aleph 2 adding extra fets = what result?

[MikeZ]

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]

Hi Mike,

I don´t 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 can´t really find the Aleph series bass heavy maybe you should try changing the placement of your speakers.

William

[Brian Donaldson]

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]

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]

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