He does update the power transformer in the kit, and modern RCA jack, looks like the capacitors are better too. In Dallas Thor? Me too. Do you provide a listening service to fellow members?
"Up for bids is a NEW production ST-70 kit by Amplitube. It is the closest thing to the original ST-70 kit that you can get! If you have never built one, or if it's been awhile, here's your chance to build the legend. This kit comes with almost everything that you need to build a 35 watt per channel tube amplifier. If you can use a soldering iron, a few simple tools, and follow the step by step directions, you can build the same kit that has been built by hundreds of thousands around the world over the last 40+ years! Every part in this kit is new except the tube cage! ALL transformers are NEW, and made in Chicago USA!
This kit uses NEW A470-S output transformers, which are reproductions of the Dynaco A470 output transformer as used on the ST70 and MkIV amplifiers.
The primary is wound the same as the original A470, same number of turns, sections and wire size, using the same patented Dynaco winding method, and made on the same core size and material. Only improved insulation material used (thus making the transformer more resistant to abuse) and nice long (10 inch/ 25 cm minimum) teflon insulated leads have been added.
This transformer has what you'd expect out of a Dynaco transformer, like healthy low frequency inductance, high resistance to distortion caused by output tube imbalance, and low distortion overall.
Output transformer specs are: 4300 ohms CT primary with screen taps, 4,8 and 16 ohm secondary. 20 Hz to 20 KHz response at 35W, within 1 db, 30 to 15 KHz at 70 watts.
New power transformer is heavier in construction, runs cooler, gives better regulation, won't buzz & hum like some originals do. Secondary B+ winding is 720VCT (360-0-360) at 300 ma with 55V bias tap, plus two 6.3VCT 5 amps & one 5V 4 amp tube filament & rectifier windings, and 55V bias tap.
The chassis is a new production unit that is an exact copy of the original including the silk screen lettering! Original condition cages are cleaned, prepped for paint, and shot inside and out with 3 coats of high quality semi-gloss black enamel. After drying for 7 days, the cage is finished with a NOS Dynaco ™label.
All the ½ watt resistors are 1% metal film, all 3 watt resistors are 5% metal oxide, and the two bias resistors are precision 1% 3 watt wire wound 15.6 ohms just like the originals! The PCB is made of 0.062" FR4 material, and follows the originals circuit faithfully right down to the wire hook up numbering and solder rings! The bias pots are premium Bourns units that cost almost $10.00 each! 0.10 capacitors are Solen fast caps rated at 630 volts, and the 0.047 capacitors are rated at 1000 volts. Both are made of the highest quality aluminum metalized polypropylene film available! The selenium rectifier has been updated with a silicon diode and the RCA jack is an exclusive Amplitube part that allows for use of modern RCA connectors. The tubes included are a new J/J matched quad of EL-34s, J/J 5AR4, and two Sovtek 7199s."
If you are an experienced with a soldering iron and have had some prior experience assembling kits, I say go for it!
