Teach It Tuesday: Setting Stereo System Amplifier Gains with an O-Scope

[@Ls.nando05]

Well I believe you guys have never messed up a system but don’t you have to tune amp while it’s under load? I have gotten different outcomes with a 2ohm sub connected. When I tune amp without a load I can turn up gain really high without clip. After I connect sub I have to turn down gain a lot.

[@Ron_Masterjohn]

Be awesome if they sell these cords made up already so we could buy them

[@slybunda]

"The JL Audio amplifiers are one of the most efficient on the market. You can see this in the lack of gain needed to reach peak performance before clipping." --- Thats not true, its not efficiency its sensitivity which is higher that results in lower increase of the gain knob.

[@danielguerrero3922]

i have that same oscope what setting do you use it on?

[@Ron_Masterjohn]

With a head unit that only puts out 2 volts on the rca preamps is there a way to add something inline that will boost those volts up higher before it hits your amps? Like the 5 volts? Curious if some DSP system or eg’s will do that?

[@carlhess512]

You really should use a ohm load resistor on each channel, if the speakers are 4ohms then use a 4ohm resistor for that channel and if your subs are 2ohms or 1 ohm then use a resistor to match the load. You will then be able to get more then 10 volts more before clipping. And using Bluetooth is the worst way possible. Always try using a cd or something else going into the head unit, but not always possible with these newer HU’s

[@Ron_Masterjohn]

Is there way on a head unit rca’s that only put out 2 volts on the preamps to put say a DSP or EQ to up those volts? Or would it be kinda dirty since originally you’re starting with just 2 volts? Have an Alpine INE-W940 I want to put in my wife’s car but I thought it had 5 volt preamp RCA’s but I see it only has 2 volt ones. She plays things loud so don’t want distortion coming out of her Poweramper amp so hoping that HU will be ok or can up those volts without making them dirty.

[@jvburnes]

Excellent vid. I just happen to have a Tektronix 465 scope so I'll use this. BTW: For the amp don't you have to measure clipping against an actual load for the clipping point to to be valid? I imagine most amps would clip under 4 or 2 ohm impedance much sooner than the very high impedance represented by the oscope.

[@paulhewson4600]

old vid but hell it was a good one!

[@c00cs1]

Thank you sir

[@rvj5046]

Why would you set the dB to -6dB on the frequency generator? What is the advantage of that and why would you not set it to 0 or differently than -6dB?

[@magictoaster806]

The music you’re going to listen to isn’t 0db so it you set your gains with 0db you’re technically losing some power. By setting the gains with a -5 db or -10 db test tone you’re accommodating for the music you’re listening too

[@rvj5046]

@@magictoaster806 Thanks a ton for your reply! I am just trying to figure this all out. I have never set amp gains properly with a scope and now that i have one I want to do it properly. Except for my brand new Pioneer AVH-2550NEX head unit, I am working old school and have a Linear Power 2002 on 2x 10" vintage The Crunch subs in a ported box I custom made tuned to 36Hz then I have a vintage Rockford Fosgate 400.4 on my front and rear 6.5" JBL component mids and tweets. I am not into the SPL thing I am striving for SQ but still want the ability to bump a little. I was setting my subs with my HU cross set at 50Hz and my frequency generator at 50Hz. I am using the same freq generator that you are btw. So should I strive to set my gain on the generator to -5 or -10 for my subs and differently for my mids and tweets on the Rockford Fosgate?

[@inee107]

whats the best o scope

[@junaidgt90]

Nice video. 👍 I wonder if all the tests were done the engine off and running off the battery at 12v. Clipping level with the engine running at 14v should be different.

[@dmoore0079]

Good point. With the higher supply voltage, there would theoretically be more clean headroom before clipping, but to be safe, it'd probably be best to set it at idle battery voltage to ensure the system would never clip regardless of whether the car was running or not.

[@Ron_Masterjohn]

Can you get as good of results using a O-Scope as compared to a DD-1+ that Steve Meade makes and sells?

[@restore64]

With that amp at only 12v (60w @ 4Ohms) it should be able to hit at least 15.49v before distortion right? 17.32v at 75w.

[@uptobatentertainment]

Use -0db tones for the loud music nowadays, also Bluetooth isn’t the best sound quality for setting up a system. If you want the most out of the system maybe -5db tone. -6 dB tone at 1khz via Bluetooth will cause clipping playing via usb or cd considering mastered songs having -6db rms peaking at -0 dbfs. Other than that great vid get easy to understand if one isn’t knowledgeable regarding this!

[@colt5189]

When setting amp gains, should the car be at operating temperature and idling? Or just running off of the battery? I'd think you'd want it and operating temperature idling since that's around where the car will normally be running at when you are driving around.

[@7ankss]

I understand that for setting the amp voltage, everything needs to be flat- but after the voltage is set, can I increase the bass value or treble value on head unit ?

[@aantonio06]

You need to put the radio settings as you listen to the music. Like he put the sub output on the radio all the way up before setting the amp. That way you get clean signal all the way through. Cause if you adjust it flat, when you want bass, you are going to bring distortion.