Still loving my PS100, an amazing piece of gear. I rely on it so much live, I’m thinking about replacing the power tubes just to be on the safe side since they look like they’re a bit toasty. I did a search and it appears the manual suggests 6550’s. I need to look and see whats in mine, but aren’t 6550’s at best a 40w tube? How is it a 100w power section with tubes capable of say 80w max? Or is 80w close enough to just call it 100w?
I’ve seen old posts about recommending JJ 6550’s from a few years ago, but I know things change as tube batches cycle through. Is that still the go to? Would KT88 be a better fit if I want to get it as close to that 100w rating as possible? I see JJ 6550’s as rated at 35w each, so that’d drop us to 70w output. I want max headroom for boosting smaller amps to compete with the big boys. I’m also conscious of tube size, since there is limited space in there so perhaps some tubes won’t even fit.
Any insights and recommendations would be great, thank you!
Is it possible you’re seeing a “40 watt maximum plate dissipation” per tube and ascribing that to a maximum power output? they’re not the same quantity. plate dissipation is how much power can be radiated away from the tube as heat. but the amount of power the tube can deliver to a load can be much more in certain cases.
take this old 6550 datasheet. https://frank.pocnet.net/sheets/127/6/6550.pdf
you see the 42 watt max plate dissipation on page 2. but then on page 3 for typical class AB characteristics it says a pair can deliver 100 watts to a load given a plate voltage of 600 volts, among other things.
you can also find plenty of historical examples of pairs of 6550s in class AB delivering 100 watts to load.
you asked about JJ’s in particular. their datasheets list “Wa” as 35 watts. this is the plate (or anode) power, or dissipation. not the same as power delivered to load.
it’s important to remember that tubes do not make power. the power supply makes power. the tubes control how that power is delivered.
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