Better transformer for a very little amp project

[Calamaro]

Just found a nice little enclosure and a smaller transformer with same output (9VAC-1000mA).

[Calamaro]

So I decided to use this external SMPS with 9VAC output. Bridge rectifiers, filter cap and regulator will be inside the amp enclosure. I know safety ground connection is made by third /green wire but in this case transformer isn't in the chassis: what about power socket ground? Do I have to connect it to star ground or to the chassis?

[AndrewT]

if the SMPS is to the double insulated standard with the two concentric squares symbol, then the output does not need and must not have a Safety Earth connection. I cannot see a square symbol in that pic.
What does the triangular symbol indicate?

The ancillary equipment may also be double insulated and again they do not need a Safety Earth connection.
You can connect all these double insulated pieces of equipment together safely without any Saftey Earth connection.

If one/any item is not to the double insulated standard then it/they must be connected to Safety Earth. Even when this piece if equipment is protected from prying fingers it must still be connected to Safety Earth whenever it sends an interconnect to another item that has any exposed conductive parts.

[Calamaro]

Searched on the web and triangular symbol is a Product Safety Test Mark:

"The German safety approval mark shows conformity with the German Equipment Safety Law. It is a recognized mark for electrical products, such as office equipment, household appliances and industrial equipment, and is widely accepted throughout Europe. The TUV Rheinland GS Mark signals to the buyer, customer and consumer that the product, as well as the user manual and production process, has been tested by an authorized institution such as TUV Rheinland and is supported by regular surveillance audits."

(from www.watt-power.co.uk/safety.htm)

No square symbols anyway.
How can you do an earth safety connection without third wire?

[Calamaro]

This one comes from another forum:

http://electro-music.com/forum/topic-8979.html
The ground connection on the primary side of your laptop switch mode power supply is a saftey feature,but due to the way the power supply works (due to defective components-it is a fault!!!-but not a dangerouse one...) there can be a large amount of noise due to the earth connection.
UNDER NO CIRCUMSTANCES DO YOU CONNECT THE POWER SUPPLY - CONNECTION TO GROUND(THE SECONDARY SIDE NEGATIVE CONNECTION )!!!-THERE WILL BE A BANG!!
Due to the fact any smps doesnt supply mains isolation(switched mode power supply) any connection to mains earth will instantly kill it...

[Rainwulf]

I am doing the same thing to the same amp chip.
Its distortion is pretty crappy, 0.3% standard, crosstalk is fairly high as well. So its nothing special by any stretch.

However so far i have found that heatsinking the chip is vital, you can run them at 12 volts. You will need about a 12 volt transformer, a bridge, and caps. Dont use a regulator with it, because 3 pin regulators are limited to 1 amp, and at full load, the chip will draw more then that.

You can also bridge the chip as well to get more power, but obviously need two chips.

Honestly, you will get more power and more quality sound by building yourself a little 4-5 transistor amp, class A. Good experience.