Having Earthed pedal without ground loop issues?

[carboncomp]

Hello guys, I picked up a UniVibe PCB clone, but got to thinking about the lack of an earth on the original.

Are my options:

1: Add an earth connection to the enclosure, be safe from 120V, and just deal with the hum should there be a ground loop.

2: Omit earth, risk 120V shock, be hum free.

Or is there a third option offering protection and no chance of 60Hz hum? 

[bluebunny]

Whilst not being familiar with the Univibe, I know I would rather face trying to fix the hum than trying to fix the dead you.

[antonis]

You may connect chassis ground to circuit ground via a bridge rectifier (compact or 4 diodes..) in parallel with a 10R/1W resistor and a 100nF capacitor..

Bridge's AC inputs should face to Chassis ground and outputs (DC) to Circuit ground..

The bridge will conduct for any "fault" current (diodes short circuited due to overload) while the 10R resistor stops any earth loop problem (hum) and the 100nF cap bypasses RF..


P.S. 1
You may use a pair of back to back parallel high current diodes instead of bridge rectifier..

If you need a scheme, just imagine chassis gnd, bridge inputs, resistor & capacitor left legs at one node and circuit gnd, bridge outputs, resistor & capacitor right legs at another node..

P.S. 2
You should estimate as Circuit ground the first GND closer to power supply (i.e. - of filter capacitor or -/+ of filter capacitors in case of dual supply..)

P.S. 3
The above doesn't implement any modification to existing mains wiring/circuit but you should always act under mains danger caution  .!!!

[carboncomp]

You may connect chassis ground to circuit ground via a bridge rectifier (compact or 4 diodes..) in parallel with a 10R/1W resistor and a 100nF capacitor..

Bridge's AC inputs should face to Chassis ground and outputs (DC) to Circuit ground..

The bridge will conduct for any "fault" current (diodes short circuited due to overload) while the 10R resistor stops any earth loop problem (hum) and the 100nF cap bypasses RF..


P.S. 1
You may use a pair of back to back parallele high current diodes instead of bridge rectifier..


If you need a scheme, just imagine chassis gnd, bridge inputs, resistor & capacitor left legs at one node and circuit gnd, bridge outputs, resistor & capacitor right legs at another node..

P.S. 2
You should estimate as Circuit ground the first GND closer to power supply (i.e. - of filter capacitor or -/+ of filter capacitors in case of dual supply..)

Thank you so much for this, if there any chance you could link me a diagram, tried google image, and got a little confused with what I was looking for 

[antonis]

Elliot Sound Products:

http://sound.whsites.net/project04.htm

Figure 3 of :
http://sound.whsites.net/project27.htm

[carboncomp]

Elliot Sound Products:

http://sound.whsites.net/project04.htm

Figure 3 of :
http://sound.whsites.net/project27.htm

Thank you, any idea on what size Diodes to use?

[antonis]

IMHO, 3A/50V should be fine..

[GibsonGM]

IMHO, 3A/50V should be fine..

That is a very interesting method of eliminating ground loop issues, Bobby.  I'll file that away for a situation like this!

 

[antonis]

That is a very interesting method of eliminating ground loop issues, Bobby.

Better not give them space to be conjured, Tommy.