Setting car amplifier gain with oscilloscope (zero clipping)

Setting the front speakers of my car with a Welleman pps10 oscilloscope.

Rockford Fosgate T1500-1bd.
Vibe Blackbox 4 x 100 wrms
Vibe SE-K compontents
Vibe Space 15s
Sony Brooklands 6x9s
Peugeot 306 system twin alternators
Main 3

Category:

Autos & Vehicles

Tags:

• welleman pps10
• oscilloscope
• gain
• rockford fosgate
• 1khz
• 40hz
• 60hz
• 50hz
• true rms
• hard house
• distortion
• clipping
• cars
• ICE
• car audio

[noumenarete]

hello sounduser, i'm sorry to tell you that using this method to set the gains in the amp will prodice distortion, you are not taking in account the load, when the amp drives a speaker, the load is 2 or 4 ohms, and in such conditions, the characteristics of the output change, damping factor, power, current, phase. when you connect the scope, the load is virtually infinite, probably around 1 Gohm. It's ok to set the max lvel of the head unit, because of high impedance of the amp rca inputs.

[sounduser]

@noumenarete So why doesn't it change whether the speakers are connected or not? All i know is its better than doing it by ear. and its how Rockford Fosgate recommend you set their amps. So its good enough for me.

[noumenarete]

@sounduser Because you are using a 1khz tone, which is incredibly easy for any amplifier to amplify. You can use the 1khz tone for testing the RCA preouts, but not the amp speaker outputs, instead, use a 60hz (make sure it's 0dbfs) then turn the volume all the way up in the head unit just before its RCAs clip, then with the speakers hooked in, check the output while setting the gains. This way, the amplifier will be handling a very large load, and clipping will be present at some point.

[sounduser]

@noumenarete okay, so ive set it with the 1k test tone. if i put the scope on now with a 60hz it should be clipping where it is set now. so will need backing down?

[noumenarete]

@sounduser basically, to test a Class AB amp (full range), use a a 1khz tone, (100hz is better). And when testing a class D amp (for subwoofer), use a 60hz tone, just make sure low pass is set to the max, say 120hz for example, or 150hz even better. REMEMBER, a D class amp, can't see a 1khz tone.

[sounduser]

@noumenarete Im using a 1khz tone on the full range amp on this video. and i use a 40hz on the bass amp

[noumenarete]

@sounduser In the video, you correctly established the maximum level at wich the head unit's rca preouts start to clip. Set the volume at that level again, then connect a 4ohm subwoofer (you use a subwoofer because a speaker can't handle the power) to the output you want to test (do not bridge), then play the 60hz 0dbfs tone. Now connect the oscilloscope leads to the same terminals the sub is connected to, this way you can see what the sub "receives". Now set the gains,Remember set xover flat

[SuperErwin71]

@sounduser thankz bro yes i see that ....good day to you..



[sounduser]

@SuperErwin71 its comes with a COM1 cable and a link to download the software from their website..

its much easier to see clipping on the laptop.

[SuperErwin71]

how di you incorporate your laptap as display for yout output sine wave display..thankss