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Thread: Modern 6550?

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    Supporting Member Randall's Avatar
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    Modern 6550?

    Any insights into what is a good sounding and reliable modern 6550? I need to outfit a sextet for an SVT-CL, but I haven't bought any in years.

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    It's weird, because it WAS working fine.....

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    Tungsol and EH

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    The problem with reliability is that generally it's a retrospective appraisal and from a small subset of the total number of tubes produced. I've used Sovtek tubes reliably in gigging amps but the last SVT quickly came back with one tube that was pulling way more current. I replaced it and no further issues.

    I don't think I've ever seen any reliability specs for modern tubes of any kind. We need a JD Power power-tube survey.

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    When I used to have my vintage SVT I used Svetlana 6550C, and they sounded great and were super reliable for 10 years, but those are super expensive now since they stopped making receiving tubes. I used JJ KT88's in my Sunn stuff and they sounded great and were reliable, so you could try those, however if you decide to go with JJ I suggest to get them from a place that pre-tests the tubes such as Eurotubes. Aside from JJ, there are the New Sensor stuff...EH, Tung Sol, etc., though I've heard hit and miss about their quality level.


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  5. #5
    Better Tone thru Mathematics bob p's Avatar
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    Here's another small-sample-size anecdotal testimonial:

    I have three amps that run either sextets or octets of 6550, two of them are SVT and one is a monster HiFi audio amp. As it turns out they're all populated either with EH or Sovtek. No complaints with any of them. I wouldn't hesitate to use JJ.

    I think it's important to play close attention to matching in high power applications, so that one tube doesn't end up taking all of the current. That's a recipe for failure. The modern SVT use comparators to keep an eye on that.

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