# How do I know how high to turn up the gain on my amp...?



## Steven T (Dec 29, 2007)

The amp is a cadence TXA-6004 powering 1 12" type R (SVC)

I was told to keep the gain low. I don't know how low though. Is halfway okay?

*SPECIFICATIONS:
*
_*
4 Ohm RMS Power: 4 x 150 Watts @ 13.8 Volts
*
2 Ohm RMS Power: 4 x 300 Watts @ 13.8 Volts
*
4 Ohm Bridged RMS Power: 2 x 600 Watts
*
Frequency Response: 20Hz - 30kHz
*
Damping Factor: >200 @ 100Hz
*
S/N Ratio: >100 db
*
Channel Seperation: >65dB
*
Minimum THD: <0.05%
*
Dimensions: 25" x 9.2" x 2.12"_


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## 89grand (Nov 23, 2006)

You'd only keep the gain low, if your head unit has real high output voltage.

Turn the gain up until the sub is loud enough at any given volume setting. Listen for signs of speaker distress, if you hear any, turn the volume gain or the volume down


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## Steven T (Dec 29, 2007)

My HU is a Pioneer 3900mp


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## Monk (Dec 11, 2007)

http://mobile.jlaudio.com/support_pages.php?page_id=143

http://i76.photobucket.com/albums/j23/steveo200077/RMSchart.jpg

Gain is very, very important. 

Please follow the instructions on those links.


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## Steven T (Dec 29, 2007)

Monk said:


> http://mobile.jlaudio.com/support_pages.php?page_id=143
> 
> http://i76.photobucket.com/albums/j23/steveo200077/RMSchart.jpg
> 
> ...


Hey thanks for the links. I don't know how to interpret any of that stuff though  nor do I have any of that special electrical measuring equipment.

Do you think halfway is safe?


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## CGG318 (Apr 9, 2007)

At the very least, use your ears. Picking an arbitrary setting isn't going to cut it.


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## 89grand (Nov 23, 2006)

Always trust your ears and nothing else...well except an o-scope.

I wouldn't use any of those settings from JL or that other thing. Setting gains with a DMM is the single most worst way to set your gains, short of just turning them all the way up for the hell of it.

Gain setting is over blown. It really does nothing more than determine when you get maximum undistorted output from the amp relative to the head units volume control. If your head units volume control goes to say 50, and your system is maxed out at setting 20, your gains are too high, if you get to 50 and it still isn't starting to distort, they're too low. If you have multiple amps, set the gain for the midrange speaker to get the volume you want, then adjust the other amps for tweeters and subs for proper level in relation to the midrange.


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## FoxPro5 (Feb 14, 2006)

You need to find out where your head unit starts to distort the signal more than anything. This is because the gain on your amp is a sensitivity adjustment, not really a volume knob. 

You could also search "gain setting tutorial" on here and see what you come up with. 

Kippel used to have a distortion test on their site but I'm not sure if it works any more: http://www.klippel.de/aura/default.html

Point is: know what loud and BAD loud is and what it sounds like. Some say "stressed" but that's too arbitrary for most to put into practice IMO. Other say "keep your gains down," but what is that supposed to mean? Down to what? Where? I understand fully why you are confused.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

IDK where it is now, but if you go out on the net and find a 1khz and 50-60hz test tones at the JL site mentioned. *Note:* i'm not a fan of there instruction of turning the HU up 3/4 of the way as an arbitrary number, ALL HU's will clip differently even in the same model line. 

Once you find the test tones (or if someone here could be so kind to hook him up with a link to one or something OR better yet, go get yourself a test CD) you can start the process... 

1. turn all gains down... If you have your front amped, start there, if not amped, start there anyway... 

2. Play the 1khz tone on repeat, turn the HU up until you hear a definite change in tone or sound.... back off.... note where you are at. Ok you now have the clipping point of the HU defined (which is my beef with JL's method) 

3. play the 1khz tone again on repeat and at the level you just found on the HU. Go to your mid/high amp and turn your GAIN up until to hear a defined change in the tone or sound.. back off slightly... done there... 

