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new smelly map day


blueballoon

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I doubt that it does put out 90W, but a pair of 6L6 tubes can do it AFAIK. It's very similar to how Pete Traynor got 90W out of the YBA-1A Mk.2, he just ran ridiculously high plate voltages on them.

 

Rated dissipation on a 6L6 is ~30W, so a pair is reliably good for about 60W RMS. Yes, you can push them harder than that, and if you have an overbuilt tube that can take hot plate voltages, and go with beefier transformers, etc. you can up the wattage... but you won't be able to go all THAT much higher, and when you do, you will be going through tubes at a faster rate - and if your "beefy" tubes are unavailable, and you try to toss in a cheap pair of MIC 6L6's from some hole in the wall music store in the middle of nowhere while you're out on tour, you are probably not going to get through a single gig with an amp that is designed to try to suck 90W out of a pair of 6L6's.

 

I am unaware of any amp that was factory spec'ed to push 90W from a single pair of 6L6 output tubes. Even the UL era Fender Twins "only" pushed 135W from a quad of 6L6's. The "two tube" version - the Pro Reverb from that same era, was rated at 70W, and they definitely need good quality tubes to run reliably for any length of time - especially if you're going to run them hard.

 

As far as the YBA-1A MKII, I'm not super familiar with that amp, but the same general principles apply. IIRC, it had various revisions over its life, and only some versions had the hot 600V B+ voltage, and 90W output. I would suspect those revisions gobble most "modern" tubes unless they've been modded by a tech to idle them back a bit. Also, weren't they EL34 / KT77 or 6550 based? I didn't think they used 6L6's. :idk::confused:

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