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Old 20th March 2002, 05:11 PM   #11
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Just because a topology is pulled inside out doesn't
mean it doesn't work. I first saw this sort of thing
in Strickland's Accoustat TNT amp.
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Old 20th March 2002, 05:58 PM   #12
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Default Common Source

Well put from a man who designed a highly successful range of common source output stage amplifiers...... the Alephs. The coolest thing about this topology is that the front end doesn't have to swing very large voltages.

H.H.
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Old 20th March 2002, 07:28 PM   #13
jam is offline jam  United States
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I believe Mr.Pass is correct in that Jim Strickland ,of Acoustat, invented this topology. Hafler currently use this output stage and a number of variants have appeared in MJ magazine.
I wonder if Mr.Pass or anyone would like to comment on the distortion characteristics of this topology.

Jam
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Old 20th March 2002, 09:23 PM   #14
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The advantage of this topology lies mostly in its ability to
be driven by a low voltage source, such as an op-amp.

The output devices themselves have no idea what's going
on, and they see the same voltage/current relationships
as a similarly biased follower.

I have admired the ingenuity of Strickland's design, but I
always felt that it was underbiased. What would be very
interesting is this circuit operated Class A.

It is very easy to do.......
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Old 20th March 2002, 09:51 PM   #15
Helix is offline Helix  United Kingdom
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Even still, it doesn't bother showing the speaker! just a 'speaker bus' This is a very bad example of a schematic, and even though to someone who finds schema simple to follow, think of the poor newby repair guy! At a first glance, there isn't any power suppy caps drawn. not helpful thanks

Also, is that a OK way of fitting a clipping LED? what if it is clipping due to overloading (from current) as opposed to overdriving.
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Old 21st March 2002, 02:00 AM   #16
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Since the drive voltage requirements are very low, about one volt at the driver transistor inputs,any signal above a couple of volts is clipping.Because of the loop feedback the voltage at this point is forced high whenever the amp output cannot follow the input.This is true whether you run out of voltage on a high impedance load, or current on a low impedance load.
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Old 21st March 2002, 02:18 AM   #17
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Actually, there is a speaker hookup shown on the schematic. It's the square symbols on the end. The main signal path is drawn out, and it even tells the speaker impedance. Also, I don't remember seeing many schematics that do show the power supply caps. It's a fine schematic, I just found the topology rather strange since I had never seen it before.
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Old 21st March 2002, 03:19 AM   #18
subwo1 is offline subwo1  United States
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It looks to me like the output is taken through the filter caps. Pretty slick.
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Old 21st March 2002, 04:27 AM   #19
FBJ is offline FBJ  United States
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Thanks for explaining that djk,
It took me a while to understand it also. Like most DIYers, we only really understand what we have seen before. And when something comes along we have not seen before, it's takes a while to get use to it. But with guys like you I am sure you will keep us straight.
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Old 22nd March 2002, 11:13 PM   #20
Helix is offline Helix  United Kingdom
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the outputs isn't taken throught the filter caps, it is capacitivly coupled
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