Another 'my amp cuts out' thread

[talltigeguy]

OK. My amp cuts out to the tower speakers. It has done this ever since I bought the thing, but most of the time it comes back on before I can even get in there to look at it. It is completely unpredictable, so I cannot make it happen by wiggling any wires.

A few facts:

PPI PCX 4125 is the amp,
Bridged to NVS Tyrants.
The gains are all the way up

While at Lake Mead 2 weeks ago it was a very hot day, 105 + degrees.
It started doing it a lot, and lasting longer than a few seconds. Always comes back on after a while, never longer than 2 minutes, sometimes for as short as 10 seconds. I wiggled every wire and that did not make it come on, or cut out, the connections all seem solid. The fuse looks good.

I check out the amp when it has shut off and the green power indicator is completely off. I expected it to be red instead of green if it were going into some kind of circuit protection mode or something, but it was not lit at all.

I then ran the tower speakers for much shorter durations at high volume and it did not seem to cut out at all.

The amp is pretty warm to touch, but not as hot as the other amp, and it never cuts out at all.

I think the amp is getting too hot...is that the truth?

[philwsailz]

Two phrases really have me concerned:

*BRIDGED*
and

*GAINS ARE ALL THE WAY UP*

Here is the probable deal...

While the NVS Tyrant is rated at "nominally 4 ohms" its actual impedance can be lower.

You have a 4 channel amplifier that is advertised as 2-ohm stable per channel. That means it will operate into a stereo 4-ohm load, but not any lower.

If you have always had the problem, I will suggest that the NVS speakers probably have a DCR resistance measurement of less than 4 ohms, like 3.2 or something like that. Assuming it is 3.2, (only for example) ohms for each NVS speaker, the amp shares that load, such that each amp channel "sees" a 1.6-ohm load. This is typically outside the normal operating range for most amplifiers.

You would be better served using a stereo amplifier, (2 channels) that delivered somewhere around 400 - 500 watts into a pair of 4-ohm loads.


Why in the world do you have the gains on the amp turned all the way up?

bad bad bad......



There are some things you can do to try to prevent the cutting out.

*re-wire the speakers to only half of the amplifier, so that each channel sees a 4-ohm load only. This will draw much less current, and the amp will be happier

*make sure that you have the crossovers turned on and set to hi-pass, at a frequency of 50 hz or higher. Recreating bass in an amplifier is power ineffieicnt, and the speakers will not do real well at these low frequencies, so consider re-setting the crosovers. It should result in lower current through the amp, with cooler operating temps...

*make sure that any bass boost in the amp is turned off or to its lowest position. Bass boost is just a power sponge, and if used to excess, only points to other system deficiencies that can be corrected by adding more woofers or larger woofers.

*make sure that the power wire going to the amp is as large as possible, and make sure all connections are tight. Bad power wiring results in voltage sag, which results in inreased current draw, and higher operating temperatures. Also, some amps have a low voltage sense and will shut off if they see too low a voltage. Maximizing voltage capabilites of the wiring will help to ensure that the amp see a strong source of power.

[talltigeguy]

Why in the world do you have the gains on the amp turned all the way up?

So that it would be louder.

[philwsailz]

So that it would be louder.

perzactly what I thought...

Gain controls are there to help you get a proper gain match between the driving device and the driven device, as well as facilitating system balance between multiple amps for proper blending between mids, woofs, tweeters etc...

A gain control is not a volume control. The amp can only put out so much power period. With a proper gain setting, the amp shoud put out max power and be just under clipping at roughly the same time the head unit is just under clipping.

Having the gains all the way up only makes the amp go to full power much quicker, sometimes with the H/U volume set to half, or less. Anything beyond that, and the amp is just clipping, sending a signal that looks less and less like a sine wave with every bump of the H/U volume control.

Also, having the gains all the way up amplifies all of the nasty noise that is tpically well below the electronic nosie floor, so you hear more hiss, more popping, more static, more motor noise, and pretty much more everything except music.

