something to ponder.
I'm not so sure about any of this having thought about it more than I would have liked..lol. Since both should be disapating (??) the same power, just placing them in the same vicinity should be adequate. The same spot on the board should have the same (or close enough) thermal characteristics so that tracking is sufficient. It could be measured if you really wanted to get picky and physically mated if necessary. I bet it wouldn't be however unless some special balancing tricks were used in the rest of the circuit. The negative feedback would just unbalance them anyway to get the proverbial 0VDC offset. Look at your final operating reading and decide for yourself. What I attempt to do with power amps is to match the input devices close as I can then balance the amp for 0vdc in open loop mode (w/o feedback) letting it come to warm temp for about 15-20 minutes. At that time I figure it's balanced about as well as it's gonna be then I apply the feedback. With jfets/mosfets, it can be an interesting game. This wouldn't normally be done in any production amp that I have seen, you'd have to make it a custom job, but I personally think it should be done on any amp. Speak of the devil - I'm working on a PS AUDIO 100C amp now that has an adjustable front end that I believe to be for this purpose. Just think about how this stuff works in a complete system and some things might dawn on you. Many times it's not possible to analyze things as they stand alone since they interface with the rest of the circuit. I think this front end match is one of them. Debatable of course,..this is audio!!!!
I'm not so sure about any of this having thought about it more than I would have liked..lol. Since both should be disapating (??) the same power, just placing them in the same vicinity should be adequate. The same spot on the board should have the same (or close enough) thermal characteristics so that tracking is sufficient. It could be measured if you really wanted to get picky and physically mated if necessary. I bet it wouldn't be however unless some special balancing tricks were used in the rest of the circuit. The negative feedback would just unbalance them anyway to get the proverbial 0VDC offset. Look at your final operating reading and decide for yourself. What I attempt to do with power amps is to match the input devices close as I can then balance the amp for 0vdc in open loop mode (w/o feedback) letting it come to warm temp for about 15-20 minutes. At that time I figure it's balanced about as well as it's gonna be then I apply the feedback. With jfets/mosfets, it can be an interesting game. This wouldn't normally be done in any production amp that I have seen, you'd have to make it a custom job, but I personally think it should be done on any amp. Speak of the devil - I'm working on a PS AUDIO 100C amp now that has an adjustable front end that I believe to be for this purpose. Just think about how this stuff works in a complete system and some things might dawn on you. Many times it's not possible to analyze things as they stand alone since they interface with the rest of the circuit. I think this front end match is one of them. Debatable of course,..this is audio!!!!
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