XPA-2 Protection Circuit Problem

[garym]

I posted this question in the "Review" section (because another user with a similar problem posted there), but re-posting it here in the hope that more XPA-2 owners will see it.

My XPA-2's protection circuit trips over any material with heavy bass played loud.

As soon as I got it hooked up (about 3 weeks ago) it seemed to me that the amp was working too hard --- for a 250W amp --- to produce the levels (for rock) I usually set. On my Denon AVR-1712 receiver that level = 0db (which represents the max usable output of the receiver, which is 90W/channel). I expected a 250W amp to have much more headroom.

On the XPA-2, the setting on the UMC-200 needs to be 60 to achieve the same level. I discovered that you can boost the preamp signal to the amps, so I boosted it 5db. That allowed me to reduce the volume setting to 55 to achieve the desired level.

That works OK on most material, but on any material with heavy bass (such as Madonna's "Vogue"), the amp trips into protection.

Today I measured the output of the amp with a DMM, to see what volume setting was needed to produce the standard 2.83V speaker test voltage with a 1K test tone. Left channel was 53.5 (to get 2.84V), the right was 52.5 (to get 2.73V).

Do those settings seem normal to others with this amp?

BTW, the protection seems to be triggered by an over-current, rather than over-temp. When it trips, the amp is cool to the touch, as cool as any other metal surface in the room.

The speakers are KLH AV-5001s. Mid-90s vintage. These are floorstanding 3-ways with a 12" woofer, 12" passive radiator, 5" cone mid-range and 1" dome tweeter in a sealed box. Rated at 8 ohms nominal and 90 db sensitivity. The bass they produce is very tight, and they can reach down to about 28Hz. There is no need for a sub for any musical material with these speakers. They will bottom out with LFE signals from some movies, though.

One of the Emotiva people suggested the impedence of the speakers may be falling too low at certain frequencies. That is quite possible. The speakers are quite old, and its possible some of the crossover caps have gone off-spec. They sound fine, however. Neither the amp nor the speakers seem to be clipping when the protection trips.

I'd like to confirm that the amp is OK before tearing into the speakers, or replacing them. I hoped someone would comment on the voltage measurements I gave to let me know whether they seemed normal, or perhaps suggest other measurements I might make to determine whether the amp is developing full power or pin down the reason for the protection trip.

Thanks!

[Vermont99]

I was over my friends house this weekend he has the same set up as me, for his main rig Salk HT3’s 84 db sensitivity and ratted up to 500 watts, 2 XPA-1’s and a UMC-1 connected with # 10 wire. Well he was playing quite loud when the left xpa-1 went into protection mode we restarted and after little while it went back into protection mode. So we started checking and found the plus terminal on the left amp was really tight, tightened all the connections and no more problem. Just something you might want to check.

[garym]

Jan 29, 2013 9:30:09 GMT -5 Vermont99 said:

So we started checking and found the plus terminal on the left amp was really tight, tightened all the connections and no more problem. Just something you might want to check.

Do you mean the connection was *too* tight? I don't understand.

Also, when it goes into protection, only the "meter" LEDs on the *right* side of the display go red. The left side LEDs stay off. Does that mean the prob is with the right channel, or does it mean nothing?

[roadrunner]

No, he was not saying the connection was too tight. He was saying the other connections were too loose and after tightening them the problem disappeared. One thing you need to know about the Emo protection circuit is that it monitors a number of potential problem areas and if it detects something that might damage your other gear it will engage the protection. Even the rate of change in current delivery from the wall outlet can kick in the protection circuit.

Do you have the amp on a dedicated circuit? What other gear do you have on the same circuit? Have you checked ALL of your cabling and electric outlets to make sure everything is snug, there are no loose strands of wire. Is your Emo amp plugged directly into the wall outlet? Have you talked to Emotiva's Tech Support personnel?

Chance are the amp is protecting some other component in you system. It will take a step by step search for what may be the root cause and can take considerable time by checking every single wire, cable and connection in the system. If you speaker is about to drop to an exceptionally low impedance the amp will detect it and will engage the protection circuit to avoid damaging your speaker.

If you don't know how to do a step by step investigation, call tech support and have them walk you thru the steps you need to take and tell you what you need to look for. Good luck and be patient in your trouble shooting task.

[sharkman]

It's possible those KLH speakers are going out of spec on the crossover. Do you have another pair of speakers to test the amp with?

[garym]

Roadrunner ----

"No, he was not saying the connection was too tight. He was saying the other connections were too loose and after tightening them the problem disappeared."

I did check that and they're as tight as a I get them without using a wrench. One other thing I'm gonna check is the speaker wiring itself. It is in-wall, and runs from the amp through a couple of j-boxes to a binding post terminal block. Gonna bypass all that with direct runs.

"One thing you need to know about the Emo protection circuit is that it monitors a number of potential problem areas and if it detects something that might damage your other gear it will engage the protection. Even the rate of change in current delivery from the wall outlet can kick in the protection circuit."

Yes, an Emo person explained that to me. It is clearly content-related, though. Trips only on certain material, consistently --- namely, music with heavy, deep bass. Most stuff plays fine at the levels I use. (I do not use the sub for music. The bass from the KLH's is much tighter and cleaner).

"Do you have the amp on a dedicated circuit? What other gear do you have on the same circuit?"

