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Old 28th September 2005, 07:53 AM   #21
LBHajdu is offline LBHajdu  United States
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I had the time so I drew up the schematic. I changed the layout slightly for more symmetry. The lines are a little bit thicker then I would like. It must be checked for errors. Iím almost positive there are some. All you need do is to fill in the values.
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Old 28th September 2005, 09:31 AM   #22
DarkOne is offline DarkOne  Slovakia
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So, here it is.

- M1-4 should be thermally coupled
- M22 & M24 have to be on heatsink with output transitors
- current limiters configure to your own taste (i use 15A), or eliminate them

2 LBHajdu: nice schematic and looks correct, I don't have pdf editing tool (can just print), so I post it this way
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Old 29th September 2005, 05:54 PM   #23
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Very elegant. Do you have any pretty pictures?
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Old 29th September 2005, 06:31 PM   #24
DarkOne is offline DarkOne  Slovakia
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Quote:
Originally posted by pinkmouse
Very elegant. Do you have any pretty pictures?
I don't have pictures, but even if I had some, I better not post them. Amp is very ugly now, it's still a prototype
Before final version I have to redesingn pcb layout, schematic will stay the same
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Old 29th September 2005, 06:35 PM   #25
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Quote:
Originally posted by DarkOne
...Amp is very ugly now, it's still a prototype
Before final version I have to redesingn pcb layout...

I know that feeling!
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Old 29th September 2005, 07:18 PM   #26
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Quote:
Originally posted by LBHajdu
Thatís very interesting, Iíve never heard of a class A\B push pull amp describe as ďvery smoothĒ. I wonder if itís distortion from the output stage. Is there a high end roll off?

I also wonder if that is why Mr. Pass didnít use this topology in his amps.
Well, I can't use them all, now can I?

I played with something similar, but I found it worked better as
a Class A, no surprise there.

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Old 29th September 2005, 07:28 PM   #27
DarkOne is offline DarkOne  Slovakia
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Quote:
Originally posted by Nelson Pass


Well, I can't use them all, now can I?

I played with something similar, but I found it worked better as
a Class A, no surprise there.


Everything sounds better in class A

I can just set bias to 5A and set current limiters to 9-10A to avoid class B operation, but I can't dissipiate so much heat
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Old 29th September 2005, 08:13 PM   #28
DarkOne is offline DarkOne  Slovakia
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Quote:
Originally posted by LBHajdu
Thatís very interesting, Iíve never heard of a class A\B push pull amp describe as ďvery smoothĒ. I wonder if itís distortion from the output stage. Is there a high end roll off?

How is the noise floor, is there any hum? This is the Achilles heal of common source operation as you know. However the symmetry must help out some what.

I also wonder if that is why Mr. Pass didnít use this topology in his amps.

Sorry LBHajdu, I missed your post.

So, i had problem with hum, it was very disapointing, but I found that was due ground loop, which I eliminated. Still can hear hum, but I have to put my ears 10cm from cone, the same is with noise (speakers are 87dB/W). I don't know if this is good result, because I haven't tried other amplifiers. I must also note that signal cables are not shielded and long and I didn't match output transistors perfectly (one half is running 1.15A and the other 0.7A bias), future versions will eliminate this (still learning).

Measured noise level with my multimeter is around 0.2mV

"smooth sound" - maybe I used wrong words. Sound is detailed, dynamic and not agressive (in my words it's smooth)
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Old 30th September 2005, 01:20 PM   #29
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very good project, any pictures ??
Congratulations

How about supply, details ??
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Old 30th September 2005, 01:23 PM   #30
DarkOne is offline DarkOne  Slovakia
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Quote:
Originally posted by psroczka
very good project, any pictures ??
Congratulations

How about supply, details ??

Thanks

Power supply is made with 900VA transformer 2x18V
2x 35A diode dridges
Capacitors are 18x 10mF/50V
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