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Old 24th November 2005, 09:57 PM   #1
XELB is offline XELB  Portugal
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Default Class A for sensitive speakers

A friend of mine is making an A Class amplifier with me( I am more like a supporter ).
Our main gool is to achive a very good amp that will "kick ***" in very sensitive speakers.
We know that we must have very low harmonic distortion from the first watt till the 5th.

For now, we got very good results in the AP machine but, we never tested it with the sensitive speakers.
We don't know how it sounds, because we are waiting for some parts to the PSU(It's going to be an inovative PSU) and we also don't have the time to work 100% dedicated to the amp.


Here is some results of the AP machine :


Click the image to open in full size.
Click the image to open in full size.




Later I will post the schematic. First let us test in real life.
(maybe this week end)
For now I can say that is 2x17W






What sugestion do you guys make for an amp like this ?
What do you guys think is essential ?
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Old 25th November 2005, 02:13 PM   #2
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Good test result. Waiting for further information.
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Old 25th November 2005, 02:22 PM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
I just checked the maths and found that 0.002%=-94db
So I suppose you are about 16bit equivalent which is pretty good.

Are your speakers in the 94db/W to 98db/W or similar?

Just awaiting the schematic and sound results.
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Old 25th November 2005, 05:14 PM   #4
XELB is offline XELB  Portugal
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The speakers have around 96 to 98dB.
The top version as around 100dB.


We are dissipating 180W.
Good heatsinks are required.




Let me introduce some new info.
Our PSU is based on this concept:
- We now that high capacitance capacitors have lot’s of problems at high frequencies
- We also now that lot’s of capacitors lower the ESR. ( parallel capacitors )
- And high capacitance is important, it reduces the oscillations of the PSU and gives you deep bass.


Our approach is:
+Vcc and –Vcc in different boards but with the ground connected directly(board to board), like a sandwich.(ground in the middle)
This is the point reference for the star ground.

The capacitor are: ( per rail )

4x 6,800uF
6x 4,700uF
12x 2,200uF
8x 1,000uF
12x 680uF
34x 330uF
16x100nF

This will give aprox. 110,000uF per rail, installed form the bigger capacitance to the smaller.



PS: We tested a "proto" board with a LM3886 chip and there's no need for snubber
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Old 25th November 2005, 06:25 PM   #5
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Do you have a photo of this?

I want to see the photos of this Capacitor Bank.

Thanks in Advance
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