Dynaco Stereo ST 70 Vacuum Tube Amplifier Undergoing Output Power & THD Measurements.MOV

[oatstao]

one of the better demo videos I have seen on youtube. Thanks for your knowledge, patience, time and detail you put into the testing. I personally own a Stereo-70 from Dyna company,an early run from 1959 era.

It is intact with original components and stays within original spec.

The bias is very steady too.The only mod was to fix selenium rectifier so far as that's all it has needed and I'm happy with the sound.

[essoterric]

I suggest picking up an oscilloscope, a couple of dummy loads (8 ohms) and an oscillator and start working on/testing audio amps and see what it grows into. Most of my equipment is 1980 vintage Tektronix equipment - government surplus. Probably got $5K in it all. New cost in 1980's would have been enormous. Beware of a lot of info on the Internet. Much is biased and misinformed but the Internet is still probably the best source. Good luck. Just go for it. I've been at it for 50 years now.

[rcmoot]

where or who would i have to learn this craft from. all this equiptment must cost some green backs . i want to learn this , since i have built some great three way cabs for my stereo at home.

[imfree707]

Hi, my guess is that since the output transformers draw more current from the output tubes as frequency goes down, you may not have enough conduction or current capability in those output tubes. Weak filter caps or rectifier might do that, too. Still a good amp, since real music will almost never tax the ST 70's abilities!

[hdibart]

Thank you;very instructive and clear

[Threemicsrecords]

Nice equipment! I have Dynaco as well but from 90's (St-80). How frequencies are represents in the signals? I understand that more voltage means more power... but how frequencies are written (so to speak)? Best!