I have an AC15C1VB that I bought for a great price from Sweetwater. It came with a Celestion Creamback speaker and JJ tubes. It sounded nice but did not have the sweet-sounding chime and grind I was hoping for. After spending much time on forums and reading tech specs, I decided to upgrade the tubes to new Tung-Sol. I ordered a matched pair of Tung-Sol EL84s, two standard TS 12AX7, and one TS 12AX7 premium gold pin for the V1 position. Bullseye. It completely transformed this amp, taking it from an average mass production product into boutique tone territory. Both channels now sound equally good, and even the onboard effects (verb and trem), which are not tube-driven (they use op amps), sound better. I highly recommend this affordable and easy upgrade, which took my AC15 from an amp I play at home to one I now play out with. It has truly become my #1 amp. I hope this helps.