If your front stage ISN'T amped skip #3

4. Play the 50-60hz tone on repeat, go to your sub amp and turn the gain up until to hear a defined change in sound, back off a little and you "should" be done... 

Very simple... I hope, would the rest of you agree? If not, why not, I would like to know if there is anything wrong with my methodology, thanks.


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## Quiet_Vette (Jan 11, 2008)

I like your method Aaron. Do you not agree that output AC voltage should be respected and tested?


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## durwood (Mar 7, 2007)

Ignore the JL tutorial. it's hog wash.

http://www.diymobileaudio.com/forum/showthread.php?t=542&highlight=setting+gain


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Quiet_Vette said:


> I like your method Aaron. Do you not agree that output AC voltage should be respected and tested?


Thanks, and IDK if I would agree or not honestly, I've never gone that route, I guess I'm "Old School" lol (at the ripe old age of 34..lol)

I think all avenues should be tested, but, ultimately, what does it come down to?? Your ears... 

I'm going to try the O-scope method this time around (going active as well) and see what happens. A guy I used to work with sold me an old Oscope for 25$ and it works just fine... I've never had it out of the box, except to see if it worked... so I'm going to have to have it on my bench once I get the garage organized...


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## JAX (Jun 2, 2006)

Why dont more amp makers have some type of indicator telling you when the amp is at max output or clipping....like on the old Soundstream Rubicons or the Custic DR series for example...

turn up radio 3/4 and adjust gain till indicator starts to flicker....makes it easier to me...

is it not accurate or what? cant be no worse than turning it till you think it sounds like ass then back a little


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## 89grand (Nov 23, 2006)

Clipping idicators are nice, I think more amps should have them.


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## Whiterabbit (May 26, 2006)

Quiet_Vette said:


> I like your method Aaron. Do you not agree that output AC voltage should be respected and tested?


at what frequency? 1000 Hz like many amps are tested at? Or 50 Hz, where its gonna be playing in this case?

If you actually have an answer for that, my next question is what does the voltage tell you? Does it tell you how much power the subwoofer is getting? Does it tell you what the waveform looks like? Does it tell you how loud the subwoofer will get? Does it indicate any performance advantage or disadvantage?

And if that seems like a loaded question, then answer whether we should care or not if we are measuring a performance advantage or disadvantage. Because we might not!


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## Quiet_Vette (Jan 11, 2008)

Whiterabbit said:


> at what frequency? 1000 Hz like many amps are tested at? Or 50 Hz, where its gonna be playing in this case?
> 
> If you actually have an answer for that, my next question is what does the voltage tell you? Does it tell you how much power the subwoofer is getting? Does it tell you what the waveform looks like? Does it tell you how loud the subwoofer will get? Does it indicate any performance advantage or disadvantage?
> 
> And if that seems like a loaded question, then answer whether we should care or not if we are measuring a performance advantage or disadvantage. Because we might not!



I like his method because it uses a test frequency and personal ear to find where th head unit starts clipping, which in turn sets the baseline for finding the gain settings using one's ears.

Now, that's not to say I don't want to test it all with a O scope to get it all perfect, that why I was asking if he felt using testing devices were considered in his testing methods.

By all means, if you know of the proper way to set the max volume and clipping...share. I do not have my own method as of yet with the exception of just listening. I would be very interested in a better, or correct method if one is decided on.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Quiet_Vette said:


> I like his method because it uses a test frequency and personal ear to find where th head unit starts clipping, which in turn sets the baseline for finding the gain settings using one's ears.
> 
> Now, that's not to say I don't want to test it all with a O scope to get it all perfect, that why I was asking if he felt using testing devices were considered in his testing methods.
> 
> By all means, if you know of the proper way to set the max volume and clipping...share. I do not have my own method as of yet with the exception of just listening. I would be very interested in a better, or correct method if one is decided on.


I would very much agree to this and OFTEN wonder, WHY 1khz??? Why not something else... Please explain?

