Check Actual Ouput Of An Amplifier?

[ISO]

No need to go to ROE for The info I wrote, its all here now.

[qu1cks1lver56]

thanks for it.

that was a really good explanation.

[ISO]

If I can't help others out there is no reason for me to be here.

[Derrick824]

Good post ISO. +2 cool points for you.

[roscoe1129]

Good post ISO. +2 cool points for you.

Thats why I pinned it for him

[ISO]

Good post ISO. +2 cool points for you.

Thank you

Thats why I pinned it for him

Thanks again Roscoe.

[Boon]

Just read this now and I agree with almost every point except one - the issue of hooking up the load when scoping the output of your sub amp (probably applies to mids as well but it's such a small difference that it's never mattered for me)

The impedance of your load seems to have a big effect on where your amp clips. I think it's to do with the efficiency of the amplifier as current increases - I think that like the power input, as the rail current increases the voltage decreases.

I'm basing this off my amplifier clipping at different places for the following setups:

Atomic AP12 Dual 2 ohm (1 ohm nominal) - Clipped at the highest gain of the group

DD 9515 D1.5 (0.75 nominal) - Large box, reasonable impedance rise - Clipped at slightly less gain than the Atomic

DD 9515 D1.5 (0.75 nominal) - Very small box, lots of port area, minimal impedance rise - Clipped at MUCH less gain than either of the other 2.

Conclusion, impedance (for whatever reason) has a noticeable effect on amplifier clipping point

This is only really important for SPL though, where you're burping a single frequency and have a fixed and known impedance rise. For a daily beater just set it a little bit below clipping (preferably with a sweep) and you'll probably be ok, it's hard to get it perfect because a speaker (especially in a ported box) is such a variable load.

[ISO]

I realized I never thanked the people that taught me everything I know about DB Drag and a 1/3 of the knowledge I bring to this forum.

Thanks to Jeff Sherrick and Eric Parsley For teaching me alot of good info way back in the day.

[ISO]

Since I talked a little about setting gains with an O-Scope in this thread, I decieded to add the info I just wrote in another thread.

When I get down to the mid tweet setup I started to screw up because I'm getting tired but my opinion for a sub amp is spot on for me and anyone that wants to use a bass knob.

Heres the link to the thread but I'm going to copy and paste it here too.

http://www.stevemeadedesigns.com/board/ind...showtopic=51719

The copy and paste:

QUOTE (Chris661 @ Aug 1 2009, 03:23 PM)

after you are done setting all the gain and everything. is it going to hurt if you start miss with the stereo EQ ? also when you start adding crossover and bass enhancers do u have to o-scope for that to? or can u just add it right up to it. after u done the o-scope for cliping on the amp and the deck.

-thanks

chriz

END QUOTE

This is what I do when I set up a system with an O-Scope.

1st-Head unit:

I make sure the head unit(H/U) is set to perfectly flat. No signal processing at all. Everything totally shut off (Accept the H/U its self). EQs set to flat and built in crossovers turned off or maxed out if they are not defeatable.

Then hook the RCA outputs from the H/U to the O-Scope to find what volume number you can go up to before it starts to clip and remember what that number is as you will use that volume number to do all your gain matching.

2nd-Amps:

Turn the gains all the way down on all amps. Bass boost too and turn the crossovers off or in the case of a sub amp without a defeatable crossover turn it all the way up. (they usually max out at 250 hertz on alot of Class D amps and shut off the infrasonic or subsonic filter.

If you are going to use a dash mounted bass knob with your amp I suggest plugging it in and turning it all the way down before you set your gains on your sub amps.

I noticed when I set my gains on my RF BD1500's the signal was perfect but as soon as I plugged in my Punch Bass (with it turned all the way down) it added a few tenths witch started a soft clipping comming out of the amp, so I left it hooked up and turned it down and reset my gains and all was good.

Just a little advice.

3rd- and this is how it works best for me no matter what amp I'm tunning (subs,mids, or tweets). Leave all amps unloaded and use a 50 hertz test tone recorded at 0 DB level and make sure no speakers are hooked up to them when hooking the O-scope up to the amps speaker terminals to set the gains.

Why do I do it like that?

On my sub amps it leaves me some leeway to use a bass boost without causeing excessive distortion or on the bass frequency control on almost all radios gives me room to adjust it up some so its not distorting as soon as I turn it up.

