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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: 6550 vs. KT88 posted by Bobaroo on August 5, 2006 at 15:18:56:
Old stock Tungsol 6550 (USA, 1960s) had a datasheet that listed 600VDC plates and 400 VDC screens; this was never revised despite the fact that those screen voltage specs are ONLY for the top-getter-only blackplates; later versions are rated for 500VDC screens in pentode and 550VDC or so on the screens in ultra-linear. You CAN push the plate harder than 600VDC if you keep the current draw reasonable and above all else DO NOT over dissipate the screens. But 600 VDC is plenty! The KT88 was rated at 800 VDC plates and 600VDC screens, and also had a plate dissipation rating of 42 watts or so vs 35 watts for the TungSols; however, if you read carfully you will see these KT88 specs are "rigged" stats; they are described by GEC as (design absolute max) Translation--- you CAN run them this hard, but they won't last. Further down on the spec sheet are what GEC calls "design center ratings"-- the ratings at which the tube can operate safely and last fairly long. The plate dissipation listed here is 35 watts, same as a TS6550. I can attest to the fact that a god TungSol will run as hard as a KT88 anyday, and IMHO sound far better. This tube is currently getting gone; good ones are less and less common and cost more and more; blackplate TungSol are seen for sale LESS OFTEN than early KT88s, and cost at least as much.
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- Re: 6550 vs. KT88 - ARC 15:18:26 08/07/06 (0)
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