The Dynaco Tube Audio Forum

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


    Bob's ST-120

    Share

    davek65

    Posts : 12
    Join date : 2011-01-22
    Location : Pittsburgh

    Bob's ST-120

    Post by davek65 on Thu Aug 04, 2011 6:19 pm

    Hi All,

    Really like this forum . Just wanted to say that the ST-120 from Bob is the best out there
    for the money . I built Bobs ST-120 in January and have over 1000 hours on it now and don't
    know why i didn't get one sooner . I've done a little tube rolling with it and keep going
    back to the Russian Gold Lion KT 88s .

    Have tried the TS-KT-120s ,Chinese KT 88 98s but am sticking with the GLs . I have all the
    upgrades except the attenuator . I have the better driver tubes that Bob sells and have 3
    sets of GL KT 88s for backup so i think Im good for a while . I've learned from reading posts
    on here that there's a difference in tube brands as far as what the end sound would be .

    Not sure about the audio difference in the driver tubes but am sure about the differences
    in the KT 88s.

    Keep those posts coming we all get some good knowledge here . ~Dave

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Bob's ST-120

    Post by costerdock on Thu Aug 04, 2011 11:21 pm

    That is great to hear Dave. I've read nothing but great reviews - I cannot find one bad one. I've mulled over the idea of a bob latino amp or a mcintosh for quite a while - I ended up with the M125s that I'm currently building. I'm keeping my fingers crossed that I've made the right choice. I'm sure I have.

    davek65

    Posts : 12
    Join date : 2011-01-22
    Location : Pittsburgh

    Re: Bob's ST-120

    Post by davek65 on Fri Aug 05, 2011 10:26 am

    I think you'll like the M-125s .The circuits are updated with modern technology and Bob's
    assembly manuals are excellent with clear pictures and you can e-mail him . He'll give you
    a quick response on any questions you have about assembly . Mine fired up the first time
    with no problems . After you've completed the kits and run them for a while try different
    power tube brands to find out the difference on the sound output . I wouldn't have thought
    there would be a difference but there really is as far as the mids and bass is concerned .

    davek65

    Posts : 12
    Join date : 2011-01-22
    Location : Pittsburgh

    Re: Bob's ST-120

    Post by davek65 on Fri Aug 05, 2011 11:08 am

    Hi Costerstock,
    Your not the only one that has made the mistake of putting the AC balance pots on
    the wrong side of the board . I made the same mistake on assembling the st 120 but
    was able to remove them and reinstall correctly . The circuit boards are double faced
    so its a tricky removal if you made the mistake .

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Bob's ST-120

    Post by mantha3 on Fri Aug 05, 2011 7:00 pm

    Just keep the Balance deals on top... ya screw up then take em off and put them on the bottom.

    Tubes...

    I have Shuguang Treasure KT88 tubes in my ST120 and they are awsome! I guess I'd pick them over the Gold Lion Re-Issue KT88s but it is hard to tell the difference. Both are solid.

    12AT7 in the voltage amp is good to tube roll. My fav. is a Siemens NOS.

    I have a Big Bottle GZ37 for a Rectifier.. not cheap. Built like a tank and a cool historic 50's tube

    McIntosh has a cool complex circuit but I don't find the sound to be better.

    jhoak

    Posts : 46
    Join date : 2009-10-16
    Age : 58
    Location : Central Florida

    Re: Bob's ST-120

    Post by jhoak on Sat Aug 06, 2011 9:10 am

    Add me to the ST-120 “fan” club please.

    I finished mine just over 6 weeks ago. It’s been playing pretty steadily ever since.

    I made the mistake of not getting the low gain driver board originally so I ended up buying the kit for one and swapping it out.

    Right now it’s running a Psvane 12AU7 in the center position and Electro Harmonix 12AU7s in the outboard positions. For the rectifier I’ve installed a Weber “CopperCap” WZ68. Output tubes are a matched quad of Tung Sol KT120s. All available options have been installed. The time delay board is an absolute essential here in Central Florida with our blinkie-blinkie power. The stepped attenuator is especially nice in my system as my preamp (McIntosh C32) has a good bit of gain.

    There are only 2 places where I “strayed” from the original kit components. (1) Since the low gain driver board specifies .33uF coupling capacitors rather than .22uF I installed a set of Mundorf .33uF 630V. (2) I purchased off of eBay one of the bias point kits to replace the normal octal sockets. The reason for this is that I have a set of specially constructed leads for my DVOM that fit these connections. If I ever decide to sell the amp (no time soon) I’ll put the octals back in

    I am very VERY pleased with what I’m hearing. Mine spends most of the time in triode mode but every now and then I’ll flip it over to ultra-linear. Several people have now been to my house and heard my system with the ST-120. To date everyone has been very impressed.

    If you’re “on the fence” about getting any one of the three offerings my advice is DO IT. Today. In kit form it’s easy to build and the step-by-step instructions are excellent. If you’re not comfortable with a soldering iron then get Bob to build one for you. Either way you’ll end up with an amplifier that sounds WAY better than it has any right to at its price point.

    Many MANY thanks go out to Bob and Roy for their fine products, excellent support, and dedication to the audio “niche” known as Dynaco/Dynakit.

    Here’s a picture of mine singing…


    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Bob's ST-120

    Post by mantha3 on Sat Aug 06, 2011 9:54 am

    Did you get the Psvane from Grant Audio? I've been toying with the idea of getting a Psvane 12AT7 to try to roll in the same spot you have yours in.


    jhoak

    Posts : 46
    Join date : 2009-10-16
    Age : 58
    Location : Central Florida

    Re: Bob's ST-120

    Post by jhoak on Sat Aug 06, 2011 10:00 am

    Yes I did. I actually bought 3 of them. After a bit of experimentation I determined that using them in the 2 outboard sockets didn't bring anything to the party.

    If you're a "paid" member at audiokarma.org you get an additional 5% off of purchases at Grant Fidelity. I bought them during their 10% off sale so with the additional 5% I got them at a pretty good price.

    I'll be selling off the other 2 soon. Look for them to be listed here.

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Bob's ST-120

    Post by Bob Latino on Sat Aug 06, 2011 10:08 am

    Hi Jeff,

    RE: >"I made the mistake of not getting the low gain driver board originally so I ended up buying the kit for one and swapping it out"

    You hadn't mentioned to me at the time of your kit purchase that you had 100 dB efficient speakers. If you had, I would have recommended the lower gain board for your amp kit. The general consensus between Roy and myself are that the standard gain board (which uses 12AT7 driver tubes) works very well for 93 dB or lower efficiency speakers. (Most speakers are in this category.) If, however, you have 94 dB efficient or higher speakers then the lower gain board (which uses 12AU7 or 12BH7 driver tubes) is probably a better idea. I have listened to both versions of the board extensively and IMHO both board versions sound the same. The only differences that you may note are those that are driver tube related. IOW some driver tubes sound a little different than others.

    Bob

    Sponsored content

    Re: Bob's ST-120

    Post by Sponsored content Today at 3:01 am


      Current date/time is Mon Sep 26, 2016 3:01 am