From e36m3_at_bmw-m.net Sat Jan 13 12:43:24 2001
From: "Sean Hester" <seanh_race_at_hotmail.com>
Subject: Re: : [E36M3] Setting Amp Gain Levels

>Now, here's my question. Are you more apt to receive a clipped signal by
>turning the Head Unit volume up high using 4 volt preouts, or by turning the
>amp's gains up high, producing the same ultimate listening volume. ie,
>there's 2 ways to get to the same loud volume: with a relative higher HU
>volume setting with a lower amp gain setting, or vice versa. Assuming a
>given high listening volume, is it best reached with more HU volume and less
>amp gain, more Amp gain and less HU volume, or a mixture of both somewhere
>in the upper middle? Thanks.

wow. god only knows. (de-je vu intentional)

short answer:

both in the middle to upper middle range.

long answer:

see... car audio stuff is so non-standard that you can't answer that. with pro audio stuff (studios, and PAs) it's completly backwards then what you wrote. since the "gains" on PA amps are unity gain (meaning they only "cut" they don't "amplify") you set the gains on the amps all the way up, unless there's a really good reason not to (trying to balance two amps for instance). and "all the way down" for a PA amp is "off" so you can't very well start from there. ;-P

ah... but i degress... sorry about mentioning how good it could be, let's talk about how bad car stuff is in comparison.

every single one is different. for instance, the alpine amps i had in my M3 were also "no signal" at "all the way down". so i couldn't use your method. but... i know most amps are "low" all the way down. which is an ok place to start. EXCEPT... the alpine head unit i had, had a "bug" where the output stage of the head distorted if you dialed the volume over 28 (out of 35), so again... problems with your method.

there is a "right" setting for the gains on an amp. it's the one where the gain knob does nothing. no cutting of signal, no boosting of it. it's usually marked as "normal" on the dial. for alpine it's the middle. for some amps it's the high end, for some it's the low end. for some you have to guess. i try to start everything there. but even that is not 100% for car amps. some amps have no headroom. meaning they distort if you go over 4v, even a little bit. if you have a head unit with a strong output signal (even though they all say 4V, i've seen it rance from 2.5 to 5.5) you're gonna get distortion unless you cut the signal by turning the amp gains down. it's all so headache inducing.

sorry for babbling... here's my patented "method"...

i set the amp to where i think no gain is. (somewhere in the middle usually) i set the head unit to the middle of it's range. then i play some tunes. i turn the head unit up until i get distortion. if it's speaker distortion you're fine. if it's "amp running out of balls" distortion you're also fine. if it's "preamp stage" distortion you have some work to do. (hopefully you can tell which distortion is which from hearing it. here's some clues if you can't. speaker distortion sounds like the thing is gonna rip apart (which it would if you kept going). with "running out of balls distortion" the music sounds fine until a big bass note kicks in, then it sounds dumb. you can keep turning it up, and it gets louder, but sounds worse and worse as you get louder. pre amp distorion is usually "buzzy" all over, and won't let the sound get very loud at all, if you try to turn it up, it DOESN'T get louder, it just gets buzzyer) if you have preamp distortion, it might be the input stage of the amp doing it, or it might be the head unit doing it. you gotta experiment to figure out which it is, and adjust the gains based on that. (turn the amp gains down. if it gets better it was the amp. or vice versa)

once you're done you have two more tests. hopefully you pass these, if you don't you're kinda out of luck. the tests are:

1. play something really soft (between songs, the handy "zero bit" track on a test cd, etc...) but turn the head volume up alot. hopefully you don't have much "hiss". if you do, you can turn the amp gains down some to get rid of the hiss, but you'll be cutting your max volume when you do that. compromise however suits you.
2. turn the head unit all the way up. hopefully you're at max volume now. if not, you can turn the amp gains up to make it louder. but you're gonna increase the hiss (from step 1) and also increase the distortion. again... compromise however suits you.

i hope all that was more help then confusion. ;-)

Date: Fri, 12 Jan 2001 19:01:09 -0800 (PST)
From: Matt Henson <hensonator_at_yahoo.com>
Subject: Re: : [E36M3] Setting Amp Gain Levels

Paul,

Hey a question about stuff I do at work every day!

The 4V output isn't about distortion or clipping, it's about noise floor. A wire in a car environment will pick up all kinds of electrical interference. Raise the signal level and the ratio of the signal to noise gets better. You shouldn't be running any part of your car system at any appreciable distortion. The best strategy is to:

1. Burn or buy CD with some 0dB test tones. 100, 1k, 10k. 0dB here means all the way up, not down. Play in deck.
2. Turn the amp gain way down and adjust the Head unit volume until it's outputs are the maximum value where you don't exceed it's outputs (4v) or the AMP's input stage. Use your ears or a scope on the output of the amp to see when it gets distorted. Hopefully it won't get distorted when the head unit it turned all the way to it's 0DB (or max) output level.
3. Turn up the AMP gain until you reach either its distortion level or the physical limits of the speakers. This will get loud. The other alternative is to just turn it up until it's loud enough for you (but not clipping) and save your hearing.

Good Luck!
-Matt

• Paul Elliott <pelliott_at_rcn.com> wrote:

  > Date: Fri, 12 Jan 2001 20:23:40 -0500
  > From: "Paul Elliott" <pelliott_at_rcn.com>
  > Subject: : [E36M3] Setting Amp Gain Levels
  >
  > Sean,
  >
  > >>meaning you're gonna have to turn up the volume alot (which is bad
  > too) you'll get more noise, and you'll be runinng everything hotter.<<
  >
  > I've got a gain setting question for you....I have a Kenwood Excelon head
  > unit driving my Excelon amp via 4 volt pre-outs. I've always read that to
  > set the levels to best keep distortion at bay, you should turn your amp
  > gains all the way down, and turn your head unit volume up....Then, when your
  > get a comfortable listening volume, youre supposed to slowly raise your amp
  > gains to provide you with the loudest listening level you might ever use,
  > without distortion..
  >
  > Now, here's my question. Are you more apt to receive a clipped signal by
  > turning the Head Unit volume up high using 4 volt preouts, or by turning the
  > amp's gains up high, producing the same ultimate listening volume. ie,
  > there's 2 ways to get to the same loud volume: with a relative higher HU
  > volume setting with a lower amp gain setting, or vice versa. Assuming a
  > given high listening volume, is it best reached with more HU volume and less
  > amp gain, more Amp gain and less HU volume, or a mixture of both somewhere
  > in the upper middle? Thanks.
  >
  > _____________________________
  > Paul Elliott
  > '99 Alpine White M3 <25000 mi Forged M dbl-spokes; Rotex pads; Dinan Stage
  > II Supercharger; Stygar Short Shift kit and Clutch Stop; Skaggs Pedals;
  > X-brace; Sound by Kenwood Excelon, Polk, JL Audio