[blipblop]

Can I ask you all two quick questions?

1. In Tangent's Pimeta write-up he says, after setting up the power supply of the PIMETA, to:

Quote:

Next, hook a power supply to the supply wires, and jumper the power switch wires together. The LED should light up, and if not, find out why. If the LED lights, check the voltages at all five chips' supply pins relative to virtual ground. If you don't get the voltages you expect, find out why before proceding.

Where exactly are the supply pins? What does that mean? and what voltages should I expect? Am I correct to assume that I should place one probe (the black one?) to virtual ground, and the other to the base of one of the chips?



2. Later on, after fully populating the board, he says to:

Quote:

Install the remaining chips and turn your amp on. Let it sit for a few seconds and then touch the chips to see if any are getting warm. If they are, you've probably got a fault of some kind. If the chips are staying cool, turn your meter to the DC millivolts scale and measure from virtual ground to each output pin: you should be getting an absolute voltage of less than 20mV. If you're getting high DC offset levels, you have some debugging to do before you plug headphones into the amp.

My ad8620 and ad8610 warm EVER-SO-SLIGHTLY, but that's it. Barely noticable. Does this mean somethings wrong?

Also, I'm not sure if I'm checking DC offset correctly. I turn on the amp, without a source, and then take one probe and touch the ground pin on the output jack and then touch the leftchannel pin of the same output jack. I get a reading of 34. I get around the same number for the rightchannel pin. Am I measuring correctly?

Thanks for your help, everyone.

 

[tangent]

Quote:

Where exactly are the supply pins?

See their respective datasheets. V+ and V-.

Quote:

what voltages should I expect?

You did build a CMoy first, right? And you did do exactly the same thing on it, right? You're expecting half the battery voltage at each supply pin relative to virtual ground, or the full battery voltage from V+ to V-.

Quote:

warm EVER-SO-SLIGHTLY

Don't worry about that. Those chips are in smaller packages than the more common DIPs, so they will tend to get a little warmer than a DIP would, all else being equal.

Quote:

I get a reading of 34.

Without a unit that means nothing to me. It could be 34V or 34mV or 34nV. You'll have to learn how to use your multimeter.