Setting gains on old school amps with newer H/U? - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 06-04-2019   #1
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Default Setting gains on old school amps with newer H/U?

Just wondering the absolute best way to go about setting gains on my old school amps when using newer headunits.
My old PPI amps have a max input voltage rating of 2.0V but, my headunit is capable of much more voltage output (4.0V+ in fact).

To ensure I don't overdrive the input signal (and possibly damage the amp) should I measure at what volume level my RCA outputs from the deck reach 2.0V max. Then, set amp gains to match?

Or, should I just be watching for when the headunit output reaches distortion and set my amp gains accordingly?

Definitely don't want to damage the amp. Thanks all!

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Old 06-04-2019   #2
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Default Re: Setting gains on old school amps with newer H/U?

leave the gains at 2V. Monitor during playback for clipping. I don't think the head unit will consistently put out 4V, so you SHOULD be ok.

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Old 06-04-2019   #3
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Default Re: Setting gains on old school amps with newer H/U?

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Originally Posted by slvrtsunami View Post
leave the gains at 2V. Monitor during playback for clipping. I don't think the head unit will consistently put out 4V, so you SHOULD be ok.
Are you saying leave the headunit gains at 2V or amp? The amp input gain is variable all the way to 2.0V.
My thinking is to use a test tone to find the point on the volume knob of the h/u where 2.0V is reached and then set amp gain for distortion based on that. But, I freely admit I may be making it more complicated than it should be. LOL.

I've always set by ear before and want to finally do it right.

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Old 06-04-2019   #4
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Default Re: Setting gains on old school amps with newer H/U?

I found Headunit output level spec's to be maximum peak voltage. Whereas old school amp input voltage is usually rms voltage.

I'm using some old school Arc Audio amps that spec input voltage at 2.5Vrms. My DSP spec's 6.5V output... I have no issues even on the loudest transients.

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Old 06-04-2019   #5
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Default Re: Setting gains on old school amps with newer H/U?

Quote:
Originally Posted by Truthunter View Post
I found Headunit output level spec's to be maximum peak voltage. Whereas old school amp input voltage is usually rms voltage.

I'm using some old school Arc Audio amps that spec input voltage at 2.5Vrms. My DSP spec's 6.5V output... I have no issues even on the loudest transients.
That's great info! Stands to reason there would be some variance. I'll probably just set my gains using the standard method and move on. Would be nice to have an o-scope to do it scientifically but, such is life.

Any additional real world input appreciated though.

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Old 06-04-2019   #6
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Default Re: Setting gains on old school amps with newer H/U?

Quote:
Originally Posted by PPI_GUY View Post
Are you saying leave the headunit gains at 2V or amp? The amp input gain is variable all the way to 2.0V.
My thinking is to use a test tone to find the point on the volume knob of the h/u where 2.0V is reached and then set amp gain for distortion based on that. But, I freely admit I may be making it more complicated than it should be. LOL.

I've always set by ear before and want to finally do it right.
You are making it more complicated. Don't forget, music is dynamic, static will give you accurate numbers, but its the dynamics that you are listening to.

glad to help.

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Old 06-04-2019   #7
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Default Re: Setting gains on old school amps with newer H/U?

I can't really hear distortion while increasing the gain on these amps. Tones and a scope could show it to you. I have an old single channel Telequipment Oscope that I keep meaning to do something with. I am only feeding them from the MS-8 though, so not driving with high voltage as you may be.

I guess technically there are ways to set your gains using a DMM (zoning in on what the amp should actually output to spec) then slowly increase from half volume on the radio until you reach desired AC output on amp - then listen. I believe JL has some pretty decent info on this topic.

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Old 06-07-2019   #8
 
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Default Re: Setting gains on old school amps with newer H/U?

Quote:
Originally Posted by PPI_GUY View Post
Just wondering the absolute best way to go about setting gains on my old school amps when using newer headunits.

My old PPI amps have a max input voltage rating of 2.0V but, my headunit is capable of much more voltage output (4.0V+ in fact).



To ensure I don't overdrive the input signal (and possibly damage the amp) should I measure at what volume level my RCA outputs from the deck reach 2.0V max. Then, set amp gains to match?



Or, should I just be watching for when the headunit output reaches distortion and set my amp gains accordingly?



Definitely don't want to damage the amp. Thanks all!
What headunit? Does it have any level settings other than volume, maybe something measured in db? My Pioneer 80prs puts out 5 volts at max volume but I run the levels at -4 db to bring it down below 4 volts to avoid overdriving my dsp.
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Old 06-07-2019   #9
 
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Default Re: Setting gains on old school amps with newer H/U?

-6 db will halve your output voltage.
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Old 06-07-2019   #10
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Default Re: Setting gains on old school amps with newer H/U?

Quote:
Originally Posted by ckirocz28 View Post
-6 db will halve your output voltage.
I'll check to see if I can adjust my output voltage on my Sony deck. This is very useful info. Thanks!

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