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driving st-70 input questions

paysonmark

paysonmark

AK Subscriber
Subscriber
I am the proud owner / rebuilder of a dynaco st-70. For my first amp I went close to stock. Changes are
Diode 1n4007
cl90
quad can cap 80 40 30 20
new (copy) 7199 pc3 board
new bias supply caps
all new wires
new 3 prong power cord
all is good and has been working well

my question is can I us the line out (headphone) of Alexa dot or tablet or my cell phone to drive the st70 inputs

thanks all
 
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You can, but it may not drive it to full power. I do this often, not with an ST-70, but other tube power amps certainly.
 
I used to use my phone to test all kind of different amps. Never has an issue on the input level.

But then I blew up my phone, as 1957 technology is more robust than 2017 :rolleyes:...

Since then I am using a $17 bluetooth adapter to drive my amps: works like a charm.
 
I've used my smart phones with my ST-70 and other tube amps. It probably won't drive the amp to full output though. Mine didn't. Do use a good shielded 1/8" jack to RCA cable. The cheaper ones tend to add noise and hum.
 
I've had lackluster results on my ipod for this. It just doesn't have enough output. The ST-70 input sensitivity is somewhere around 1v I think, so if you can get at least that much, it will drive to full power. If not, it will produce somewhat less power.
 
Brice said:
I used to use my phone to test all kind of different amps. Never has an issue on the input level.

But then I blew up my phone, as 1957 technology is more robust than 2017 :rolleyes:...

Since then I am using a $17 bluetooth adapter to drive my amps: works like a charm.
Click to expand...
I must admit that all the apps that one can upload to your smart phone makes them very versatile. But i also wonder about the actual real word usefulness of your phone doing all these things. My son has this app that he was trying to use to help level this water tank we were setting up. But in the bright outside light no one could see a dang thing on the screen. It was pretty useless in that case. Oh, and not to mention it took him like 5 minutes to find the app. Verdict. vintage bubble level wins over i phone app!
 
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