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Hi guys, some dialog on Q6. The arrow on the schematic indicates the CCW rotation direction. When the pot is fully CCW it is at the 5K end of the pot so it puts 6K ohms across the Q6 base - emitter junction and this corresponds to the MINIMUM bias setting achievable. Conversely when the pot...

Legendary Levon Helm of the Band died yesterday, finally succumbed to the throat cancer that has been plaguing him for years. I had the good fortune to see him with his original The Band members in the early 70s at New Paltz NY. Phenomenal show. Recently I have traveled to Woodstock NY to see...

1. The minus 20V regulator is now completely symmetrical with the positive regulator and employs the complement to the TIP31C, the TIP30C. My ongoing quest for improvement in turn on and turn off thump reduction. This I have modeled into the current RevA board in true dead bug fashion. 2. Added...

Here are some pictures of the left and right channel DMM connection points for the White Oak Audio Design PL14_20 RevC Control board. Be careful not to short out meter probes when taking these readings, turn off power when attaching the meter clips then apply power to avoid damaging the amp.

For device matching, usually you are most concerned about base emitter voltage matching. What usually works well is a fixture with the base grounded, the collector attached to a positive DC source and the emitter connected through an appropriate value resistor to a negative DC source. DMM...

The emitter resistors provide local negative feedback to force sharing amongst the 5 output devices that are paralleled. Bipolar transistors exhibit a negative temperature coefficient on the base-emitter forward junction voltage. Thus if an identical voltage is applied to all 5 base connections...

Hand me one of those Ghirardellis Lee, they look good :-)

Make sure you get quality caps when you replace them. BE CAREFUL. THERE IS A VERY LARGE ENERGY HAZARD IN THESE CHARGED CAPS SO BE SURE TO OBSERVE PROPER SAFETY PRECAUTIONS! Here is what I recommend once you get your new caps to "form" them properly before installation. 1. Using your...

Published this document earlier in one of the long threads and it is now buried somewhere in those archives. Bringing it to its own thread to make it easier to find. Description of the latch up possibility. When power is applied to the PL amp, the +/- bulk caps charge rapidly to provide the...

A question from Skratch got me investigating the VU meter characteristics a bit more so I thought I would post the data and calculations I worked on here.