High voltage when tuning with DMM

[akheathen Premium Member]

ok, i still didn't grab the clamp yet, but i did take some profound quick numbers on imp. rise........ i was testing an amp i have on the bench with a 500w koiiler 12" in about 1.2 sealed. 2 sweeps, and you would be supprised how far off the wattage is without clamping. so, it's a 4ohm, and i played 2 tones @ 36, and 57hz. here are the #'s

57hz= 18.24vac @13.5vdc should be 83watts, but..... 1.26a means, it was actually sitting @ 22.98watts @ 14.47ohms

36hz= 17.3vac @12.9vdc should be 74.8watts, but..... 2.5a means, 43.25watts @ 6.92ohms

so, the 83watts=23

75watts=43

oh, and that was with the gain set at 20.3vac@57, and 20.5vac@36(didn't touch the settings at all once there wan no audible distortion, etc), and the ps voltage sitting @ 14.7 unloaded. although, there was no way of measuring clipping, i still think this kind of illustrates an average condition, similar to the one in question.....

 

[Bassin Buick]

As posted running a single channel at 4ohms on 2ohm stable amp is not going to tax the psu to the point where you are going to see much or any rail sag... next time try both channels driven at 2ohms and see what happens... the non true RMS DMM is also fail territory...

Don't have one. LOL. And i wasn't talking about the amp power supply , i was talking about the power supply i was using to power the amp. Only 10A on the 12v line. Its just a computer PSU that i use to power up decks when i get them to resell.

 

[Bassin Buick]

ok, i still didn't grab the clamp yet, but i did take some profound quick numbers on imp. rise........ i was testing an amp i have on the bench with a 500w koiiler 12" in about 1.2 sealed. 2 sweeps, and you would be supprised how far off the wattage is without clamping. so, it's a 4ohm, and i played 2 tones @ 36, and 57hz. here are the #'s57hz= 18.24vac @13.5vdc should be 83watts, but..... 1.26a means, it was actually sitting @ 22.98watts @ 14.47ohms

36hz= 17.3vac @12.9vdc should be 74.8watts, but..... 2.5a means, 43.25watts @ 6.92ohms

so, the 83watts=23

75watts=43

oh, and that was with the gain set at 20.3vac@57, and 20.5vac@36(didn't touch the settings at all once there wan no audible distortion, etc), and the ps voltage sitting @ 14.7 unloaded. although, there was no way of measuring clipping, i still think this kind of illustrates an average condition, similar to the one in question.....

Yeah , i guess so. LOL. I didn't really think much about imp rise till i started looking at data sheets on parts express (i'm shopping for new door speakers)

 

[akheathen Premium Member]

lol, yah, my little 40watt micronta doesn't quite cut it. i had to rig up a sla batt, and a decent charger to get respectable power. and, i only use true rms meters, but they don't have to be $400 to get by. my fluke87 was $800, but i've seen them as low as $30 at times in brands, like craftsman. the craftsman i have up at work actually turned out to be a decent daily meter, once i calibrated it. only reason i need to go grab a clamp, is because you basically need one for more than 10 amps. i was looking for a clamp attatchment, but can't see spending 150, if i'm not going to use it to make money.... shoot, i'm even him-hawin on buying an oscilloscope. i did get this idea earlier today....... take an old 200a charger/starter, throw in some alt. diode trios, an old 1farad cap i have layin around, and make some chokes. then, supply it off of a 15amp rotary dimmer switch and possibly bulding a drive board, or just relay panel. pretty much can scrounge all of it around my garage, and have a nice new 1k/2k bench power supply. sure would be nice to just find a good deal on one, though, even broken with a good transformer.