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Re: "Split feedback" amplifier topology:

195.58.50.210

Posted by klaus on November 26, 2000 at 07:36:25

In Reply to: "Split feedback" amplifier topology: posted by ChrisVH on November 25, 2000 at 16:14:31:

Interesting, alhough one point makes me fell like it was not actually tested, at least in the way the 'Pushpull mod' is described.

Quote:
"You can also apply a load, a high quality non-inductive resistor from output stage (A) to ground, for giving the push-pull pair of (A) the same loading as the 4 residual pairs of (B). To do this, divide you speakers impedance (i.e. 8 Ohm) by the count of (B) pairs (this is 4). The result is 2 Ohm that should be applied to (A) for load matching."
Seems like the opposite. Section B with four devices runs 8 Ohm speaker, section A should be loaded with 8*4=32 Ohm, to equalize current for each device. After all, it's not safe to load any single transistor pair with 2 Ohms where the designer puts 5 pairs.

And, I am afraid the author's reference to a 'mod' in an existing amp is misleading. For a start, most amps on the market don't have a luxury of 5 transistor pairs a channel. 1 or 2 pairs, usually. So there's no spare 'section A' to be cut off. And a 50-100% more power consumption. I'd like to test the idea with my current amp project, but there's no way to place four more devices on a custom heatsink, and I hate the idea of buying heavier-than-I-got-already transformers...

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