Bipolar Power Amp With Single Ended Input Stage Inpired by Mooly - diyAudio
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Old 12th May 2012, 06:00 PM   #1
Mooly is offline Mooly  United Kingdom
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Default Bipolar Power Amp With Single Ended Input Stage Inpired by Mooly

Quote:
Originally Posted by Tekko View Post
And there is a prototype circuit up and running, using a MJL4281A and MJL4302A as output devices and 2x43VDC rails.

When i punish it hard by driving a two ohm load, it distorts badly when it reaches about 10V peak output.
There won't be enough drive current for bjt's I imagine.
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Old 12th May 2012, 06:06 PM   #2
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by CBS240 View Post
Hi

In my latest amp I used for the DC servo comparator a new device called and E-pad from Advanced Linear Devices.......................... The amplifier should be bias without the DC servo to be very close to 0VDC. Temperature will cause minor drift, this where the servo comes in.
Thanks for the link.

These are all areas in the design I need to look at. At the moment it has been as much an exercise in gettig to grips with LTspice as much as anything. And I think I have a total "newb" question on something I can't just figure out which I'll post if I get stuck.
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Old 12th May 2012, 07:02 PM   #3
pergo is offline pergo  Italy
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Quote:
Originally Posted by Tekko View Post
And there is a prototype circuit up and running, using a MJL4281A and MJL4302A as output devices and 2x43VDC rails.

When i punish it hard by driving a two ohm load, it distorts badly when it reaches about 10V peak output.
you need triple EF output
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Old 12th May 2012, 08:50 PM   #4
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Mooly and pergo, indeed, it works but needs some work.

I already had to lower the 15k resistor in the constant current source to 5.6k to get any audio through this thing, and its possible i also have a faulty transistor in there as i used transistors pulled from other projects as i am currently all out on 2N5551's and only have two 2N5401's left.

Atleast the MJL4281 ans MJL4302 proved to be really rugged devices as they lived through the whole ordeal.
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Old 12th May 2012, 09:07 PM   #5
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This is the current test circuit: http://i.imgur.com/IQPMi.png

http://i.imgur.com/zli3E.jpg
http://i.imgur.com/ireSc.jpg
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Old 12th May 2012, 09:49 PM   #6
pergo is offline pergo  Italy
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add capacitor in parallel with R15
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Old 12th May 2012, 10:11 PM   #7
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Or replace it with two 47 ohm resistors tied to the output node.
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Old 12th May 2012, 10:22 PM   #8
pergo is offline pergo  Italy
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you use only 1 pair output bjts in the real built circuit?
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Old 12th May 2012, 10:34 PM   #9
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Quote:
Originally Posted by Tekko View Post
Mooly and pergo, indeed, it works but needs some work.

I already had to lower the 15k resistor in the constant current source to 5.6k to get any audio through this thing, and its possible i also have a faulty transistor in there as i used transistors pulled from other projects as i am currently all out on 2N5551's and only have two 2N5401's left.

Atleast the MJL4281 ans MJL4302 proved to be really rugged devices as they lived through the whole ordeal.
You are so optimistic by using only one input BJT and expect the amp to be perfect that's why I give you this improved SE input stage to play with.
Attached Images
File Type: jpg SE INPUT STAGE.jpg (234.7 KB, 263 views)
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Old 12th May 2012, 10:55 PM   #10
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LC, you and your obscure and weird parts :P And a IPs which alone is about as complex as the entire amp feels a bit like more work than it is worth.

If i wanna build the perfect amp, i'll just make use of the LME49810's i have laying around.

Yes my test circuit uses only a single pair of outputs.
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