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    Lurker SP14 Build

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    Fitero

    Posts : 8
    Join date : 2015-05-10

    Lurker SP14 Build

    Post by Fitero on Tue Aug 25, 2015 10:50 am

    Hello!  I've been a lurker for awhile, and have been a grateful reader of the experience and knowledge generously posted here.  I found this forum while researching the SP14 preamp.

    I get a great deal of enjoyment poring over photos and descriptions of other peoples' builds.  In that vein, it is my turn to return the favor, and post some photos and comments regarding my own humble experience building the SP14.

    I bought the beautifully made circuit board from Roy and began ordering components from different sources.  The basic circuit board assembly was straight forward.
    A number of years ago, I bought a rough radio case on Ebay, with the idea of repairing the woodwork and installing a tube buffered gainclone amp that I had made in it.
    The amp ended up living it's life in a wine box instead, and the radio case got used as a sort of end table.
    I decided to build the SP14 into the old radio case.  I built a chassis that I could slide into the case easily without modifying it.  
    I left the chassis out of the case for a time while I spent time swapping output capacitors and tubes, playing with how the combinations varied the sound.  In the end, I didn't like any combination of bypass capacitors that I could come up with, and ended up with the Audyn, True Copper, 1.5uf caps in the main output position.

    At the same time, I began obsessing about what tubes to get.   Rolling Eyes I was intrigued by favorable comments regarding the E-1148/VT232 tubes, so I got a dozen of those from a vendor in Lithuania.  I contacted another vendor in China, and had him send me four adapters disassembled so that I could modify them to fit in the SP14 space available.  

    Now, I am enjoying swapping in and out different valves, which so clearly imprint their character on the sound.
    I only have a couple of Mutt n Jeff pairs of 6SN7 and some 7N7 to try with the VT232 at the moment.  I bought some adapters to try 6F8Gs too, but haven't bought any yet.

    As others have stated, the particular sound of a tube is slightly more pronounced when placed in the input position, as opposed to the same tube in the secondary position.  

    I had a very nice Marantz 7 that I sold to make this preamp, and I am not missing it in anything other than a nostalgic way.  I am very happy.

    This is a link to some photos on Picasa: https://picasaweb.google.com/fitero64/VTASP14Preamp?authuser=0&authkey=Gv1sRgCM-SrL-5lO3PYg&feat=directlink

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Lurker SP14 Build

    Post by deepee99 on Tue Aug 25, 2015 5:20 pm

    Fitero,
    Very sweet looking and nicely executed.

    evoroadster

    Posts : 39
    Join date : 2015-06-16
    Age : 66
    Location : Honolulu, Hawaii

    Re: Lurker SP14 Build

    Post by evoroadster on Tue Aug 25, 2015 7:19 pm

    Very impressive.

    Fitero

    Posts : 8
    Join date : 2015-05-10

    Re: Lurker SP14 Build

    Post by Fitero on Wed Aug 26, 2015 8:17 am

    Thanks for the kind comments.

    litefootdan

    Posts : 16
    Join date : 2014-03-21

    Re: Lurker SP14 Build

    Post by litefootdan on Thu Aug 27, 2015 10:46 pm

    Nice to see you here Fitero, that sure is some handsome work you've done!!!

    Fitero

    Posts : 8
    Join date : 2015-05-10

    Re: Lurker SP14 Build

    Post by Fitero on Sat Aug 29, 2015 10:22 am

    Thanks again!
    I am off to a local estate sale in search of more valves to try.

    Though it is clear that my sources are now the weakest link in my system, I am still drawn to the "what if" tube swapping thing. Somewhat luckily, I don't have much disposable income right now, otherwise, I would end of like some of you, with large collections of tubes that were tried and passed over.

    Fitero

    Posts : 8
    Join date : 2015-05-10

    Re: Lurker SP14 Build

    Post by Fitero on Wed Oct 21, 2015 2:41 pm

    I had a niggling 60hz hum that I could make swap from one channel to the other by changing my volume control grounding to the pc, so I finally broke down and yanked out all the 24ga, solid core wire and replaced it with 22ga, stranded, shielded wire.

    Now, the hum is gone, it is silent and sounds absolutely marvelous!  

    I am using 6SN7W, metal base in the input position, and some Sylvania, 6SN7A, green labels in the second position.  I'm in no hurry to try anything else at this point.

    I am a dolt, and haven't been able to upload a photo to this message, so here is a link to a Picasa page with it;

    https://picasaweb.google.com/lh/photo/o3kKuupb6Hvp2CjmMP3eYE54uLkNAkKgl_idIg-x478?feat=directlink

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