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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all products

    SP14 hum during warmup


    Posts : 19
    Join date : 2021-02-12

    SP14 hum during warmup Empty SP14 hum during warmup

    Post by bobgroger Sat Jul 17, 2021 9:53 pm

    I know you are supposed to turn the preamp on and warm it up before turning on the amp. BUT... I have a 120 hz hum during warmup that seems to be very dependent on tubes and their locations. In all cases the hum is gone when warmed up, not the noise with some tubes. I have 10 old stock 6SN7 tubes. Some are microphonic. Some hum worse than others. Some are noisy. Are new manufacture tubes any better?

    Posts : 139
    Join date : 2017-08-10
    Location : MetroWest, MA

    SP14 hum during warmup Empty Re: SP14 hum during warmup

    Post by DavidR Yesterday at 2:00 pm

    Some new production tubes are OK. My beef with them is that they do not sound toobie/warm. Remember, Russia and Yugoslavia (or whatever the other country is) are not the pinnacle of production/manufacture. China is the other source with cheap tubes. However, you can get some nice tubes, like Psvane, but you pay the price.

      Current date/time is Wed Jul 28, 2021 2:59 pm