Remember if you use a 0 DB recording, that gives you adjustments up to 5% distortion without your bass sounding real shitty.

As far as mids and tweets go I still use a 50 hertz 0 DB test tone for the same reason it gives you a little leeway if you have an EQ and my results from useing a 0 DB 1,000hertz test tone to set my mid,tweet gains has not turned out to favorable and it seemed like I lost any room to adjust any frequencies up on my tweets without negative results.

If I set my Sundown SAX-100.2 at 50 hertz and get the gain perfect it may read 55.2 volts bridged. Then leaving everything hooked up I change the track to 1,000 Hertz and the voltage drops to 44.3 and gives me the room to adjust an EQ with minimal chances of running into clipping.

I did set it at 1,000 hertz one time but I couldn't really adjust anything, everything I touched made them sound worse.

I might not be makeing any sense so I'm stopping I have been typing for 4 hours. Sorry for the confusion if I screwed up my own post.

Just use a test tone disc that is recorded at 0db and that should leave you enough play in the clean voltage area to use your EQing without running into clipping very badly.

[ISO]

This belongs to the thread that the post above goes too.

I don't have much time to answer abunch of questions tonight but I left out a real important detail about setting your gains with a bass knob.

Someone correct me about amplifier companies if I'm wrong about RF being the only company useing a dash mounted bass boost instead of a gain control knob.

Of coarse RF uses a bass boost circuit in their dash mounted knobs and that is why I told you to set your gains with it turned all the way down and use the 0db test tone recording and that gives you the ability to use the dash mounted bass boost and have a clean amount of bass boost before clipping.

95% of all the other companies use what are called dash mounted bass knobs or dash mounted line level controls in their amps. The difference is a dash mounted line level controller does not boost bass instead they turn your whole spetrum of bass down that the amp is playing.

In this case when you set up your gains with an amplifier that has a line level control, you want to plug in the dash mounted controller and turn it all the way up then set your gains.

Why? because the line level control on those amps are actually at 0db turned all the way up(this is equall to not even haveing the controller hooked up to the amp at all) and as you turn it down it goes into the negatives which gives you less overall bass.

The instruction manuals should tell you what you have (like I said I think only RF uses a bass boost).

Examples:

Here are the specs on acouple of amplifier companies.

1st - Rockford Fosgate T20001bd (since you have one) says in their manual:

Remote Bass – The Para-Punch Remote Bass connection is made with a RJ-45 cable and can be installed

in a variety of ways for easy control access. One control is used to boost low frequency information to

overcome road noise and put the bass in your face.This Bass control is a narrow band adjustment

variable from 0dB to +18dB with a Gyrator based Punch EQ that eliminates frequency shift with boost.

The other control is used for adjusting center frequency variable from 35Hz to 70Hz.

This is under the specifications section of the manual:

Equalization (Variable Punch Bass) Variable from 0dB to +18dB @ variable 35 to 70Hz

Look at the bold print and it says 0db to +18db - that means that control turns bass up.

Same goes for my older RF bd amps that only boost one frequency.

The 2003 BD amps specifications page says: Equalization (45Hz Punch Bass) Variable from 0dB to +18dB @ 45Hz

Now lets look at the Kicker amps and I have to use their old explanation as they don't really explain what it does as well in the new manuals.

The Kicker RGX Module explanation and what most amplifier companies use in their bass knob designs.

The manual for the RGX module (Remote Gain Crossover Module) says:

RGX (Active Remote Gain Crossover Module)

Control amplifier gain from your dash for balancing amplifier output

Controller range - Fully clockwise: +0dB; fully counter-clockwise: -26dB

This is the same for all Kicker amplifiers and as you can see instead of boosting bass, it lessons the amount of bass the amp puts out.

That is why when you use a line level control you set your gains with it turned all the way up.

I'll give you a tip: When setting a line level control bass knob and useing a 0db record to set your gains with an O-scope I suggest turnning it 2/3rds to 3/4 the way up instead of all the way up so you can still boost the bass some for those songs that just don't have much bass but when you go to listen to rap make sure the control is turned back to wherever it was when you set your gains as rap usually has the bass emphisized already and will clip your amp hard and may harm or blow your subs.

The explanation I used from Kicker applies to most amps out there except Rockford Fosgate and maybe some company that I have never heard of.I hope this helps clarify some things about dash mounted devices and setting your gains.