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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


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    PH14 With Volume Control

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    Rec


    Posts : 43
    Join date : 2020-03-11

    PH14 With Volume Control Empty PH14 With Volume Control

    Post by Rec Thu Oct 06, 2022 9:46 am

    Ive been using a PH14 for some time. I find the output level / gain to be too high for my pre-amp, and I think is overloading the input on my pre-amp.

    Ive seen EAR 834 with a volume control, and this circuit is clearly a clone, so I assume this is a possibility.

    I started by adding a 50K pot to the output of the ph14. This reduced the max output even at full volume. So I looked around the web and found the schematic below. I removed the 220K resistor on output and implemented the circuit on the right (left is original). This seems to provide a reasonable degree of signal, but I can't help im missing something basic. Is there another way to adjust the gain with a pot? I have also read that using a 5751 for the gain stages will also reduce the overall gain of the ph14.

    Does any one have experience or insights with this issue? Appreciate any insights.

    PH14 With Volume Control Img_4810
    Dave_in_Va
    Dave_in_Va


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    Join date : 2013-04-02
    Location : Mid. VA

    PH14 With Volume Control Empty Re: PH14 With Volume Control

    Post by Dave_in_Va Thu Oct 06, 2022 11:05 am

    I'm not a tech but I know the 5751 has 30% less gain than a 12AX7.
    Seems like it would work to that extent.
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    Rec


    Posts : 43
    Join date : 2020-03-11

    PH14 With Volume Control Empty Re: PH14 With Volume Control

    Post by Rec Thu Oct 06, 2022 1:58 pm

    Thanks yea maybe I’ll try new tubes. Wondering if any one has similar experience. Thanks
    tubes4hifi
    tubes4hifi
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    PH14 With Volume Control Empty Re: PH14 With Volume Control

    Post by tubes4hifi Sat Oct 08, 2022 10:42 am

    your circuit with volume only has about 30K to ground compared to the 220K original, but would work better with a 100K or 250K volume pot.
    Changing one or two or three tubes to 5751 should make a big difference in gain.

    Rec likes this post

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    Rec


    Posts : 43
    Join date : 2020-03-11

    PH14 With Volume Control Empty Re: PH14 With Volume Control

    Post by Rec Sat Oct 08, 2022 10:57 am

    Understood. I have no need for another potentiometer in my life. So going to buy some new tubes. Thank you Roy.

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