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FetZilla groupsbuy 4

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#82
Jozua said:
Meanman1964

Any chance of a groupbuy for the output devices?

Especially if there is a specific brand that sounds better than the others.

Regards
Click to expand...

Do you mean for this groupsbuy?I'm offering a parts kit with this amp yes also the output fets.I'm using the ALF08P(N)20V fets with good result other brands I don't know.I think the Exicons are the same quality.A few guys of the groupsbuy are planning to use the 2SK1058 - 2SJ162 from Renesas those are cheaper.
 
#83
AC voltage and Heatsink questions

Hi meanman1964,
Will it work well with a 2x24Volts AC secondary transfo, or will i have to change something ?
What is the recommended heatsink's efficiency for +/- 35V DC : 1°C/W, 0,7°C/W, other ?
What is the size of the PCB ?
Thank You for your work.
Bye.
 
#84
I'm using 2x24Vac myself only a minor setting will be different.The board size is 230mmx69mm.My heatsinks are 290mmx90mm and the temparture is max.38-40°
 

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#85
As a rule of thumb you can say: using a 1C/W heatsink means: each Watt that the amplifier comsumes will add 1C
to the existing room temperature on the heatsink.

So: if your room temperature is 20C and you play your music in a way that the amplifier consumes 40W, this will result in about 60C on the heatsink.

I always take care that a heatsink does not get hotter than 50C and therefore think that it would be better to go for a 0.5C/W heatsink.
Please find out how much wattage one channel of the FETZILLA consumes yourself.

Best regards - Rudi_Ratlos
 
#91
PSU caps Questions

Hi Meanman1964,

What is the maximum size of the PSU CAPs (30, 35 mm) ?
10 mm Snap In are OK ?

Do you plan to include these Caps in the component kit ?

As an option ?

Considering the output current (400/450 mA), do You think 105C grade is necessary ?

(In my opinion 4700 µF is a too small value)

Regards.

Eric.
 
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#95
Hugh's comments on cap supply in the psu are as follow:

http://www.diyaudio.com/forums/aksa/191053-swordfishy-aspen-fetzilla-power-amp-11.html

Post 104:


Dinesh,

I really would discourage you from building a huge power supply. It will not sound so good.

I have done extensive testing with Class AB amps on this issue and found again and again that the very high charge pulses found in high cap power supplies actually militate against good sonic performance. The problem is that these very high charge pulses interfere with the voice coil earth return through the filter caps, causing intermodulation.

I find it's never necessary to go much more than 4,700uF on a 50W amplifier.

The FETzilla uses two 3,300uF caps separated by interelectrode resistors, each of 0.15 ohms. This quarantines the charge pulses principally to the first cap after the rectifier, with the second cap handling much reduced charge pulse and all of the speaker return current. This arrangement gives palpably better sound.

Cheers,

Hugh
__________________
Aspen Amplifiers P/L (Australia)
Aspen Amplifiers


Hugh mention this quite a a lot, he has reasons that high cap psu attracts high refresh currents that over mask the sonics of the audio signal. It's a very interesting comment!

Regards

ML
 
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