Effects of overtaxing IXYS diode bridge?

[reiver]

Final...

The diodes were IXYS L413s which I show as "HiPerFREDTM Epitaxial Diode with soft recovery". but I think they're out of production.

My speakers are Klipsch Fortes which are a nominal 8 ohms and pretty easy to drive.

I'm betting the diodes are simply overheating or not up to the demands of the power supply. They were a project that I put together to see if they were sonically superior to a stock bridge, so I'm ready to pull them out.

Thanks for all the speculation, my new 'stock' rectifier bridge should arrive in the mail in a couple of days, I'll keep everyone posted.

-Bryan

 

[jan.didden]

Re: Final...

[snip]I'm betting the diodes are simply overheating or not up to the demands of the power supply. [snip]-Bryan

Hi Brian,

OK, if you want to solve this by betting, I really can't help you. Good luck.

Jan Didden

 

[jan.didden]

In a class B power amp, the average current drawn from each +/- power supply is exactly the peak load current divided by PI (3.14). For 100W in 8ohm this is 5A/3.14=1.7A while in 4ohm is about 3.4A. On top of that comes the output devices bias current (making for class AB, can be significant) and the currents required by the input stage, VAS, drivers (which are usually negligible).

Thanks, good rule of thumb to know!
But, to be sure, that is with full power sine wave, right? With music, it's much, much lower.

Jan Didden

 

[syn08]

With music, it's much, much lower.

Intuitively, yes, but not easy to prove. The PI comes from integrating the collector current over a sine period. If you look at music as a collection of single tones (some people will shudder here) you would need to average both over periods and amplitudes to get an estimate. It's the amplitude average only that would lead to a lower average current.

Interesting enough, a white noise input signal will lead to a higher average current, about the same as the current required by a 50% square wave, about 2.5A (for 100W output in 8ohm load) and 5A respectively (for 200W into 4ohm load).