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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


    Noobie to tube world.

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    rickelrod

    Posts : 7
    Join date : 2013-02-05
    Age : 50
    Location : Berryville,VA

    Noobie to tube world.

    Post by rickelrod on Tue Feb 05, 2013 11:24 am

    Hey all,
    My name is Rick and I am a newly proud owner (in waiting) of an ST 70.I wont have the new to me unit in my possesion until next week as it was just shipped yesterday.This will be my first tube amp! I bought it from a fella on another site and I think I made a good purchase.Currently I plan to play it through some KG4s I have here. I'd like to list the description of the mods made to it by the previous owner as described by him and would like some input from you guys with knowledge on this unit.Thanks in advance and I am looking forward to learning from all of the info available on this site!

    Regards,
    Rick

    This is a ST-70 that I purchased a few years ago and discarded everything but the cases and transformers. The chrome has some pitting and some of the lettering has rubbed off over the years. But on the insides the original circuit board has been replaced with a Triode Electronics board that gets rid of the 7199 tubes and replaces them with 12AX7's & 12AU7's. I upgraded this board with metal film resistors, Aura coupling caps, ceramic & gold plated tube sockets. The output tube sockets are also ceramic and gold plated. The Multi-cap is still there but only for show. It's function has been replaced by banks of Nichicon 450V capacitors with at least doubling the stock capacitance rating on each amplification stage to give a more focused soundstage and stronger bass than a stock unit. The input and speaker jacks are Cardis and are wired to the 8 ohm taps. The amp also has switches on top to switch between triode and pentode mode. The internal signal wiring is teflon cover silver. The driver tubes are Electro-Harmonix and the output tubes are matched set of Sevelanta EL-34's.


    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Noobie to tube world.

    Post by Bob Latino on Sun Feb 10, 2013 8:28 am

    Hi Rick,

    See if you can post a photo or two of your amp > maybe the top of the amp and the inside wiring. There are many ways an ST-70 can be rebuilt and sound great. Sorry I didn't see your post before. I have been dealing with a blizzard here in the Northeast ..

    Unless those Nichicon 450 volt rated caps are in series which doubles the voltage rating to 900 volts, 450 volt rated caps are really too low for an ST-70 amp especially with todays higher line voltages. Dynaco wisely used a 525 volt rated quad cap. When you turn the amp on I am sure that the initial power surge is over 450 volts but if the amp is still playing - evidently those 450 volt rated caps can take the surge ...

    Bob

    rickelrod

    Posts : 7
    Join date : 2013-02-05
    Age : 50
    Location : Berryville,VA

    Re: Noobie to tube world.

    Post by rickelrod on Sun Feb 10, 2013 10:48 am

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    Hi Bob. Thanks for your reply. Here are a couple of pictures. I should receive the unit tomorrow.I purchased it from a fellow AK member. I also bought a PAS2 which has been modded from a different AK member. I hope everything works as it should.

    kevinmi

    Posts : 54
    Join date : 2009-11-17

    Re: Noobie to tube world.

    Post by kevinmi on Sun Feb 10, 2013 3:01 pm

    The tube amp will sound good through the KG-4's, but if you ever have an opportunity to upgrade to the bigger and more efficient Klipsch speakers like the Cornwalls, LaScalas, Belles, or Khorns, you will be truly amazed at how good (and loud!) the tube/Klipsch combination can sound.

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