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Rod Elliot P3A Layout - Critics
Rod Elliot P3A Layout - Critics
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Old 2nd July 2013, 10:39 AM   #251
JLesterP is offline JLesterP  Philippines
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Default please criticize

My old layout (in the pic) showed no signs of oscillations under scope.

Is my new layout good? Or decoupling is too far?
Should I change my old layout into this?
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Old 2nd July 2013, 11:58 AM   #252
Bone is offline Bone  United Kingdom
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If it aint broke dont fix it!
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Old 2nd July 2013, 12:56 PM   #253
JLesterP is offline JLesterP  Philippines
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I'm not fixing it, im improving it
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Old 2nd July 2013, 08:07 PM   #254
Ian Finch is offline Ian Finch  Australia
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Quote:
Originally Posted by jlester87 View Post
..... im improving it
OK, then improve the thermal coupling between drivers and bias transistor so it doesn't take ages to stabilize and responds usefully to changes in dissipation.

According to the pics, you don't have a driver heatsink anyway, so what bias current are using now? You don't need to move much to allow better coupling with just a single heatsink for all 3 transistors, assuming you don't already have this arrangement but just haven't shown it here.
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Old 3rd July 2013, 01:37 AM   #255
JLesterP is offline JLesterP  Philippines
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Hi, the drivers will be connected on a single heatsink. Bias transistor and Q5 are thermally coupled (glued by thermal epoxy), thus changes in Driver transistor Q5 will be quickly monitored by Q9.

5W output collector resistors are on the underside of the PCB.
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Last edited by JLesterP; 3rd July 2013 at 01:41 AM. Reason: Added picture
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Old 3rd July 2013, 02:47 AM   #256
Bigun is offline Bigun  Canada
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Rod Elliot P3A Layout - Critics
Nice layout - I also used this approach for my TGM1, TGM2 and TGM3 - having power rails on one side and sensitive parts on other side.
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Old 4th July 2013, 10:30 AM   #257
JLesterP is offline JLesterP  Philippines
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Thanks Bigun

What I liked with P3A(sziklai) is that only the O/P transistors are mounted on the main heatsink. This simplifies the work on the amp case. Also it has low parts count, so it is as easy to build as chip amps.
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Old 4th July 2013, 10:49 AM   #258
TonyTecson is offline TonyTecson  Philippines
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Rod Elliot P3A Layout - Critics
that is why this amp is highly recommended for newbies.....as well as oldtimers....
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Old 4th July 2013, 12:07 PM   #259
JOHN BALI is offline JOHN BALI  Indonesia
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Hi Tony, where is the oldtimers
I must give it a try...
Quote:
Originally Posted by AndrewT View Post
The Power Ground does not need to be connected to the Signal Ground by using PCB traces.
The Power Ground and the Signal Ground need to be referenced to the same voltage. This can be on board, or it can be off board.

If you are building more than one channel into your amplifier, then I assert that the Main Audio Ground (where Signal ground and Power Ground meet) must be off board.
Quote:
Originally Posted by gmphadte View Post
John Bali
The big filter capacitors have to be located close to the power transistors in order to reduce the inductance added by the long track.

Gajanan Phadte
Quote:
Originally Posted by Bigun View Post
Nice layout - I also used this approach for my TGM1, TGM2 and TGM3 - having power rails on one side and sensitive parts on other side.
So many critics to my own layout, thanks guys...
time to improving it
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Old 4th July 2013, 12:26 PM   #260
TonyTecson is offline TonyTecson  Philippines
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Rod Elliot P3A Layout - Critics
Quote:
Originally Posted by AndrewT
The Power Ground does not need to be connected to the Signal Ground by using PCB traces.
The Power Ground and the Signal Ground need to be referenced to the same voltage. This can be on board, or it can be off board.

If you are building more than one channel into your amplifier, then I assert that the Main Audio Ground (where Signal ground and Power Ground meet) must be off board.

so many words....what does it amount to?

why can't AndrewT just show us in pictures what he's got so we can appreciate what he says....
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