I'm going active with my current WIP install and 1khz isn't gonna do SQUAT for me setting up gain for my tweets..but, they'll be getting >100w so I doubt i'll even CRACK the gain with the 8v output from the 7100 i'll be using... yes/no??


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## J0ne (Aug 7, 2007)

Aaron'z 2.5RS/WRX said:


> IDK where it is now, but if you go out on the net and find a 1khz and 50-60hz test tones at the JL site mentioned. *Note:* i'm not a fan of there instruction of turning the HU up 3/4 of the way as an arbitrary number, ALL HU's will clip differently even in the same model line.


I have wondered-why wouldn't it be safe to turn your HU volume to max if you are not using the HU's internal amp?


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## J0ne (Aug 7, 2007)

gentlejax2 said:


> Why dont more amp makers have some type of indicator telling you when the amp is at max output or clipping....like on the old Soundstream Rubicons or the Custic DR series for example...
> 
> turn up radio 3/4 and adjust gain till indicator starts to flicker....makes it easier to me...
> 
> is it not accurate or what? cant be no worse than turning it till you think it sounds like ass then back a little


x2 to this.

Maybe to avoid amature installs?


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## 89grand (Nov 23, 2006)

J0ne said:


> I have wondered-why wouldn't it be safe to turn your HU volume to max if you are not using the HU's internal amp?


Because a lot of decks actually distort on the preamp outs when the deck is turned all the way up.


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## italyix (Sep 9, 2007)

What do you do then when you have an active xover before the amps, and using it to xover the low and high to the amps? How do you then set gains on that? Max out the gain on the amps and go with the active? How do you measure both low and high?


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## Foglght (Aug 2, 2007)

I had a question on this subject. 

Everyone has always told me to not treat the gain setting as a volume knob. I understand why for the most part. But, what is the difference between attenuating the sub channel on my 701 down 10db, decreasing the output gain on the Audio control matrix, and turning the gain down on the actual amplifier?

What is the difference between those 3 things?


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## mtnickel (Mar 15, 2005)

You would want to turn down the one which has the worst S:N ratio.

The greater the signal going into any unit, the lesser the noise will be created by that unit.

In your case, i'd say you'd want to maximize the output of the 701 as it is doing most of the signal processing and is probably the cleanest.



Foglght said:


> I had a question on this subject.
> 
> Everyone has always told me to not treat the gain setting as a volume knob. I understand why for the most part. But, what is the difference between attenuating the sub channel on my 701 down 10db, decreasing the output gain on the Audio control matrix, and turning the gain down on the actual amplifier?
> 
> What is the difference between those 3 things?


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## mtnickel (Mar 15, 2005)

With no osciliscope, i can't really find the clipping point, but just use common sense and the method described (regarding waiting for the sound to be distinguished, then back it off).

I require a volt-meter to balance left and right though. With a bridged 4 channel, you have independent gains, and you can level match with a DMM best.


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## Foglght (Aug 2, 2007)

mtnickel said:


> You would want to turn down the one which has the worst S:N ratio.
> 
> The greater the signal going into any unit, the lesser the noise will be created by that unit.
> 
> In your case, i'd say you'd want to maximize the output of the 701 as it is doing most of the signal processing and is probably the cleanest.


So if the matrix says it can produce a fairly high output voltage to the amplifier, say 8-9volts, and the amp supposedly says max voltage input is 4v, what's the worst that could happen?


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## speakerboy (Oct 2, 2007)

I think JL's tutorial makes sense for their amps, but not for anything else. 
I don't know if there are any halyway decent headunits that clip before the 3/4 volume mark. This keeps the headunit from clipping.
They will know the AC voltage output for their amps, at a given and where they start to clip.

It makes a lot of sense for them actually. Sure the gains will most likely be set a little too low, as most HU's have more headroom than 3/4 volume, but that shouldn't hurt anyone. It protects their amps, the speakers that are powered, and keeps their stuff from sounding like complete crap. 

I love the sound of square waves in the morning!


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## mtxflorida (Mar 27, 2009)

5.18 How can I use an oscilloscope to set the gains in my system? [AO]



i have found this page goes into very nice detail on how to use an o scope to set gains


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