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Old 18th March 2005, 09:11 PM   #1
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Default Current Sources

Can the Pass amp current sources be replaced with something like the LM133?

Or is there an advantage to the discrete current sources?

Just curious.

vinay
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Old 19th March 2005, 04:23 AM   #2
PRR is offline PRR  United States
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> Can the Pass amp current sources be replaced with something like the LM133?

??? Only "LM133" I can find is Landmark's Very High Brightness LCD Module. I don't know if it can be a current-source, but that sure is the expensive way to do the job.

Did you type "LM334" and line-noise corrupted your bytes?

> Or is there an advantage to the discrete current sources?

The LM334 is a 3-stage BJT amplifier, probably not as hyper-linear as we might like in fine audio. Dumb current sources have simple inoffensive flaws.

I have no clue which of the many "Pass amps" you are pointing at, but the LM334 is only good for milli-Amps and I know Nelson has some designs that suck many-Amps. At that level, the LM317 volt-reg strapped as a current-regulator is popular. This thing has about 6 active stages with 26 total transistors: not at all the simple thing it appears to be.

Sure you can adapt different current-source techniques and technologies. What you get may not be quite the same as the original. Putting these many-stage chips in place of a dumb FET may give you better numbers and worse sound. Or may not.
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