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    VTA SP9 preamp with tone controls

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    tubes4hifi
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    VTA SP9 preamp with tone controls

    Post by tubes4hifi on Fri May 06, 2011 12:26 am

    I just finished building this preamp for a customer, the SP9 preamp with tone controls, and added PH12 phono circuit.
    This came out fairly nice. The circuit is also available as a plug-in replacement for the PAS3 PC5 line amp.
    I've had this circuit for about 4 months now and thought it would be a popular choice, maybe just not enough info posted on it.
    Check out photos here:
    SP9 preamp
    yes, it's dead quiet, and the tone controls work very well

    quad

    Posts : 14
    Join date : 2010-11-25

    Re: VTA SP9 preamp with tone controls

    Post by quad on Fri May 06, 2011 10:18 am

    That looks awesome. Great work.

    Pooch

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    Age : 66
    Location : Wa

    Re: VTA SP9 preamp with tone controls

    Post by Pooch on Fri May 06, 2011 4:11 pm

    Nice job, Roy. Beautiful work. Do you twist the black and red wire in an electric drill? How long a length at a time. It all looks so evenly wound. I have trouble getting the winds all looking the same. Small pieces i use one of those aviation wire twisters, made for safety wiring of parts.
    Gordy

    tubes4hifi
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    Re: VTA SP9 preamp with tone controls

    Post by tubes4hifi on Fri May 06, 2011 6:25 pm

    yes, I definitely use a drill to twist the wires, as long as my arms can reach, about 4-5 feet.
    I used to tie some wire off on a doorknob 10-12 feet away, but it's easier just to do in with my arms spread out.

    j4570

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    Join date : 2010-08-30

    Re: VTA SP9 preamp with tone controls

    Post by j4570 on Fri May 06, 2011 9:18 pm

    So who is R. Waters, the circuit designer?

    J. Waters

    j4570

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    Re: VTA SP9 preamp with tone controls

    Post by j4570 on Fri May 06, 2011 9:21 pm

    Also, this must be the 16" chassis?

    And do they come predrilled?

    That's a nice looking setup, particularly for the money.

    tubes4hifi
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    Re: VTA SP9 preamp with tone controls

    Post by tubes4hifi on Fri May 06, 2011 11:12 pm

    yes, the circuit design was by private consulting with R Waters who has great experience using computer design to optimize tube audio circuits, in order to get the highest performance possible with the least amount of added distortion due to the necessary additional gain needed to overcome the high losses in a tone control circuit. He did an original design for the PAS3 upgrade about a year ago and then
    I asked him to let me license the design to my specific needs. Then the PCB layout was done by myself optimizing the traces, layout,
    and ground planes, and integrating my tube preamp power supply.
    The 16" chassis is available completely undrilled, or finished and ready to install all components, just like all of my preamp designs.
    There is also a 12" version available if you don't need room for a phono preamp.
    Tubes4HiFi preamps link

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