Send us your Dynaco ST-70 with good transformers and we will indeed transform it. We use Tubes4Hifi's outstanding 6SN7 board and add truly massive fltering.The VTA-70 uses three triode sections per channel. The first triode is a voltage gain stage. Two triodes are used as the phase splitter/driver for each channel. The splitter/driver is a long-tailed constant-current pair. Each of the three 6SN7s has its own 47uF filter cap, which comes after all the filtering before it. The board also has a complete replacement bias supply. The board reduces idle current from 50 mA per tube to 40 mA and provides individual bias for each tube. We run a line from each grid to pins on the octal socket so you can adjust idle current with a simple DMM or VOM. We replace the original 20 uF - choke - 20 uF filter with 50 uF - choke - 500 uF. The input capacitor is two 100 uF capacitors in series with equalizing resistors that also serve as a bleeder. We leave in the original choke, as its fairly high resistance suppresses power supply ringing. We then set bias and listen for several hours to make sure the amp is performing the way it should. What we need:
- Your amp, well-packed and with good transformers and choke. You are also responsible for output tubes and the rectifier. You pay for shipping both ways. We provide:
- A total rebuild. Every resistor and capacitor is new. If you need a socket that is also included. We also provide good quality tested, matched and auditioned 6SN7s. If you have a brand preference let us know and we'll try to supply it from our stock. We also add a three-wire power cord and fuse. Your ST-70 will sound vastly better. Bass is improved from flabby to what is almost certain to be the best you've ever heard from a tubed amp, and better than most solid state amps. Highs are markedly improved too. If you want to do the work yourself, we pretty much just told you how. If you thnk you'd like to have us do it for you, contact us to discuss. We're Electron Addict
108 W 2nd St
Papillion NE 68046 402 916-4757
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