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    Technical question concerning input grounds



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    Join date : 2014-09-26

    Technical question concerning input grounds

    Post by gabe on Fri Sep 26, 2014 7:25 am

    I'm new to the tube world having recently acquired an ST-70.  I made some mods including moving the power switch to the front panel, adding a volume control, added a second input jack (stereo mini) on the back panel and replaced the stereo/mono switch with a front/back input selector.  In the process of doing this, I noticed that the grounds of each input go through a separate 10 ohm resistor to amp ground.  I'm puzzled at the purpose of these resistors.  Aren't the input grounds already grounded together at the source equipment?  I had already made all my mods which essentially has all of the input grounds connected directly to chassis ground before noticing the 10 ohm resistors and the amp seems to play just fine.


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    Re: Technical question concerning input grounds

    Post by GP49 on Fri Sep 26, 2014 12:19 pm

    It lifts the input grounds to help avoid a ground loop through the two shields of the cable connecting the power amplifier to the (assumedly common-grounded) preamplifier. If you are not getting hum, as you probably would not if you are using the three-conductor stereo mini jack, you can leave it alone.

    If you removed them, don't forget you did case you run into a ground loop problem later.

      Current date/time is Sat Oct 22, 2016 10:07 pm