[MikeC]

Or one AKSA channel to be precise.

It is almost one month since I finally got my complete AKSA/Orion system up and running. I will write it up, and post photos, in due course. It is a completely new system, from source through to speakers, and it is still running in and having some minor glitches ironed out. Suffice to say that it is absolutely brilliant and improving. My only complaint is since I started, Hugh added the LF amps, and SL has just added a tweeter.

My problem is this: one 100W N+ module serving duty as a bass amp exhibits a slight but audible roar with the power off.  This goes away when I either pull the mains plug or switch the amp on. There is no problem with the midrange or tweeter amp in this channel, nor with the complete amplifier for the other channel.

I am using a soft touch switch to activate a pair of relays to switch the mains, one relay for the bass amp and one for the mid and treble amps. Each amp module is individually fused after the relays. Each relay has an Evox Rifa 0.22uF/100R contact suppression cap across the contacts to reduce arcing. I initially thought that the cap used in the problem case was leaking, and swapped it out, with no change. Even more strange is that the problem is intermittent. Sometimes it is there and easily audible when entering the room, sometimes it is quieter and sometimes the amp is completely silent, as it should be.

The bass amps are a deviation from standard in that I am running them off a 500VA transformer with 50% greater reservoir capacitance than standard feeding 42V rails. I am not convinced that this would have anything to do with the problem, especially as it only affects one channel. There will obviously be some leakage current through the suppression cap, and this is obviously exciting the amp in some way, but I don't understand the mechanics of this yet. I would greatly appreciate someone explaining this to me. Even more, I need a cure or an exorcist.

Cheers

Mike

[AKSA]

Ah, exorcism clearly required here.......!!   

Mike, the physics tells us that no current can be delivered to the speaker if there is no energy on the supply rails.  Check that there is in fact no voltage at any time on the rails, perhaps by putting a meter on the rails full time, even when switched off.

If this checks out, and there is still audible noise but no voltage, try disconnecting the speaker leads at the amp.  Is the noise present?  If so, then the problem is confined to the speaker leads and the drivers alone, and while this defies comprehension it at least indicates the general location where you might conduct your exorcism ceremony.

Congratulations on getting your complex, multiamp Orion system up and running!

Cheers,

Hugh

[MikeC]

Hi Hugh

Thanks for the reply, and you have pretty much confirmed what I am already guessing. Today I discovered that when I switch on the GK-1, the roar goes away.  This would indicate some sort of ground loop or earthing problem, but that would require some power at the amp or power to be supplied through the interconnects when all the other components are also off. I did try to play some music with the power amps off and the volume turned up to 11. The result - dead silence, absolutely nothing from any drive unit at all at a distance of about 2" from each. I did turn the volume all the way back down before switching on the power amps, but there is clearly insufficient leakage current through the suppression caps to run the amp at all.

You have seen some photos of the amps and speakers (unless they were also bounced by bigpond), but I want to make sure I do the whole system justice before I post a full description here.

Mike