Doesn't sound like much of an 'engineer'. Good grounding is the foundation of a great studio and despite the volumes of grounding techniques and theories in the end you go with whatever works best in the immediate situation. Sometimes star ground, sometimes distributed ground and sometimes even removing the 'ground pin' if the metal 19" rack itself is grounded. Now to fix your problem, I have used 600 ohm to 600 ohm line matching transformers which have a 'shield' wire between the two windings and I connect that shield to only the input device or only the output device, not both. Which ever gives less hum. You could also use an isolation transformer on the mains input of your amplifier. Sometimes a 120/240 'control' transformer of maybe 500va rating can work. They usually have 4 120 volt windings so they can be used at 120 or 240 as 'isolation'. Then definitely 'float' the ground of you amplifiers input. There is no danger of shock because the amplifier is now 'isolated' from real earth reference. I am both a guitar player for 3 different bands and styles of music and worked for 13 years as a professional broadcast engineer having built many studios over my career and played in dozens of other people's studios with all kinds of 'work-arounds' to reduce hum and digital noise. Best wishes!!
I think you're talking about a ground loop... that's not the problem here, it's shielding that's the problem...
Hello ELS122:
The function of a chassis earth are many and SAFETY RELATED.
Besides an RF shield and reducing ground current hum the earth ground is essential to provide a safe current return path if the device insulation line to chassis fails.
DANGER, TOUCHING THE DEVICE WHILE YOU ARE STANDING ON A GROUNDED FLOOR (eg concrete, wet area) CAN RESULT IN A SHOCK OR DEATH.
At least one famous R&R performe was electrocuted in this way.
GROUND IT ASAP and get rid of your incompetent and dangerous "engineer"
Bon Chance,
Jon
I know it's safety related, but I just don't see the huge deal about it in something that only I'm going to use and I have considered every percaution I can think of when wiring the amp, so there's an insanely minimal chance of something going wrong, except maybe for the power transformer shorting but it hasn't ever been in a humid or in other ways a bad environment that would damage the insulation.
DANGER, TOUCHING THE DEVICE WHILE YOU ARE STANDING ON A GROUNDED FLOOR (eg concrete, wet area) CAN RESULT IN A SHOCK OR DEATH.
well that's only if there's a current path between the Live wire, and Ground. and 'DEATH' is only really if there's some major failure in the circuit that connects the chassis to the live wire.
like for example:
a shorted 'death cap' in an old amp that has a 'death cap', or just some live wire that's shorted to the chassis.
At least one famous R&R performe was electrocuted in this way.
Ace Frehley you mean? that was a railing that somehow was Live... I doubt it could just be Live because it had no earth on it. there must've been some cut wire or something that pressed against it. ofc if it was grounded it would've tripped the circuit breaker (or just melted the wire and someone would've noticed that there's a smoking wire there).
and in a way, most likely
everyone who's played a vintage Fender amp has been electrocuted, it's basically in the design. if the 'death cap' is connected to Live and the chassis instead of Neutral, it would conduct around 2mA of current trough the cap, which would give you a pretty decent shock if you touched anything grounded. like for example wet concrete while bare foot, or a grounded cable, etc.
so in short, yes I understand the risks. I'm not THAT worried about it. and I've decided instead of adding a ground switch and a 'death cap', I'll just get a extension cord with a ground next time to a gig and plug it in into a grounded socket.
also the
and get rid of your incompetent and dangerous "engineer"
isn't really an option in my case... and I think I just can prove to him the benefits of having things grounded and make him ground everything.