Grounding questions

[Stunch]

On the original Dynaco ST-35, there is a ground wire between the middle lug of the chassis mount 5 lug terminal strip and a tab of the quad cap. Just wondering why since the quad cap makes contact with the chassis anyway.

Also, some people think it prudent to wire the amp up with a 3 wire cable and connecting the ground wire to the the same middle lug of the terminal strip. Others say it's not important since it wasn't done originally and there could be hum issues if 3 wire cable is used upstream with a preamp for example.

Thoughts and thanks

[EWBrown]

The connection from the can of the quad cap to the grounded center lug of the terminal strip is there to ensure a better, more reliable grounding point to the chassis, the twisteer mounting lugs on the cap are only a mechanical connection, and may or not be reliable. The can cap is aluminum, (the solder lug is plated in order to accept solder) and the chassis is plated steel, and there could be electrolysis or corrosion between the two dissimilar metals, over the decades.

If you use a 3 wire power cord, jsut connect the ground (green or green/yellow) lead to the same grounded center lug on the terminal strip.

HTH

/ed B in NC

[Stunch]

Thanks for your reply. I figured that was the reason, but was curious. One other thing: I am thinking of adding a thermistor to my build, but am hesitant since voltage at my place in the summer is around 118V and am concerned that the tube heaters won't be operating optimally if the thermistor drops voltage even lower. In the winter I have seen it as high as 121.8V. Is this too high without using a thermistor? Thermistor for winter, omit for summer?

I was thinking of using an outboard on/off switch for the amp. I guess I could wire it to the hot leg if needed, without adding it to the amp.

[corndog71]

I was thinking of using an outboard on/off switch for the amp. I guess I could wire it to the hot leg if needed, without adding it to the amp.

Dynakitparts sells these with their ST35 kits as well as separately.