Earth ground and ground loops

[Maxxarcade]

I am aware that ground loops can be a problem with tube chassis, but I have an issue that I would like to work out.

My tube amp chassis is earth grounded for safety. Another component with earth ground is my Reel to Reel, and possibly my turntable preamp.

What I would like to do, is install a couple 3 prong outlets on the back of my amp chassis, which are individually fused and connected through the amp's power switch. What are the odds that I'm going to run into a ground loop? I really don't want to float the chassis ground on the amp, and I'm not sure how much an isolated RCA cable would detract from the sound.

 

[Blast]

What is the reason for doing this? To turn on two other pieces of equipment at the same time the amp is turned on?

 

[drewbolce]

Is the earth ground a modification? Vintage tube amps typically used a floating ground two wire system. Simply adding a three wire power cord and attaching the earth ground to the chassis guarantees a ground loop.

 

[jaymanaa]

Make sure you check the amp rating of your power switch. With the other components all hooked in with seperate fuses, you could have a pretty good inrush when powering on. Everything I build now, has the negative side of the circuit isolated from the chassis, then the chassis gets the third prong ground.

 

[highfigh]

I am aware that ground loops can be a problem with tube chassis, but I have an issue that I would like to work out.

My tube amp chassis is earth grounded for safety. Another component with earth ground is my Reel to Reel, and possibly my turntable preamp.

What I would like to do, is install a couple 3 prong outlets on the back of my amp chassis, which are individually fused and connected through the amp's power switch. What are the odds that I'm going to run into a ground loop? I really don't want to float the chassis ground on the amp, and I'm not sure how much an isolated RCA cable would detract from the sound.

Adding the outlets will cause your power cord and switch to be inadequate for the current flowing through them. Also, the fuse is often placed before the switch. If everything uses the hot and neutral from the same source, ground loops are unlikely. Resistance on the neutral is where ground loops are common.

 

[Maxxarcade]

The tape deck and turntable are very low current draw, and I usually only have the TT turned on when the amp is on. Lots of vintage and modern amps and receivers have switched outlets for convenience, and I just wanted to have that with my tube amp.

Since this is a fresh build, I'm open to the possibility of isolating the signal and chassis ground if it's not too hard to do. This is basically a Magnavox 175 in a new enclosure, with an added preamp/tone control and input switching.

As for the fusing, I was going to bring the AC into the switch, then out to three 2 amp AGC fuses. One for the amp, and one for each accessory outlet. The switch is rated for 6 amps, so it should not be a problem.

 

[jaymanaa]

Isolating is no big deal. Just don't connect anything to the chassis. Most RCAs come with plastic washers, and if you insulate your speaker posts where they go through the chassis, you'll be most of the way there. Be careful to not use the center grounded terminals on solder tags too.

 

[Blast]

... because if that's the only reason (did you answer my question?), I would highly recommend plugging everything into a power strip and leaving the construction of the amp alone.
Brian