We recently had a Landgraff Custom 50 on the bench. It was sold by the owner and when he tested the amp before sending it out noticed some strange sounds, a bit of howling at certain frequencies and a loss of bandwidth generally. I suspected tubes, but the owner shipped me the amp so that I could go over it and make sure it was ready for the new owner. John Landgraff died while I had the amp, unfortunately.
Landgraff was based in Florida, where he had been making critically acclaimed amps & overdrive pedals for many years. He wasn't particularly well known to the general music community, and didn't produce many amps, but he was truly a great amp and pedal maker.
This Custom 50 is one of the best sounding amps I have ever played in fact. A wonderful amp with a huge sound, incredible harmonic content and wildly dynamic responsiveness.
I replaced two of the preamp tubes and the phase inverter, installed a new rectifier, re-flowed several soldier connections, cleaned the pots and jacks, tightened down a few screws and the amp was good to go. It was a real privilege to work on one of John's amps. The timing didn't work for the seller though, as the amp probably doubled in value a week after it was sold! But the new owner wanted to play the amp, and didn't buy it as a collectable, so everyone was happy.
I was really impressed with the quality of the work in the amp build. Great components and lead dress. The design also had some very cool options, such as like being able to use one side of a 12AX7 for each pair of inputs, or to cascade the two sides of each twin triode. You could also shift between a 56K & 100K slope resistor in the tone stack, and flip between a solid state and tube rectifier. Truly a great and versatile amplifier!