Cambridge Audio A500 Amplifier problems!

[camallison]

...I found this:

"When fitting a toroidal transformer, it is important to avoid making an unintentional short-circuit through the core (e.g. by carelessly fitting a steel mounting bolt through the middle and fastening it to metalwork at both ends). This would cause a large current to flow through the bolt, converting all of the mains input power into heat, and blowing the input fuse. To avoid this, only one end of the mounting bolt must be fixed to the surrounding metalwork."

This is why toroids are supplied with rubber washers and normally a warning note - a bolt to the chassis connected at both ends would be a heavyweight shorted turn - the xfrmr will get toasty and die.

There are many plus points for toroids - the main ones from an audio standpoint are less stray flux (contained in the core), compact size/weight, better efficiency (higher flux densities are possible), lower power consumption when off-load, less magneto-constrictive hum, etc.

>> from an audio standpoint are less stray flux (contained in the core),

I agree Nick - my main use of them is in audio equipment and PC-based sound systems - lovely job they do.

Colin