New construction st120

Hallo friends
Almost ready to start my second build, still missing other components that are on the way.This time I will make a ST120 from the very famous Bob Robert Latino, my idea is to use Hammond output transformer model 1650NA, and the power transformer made here in Italy and for the driver card instead I will buy it directly from Bob.

I don't see it on Bob's web site any more, but, the autobias board has been a blessing to my ST120.  I wouldn't build another without it.

This is the only legit looking place I see it today:  https://www.audioamp.eu/automatic-bias-control-module-for-dynaco-st70-ab-q-st70-st120/

at the moment they start with the construction of the st120 as per project, then any tricks in the evaluation phase, however I had read and seen this system. I will evaluate, thanks a lot for the suggestion

Other notes:

• Upgraded tube sockets, capacitors (C5,C6,C7,C8), and use KT88s for the power tubes.
  
• High quality Circuit breaker of the same capacity instead of the slow blow fuse.  Circuit breaker pop delay is same as slow blow fuse.
  
• A fuse and MOV at each power tube with the auto bias board. There are micro sockets for the fuse (it saved me the power tube when I had a bad power tube).      
       https://dynacotubeaudio.forumotion.com/t3627p50-auto-bias-board-on-roy-s-website#35422 
  
• Don't use a solid state rectifier.  I have used a Telefunken GZ34-TK without any issues.
  

transformer made in Italy for my ST120

Interesting with an european source of "dynaco" transformers. Who is this source ? Do they have a webpage or contact information ?

I certainly give you the link. If interested, ask what kind of amp model you need to make.
https://www.raoli.it/

You most certainly will want the metal "shielding" on the bottom of that transformer. 50 cycle hum will drive you nuts to hunt down.

If you are referring to the metal cap, I cannot mount it because it would not fit into the frame. The transformer in turn has a shielding inside, not visible due to the cover with the paper, moreover it will then be connected to the gnd of the electricity network so theoretically I shouldn't have any problems. For example, with the ST-70 I have no problems, also a transformer made in Italy

jonny6336 wrote:This time I will make a ST120 from the very famous Bob Robert Latino,

I had no idea that Robert was Bob’s middle name.

Driver board ready

Hi friends, the quartet selected and paired for my realization of the ST120. The driver tubes, on the other hand, will obviously be a trio of 12AU7A RCA Black Plate 45 ° Square Getter Tubes Made in the USA '57

Slowly, but construction proceeds

Here are other details, quadruple capacitor arrived and I inserted the thermo sheath to isolate the 4 positive branches from the frame if they could accidentally touch. Plus the ESL capacitor.

jonny6336 wrote:Slowly, but construction proceeds

Nice jonny6336..... That power transformer is massive. How much taller is the lamination stack on it compared to the original VTA ST 120 ?

Tom

It is a 450mA transformer having 120x100 measures. Without cap it is in line with the condenser

jonny6336 wrote:It is a 450mA transformer having 120x100 measures. Without cap it is in line with the condenser

Holy God. lol !  I bet it weighs around 10 pounds by itself? lol

Oh my, that’s a big one!.

Earl wrote:Oh my, that’s a big one!.

Earl... I 2nd that lol. It's definitely a beast !

For the specifications that Bob said regarding the anode current the reel to hold the copper for 450mA and all tube filaments it took bigger. All in all it fits on the frame and doesn't make a bad impression

jonny6336 wrote:For the specifications that Bob said regarding the anode current the reel to hold the copper for 450mA and all tube filaments it took bigger. All in all it fits on the frame and doesn't make a bad impression

"impression".......... Well ? The transformer was standing up there looking like a steel mountain on a small island lol

Another step is completed, pendode / triode selector wiring. Only the exit transfers are missing, and then we can say it's finished.

Very nicely done! Still working on my VTA-ST120 build. Just got done painting the transformers. I was wondering why you chose to have your transformer made in Italy cost of shipping? Thinking I would like a trio for mine if they are better for the amp? lol.