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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    SP-6 Preamp

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    gothover

    Posts : 9
    Join date : 2009-01-01
    Age : 45
    Location : Spring Valley Lake Ca.

    SP-6 Preamp

    Post by gothover on Fri Jan 02, 2009 1:30 am

    I just ordered an Tubes for HiFi SP-6 preamp kit and power supply, and was wondering if any of you have done any worthy modifications, ie. Cap upgrade, ss rectifier, internal wiring suggestions attenuator or Alps pot etc?

    Suggestions welcome.

    Thanks DH.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    SP6 upgrades

    Post by tubes4hifi on Sat Jan 03, 2009 7:42 pm

    cap upgrades are easy and probably make the most improvement, although these kits are now shipping with Solen caps in most locations, only using 715P types in the phono RIAA section, I'll be researching upgrades for those for better matching and performance.
    SS rectification is NOT recommended, I could write tons on what I've learned and listened to over the past few years, but in a tube preamp, you WANT a tube rectifier.
    None of the voltages in the SP6 are regulated, and they are designed to work with the PAS211 or PA522 power transformer, any substituions here would change the voltages at all points in the circuit, and the series resistors in both the filament circuit and the B+ circuit were optimized to use the PAS power transformer. Same with the power supply capacitors, there is a reason the first 2 are 22uF and the rest are 33uF, although I have a new source of caps that would allow those 33uF to be upgraded to 47uF.
    For a volume pot I would recommend as a minimum either the Blue Alps OR the Black Noble. I have both available.
    I also have a very nice chinese clone of the $175 Goldpoint 24 step attenuator I can sell for $35.
    In my experience doing my "ultimate preamp" last year, I found a very nice combination of rotary switches combined with precision resistors gave me the best results and a nice low cost, using one dual rotary selector for master volume and two mono rotary selectors for left/right gain/balance, you can see more info on that here:
    www.tubes4hifi.com/pre1.htm
    Lastly, let me mention that I am currently in the process of putting together a totally regulated power supply that will work with both the stock Dyna PAS3, and with my VTA SP6 kit.
    It will include a new toroid transformer and a regulator PCB, total cost will be approximately $100 but I'm not expecting it to be finished until mid or late February due to long lead times with Chinese suppliers.
    I will be able to offer this as a test product within a couple weeks (mid-January) if any enthusiastic DIYers would like to do an evaluation for me.
    In addition, by using some Chinese suppliers I will be offering a complete chassis kit similar to what I now show for $350 for around $200. This will only be possible by doing production quantities of the SP6 kit rather than just a few at a time as I have for the past 4 years, which is why I have finally started to run a few ads on ebay for the SP6 kit.
    More news, I expect to offer a line-only version of the SP6 by the end of January, and offer a basic chassis for under $40 to go with the PCB/kit/tubes/power supply for around $160.
    Roy www.tubes4hifi.com
    PS - my work schedule doesn't allow me time to visit this forum as often as I should, so feel free to always contact me directly at either of these emails . . .
    info@tubes4hifi.com
    roymottram@yahoo.com


    Last edited by tubes4hifi on Sat Jan 03, 2009 7:45 pm; edited 1 time in total (Reason for editing : replaced Alps for Noble with Alps OR Noble)

    gothover

    Posts : 9
    Join date : 2009-01-01
    Age : 45
    Location : Spring Valley Lake Ca.

    Re: SP-6 Preamp

    Post by gothover on Sun Jan 04, 2009 10:14 am

    Thanks Roy I am looking forward to the build, I am pleased to hear about the up and coming additions to your already fine list of products.

    I currently have a Goldpoint and Alps Blue, I may try both. As for the cap upgrades, Solens are a respectable nice nice sounding reasonably priced capacitor. The ones I have used as upgrades in the past are Jantzen, Clarity, Kimbercap, Sonicaps, Dayton, and Auricaps. I even used Mundorf oil filled once but the cost to performance ratio was exceedingly high.

    gothover

    Posts : 9
    Join date : 2009-01-01
    Age : 45
    Location : Spring Valley Lake Ca.

    Re: SP-6 Preamp

    Post by gothover on Sat Jan 10, 2009 8:54 pm

    Roy
    Lastly, let me mention that I am currently in the process of putting together a totally regulated power supply that will work with both the stock Dyna PAS3, and with my VTA SP6 kit.

    DH
    I am a bit confused, because the sp-6 has an on board regulator. Or is this for the line stage only version?
    Also this would be a great all around DIY PS for tube based project. A good quiet regulate power supply for around $100 will be outstanding.

    Roy
    I will be able to offer this as a test product within a couple weeks (mid-January) if any enthusiastic DIYers would like to do an evaluation for me.

    DH
    Keep me in mind, I am always enthusiastic about projects.

    I just informed m Father about your ps, and he posed the question, "Are you regulating the AC voltage?" If so he is also very interested in finding out more about this product. If that is the case I may have answered my previous question.

    gothover

    Posts : 9
    Join date : 2009-01-01
    Age : 45
    Location : Spring Valley Lake Ca.

    Re: SP-6 Preamp

    Post by gothover on Sun Jan 18, 2009 10:20 pm

    Here is a link to my preamp build on the Klipsch forums. http://forums.klipsch.com/forums/t/114302.aspx

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    new version SP6 - SP8 preamp with regulated B+ and regulated filaments

    Post by tubes4hifi on Sun Feb 15, 2009 3:47 am

    my SP6 design has done well the past few years, but I've always wanted to try it with regulated B+ and regulated filaments. It works great as it was, as the B+ is CRCRCR filtered!! The filament supply already used a trick to completely eliminate hum, but new designs are fun, so . . .
    The new PCB is ready and for sale on my webpage here at www.tubes4hifi.com/pre8.htm
    The regulator circuit is also available as an add-on for ANY preamp, or to add into a PAS3, but it will require either a new transformer or additional filament transformer.
    Visit my webpage or email for more info . . .
    roymottram@yahoo.com www.tubes4hifi.com

    gothover

    Posts : 9
    Join date : 2009-01-01
    Age : 45
    Location : Spring Valley Lake Ca.

    SP-6 Preamp

    Post by gothover on Thu Mar 05, 2009 3:55 am

    Roy, I have been running this preamp for more than a month now, and want you to know it is just a joy. I especially like listening to phono once more it is a real treat. Very Happy

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