# Setting gains on LOC and amp



## djkms (May 3, 2013)

Hello all,

I have been reading up on properly setting my gains. I see that I can do it by ear, O-Scope and DMM. I like the DMM route because I'm getting old and my hearing is not what it used to be. I have a hard time being able to tell when music starts clipping. I can hear when it distorts and sounds like crap but I am not positive that when it starts sounding like crap to me is the initial point that it starts clipping! 

Right now I have my LOC gains about half way. No testing involved, just figured this was safe. My amp gains are a little over halfway on the mids/tweets and the sub. Amp is a Alpine PDX-v9 and the signal is coming out a 2 channel LOC with gains. at the moment channels 1/2 go to front components, 3/4 are unused (until I upgrade components to run active separates) and channel 5 is going to my sub. The LOC gets its signal from the front output of my HU.

I was thinking about going the DMM route but I read a lot of people bagging on it, so hear I am, going to try the ear method. Hopefully I can concentrate enough to hear clipping right away. So on to my questions.

1: Is it better to set the gains with tones or music? I read music is better because of the peaks but wouldn't tones be better for someone like me to hear clipping sooner? Maybe my mind is just tricking me out to think that I dont hear clipping in the multiple layers of music??

2: How do I properly set the gains on my LOC and amp? From what I read I think this is correct; turn the gains all the way down on my amp and LOC, turn my HU up to 80%ish then start turning up my LOC gains until I hear clipping and turn it down a bit. Then start turning up my amp gains again until I start hearing clipping again?

---

For those who have set gains by ear and DMM, which way do you prefer and why? Which way is safer do you think?

I know this subject has been beaten to death, I just want to make sure I am doing it right. My LOC is behind my stock dash and is a real PITA to get to so I want to set it once and forget. The amp is kind of a pain to get to as well. 

Any other thoughts appreciated. Thanks


----------



## minbari (Mar 3, 2011)

I always set them with music. for me it is really hard to hear distortion in pink noise and if you set it with a test tone it will be set way too high for music. (unless you have your test tones set for -10-15db or so)

just pick some very dynamic music with good bass content. nothing wrong with getting it wrong the first try too, you can always adjust it later if it is not set loud enough or set too loud.


----------



## djkms (May 3, 2013)

Well after some exhaustive research I decided I don't want to trust my gain settings to ear alone. I picked up a ARM DSO Nano 201 to adjust my gains this weekend. 

I think I am on the right track here?
I found a tone generator online and created 2 tones to test with.
audiocheck.net_sin_50Hz_-3dBFS_10s.wav
audiocheck.net_sin_1000Hz_-3dBFS_10s.wav
I assume -3db is good (I listen to electronic dance music mostly) since I am using a Oscope?

I know I start with the HU speakers first and see what volume my speakers clip at right? Do I do both tones or just one of them?
Next is my LOC. Do I test through my RCA's coming out or through the speaker outputs of the amp and turn the gain all the way down on the amp and adjust my LOC until it clips? Again, do I use both tones or just one?

Do I do x1 or x10 setting on my DSO for the HU test?
If I do the test through the RCA I assume its x1 and through my amp speakers its x10?

Thanks for the help!


----------



## minbari (Mar 3, 2011)

I would be setting gains at least -10db. you dont want to be listening to music with gains set within 3db of max output. crest factor, even on mp3, is 10 db.

that depends on the voltage range if the DSO. if it is 0-5v, then even RCA might require the x10 setting. if it is 0-20v, you would be able to use x1 even on some smaller amplifiers.


----------



## djkms (May 3, 2013)

minbari said:


> I would be setting gains at least -10db. you dont want to be listening to music with gains set within 3db of max output. crest factor, even on mp3, is 10 db.
> 
> that depends on the voltage range if the DSO. if it is 0-5v, then even RCA might require the x10 setting. if it is 0-20v, you would be able to use x1 even on some smaller amplifiers.


Wouldn't a -10db tone be dangerous? More chance of clipping right? Unless I misunderstood what you are saying? I thought a 0db test tone ran through the system with a Oscope would give me virtually no chance to have my music clip and the lower the -db the more chance I have of clipping?


