"However, the amplifier will still maintain 5.657-volts at its speaker terminals when the load changes from 8"

Posted by Caucasian Blackplate (P) on March 11, 2019 at 08:46:01

In Reply to: RE: It is not a contest and we're both right posted by John Elison on March 10, 2019 at 18:59:34:

"However, the amplifier will still maintain 5.657-volts at its speaker terminals when the load changes from 8-ohms to 4-ohms "

Yes, it will, but if the transistors in the output stage are biased to be always on (class A) for 4W into 8 ohms, as you lower the impedance, you will leave class A as this current demand is exceeded. Transistors are biased for a standing current, not in terms of voltage.

Here is that behavior demonstrated in Aleph 3 measurements, with the lines being 8, 4, and 2 ohms starting at the bottom. The first deviation on these curves is at about 20W, 12W, and 6W respectively. While the curve for the 8 ohm load turns up to vertical almost immediately afterwards (running out of rail voltage before cutoff), the 2 and 4 ohm curves show a likely transition into a small region of class B operation at those higher powers with those lower impedances.

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Follow Ups Full Thread

Topic - Class A power in A/B amp question - George6 18:23:50 03/09/19 (22)

you could also try to figure out if you like how the amp sounds driving your speakers - Chip647 15:03:58 03/13/19 (0)

Angels on a Pin question - bare 09:55:48 03/13/19 (0)

Ha Ha! - Duke vs John - who wins? - cawson@onetel.com 06:09:52 03/10/19 (11)

It is not a contest and we're both right - 13th Duke of Wymbourne 13:21:46 03/10/19 (9)

RE: It is not a contest and we're both right - John Elison 18:59:34 03/10/19 (6)

"However, the amplifier will still maintain 5.657-volts at its speaker terminals when the load changes from 8" - Caucasian Blackplate 08:46:01 03/11/19 (0)

RE: It is not a contest and we're both right - 13th Duke of Wymbourne 21:18:06 03/10/19 (4)

Interesting! - John Elison 05:44:55 03/11/19 (3)

Addendum - 13th Duke of Wymbourne 19:21:59 03/11/19 (2)

RE: Addendum - John Elison 12:52:46 03/12/19 (1)

A summary - 13th Duke of Wymbourne 18:47:37 03/12/19 (0)

RE: It is not a contest and we're both right - George6 17:40:08 03/10/19 (1)

RE: It is not a contest and we're both right - 13th Duke of Wymbourne 18:31:26 03/10/19 (0)

RE: 13DoW is correct. - BenM 10:50:29 03/10/19 (0)

RE: Class A power in A/B amp question - 13th Duke of Wymbourne 20:13:27 03/09/19 (1)

+1 nt - Caucasian Blackplate 10:10:12 03/10/19 (0)

RE: Class A power in A/B amp question - John Elison 18:54:45 03/09/19 (5)

RE: Class A power in A/B amp question - triamp 19:19:57 03/10/19 (1)

RE: Class A power in A/B amp question - John Elison 06:36:30 03/11/19 (0)

RE: Class A power in A/B amp question - 6bq5 12:07:49 03/10/19 (2)

RE: Class A power in A/B amp question - Hornlover 08:24:06 03/11/19 (0)

RE: Class A power in A/B amp question - John Elison 12:17:37 03/10/19 (0)

Follow Ups

"However, the amplifier will still maintain 5.657-volts at its speaker terminals when the load changes from 8" - Caucasian Blackplate 08:46:01 03/11/19 (0)

"However, the amplifier will still maintain 5.657-volts at its speaker terminals when the load changes from 8"

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