Oscilloscope to Amp. Clipping?

[mightycrappy 10+ year member]

Ok sorry for a noob question. I seriously tried searching for this but could not find the answer.

We are/were going to hook his amp up to an Oscope and try and see when it clips.

That would be like benchmarking it, correct?

In order to do that we would need a dummy load right? How do we know what size resistor to use? It's apparently a 900W RMS amp and we were going to check.

When we get the right sized dummy load, do we just hook it amp up to scope and turn up gain till it clips and that's it?

I went to the BCAE1 gain setting oscope page, but that seemed confusing as all hell.

Can anyone out there give me some quick help?

BTW would we need a resistor to test HU? Would we test the sub preouts or the speakers?

Click to read more...

 

[kross 10+ year member]

To see clipping you don't need to put a load on the amp. Just keep turning the gain up and you'll see the point where the tops of the waveforms get "clipped" off.

Also, if you actually used a 4-ohm resistor, with that much power it would burst into flames. I don't know of any 4-ohm resistors rated for 900 watts.

 

[mightycrappy 10+ year member]

So, just hook up pos. to pos. neg. to neg. and start turning gain up?

Why do some people use dummy loads then?

 

[kross 10+ year member]

Yeah that should work. I don't know about the dummy load. I think that's used to measure THD at certain power levels. Anyway, I just read through that link above, I skipped all the theory stuff, and went to the "Gain Setting Overview" section, and didn't see any mention of attaching a resistor or any other kind of load to the amp.

 

[mightycrappy 10+ year member]

Cool. I just wanted to make sure I wouldn't mess up his amp or my Oscope.

Thanks

 

[thch 10+ year member]

the oscope should be fine. some amplifiers may not like being run this way. most will work just fine. the downside to not using a test load is that the amp's power supply is unloaded, and may be able to provide more clean output in this condition. Because testing sine waves on an oscope doesn't actually prevent clipping, and because the penelty for mild clipping is low, this isn't a huge concern.

 

[smd4life 5,000+ posts]

i would clamp the leads on the amp in the car....on the sub he's running

 

[IgnoreMe 5,000+ posts]

1) use jmac tutorial on this site as its dummy proof

2) follow it to a T

3) replace the dmm with an oscillioscope

4) watch the square wave...youll know it when you see it

easy as pie.

 

[mightycrappy 10+ year member]

Cool, thank you very much for the advice and the replies.

It's Much appreciated.

We would keep his sub hooked up while we test, but it's only a TC-1000 and the amp puts out around 900W RMS. So we're afraid if we tried that it would mess up the sub.

Thanks again everyone. //content.invisioncic.com/y282845/emoticons/fro.gif.c695f1f814b01c4ad99fe7f8cccadd29.gif

 

[luvinthebass 5,000+ posts]

use a 1 khz tone at 0 db and turn up ur head unit till the sound doesn't sound the same as it did...it's now clipped, back it down a notch and it's clean again, screw an oscilloscope

 

[mightycrappy 10+ year member]

Yeah well I have an Oscope and his Sub won't do full power of the Amp. So that won't work.

That's why we are testing with a Oscope. To see what his Max is on the Amp. Because if it's ALOT more than the sub can handle, he wants to get another sub.

Not to mention it's fun to mess around with an Oscope.

We used a 50Hz -6db sine wave. He is able to tune his Amps gain all the way up without any clipping. Brought it up to around 1200W, when amp is only rated at 900W. I always thought I read to never turn gain all the way up or something like that. He turned on the Bass Boost also, but I told him to keep that shit off.

BTW George it's a Sine wave clipped not a square wave (square waves are digital).

 

[thch 10+ year member]

I wouldn't call square waves Digital simply because they are commonly found in digital systems. They are found in many analog applications as well.

 

[IgnoreMe 5,000+ posts]

like thch said not all square waves are digital.

but from that statement i think your misunderstanding me. the wave wont turn completely square. the wave will look like a standard A/C wave but just the tops will be flat