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Re: Low vs High Operating Points

Posted by kurt s on May 8, 2007 at 19:48:59

In Reply to: Low vs High Operating Points posted by danlaudionut on May 8, 2007 at 03:45:27:

>>I was wondering if that had to do with:
1) lower B+ - keeping away from max voltage
2) lower current - lower max dissipation
3) higher Z OPT - flatter load line
<<

None of the above. A lower operating poing is less linear. This can be either good or bad depending on where it ends up. If you are delivering it to a 16 ohm 115 dB horn, then you don't need 1000VDC plate curves working to linearize the sound. It's linear sounding at 150VDC.

It will "warm up" at the lower operating voltages a tad. If this is what is needed, then this is what you want to pursue. If the sound is still too warm, then go up in voltage and linearity.

I operate 45's at 180 VDC and 15 mA. This is below it's max rating, but I'm running them into 112 dB horns from 250 Hz on up. It doesn't need max power, it needs a nice easy operating point that's still linear to the speaker and won't burn out the 45's quickly. So I like it at that operating point. Plus it's easier to get those voltages and currents. Any more voltage and current and it starts to "gray out" the sound, meaning the harmonics are washing away, something not good to the SET amp crowd.

This is what DIY is all about - tailoring the sound of the amp to the speakers, a good distance ahead of "off the rack" amps and speakers.

Kurt

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