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Old 26th November 2016, 05:39 PM   #1
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Default Issue with new ATI NCore amp.

Hi All.

I just picked up an ATI AT528NC to be used with my Linkwitz Orions. Unfortunately with no inputs connected, and only a single speaker output to any channel, the amp channel periodically cycles with an small audible click during the cycle. The cycling is happening every few seconds like clockwork.

I am waiting to hear back from ATI due to American Holiday last week. This problem happens on every channel, and doesn't matter which particular speaker driver is connected to that channel (e.g. its not a problem with the load)

There is a dip switch on the input which can be set to Balanced vs unbalanced. The cycling issue does not happen in balanced and always happens when set to Unbalanced. The cycling happens whether an input is connected or not. I connected an RCA shorting plug to the unbalanced input, and the cycling stops.

Any ideas? Looks like the amp is defective? I'm wondering if its a fluke QC problem, or is there a design flaw in this amp? Anyone else have experience with this amp? My serial number is "022" so I'm guessing there aren't many of these in the wild yet.

They did offer to return it, which I am thinking is my only option, but appreciate any insight you may have in the mean time.
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Old 26th November 2016, 07:49 PM   #2
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Does the problem occur without a load connected?
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Old 26th November 2016, 07:52 PM   #3
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Quote:
Originally Posted by 5th element View Post
Does the problem occur without a load connected?
No, with no speakers connected, and no inputs, I see all blue lights on the NC500 modules and they do not seem to cycle.
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Old 27th November 2016, 05:07 AM   #4
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Connecting a load to a properly functioning NC amplifier should not make an iota of difference.

If a DC offset were present on the output of the amplifier then the amplifier would shut down regardless of if there were a load attached or not.

If something was oscillating and sending a high magnitude, high frequency signal into the amplifier then attaching a load could potentially trip the over current protection causing the amplifier to cycle in and out of shut down.

I would be surprised if the Ncore modules were faulty as these are presumable provided by Hypex directly.

If the input stage was faulty or finicky then it could be oscillating. If you introduce a shorting plug to the input of the SE inputs and the problem goes away, then this sounds like it is the very first stage, within the input stage, that's faulty/finicky. Grounding the input could very well shut down the oscillation.

Connecting the input to a low output impedance pre-amplifier, would (I would have thought) result in much the same result by bringing the input of the amplifier to ground.

Can you try the amplifier with other sources and see if this solves the problem? Leave the channels you're not using in balanced mode for the time being.

The other, but unlikely, cause could be a systemic fault caused by ground loops or something.

Do you have an oscilloscope?
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Old 27th November 2016, 09:52 PM   #5
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Thanks for the information!

I don't really have another source to try other than the 8 outputs on the Orion ASP.

If I connect the ASP outputs to the amp inputs one-by-one, eventually I'll reach a point where the clicking returns (I can't seem to get a full 4 outputs connected from either speaker. The same pattern happens whether I use the left speaker vs right, as well as left ASP outputs vs right ASP outputs.

For example, I can get tweeter, midrange, and upper woofer connected both speakers and ASP out. As soon as I add the upper woofer, the woofer starts cycling. This pattern doesn't matter which amp inputs I have connected, and follows speaker changes and ASP changes.

I actually just placed an order for a Tektronix 465 on ebay, but it probably won't arrive in time to help with this. I do plan to use the scope to look for op-amp oscillation. What would you suggest I look for with the scope if it arrives in time? (keeping in mind, I'm not an EE)


Quote:
Originally Posted by 5th element View Post
Connecting a load to a properly functioning NC amplifier should not make an iota of difference.

If a DC offset were present on the output of the amplifier then the amplifier would shut down regardless of if there were a load attached or not.

If something was oscillating and sending a high magnitude, high frequency signal into the amplifier then attaching a load could potentially trip the over current protection causing the amplifier to cycle in and out of shut down.

I would be surprised if the Ncore modules were faulty as these are presumable provided by Hypex directly.

If the input stage was faulty or finicky then it could be oscillating. If you introduce a shorting plug to the input of the SE inputs and the problem goes away, then this sounds like it is the very first stage, within the input stage, that's faulty/finicky. Grounding the input could very well shut down the oscillation.

Connecting the input to a low output impedance pre-amplifier, would (I would have thought) result in much the same result by bringing the input of the amplifier to ground.

Can you try the amplifier with other sources and see if this solves the problem? Leave the channels you're not using in balanced mode for the time being.

The other, but unlikely, cause could be a systemic fault caused by ground loops or something.

Do you have an oscilloscope?
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Old 27th November 2016, 11:56 PM   #6
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I'm sorry if you already said this and I've just not understood, but does the amplifier behave the same regardless of what outputs on the ASP you connect?

Is it possible that something within the ASP is faulty and causing the amplifier to trip its protection circuits?
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Old 28th November 2016, 12:52 AM   #7
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It doesn't sound like your setup is incorrect in any way. I would suspect some issue with the amplifier and would wait to hear back from ATI with further guidance.
The only thing you might try (since you note the problem is not there using the XLR inputs) is to use an external RCA/XLR adaptor at the inputs for a test.

The Orion ASP outputs all have common ground outputs, but that should not cause an issue with any decent multi-channel amplifier.

Cheers,

Dave.
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Old 28th November 2016, 12:56 AM   #8
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Apparently we think alike. I wondered if that would solve it as well, but part of my reasoning for purchasing this amp was the smaller footprint over the AT1506. If I use those connectors it may mask my problem, but at the cost of sticking out in the back too much for my application.

Also I think I probably won't feel comfortable spending almost $5k cdn on an amp that has such issues.

I'll see what ATI suggests tomorrow.

Quote:
Originally Posted by Davey View Post
It doesn't sound like your setup is incorrect in any way. I would suspect some issue with the amplifier and would wait to hear back from ATI with further guidance.
The only thing you might try......since you note the problem is not there using the XLR inputs.....is to use an external RCA/XLR adaptor at the input.

Cheers,

Dave.
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Old 28th November 2016, 06:30 PM   #9
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So just to reiterate you've tested all of the outputs of the ASP individually, to check that they are all operating correctly?

If you know the ASP is good then the amplifier is obviously to blame. Depending on how the system is wired internally you may be getting ground loops forming between the ASP and amplifier that get worse the more interconnects you add into the system.

The reason why the ATI amplifier is expensive is because of the 8 ncore modules not because of any decent engineering on ATI's part. I mean technically speaking the engineering goodies are in the ncore modules themselves. It would be easy for a third party to botch an external input board.
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Old 28th November 2016, 06:36 PM   #10
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Before I reply with that confirmation, I am going to check them all one-by-one to ensure each and every ASP out is working for that channel one-by-one.

I will also check the RCA sleeve with ASP ground to see if there are any channels that have grounding issues. As Davey indicated, the ASP outputs all share a common ground, so I doubt this is the case but I'll measure each one and confirm.
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