Soundstrean Rubicon Class A 5.2 strange Power-On

[azvrt]

Hi,

I have a Rubicon 5.2 which otherwise appears to be working flawlessly, but I´ll try to describe what happens when the remote wire is connected.

Usually, these amps will immediately draw a little current when the remote wire is connected, and after a second or two will idle.
With this one, the needle of the analogue indicator of our power-supply goes back and forth between 0 and 1 ampere (approx.) 3 or 4 times before idling normally at just under 1.5 ampere.

It makes me think of the kickstarter of a motorcycle, where you´d have to kick a couple of times before the engine turns on.

I´d say the turn-delay is pretty normal, about two seconds or so. So the back and forth going of the needle happens within this time-frame.

Any ideas ?

[gisewhcs]

If it's in working order I just wouldn't care about it.
My Atlas VIII and my Saturn Gen.X even make my headlights dim for a split second when they turn on.
First the Saturn and then the Atlas.
And my electrical system is strong enough to keep voltage steady under load, so it's most probably just the inrush current of the secondary capacitors.
What kind of (ampéres) power supply are you using?

[azvrt]

On the test bench you mean ? It's an adjustable power supply, the analogue indicator shows up to 3 ampere.
I've never had problems with this power supply before, there's definitely something not quite right with the amp.

Yes I thought about putting it in the car, but my father thinks this problem should not be very hard to solve (he could be wrong of course) so we'll probably have a look at it.

[gisewhcs]

I think there is no problem at all.

I'm not familiar with those class a soundstreams, but they most probably have huge capacitance in the secondary.
And those capacitors just need their current to get charged.

[azvrt]

I think they are charged whenever you hook the 12 volts up to it, not when the remote wire is connected.

I always turn on the power supply first, feeding the amp its voltage, then conect the remote wire. By the time the remote wire is connected, the caps should be charged already.

[gisewhcs]

Not the secondary ones.
Those are getting charged when the SMPS inside the amp turns on, not when you just hook up 12V and ground.

[azvrt]

Ok thanks I was unaware of that.

However, I´ve powered on dozens of Soundstreams including the bigger brother 10.2 and never experienced this, so I am pretty positive this is not normal.

[gisewhcs]

You even say that this amp idles at 1.5A (what tells me it's NEVER a real class a amp...), so why do you care about ~1A while starting up?
I don't really get your point, I'd put it in my car with a good feeling.

[azvrt]

Of course they are not true Class A amps.
The older Soundstream high bias amps (such as Class A 6.0) idled much, much higher, but that resulted in heat issues. Therefore, for the later models they dropped the bias drastically.
I agree with you that at such a low amperage, one can barely even call it a high bias amp. But the internals are technically similar to the older high bias models and different to the non-high bias models, and they sound great to me.

The 1 ampere while starting up does not concern me, what concerns me is that the needle goes back and forth between 0 and 1 ampere three or four times before idling at 1.5 ampere. The back and forth going is what is not normal.

Thanks for your input,and I agree I could put it in the car, but chances are it will be defective at some point as a small problem often is the beginning of larger problem, if not attended to.

[gisewhcs]

Do you have a bigger PS for testing?
If your PS has a current limiter, is it set open?
Pull the fuses, put a 10A in there and start it up again.
Perhaps it's the small PS that's breaking down too much, so the SMPS from the SS can't start up at the first try, while charging the secondary caps.

Goede nacht!