----------



## minbari (Mar 3, 2011)

you want to set the gains with the posibility for clipping. not crazy amounts, but some. otherwise you will be turning the volume all the way up all the time to get a decent volume level. what happens whew you have an older recording that is quieter? you wont be able to turn it up loud enough with your HU at 100%. You also have to consider if you are using test tones, that you wll get ALOT more power out of an amplifier at only 1 freq as opposed to a full spectrum signal.

you can set it wth -3db, but I think you will find that wont work.

BTW: I set mine with -14db pink noise. have not blown anything up yet


----------



## djkms (May 3, 2013)

Ahh OK. I think I will create some more tones and put them on my usb stick. I suppose -6db and -10db will be good and try to judge the system from there. I wish I could find the link to the forum that stated what db to use by the type of music you listen to. It stated that -10db is better for rock music and such and -3db is better for rap. I would assume that electronic/dance music would crest closer to rap then rock.

It seems everywhere I looked for tones they are all at 0db (even from ampguts.com listed on the top of this page). I couldn't find a good source for -db tones so I found a generator to make them myself. If 0db is not really good why is it then the most popular db of tone to download? Seems most people would want to get the most out of their gain without clipping and 0db would limit that? Sorry, not trying to question your expertise, just wondering why -db tones are hard to come by.

Also, the DSO rating is:
Max Input Voltage 80 Vpp (by × 1 probe)


----------



## minbari (Mar 3, 2011)

djkms said:


> Ahh OK. I think I will create some more tones and put them on my usb stick. I suppose -6db and -10db will be good and try to judge the system from there. I wish I could find the link to the forum that stated what db to use by the type of music you listen to. It stated that -10db is better for rock music and such and -3db is better for rap. I would assume that electronic/dance music would crest closer to rap then rock.


I would have to check on that, I am not sure that crest factor has as much to do with music style as it does format. CDs as an example back in the 90's were closer to 20db. now they are more like 10db because they have pushed the mixing closer to to the 0db mark. this makes them sound louder, but reduces crest factor and therefore dynamics. most rap and music with bass heavy synth bass will have some benefit to setting closer to 0db, because you have soo much bass content EQd in from the recording studio. The theory is the same for both though, you just have to watch your volume knob more.


> It seems everywhere I looked for tones they are all at 0db (even from ampguts.com listed on the top of this page). I couldn't find a good source for -db tones so I found a generator to make them myself. If 0db is not really good why is it then the most popular db of tone to download? Seems most people would want to get the most out of their gain without clipping and 0db would limit that? Sorry, not trying to question your expertise, just wondering why -db tones are hard to come by.


I cant say for sure why they are harder to come by. The Focal test disks as what I used and they are -14db. I also have 0db test tones, but I use those more for setting eq curves at moderate volume and not setting amplifier gains.

it is possible that 0db are more popular because it is safer. if you properly set your gains with a 0db tone you will never see full power out of the amplifier with music. you are unlikely to damage the amplifier or the speakers since 1/2 the power will be wasted.


> Also, the DSO rating is:
> Max Input Voltage 80 Vpp (by × 1 probe)


I assume that is in the x10 position correct? ( I doubt it will measure 800 volts.) that would give you 0-8vpp. so you were correct in your original assumption. x1 for RCA and x10 for amplifiers would work fine.


----------



## djkms (May 3, 2013)

Thanks for your help!

Here is the link of the tutorial I found if you are interested:
Car Audio Classifieds


----------



## minbari (Mar 3, 2011)

ha, good read. at least we both agree on the 0db setup


----------



## xaf-audio (Apr 23, 2021)

djkms said:


> Well after some exhaustive research I decided I don't want to trust my gain settings to ear alone. I picked up a ARM DSO Nano 201 to adjust my gains this weekend.
> 
> I think I am on the right track here?
> I found a tone generator online and created 2 tones to test with.
> ...



Sorry to raise up this old thread lol. But how did you set the gains on the LOC...did you measure the output voltage on the RCA outputs of the LOC? 

My LOC has gain adjustments, and the default voltage output is barely 1volt going in to my amp...I'm thinking if I can bump that voltage up to at least 4volts my amp won't have to work as hard.


----------

