 maybe :confused: Since the amp has no tone controls, it's pretty muddy with my PRS, but the new tubes brightend it up a bit. It also needs a new speaker for it to sound up to it's full potential. Normally I crank the amp up to around 10-12 o'clock where it's got full blown tube saturation and use the volume knob on my guitar to adjust the amount of overdrive or cleanliness. It's a real fun amp to play on, but it's just lacking with the stock speaker.

I also changed out the tubes in my XXX head and WOW :eek: what a difference! Before, it sounded good. Now, it sounds great.