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Thread: Valve life & changes

  1. #1
    Join Date: Jan 2021

    Location: West of Scotland

    Posts: 22
    I'm Martin.

    Default Valve life & changes

    I have a pair of Icon MB90 monoblocks that are just over 3 years old which I have owned for a couple of months. This is impossible to answer exactly, however by my reckoning the KT150s have probably done 2500 hours as a guess, so is it about time to consider changing them? Thus far they seem fine and they aren't showing signs of low emission but I would rather change them before there is a big bang.

    The input valve is a 6SL7, I have a pair of Sylvania JAN which could be NOS made in 1951, any good? The phase splitter is 6SN7/CV181, what might be a good recommendation for this. I have a pair of new Psvane CV181 but if theres a better suggestion I'd certainly consider it.
    Regards
    Martin

  2. #2
    Join Date: Jan 2008

    Location: Norfolk, UK

    Posts: 5,662
    I'm BigBobJoylove.

    Default

    I have the Sylvania 6SL7s in the cupboard. They're ok. In my experience however, the best 6SL7 I've heard is the late 50's RCA 5691 Red Base black plate. I use a pair of NOS in my buffer stage. Pick up a NOS single for around 60, or a NOS tested matched pair for 120-130; they're getting rare though.

    Also excellent is the Melz 6H9C metal base from the 50's. Superb valves and they're more numerous. Grab one for about 40 from Russia or Ukraine on eBay, a NOS tested matched pair for around 90.

  3. #3
    Join Date: Jan 2021

    Location: West of Scotland

    Posts: 22
    I'm Martin.

    Default

    Bob
    Thanks for the thoughts, I have substituted the Sylvanias for the Tungsol gold pins. There is a difference, the top has opened out compared to the Tungsol ones though they weren't too bad. I don't doubt the RCA 5691s would make a difference as well, whether enough to justify the cost is debatable. I think I might do something re the 6SN7 phase splitter, currently Psvane CV181 (which might actually be 6SN7), Shuguang Black Treasure seem well thought of but thats another 143 plus postage, again whether the fairly minor change justifies the expense is frankly open to question.
    Regards
    Martin

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