Having your gains wide open does not make the system any louder, it just makes it easier to overheat, break, catch fire, etc...

But, if that is your cup o' tea....

[talltigeguy]

In all seriousness, I have not fussed with the gains as that the speakers sound terrific the way they are set up. I may consider turning them down.

The same problem occurred when I had the NVS addictions and the gains were only about 2/3 of the way up.


Thanks for your thoughts.

This amp is a 4 channel amp that puts out 125 Watts per channel when it is not bridged, but puts out 500 Watts when bridged. The Tyrants are rated to be 500 Watts RMS. Unbridging them would leave them severely underpowered, I think. I really don't want to have to get a different amp,as that this one is pretty pricey and I don't want to dump more money in to the system.

Thanks for your thoughts!

The wire is 4 guage and is about 20 feet in length. I have toyed with the idea of running 0 guage and putting in a distribution block, but for now the wire goes straight to the battery. The amp only accepts 4 guage, it would be impossible to get it bigger. The wire does not feel warm to touch when the amp cuts out.

Good thoughts about the resistance...maybe a call to Duane at NVS is a good idea.

I have the crossovers right and even measured things witha 200HZ test tone. I will double check the bass boost, but I think it is off.

Is the wiggle test good enough to see if my connections might be bad? It does not cut out when I wiggle the power or ground wires at the amp, fuse or battery.

[talltigeguy]

Also, this problem never happened this bad until I put in the WS420....Mmmmm.

Definitely the gains need to be turned down as that my input is stronger now, right?

[philwsailz]

In all seriousness, I have not fussed with the gains as that the speakers sound terrific the way they are set up. I may consider turning them down.

The same problem occurred when I had the NVS addictions and the gains were only about 2/3 of the way up.


Thanks for your thoughts.

This amp is a 4 channel amp that puts out 125 Watts per channel when it is not bridged, but puts out 500 Watts when bridged. The Tyrants are rated to be 500 Watts RMS. Unbridging them would leave them severely underpowered, I think. I really don't want to have to get a different amp,as that this one is pretty pricey and I don't want to dump more money in to the system.

The wire is 4 guage and is about 20 feet in length. I have toyed with the idea of running 0 guage and putting in a distribution block, but for now the wire goes straight to the battery. The amp only accepts 4 guage, it would be impossible to get it bigger. The wire does not feel warm to touch when the amp cuts out.

Good thoughts about the resistance...maybe a call to Duane at NVS is a good idea.

I have the crossovers right and even measured things witha 200HZ test tone. I will double check the bass boost, but I think it is off.

Is the wiggle test good enough to see if my connections might be bad? It does not cut out when I wiggle the power or ground wires at the amp, fuse or battery.

Unsure about the wiggle test, but a proper test is this:

Get out your Volt-ohm meter and check the voltage RIGHT AT THE AMP with the stereo playing full tilt boogy. Use the red and black probes and test right on the positive and negative power terminals of the amp. If you are getting down below 11 volts, you have a problem maybe somewhere in your power wire. If this turns out to be the case, a big fat run of 0 or 00 to the amplifier mounting area and then #4 or a short run might well improve things.

Checking with Duane is worth-while, but if he confirms my suspicion, you are still in a situation where you have an instablility condition between your current amp and your speakers. I still am just dismayed to see so many people buying 4-channel amplifiers for 2-channel applications. Your experience rings resonant; bridging is just not a good solution pretty much every time. It is a compromise that was born out of necessity 20 or so years ago that somehow took on a life of its own, and has become a buzz word of sorts.

Forgive the soapbox, but I want to repeat the mantra for any others reading this... Please guys, bridging is a band-aid...

Let's hear what Duane says, but you might be in the market for a 2-channel amplifier....

[philwsailz]

Also, this problem never happened this bad until I put in the WS420....Mmmmm.

Definitely the gains need to be turned down as that my input is stronger now, right?

