I inherited some amp projects from a relative, since we shared an interest in single-ended amps. He had four of these red Bogen CH8 PA amps from the Fifties. The original design used a 6SF5 for the Mic channel, and a 6SJ7 for Phono. Those went into a big fat 6L6, with a 5Y3 rectifier. There was a 4-position tone switch.

Each one of his amps were set up differently. On this one, a socket was added to allow a 12AX7 to join the crowd. The RCA and mic inputs were replaced with 1/4" jacks. The 4-position tone switch was replaced with a standard Tone pot. Now, the Mic input is basically a Champ -- runs into the 12AX7, and then to the 6L6. Volume is controlled by the Mic volume. So you get a Champ, but with a 6L6 power tube -- which is fun, right?

The kicker is that the Phono input now runs into the 6SF5, then into the 6SJ7, and then into the 6L6. You're still only getting 2 stages of gain, but you're running through octal tubes. The feel and tone is totally different from the 12AX7 channel. It's a lot of fun to play with, and I can attest it's inspired some new sounds. This is a handwired, point-to-point design and runs pretty quietly. Speaker jack accomodates 4, 8, or 16 ohms with a rotary switch.

The amp collection is way too big, and my wife has been making "hoarder" comments, so I really have to clear out some of the herd. I'll add more shortly