Always on the quest to pack more power into a single tube, the 6550 was launched in the 1950’s by Tung-Sol. Tung-Sol are an American company who specialise in vacuum tubes. They still sell their reissue of this famous valve.
The 1950’s version was rapidly improved in the 1960’s to produce the MKIII version.
The 6550 tube or 6550 valve has a plate dissipation of 42 Watts. This mean it can handle a LOT of power. Compare this with, for example, the 6L6GC which can handle 30W or the EL34 which can handle 25W.
The 6550 valve allows for amplifier designs up to 100W (peak) using just a pair of valves. This would normally require four EL34s. Ampeg started using the 6550 valve in their SVT range of amps, typically 6 per amp yielding an awesome 150 watts of raw power. A side advantage is you can also do your toasted teacakes on the heat chucked out by 6 of these 6550 beasts.
The 6550 tube was also used in many Hi Fi amps from the 1960’s. It’s fascinating to note the harmonic distortion for these valves is about 10%. TEN PERCENT!! Compare that with the 0.005% for a good transistor Hi Fi amp! This doesn’t matter if you are using the 6550 tube in a guitar amplifier of course, since a guitar amp is effectively a fuzz pedal in a big box!
The JJ 6550 is a ‘straight bottle’ version of the original Tung-Sol (which came in a pear-shaped bottle). These JJ 6550 produce a really excellent sound in bass and guitar amplifiers. They are also sensibly priced. Often a JJ 6550 will be half the price of a Tung-Sol 6550 reissue.
Technically, the 6550 valve is a high power beam pentode. That means it has five electrodes. A cathode, an anode and three grids. It has a standard octal base with keyway for lining it up with the socket.
If you are looking to buy JJ 6550 valves or JJ 6550 tubes, then look here.