I have some cheap GEM SOUND amps, all very well made in terms of construction and hardware but the designs are pretty simple. I found to get them to produce their rated wattage, I have to have my preamp cranked to max and the amps clipping indicators pretty much stay lit.
No heat or audible distortion but I'm sill curious to know if I should be concerned.
I understand it indicates signal clipping but am I risking the life of the chips?
No heat or audible distortion but I'm sill curious to know if I should be concerned.
I understand it indicates signal clipping but am I risking the life of the chips?
It's just a single LED that turns red, and stays red lol.
I'll presume the circuit isn't very accurate based on the lack of distortion even when it's well passed turned red and no longer flickering. $130 Gem Sound XP-550 rated to produce 450 RMS@ 4 ohms per channel. 300 RMS @ 8 ohms per channel.
The XP-550!
So in other words, a cheapo with great specs, heavy duty enclosure and some nice strong cooling fans designed to be run into the ground in probably a couple years of heavy use.
Actually building an accurate clip indicator shouldn't be that difficult in a typical differential input stage power amp. When the input and feedback start to diverge, you're clipping. At times I've noticed digital recordings that clip in the form of 3 (counted them) consecutive FS samples.
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I figured there must be an impedance input issue which I may decide to deal with if things start cooking but really that may mean increasing the value of the input resistor and losing even more volume. These amps will be for driving PA cabs using fairly cheap piezo tweeters so I can live with cooking them granted they survive at least a few applications of hard volume.
If I cook the woofers, that's a different story but since I built the cabs myself they'll soon be equipped with fuses on the woofer leads.
I also metered them earlier, I was getting 140 watts RMS at 8 ohms and flashing the clipping indicator even though my sound was really clean. Less than half the claimed output though. I wonder if the FTC will actually get off their fat lazy ***** and discipline Gem Sound if I file a complaint. You figure if these people did their job, the audio world wouldn't be full of companies selling equipment that doesn't perform at the level claimed.
I guess it could just be that they attained that wattage when using a 1khz sine wave which is the standardized test tone. As soon as I cut the base on VLC Player's EQ, no more clipping. That's fine since I intend to use these cabs for volume rather than bass but it does leave me in a bind when the time comes to drive my dedicated subwoofers.
Maybe if I implement a mild high pass filter on the inputs I can tame the bass enough to push a lot more volume, then bring in the bass and effectively reduce the point at which the clipping becomes so obscene since it's all a product of the bass in the signal. Rolling off a moderate amount of the bass will probably allow me to attain 300 watts RMS (give or take) at 4 ohms but I doubt anything short of running 220 on it's 110 setting will get me 450 RMS per channel lol.
Nope, it's all the nature of these amps.
When I power the same speakers with my powered PA mixer rated with the same wattage as the rack mount power amps, the entire sound spectrum is beyond obscene. I can't even put it on 5 without first checking my will.
This adds to the assumption that the Gems aren't able to produce the rated wattage in the low frequencies. This is why equipment is so deceiving on both the amplifier end and driver end. An amp might produce 300 watts in the mid bands but only 100 watts when driving the bass bands. Just as a speaker can be rated 500 watts but the voice coil can only handle 150 watts at 80Hz. So you filter out everything else with a crossover, feed it 300 watts at 80Hz then wonder why it fried.
It's the deceitful industry standard of using a 1khz sine wave to produce the specs the speakers are marketed under.
Sine waves have nice smooth tops. Music is peaky. This means that music, of almost any type, will trigger clipping when the average power is less than you can get with a sine wave.
In addition, amps differ on how much the supply voltage sags under continuous load and how the manufacturers rate them - tone burst or continuous tone. The cheaper the amp, the more likely it is to sag badly but be rated for maximum possible output from a very short burst. I have no idea which combination of these effects you are getting.
In addition, amps differ on how much the supply voltage sags under continuous load and how the manufacturers rate them - tone burst or continuous tone. The cheaper the amp, the more likely it is to sag badly but be rated for maximum possible output from a very short burst. I have no idea which combination of these effects you are getting.
By now you've expressed enough interest in actual performance and a desire to handle it personally that you may as well bop on over to Ebay and pick yourself up a nice 50 dollar scope if you aren't ready to plop down for something serious right off the bat. Even the biggest POS scope is going to tell you whether your bass is clipping so long as it isn't broken or totally shot. Compared to a scope, especially for bass, a clipping indicator is going to lie to you. WIth the oscilloscope, not only will you be able to know whether there is clipping, you'll be able to see where.
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