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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 Dynakitparts.com products


    Proper technique to test a pre-amp

    Mr C
    Mr C

    Posts : 96
    Join date : 2019-07-11
    Age : 65
    Location : Visalia CA.

    Proper technique to test a pre-amp  Empty Proper technique to test a pre-amp

    Post by Mr C on Mon Oct 26, 2020 8:24 pm

    When testing the ST-120 I will put a dummy load on the speaker terminals, A 100 watt 8 ohm resister on each side. Input a sine wave at about .75 V. and short out the input not being used. To measure a sine wave through an SP-14 is it necessary to have a dummy load and short the input? I have an audio generator and an Oscope. Whats the technique for testing a pre-amp?
    tubes4hifi
    tubes4hifi
    Admin

    Posts : 1667
    Join date : 2008-11-30

    Proper technique to test a pre-amp  Empty Re: Proper technique to test a pre-amp

    Post by tubes4hifi on Wed Nov 04, 2020 2:00 pm

    no load required. I usually input about 2v p-p (about 700ms rms) and at full volume you should have around 18v p-p output.
    Most important tests are already in the build manual. Check B+ voltage and voltage across D13
    Mr C
    Mr C

    Posts : 96
    Join date : 2019-07-11
    Age : 65
    Location : Visalia CA.

    Proper technique to test a pre-amp  Empty Re: Proper technique to test a pre-amp

    Post by Mr C on Wed Nov 04, 2020 3:06 pm

    Thanks Roy.

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