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    It's a boy..!

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    Pat R.

    Posts : 54
    Join date : 2015-02-26
    Location : SE Pennsylvania

    It's a boy..!

    Post by Pat R. on Sat Feb 28, 2015 3:32 pm

    Well no not really.. it's a VTA ST 70.. it just came into the world this afternoon. My tubes arrived via USPS this morning and the first place I went was the work bench in my basement workshop..

    Let me start by saying I have rebuilt many many amps and preamps, so I'm no stranger to how they are contructed. This kit was a real gem. All the marked parts bags made layout for assembly so much easier. It went together much easier than I had anticipated, especially since I'm the "put the bike together first, then read the instructions kinda guy".. and for this build I relied on the picture and diagram as much as I did the written instructions. After building I checked, double checked and checked again.. including inspecting each solder joint with a BIG magnifying glass..

    Now I know these next parts will probably give some of you (Bob?) kittens.. but I wired up the speakers to the four point terminal board I ordered from Dynaco Parts.. yes I know.. I went old school look.. I wanted the flexibility on this amp of 4/8/16 ohm speakers, plus those big ole gold plated terminals reminded me of someone puttin' 22's on their 1968 Firebird.

    And here is the kittens part.. I plugged the amp into my variac and in stages I brought it slowly up to voltage. First with the rectifier, then the miniatures and finally the output tubes. No problems.. nice warm glow from each tube, no glowing plates, no noise from the speakers.. The speakers I am using for testing purposes in my shop are a pair of Mirage m190 bookshelf speakers. Small, inefficient, but quality..

    After a few minutes of warm up at full voltage, I shut it down. I then fired it up again and set the bias for each tube. I can say that the pots are very sensitive so I set the bias at around .39999 or as close to .4 as I could get without going over. Once that was done I plugged in my preamp. This is a newly acquired HK Citation I that I just rebuilt before building the ST 70. This means that it's not broken in yet either. I picked a CD which just happened to be Pink Floyd Dark Side of the Moon. Once it started playing I could hear how good this amp was! Even on these little speakers the response is great. I can't wait to hook it up to a pair of efficient Alnico Magnet speakers (what tube gear is meant to be played through).

    I'm really going to enjoy breaking this amp in! It was a real pleasure to build the kit. This was my first kit and certainly not my last. Over the next year or so I'm hoping to build at least another one, possibly two.

    Sorry this build went so smooth, not much to talk about! haha

    clown

    Only thing I would like to see someone come up with is a way to cover the circuit board.. maybe a stainless steel plate to match the amp with tube holes cut into it, that could be mounted like a cage or on SS standoffs with SS screws.. this sounds like something I might have to do! hah

    Pat R.

    Posts : 54
    Join date : 2015-02-26
    Location : SE Pennsylvania

    Re: It's a boy..!

    Post by Pat R. on Sat Feb 28, 2015 4:31 pm



    You can see if you look closely I added the diode mod to the rectifier base.



    Neat workbench?.. ah, I know where everything is!

    Maintarget

    Posts : 208
    Join date : 2013-02-10

    Re: It's a boy..!

    Post by Maintarget on Sat Feb 28, 2015 5:55 pm

    Congratulations,nice job on the build!

    Cubdriver

    Posts : 68
    Join date : 2014-01-21
    Age : 51
    Location : Southeastern Litchfield Co, CT

    Re: It's a boy..!

    Post by Cubdriver on Sat Feb 28, 2015 8:38 pm

    Looks like a nice neat build. Well done! Enjoy!

    -Pat

    Pat R.

    Posts : 54
    Join date : 2015-02-26
    Location : SE Pennsylvania

    Re: It's a boy..!

    Post by Pat R. on Sat Feb 28, 2015 9:02 pm

    Thanks Guys.. and most of all it was both fun and relaxing to build..

    Now that it's got a few hours on it already it's starting to mellow out.. Nice sound! Can't wait to hook it up to the big boys.

    Pat R.

    Posts : 54
    Join date : 2015-02-26
    Location : SE Pennsylvania

    Re: It's a boy..!

    Post by Pat R. on Sun Mar 01, 2015 3:29 pm

    Just checking back in.. after putting as many hours as I could on the new amp (and my freshly rebuilt Citation I Preamp).. I did a bit more listening this afternoon.. as I mentioned for now I'm using a pair of bookshelf speakers (mirage 190) for testing in my shop since it's too small for the Altecs down there.. Today I decided to add a subwoofer.. The Citation has a center channel out and I happened to have an Infinity 100w powered subwoofer laying around. So I hooked it up and while playing a test CD adjusted the blend control to my tastes.. The only drawback to modern speakers is that they are power munchers, not near as efficient as old Alnicos. I think the 604C is about 108DB at 3' or somewhere close to that. So I have to crank it up a bit more to get the volume.

    I just can't say enough about this amp (and the preamp must be pretty good too).. first off it is DEAD silent! No hiss, no noise, just silence.. Now playing Michael Jackson Off the Wall CD and also a Fleetwoods CD and running them through the tracks. At flat response on the Pre. This get up sounds so much better than I could have anticipated. You guys know all the terms.. warm, detailed on and on..

    On the Fleetwoods I did a comparison of UL and Triode.. I'll say the triode mode is more mellow, I just happen to like the punch of UL.. My Altec 604C's are supposed to really shine with a triode amp so that's on the list. I had a pair of Altec Valencias but the horns were a bit "honky".. great Altec sound but certainly happier in a larger environment. I'll bet this amp in Triode mod would tame those horns a bit.

    Also at this point, there is much discussion about different tubes.. I'm sorry, I just can't see the reason to roll tubes. It sounds great the way it is.

    Color me a happy camper..


    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: It's a boy..!

    Post by tubes4hifi on Sun Mar 01, 2015 11:45 pm

    I thought this old post was a "sticky" and maybe it should be moved there, but yes, their are covers available by custom order . . .
    this photo is from FOUR years ago and the board has been updated a couple times since then . . .

    http://dynacotubeaudio.forumotion.com/t622-new-product-vta-driver-board-cover-photo?highlight=plexi+cover


    Pat R.

    Posts : 54
    Join date : 2015-02-26
    Location : SE Pennsylvania

    Re: It's a boy..!

    Post by Pat R. on Mon Mar 02, 2015 8:44 am

    Nice cover.. can I have one in polished stainless please... Twisted Evil

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: It's a boy..!

    Post by tubes4hifi on Mon Mar 02, 2015 12:42 pm

    only available in plexiglass or aluminum

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