Hypex amplifier project successfully completed

[kvholio]

Originally posted by cirrus18

Look at your CD player, I bet it's only got a two pin mains plug and it will, more than likely, have a metal case to.

You're right.
But unlike your amplifier it doesn't come with round holes in the bottom that appear to allow easy access to the backside of the pcb's.
I'm thinking small screwdriver or -even worse- small prying babyfingers.

Your reliance on your signal-interconnects for connecting your equipment to safety-earth is unsafe.
Firstly, you can't be sure the connection is always there,
and secondly, during a fault-condition it's likely that one of those interconnects (or a small pcb-trace) will fry and disconnect before your mains fuse ruptures.

Best regards,

Klaas

[bver100]

Hi Cirrus 18

I am sorry that my comment about safety offended you, that was not my intention. Even if you are unconcerned for your own safety there is always the possibility that others will look at your pictures and not recognise the dangers.

To clarify, if you want to build a piece of equipment that is safe without an earth (from the chassis of your unit to the earth conductor of it's mains cord) you have to make sure that it meets the requirements of 'double insulation' or class 2 construction. This means that you must maintain certain minimum creepeage and clearance distances from all parts that can be considered live to all parts that are to be considered safe. Further you must ensure that in the event of a fault (a wire coming loose for example) that these clearances are still maintained. Using a class 2 power supply is of course a pre-requisite. Nice work BTW Hypex !

If you look carefully at the CD player which uses a two core mains cable you will be able the see a double insulated symbol, it is a pair of concentric squares. If you then take a look inside you will see that the manufacturer (assuming that the unit is from a reputable company) has taken some trouble to make sure that there is no possibility of any mains side wiring coming in to contact with anything else. The fact that the player has a metal base means nothing in this context, it is the spacings that matter.

Even if you earth the chassis you still need to ensure that there is no possibility of anything live coming in to contact (or too close to) anything else. So for your amplifier, in addition to the terminal block fuse holder and wiring, you need to keep well away from pretty much anything on the main input half of the Hypex supply including the vertical PCB. This is made very clear by Hypex in their SMPS180 application note.

[Nanook]

here's my 2 pence worth (or cents or pennies ...)

A safety ground is exactly that. Wiring the case to earth is a smart thing to do. In fact a buddy used to connect everything in his system (all components) together with a ground to his power amp. They were "daisy chained", and the results were an improvement in sound. A bit of a PITA, but the cost is ridiculously cheap, and all components see the same ground. No loop problems, at all. I think a smart thing to do with any component is to add a ground lug/thumbscrew to all components, and wire them together ...

Note this is not the same as a signal ground, which if using RCA connectors,really is a "return" rather than a proper ground.

Please notw, I am not a designer or advanced electronics type, so if I'm wrong, let me know...but provide specifics please.

stew