No, and don't intend to install one. All of the audio gear is on the same 20A circuit.

"Is your Emo amp plugged directly into the wall outlet?"

No. All components are plugged into a surge protector.

"Have you talked to Emotiva's Tech Support personnel?"

Not yet. Hoped someone here could help first. Would especially like to know whether those voltage measurements I gave are typical.

"If you speaker is about to drop to an exceptionally low impedance the amp will detect it and will engage the protection circuit to avoid damaging your speaker."

Yes, that is a distinct possibility. I'm gonna try feeding the system some low-frequency test tones and measuring the speaker impedance while they're playing. I have REW; I think I can do an freq/impedance plot with it.


Thanks, Roadrunner

[garym]

Jan 29, 2013 19:28:14 GMT -5 sharkman said:

It's possible those KLH speakers are going out of spec on the crossover. Do you have another pair of speakers to test the amp with?

No, unfortunately. Wish I did. But you could be right. I'll tear into them and replace the caps if necessary, but would like to rule out a prob with the amp first.

[shift]

Well I'm kind of curious now also.

I recently purchased an UPA-700, and it's been working wonderful with my umc-200.

However.... Last night I wanted to watch a movie in the late evening , so I had to shut the bass off on the subs and set my towers to "large" on my umc200. Next thing I noticed was my amp shut off, the power button and the digital lights on front (just the amp) started to flash and orange color. I then turned off the umc200, which also triggers the upa700 to turn off and turned it on and did it again. I found this very odd as this was late night movie watching and I done this plenty times before and never experienced this.

((note*** the reason why I set my speakers (front left n right) to large is because they have built in amplified subs on the towers to get me some bass/ ((model# dp7006)).

So I got my rear end up and decided to press the power Button on the front of the amp and turned it back on and it then never have the issue again.

So my question was why did the amp even start doing that?

Thanks

[garym]

Did the amp go into protection as soon as it came on, or when playing a particularly loud, bassy passage?

In my case it was the latter. On the XPA-2, if the prob is in the left channel, only the red LEDs on the left side flash when it shuts down (and similarly for the right channel). My XPA-2 was tripping on the right channel. So I swapped the speakers. At about the same point in the same bass-heavy piece, the amp then tripped on the *left* channel.

So I figured there was something wrong with that speaker. I tore into it, and discovered a blown tweeter. I haven't fully diagnosed the prob, but I suspect the loss of that tweet dropped the overall impedance of the system, causing a higher than normal current draw from the amp.

If your amp is tripping immediately upon power up, you probably have a different problem. But the prob has now gone away?

[shift]

So I figured there was something wrong with that speaker. I tore into it, and discovered a blown tweeter. I haven't fully diagnosed the prob, but I suspect the loss of that tweet dropped the overall impedance of the system, causing a higher than normal current draw from the amp.

You know what, after thinking about it I remember a few days back I heard like a static sound on the left tower, but it was not consistant as it went away while listening to next song (when I switched).

I do find it being odd if this was the case, the amp should have detected it and did the same (then) as it happened last night . So I am going to say its not a speaker issue. I just hope it was just a flaw or bad JUJU juice going to the amp that didn't like the taste

As for last night movie, the amp just kicked off about 20 minutes (not warm or hot) and it occured with this problem when I just changed my towers to large and shutting off my subs manually on each of the subs amps.

I will toy around with it again tonight when I get home, just was weird that I had to get up and manually turn off the amp power and turn it back on to not see the issue happen again.

[Deleted]

GaryM, I recommend you disconnect the amp from the surge suppressor and direct connect it to the wall outlet. It is quite possible that the surge suppressor is limiting the current available to the amp. And, besides, all of the Emo amps have surge suppression built-in...

-RW-

[garym]

Feb 21, 2013 9:43:38 GMT -5 @rlw said:

GaryM, I recommend you disconnect the amp from the surge suppressor and direct connect it to the wall outlet. It is quite possible that the surge suppressor is limiting the current available to the amp. And, besides, all of the Emo amps have surge suppression built-in...

I don't know how that could happen, rlw. The only way a surge protector could limit current is if it tripped. They will pass any current demanded, as long as the trigger voltage is not exceeded.

I suspect Emotiva recommends against them because they believe those devices can add some noise or distortion products to the line signal. But maybe an Emotiva guru can clarify.

I'm now using Klipsch RF7IIs, and the prob has not recurred. But the Klipsches are much less demanding of the amp. After I repair the KLH's I'll try them again.

[creimes]

It is recommended to not have the amps plugged into a power bar(surge protector), it can and most of the time will limit inrush current spikes when the amp needs that power to supply those heavy bass hits, and more so cheaply made surge bars. I have always had my amps plugged direct into wall like recommended.

Chad

[Deleted]

> I don't know how that could happen, rlw. The only way a surge protector could limit current is if it tripped. They will pass any current demanded, as long as the trigger voltage is not exceeded.

Some surge protectors use inductors for rfi protection. Inductors imped sudden current flows, which upsets high-power amplifiers.
/b

[garym]

Feb 21, 2013 11:14:22 GMT -5 @rasputin said:

Some surge protectors use inductors for rfi protection. Inductors imped sudden current flows, which upsets high-power amplifiers.

That would not apply to most (cheap) surge protectors, which use only MOVs or thyristors. They don't provide a whole lot of protection, either, but they are convenient power strips.