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
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