Symasym 5.3 "AAK model" builder's thread - Page 70 - diyAudio
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Old 28th September 2009, 09:58 PM   #691
AndrewT is online now AndrewT  Scotland
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I can find the two traces C27, C26, Zd1 etc and C24, R29.
But where do these two traces meet?
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Old 28th September 2009, 10:28 PM   #692
AAK is offline AAK  United States
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C24 and R29 connect to ground. The red trace is there to make sure that both pins are connected to ground on the top side of the board (green plane) if one of the through holes fails to connect. Probably not necessary, but it doesn't hurt just in case.
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Old 29th September 2009, 08:52 AM   #693
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I built up 4 of the previous boards. Very pleased with them too. A pair of these boards forms my power amp in my main hifi setup, and has done for a while. So I'm keen to have a go at the next version.

I'm no designer but here's an idea.

Is there any value in having a separate regulated power supply for the front end? But keeping the power supply for the main drivers on board.
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Old 29th September 2009, 01:30 PM   #694
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by AAK View Post
C24 and R29 connect to ground. The red trace is there to make sure that both pins are connected to ground on the top side of the board (green plane) if one of the through holes fails to connect. Probably not necessary, but it doesn't hurt just in case.
Is any of this "plane" connected to another part of the circuit?
Could a hum voltage be imposed across your input circuit and create the noise you are hearing?
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Old 29th September 2009, 02:13 PM   #695
AAK is offline AAK  United States
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The green ground plane connects all the grounds in the amplifier section together and connects to the power supplies red ground plane found in the center of the board labeled GND. This is the star ground where the speaker's ground wire connects to.

It turns out that after looking into it some more last night the hum is only audible when the amp is first turned on but goes away once it warms up. So it shouldn't be a problem, but I will investigate it further and possibly try a different bias circuit for Q9 and Q10. Other than THD looks great, comparable to my original board and MikeB's design.

Thanks Andrew for looking into it.

Regards,

Al
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Old 30th September 2009, 02:23 AM   #696
AAK is offline AAK  United States
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Hi chalkandtalk,

I'm glad you liked the boards. I don't think that adding a seperate regulated PS would any value, plus I'd like to keep it simple. But I'm working on a external PS for those that would like to use a single transformer for two channels. I may also try just the amplifier without the PS on the same board. Since the amp alone measures 2.95" x 2.65" this may interest some. It would be no bigger than a chip amp but with better sound.

Regards,

Al
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Old 30th September 2009, 10:07 PM   #697
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Hi all.

The PS on the amp board mean no harm only benefits I guess, since the transformer must be kept away? If you are not going to make two boxes - the amp and the PSU.
AAK is your PCB double-sided?
Besides, there is a reserve space to make traces more thicker for better audio performance and lower circuit impedance sake, if I'm not missing smth.
Do you know the shipping cost by post to Ukraine?

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Old 2nd October 2009, 01:38 AM   #698
AAK is offline AAK  United States
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Hi AndriyOL,

The PCB is double sided. The green layer is on the top side, red bottom. Signal traces are 52 mils which is more than enough. The power traces are 110 mils, they could made thicker but it should be Ok considering the trace length is 1.6".

Are you interested in the four unpopulated boards, or the assembled prototype boards with heat sinks?

Al
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Old 3rd October 2009, 12:21 AM   #699
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I think if impedance of routs is lower it's always better plus more reliable traces despite there is nothing to sacrifice instead.
I presume that green layer is a ground plane. Have you thought using single point ground system, adding snubbers to PSU? It may have far better performance results.
I can't find R3 on your PCB, likewise R5, R7 on the schematic.
I guess two 220uF as C18-21 will have worse ESR than one 1mF cap.
Maybe you should try to place output devices on the bottom side of the board, due to better heat distribution through whole heatsink, cause it always coming up. Otherwise bottom side will be cooler than upper side. From this point it would be better I think if output devices be placed in parallel at the bottom center of the heatsink and between each other.

I'm interested in your finest unpopulated four or maybe eight boards.

Regards,
Andriy.
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Old 18th October 2009, 01:50 PM   #700
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Quote:
Originally Posted by AndrewT View Post
the symasym PCB had all the returns (grounds) incorporated.
Where can I find the original symasym PCB design?
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