About using a scope to set the gains!!! Advanced Question

[mledez 10+ year member]

Hello,

I need some help with the amplifier gains using test tones, I have a velleman scope and I used a 50hz tone to set my amplifier gain "Sub Amp of course", the max gain getting a perfect sine wave "I mean, Without scuared tops"...

We all know that lower frequencies demand more power, so here's the problem...

Supose I used a 50hz tone, getting 500RMS at that frequecy... Perfect sine wave

But, when I play a 30hz tone the output goes to WOOOOOW, 750RMS and the signal gets a little clipped, so my question is... At which frequency I need to tune my amp?

50hz, 60hz ??? or the lowest frequency I want to reproduce with the sub? (In ported boxes, limited by a SS filter)

Thanks, and don't look my english

Click to read more...

 

[lostdaytomorrow 10+ year member]

Your English is actually just fine. Better than most American teens.

Sorry I can't answer your question though. I would think a normal 50hz sine, and then back it down a notch when you get to the square wave.

 

[dman4486 5,000+ posts]

I would say it depends on how often you plan on playing the lower frequency. If you are planning for more 40hz+ play, then tune at your original 50hz and don't crank the volume when you do want to play the 30hz tone

 

[mledez 10+ year member]

I would say it depends on how often you plan on playing the lower frequency. If you are planning for more 40hz+ play, then tune at your original 50hz and don't crank the volume when you do want to play the 30hz tone

I mostly listen hip hop, and reggae... So I play "or think it" frequencies below 40hz.

 

[nauc 10+ year member]

is your bass boost off, is your eq set to flat

 

[MikeyB 5,000+ posts]

I use a 60hz tone when I use my dmm

 

[mledez 10+ year member]

is your bass boost off, is your eq set to flat

Yeah, it's off. My amp is a RF T600-2. So the bass boost is fixed at 45hz. Tomorrow I will try to do something... Set the gain using 40hz and raise the boost 1 step before the signal get squared. I'm thinking on that because... next to 40hz all the frequencies higher will show less power, so I can increase it using the boost... What do you think ?

 

[mledez 10+ year member]

I use a 60hz tone when I use my dmm

Ok, But what happens when you measure the output using a 40hz ??? Have you tried it ???

 

[MikeyB 5,000+ posts]

Ok, But what happens when you measure the output using a 40hz ??? Have you tried it ???

Edit- 50hz tone, according to the gain setting tutorial and jl's gain setting guide a 50hz tone is the tone to use.

 

[spoonraker 10+ year member]

Your amp shouldn't put out any more or less power when the only thing you're changing is the frequency of the test tone. My guess is that one of your tones was recorded at a different volume. It could also be that you have a very smooth roll off at your low pass filter so it's sending slightly less power to the speaker at frequencies near that point. Put both your low pass and subsonic filters on the steepest roll off you can and pick a frequency that is right between them and tune according to that, and then put all your filters back to the regular crossover curves.