I keep getting confused about when it is and isn't good to connect the circuit common to safety ground. What's the right way to do it? Are there any official standards that relate to safety?
I'm building a musical instrument amplifier, where the part of the connectors that you grab on to for plugging things in and out are connected to circuit common. The circuit common is the center tap of the transformer secondary. It seems to me like anything that the user can touch should be connected to safety ground. On a power amplifier I have, the input and output negative leads are connected to safety ground, but on a pair of powered speakers (speaker outputs not accessible), the input negatives are NOT connected to safety ground. Also on a modular synth system I have, the connector negatives are not connected to safety ground, and it also has a linear, bipolar supply like what I'm building, albeit lower power. Another synth which uses an external SMPS does not have the connector negatives connected to either power lead.
What should I do?
I'm building a musical instrument amplifier, where the part of the connectors that you grab on to for plugging things in and out are connected to circuit common. The circuit common is the center tap of the transformer secondary. It seems to me like anything that the user can touch should be connected to safety ground. On a power amplifier I have, the input and output negative leads are connected to safety ground, but on a pair of powered speakers (speaker outputs not accessible), the input negatives are NOT connected to safety ground. Also on a modular synth system I have, the connector negatives are not connected to safety ground, and it also has a linear, bipolar supply like what I'm building, albeit lower power. Another synth which uses an external SMPS does not have the connector negatives connected to either power lead.
What should I do?