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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


3 posters

    SP-14 amplifier matching

    Fitero
    Fitero
    Fitero


    Posts : 21
    Join date : 2015-05-10
    • Post n°1

    SP-14 amplifier matching Empty SP-14 amplifier matching

    Post by Fitero Wed Feb 08, 2017 8:52 pm

    I've been a happy owner of my SP-14 for a year or so. I've paired it with a number of solid state amplifiers in that time.
    I have access to a good selection of amps and have taken advantage of that to see what I like better.

    Recently I decided to assemble a Maya200 from Aspen amplifers aka AKSA. When driven by the SP-14, a lot of the bass disappears!
    Hugh, of Aspen amps told me that some tube preamps have a hard time driving the relatively low 26K input impedance of the Maya amplifier.

    I installed 1uf, Audyn, True Copper caps on the output of the SP-14.

    What do I have to change to make the SP-14 more compatible with the Maya?

    I'd be thankful for any suggestions.

    Peter
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    Onlinepeterh
    peterh
    peterh


    Posts : 1869
    Join date : 2012-12-25
    Location : gothenburg, sweden
    • Post n°2

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

    Post by peterh Thu Feb 09, 2017 12:45 am

    Fitero wrote:I've been a happy owner of my SP-14 for a year or so.  I've paired it with a number of solid state amplifiers in that time.  
    I have access to a good selection of amps and have taken advantage of that to see what I like better.

    Recently I decided to assemble a Maya200 from Aspen amplifers aka AKSA.  When driven by the SP-14, a lot of the bass disappears!  
    Hugh, of Aspen amps told me that some tube preamps have a hard time driving the relatively low 26K input impedance of the Maya amplifier.  

    I installed 1uf, Audyn, True Copper caps on the output of the SP-14.  

    What do I have to change to make the SP-14 more compatible with the Maya?

    I'd be thankful for any suggestions.

      Peter

    You have to add a buffer to the output. Either an internal built into the sp-14 or
    an external buffer connected between the sp-14 outputs and thepower amp.

    A buffer could be a "catode follower" or a silicon equivalent.
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    Fitero
    Fitero
    Fitero


    Posts : 21
    Join date : 2015-05-10
    • Post n°3

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

    Post by Fitero Thu Feb 09, 2017 9:58 am

    Thank you for the guidance Peterh.

    As luck would have it, I just completed assembling a buffer which I had intended to use for another project. I will install it and give it a listen.

    Regards,
    Peter
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    Roy Mottram
    Roy Mottram
    Roy Mottram
    Admin


    Posts : 1839
    Join date : 2008-11-30
    • Post n°4

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

    Post by Roy Mottram Fri Feb 17, 2017 6:22 pm

    it seems PeterH doesn't know or realize that the SP14 DOES have an output buffer stage, the well known AIKIDO output (Broskie modified cathode follower).
    The output impedance of an SP14 with standard 0.33uF output caps is around 600 ohms, and has freq response flat down to below 10Hz into a 50K load.
    Changing the output cap to 1.0uF should be enough of a change for it to work well with 26K input impedance on an amplifier.
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    Onlinepeterh
    peterh
    peterh


    Posts : 1869
    Join date : 2012-12-25
    Location : gothenburg, sweden
    • Post n°5

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

    Post by peterh Sat Feb 18, 2017 3:34 pm

    tubes4hifi wrote:it seems PeterH doesn't know or realize that the SP14 DOES have an output buffer stage, the well known AIKIDO output (Broskie modified cathode follower).
    The output impedance of an SP14 with standard 0.33uF output caps is around 600 ohms, and has freq response flat down to below 10Hz into a 50K load.
    Changing the output cap to 1.0uF should be enough of a change for it to work well with 26K input impedance on an amplifier.

    I stand corrected, i have no schematics or experience of sp14.
    But i know that low freq. loss when connecting to a low impedance load is a symptom of
    "too high driver impedance".
    If that may be cured by changing output cap - excellent! That saves an external buffer.

    This forum is a great place to learn!
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    Fitero
    Fitero
    Fitero


    Posts : 21
    Join date : 2015-05-10
    • Post n°6

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

    Post by Fitero Thu Feb 23, 2017 8:50 am

    Thank you Roy for chiming in here with your expertise.
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    • Post n°7

    SP-14 amplifier matching Empty Re: SP-14 amplifier matching

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