That is a start. Also, how radical is your EQ settings for each band?

Minor tweaks can improve things, but if you have really large boost settings, it can be a good pointer that something is missing in the way of your speaker complement.

Equalizers are tricky; it is easy to boost stuff with the EQ, but is more system-friendly to cut frequencies. Put it this eay: if you find that you have to boost a lot at, oh let's use a random frequency of 250 Hz, you can attain the same thing by cutting frequencies above and below 250.

IF you find you are hammering hard on real low eq settings, like turning 60 up a lot, it really should be telling you that you need more woofer cone area, or a louder woofer, or more subwoofer amplifier power...

Finally, (and I want to try not to write a book) on the intersting topic of out-of-phase conditions, specifically where two speakers are trying to play the same frequency range, but are electrically or acoustically out of phase, it is IMPOSSIBLE to equalize for that frequency band to correct for it.

[talltigeguy]

I appreciate the thoughts.

Those are great ideas and I will see what I can come up with.

I just bought a DVM, I might be able to use it for the first time now!

[talltigeguy]

Spent all day yesterday on the lake pulling young men from my church on tubes and teaching them to wakeboard. It was heavy work on the tower speakers as they love to hear some music blast while riding the tube.

I did what Phil recommended and turned the gains down some, to about 2/3 of the way. I do not notice any difference in volume or sound quality with the gains going down, so I am pleased as peaches that the speakers and amp combo I have seem to be pretty forgiving that way.

I busted out the DVM and tried to figure how to use that thing. I did figure out that my tower speakers are at 3.8 Ohms, when measured from the end of the wire at the amplifier. (My Wetsounds run with 2 speakers in parallel are at 2.6 Ohms, BTW, but that is another amplifier).

After pushing the speakers hard all day, everyone was very impressed with the loudness and clarity.

The amp cut out once on me, and that is it. It lasted about 10 seconds and then it was good, although I made a little more conscious effort to turn it down after that. It was just about as hot a day as it was when I had it cutting out a lot. So I think that putting the gains down a little has helped, but this problem has been so inconsistent and rare that I won't know if it helped for sure.

Thanks for the thoughts Phil!!!!!

[Coach]

Spent all day yesterday on the lake pulling young men from my church on tubes and teaching them to wakeboard. It was heavy work on the tower speakers as they love to hear some music blast while riding the tube.

I did what Phil recommended and turned the gains down some, to about 2/3 of the way. I do not notice any difference in volume or sound quality with the gains going down, so I am pleased as peaches that the speakers and amp combo I have seem to be pretty forgiving that way.

I busted out the DVM and tried to figure how to use that thing. I did figure out that my tower speakers are at 3.8 Ohms, when measured from the end of the wire at the amplifier. (My Wetsounds run with 2 speakers in parallel are at 2.6 Ohms, BTW, but that is another amplifier).

After pushing the speakers hard all day, everyone was very impressed with the loudness and clarity.

The amp cut out once on me, and that is it. It lasted about 10 seconds and then it was good, although I made a little more conscious effort to turn it down after that. It was just about as hot a day as it was when I had it cutting out a lot. So I think that putting the gains down a little has helped, but this problem has been so inconsistent and rare that I won't know if it helped for sure.

Thanks for the thoughts Phil!!!!!

I would almost guarantee that turning the gains down will help. I deal with the insane heat all summer and I have to open my hatches up to get some air on the amps and the cabin will cut out still from the heat. That is the one set of speakers that are running in series on 2 channels which I think increase the Ohms which make it work harder. Another thing to do is dial in the point at which the highs and lows are hitting. I found my cabin speakers where coming in way to early and creating a lot more bass then I need them to. Once I moved that frequency point up to around 100 Mhz that help that amp from overheating. I run a bit more bass in the tower and have it come in at 80 Mhz but I don't have anything running in series on the tower.

Glad you got it working! Nothing better than your system working the way it is suppose to!