[CButterworth]

I installed a single blue LED on my AKSA 55 running at 0.5mA using a 68K 1W resistor.  It is located on the right channel power supply unit.  Anyway, it works great and looks cool.

Alright, when I switch off the amplifier,  I get a very quiet, very brief hum from the speakers (I remember seeing a post on this from Hugh, and it is quite normal).  However, the Left speaker makes this sound a split-second before the Right speaker - so close together that the sounds overlap slightly. The difference is very slight.

My questions are:

1.  Is this caused by:
     A.  The differences between the components on L & R amps (eg slight resistor differences)
     B.  The Effect of the LED drain on the R channel
     C.  The Effect of the 68K resistor
     D.  The slight differences in bias settings between R and L channels
     E.  All of the above

2.  Does this matter?

3.  Would a 68K (NO LED) on the Left channel prevent this, and be better for the amplifier / speakers?  I did see somewhere that folk were getting the occassional spark when tinkering with the amp.  Would it prevent this?

Again, I love the sound of my amp and cannot wait to upgrade the rest of my system.  I spend a lot of time at work listening to music through my Meta42 headphone amp and Grado headphones.  They sound really good and clear, but "sterile" compared to the AKSA which reveals almost as much, but sounds much more natural - a definate bonus.

Thank-you
Charlie

[AKSA]

Hi Charlie,

Thanks for your post;  I must say you really are a keen observer!

In truth, none of the above!  Differences between the amps, as long as bias is equally set, are very minor, around 3% maximum.  The reasons are to do with the cranking up of the power supply, and minor differences in the transformers and reservoir capacitors, which have +/-20% capacitance ratings.  These will make a difference to the rate at which voltage builds on the rails, and during the transition you will hear buzzes as the caps charge at high current and ripple ratings are greatest.

It is of no significance in operation, although these initial charge currents are high, many amperes, and the rectifier bank is heavily stressed during this period.  But that's OK, it's designed to take a pulse current in excess of 70 amps.

Cheers,

Hugh

[CButterworth]

Well, I found an earlier reply by Hugh to a post that I made a while ago.  He seems to think that bleeder resistors are not vital as the amp should draw thew current almost down to zero anyway.  He also recommended 10K 1/2W resistors for the non-LED bleeders.

Charlie