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-   -   aleph 2 adding extra fets = what result? (http://www.diyaudio.com/forums/pass-labs/34414-aleph-2-adding-extra-fets-what-result.html)

MikeZ 20th May 2004 08:33 PM

aleph 2 adding extra fets = what result?
 
I was wondering if I added 1 or 2 more fets on the output of my aleph 2 what the result would be? I know it will generate more heat, what effect will it have on the sound. Currently with my speakers it sounds a bit bass heavy. My guess is it would change the bias and decrease the bass some while simultaneously increasing power output.

Has anyone done this and/or comments appreciated. Thanks Mike

wuffwaff 20th May 2004 09:41 PM

Hi Mike,

I donīt think adding on or two fets will help reducing the bass heavyness.
What you can try is to change the ac-current-gain (make it a bit lower).
Since I canīt really find the Aleph series bass heavy maybe you should try changing the placement of your speakers.

William

Brian Donaldson 21st May 2004 03:36 AM

With all other things remaining equal, adding output fets will increase total bias, but not effect output power unless you are current limited by low impeadance speakers.

MBK 21st May 2004 04:50 AM

Assuming your speakers are designed correctly in the first place, I see two possible reasons for bass-heaviness:

- your room has a resonance there. If that's the case, a notch filter before the power amp (or in the speaker X-O) might help.

- your speakers have a resonance there which is supposed to be damped by the amp, but which the power amp doesn't manage to control. In that case, a lower output impedance may help bass control, and here, if I'm not all mistaken, a couple more FETs in the output stage could actually help.

To leave total bias constant, you may decrease bias per FET.

hifimaker 21st May 2004 03:31 PM

Hi Mike,

Before moding the amp, have you tried rearranging the speakers. Placement can have a huge effect on sound.

Pull them away from the walls, and put them on stands with spikes, etc.

Just a thought,

-David


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