[atenolol50]

i've managed to get to step 6. "Check audio output & bias stability".

when i flick the switch on, i get a fairly loud thud/pop from the speakers.
any damage to the speakers?

also on this same step,
i am having some difficulty getting the voltage across the emitter resistors to stabilise at 55mV.

after 15 mins of play, i adjusted it to 55mV from its reading of 58mV.
i then turned the vol up a wee bit (any louder - neighbours will pay me a visit), play it for another 15 mins, the bias gets to 63mV.
i'll try play a CD for 30 mins and measure again.

[AKSA]

Ate,

This is normal, offset varies slightly with mains voltage, it's not significant, see here:

http://www.audiocircle.com/index.php?topic=10748


Bias stability on the AKSA is good, better than most SS amplifiers.  Don't be too concerned about minor deviations of +/-10%.  Just set it after half an hour idling at room temperature.

The loud pop will get smaller, this too is not in any way damaging, and is normal.  It will never hurt the speaker.

You need to listen to it now, and bed the amp down in a decent enclosure!

Cheers,

Hughhttp://

[atenolol50]

yes sir.

the amp's in the chassis.
other than the "thud" on power up and the bias values which i need to tame ...
its singing  

will set the bias again using the method suggested.

thanks.

[atenolol50]

spent more time on my 55:

left the amp idling for 30mins.
the heatsink only a little warm.
voltage across TP1 and TP2 less than 50mV.
i raised it to 55mV.

played a CD for 30mins.
voltage across TP1 and TP2 now rather high at  65mV.
the heatsink's hot.

should i re-adjust to get a lower reading across the emitter resistors?

apologies if i appear to be asking the same qns again and again.

[ginger]

If the heatsink is getting significantly warm the bias level is too high. Like you I experimented with various levels. I finally put a blanket over the amp and ran it at reasonable volume until the heatsinks were warm to touch (babies bath water temperature, not hot) and then set bias for 56mV.

The expectation is that higher bias level means more operation in Class A before the transition to Class B and you should get better fine detail. I found that this did not happen. Higher bias levels sounded grungier and levels above 70mV sounded seriously crap.

Cheers,
Ginger

[atenolol50]

thanks for tip, will work on the bias for a while more.

and yes, the "pop" is no more

i noticed that there's a little hum when the input jacks are not connected.
quiet when hooked up to the CD player.
why so?

[PSP]

It is absolutely normal for an amp to have very slight hum with nothing attached to the inputs.  Get a couple of cheap male RCAs and solder a wire between the center conductor and the outside return on each RCA.  Plug those into the amp and listen... if there is hum with shorted inputs (I doubt there will be) look for signal leads that could be repositioned, etc.

Good luck,
Peter

[SamL]

Is it OK if my Aksa100n is cold all the time? Just wonder if this is normal as I just can't get it to go pass "cold". It is set to 55-58mv after 2 hours of playing and 20min of rest.  Continue with another hours of listening but the heat sink is still cold. Just to make sure, I touch the T7, T8, T9, T10 and the temperature is only slightly warm but below the 37C body temperature. Is this bec my AKSA100n is not in a case and is laying bare on the table? Room tempreture is around 17-20C.
I am using a 10K passive attenuator and playing between 9-10.30 o'clock.

TIA,
Sam