Topic: How to match amp gain to your HU.

[iamkroll]

hi guys.
im in the process of trying to set the gain right for my amp. i read somewhere that matching ur HU and amp gain is important --- avoid distortion/clipping and amp runs cooler if matched properly. i have tried reading the available materials online and somehow i just couldn't grasp it. can anyone help me with this? i can only do it by ear coz i dont have the necessary equipments (oscilloscope, multimeter) in hand.

i think i read somewhere that getting the correct gain is important. it tells the amp what ur HU output voltage is so the amp will work in accordance to that voltage...... or something like dat lahh i oso forgot! if this is what i remember correctly and is a fact, i would love to achieve this with my HU-amp gain level matching.

"turn 3/4 of max HU volume and increase amp gain till hear distortion and back off a little" is common and ive tried it. didnt seem too work. so if anyone can suggest another way that would be very helpful :D thanks! 

[bafukie]

no other way to know whether ur amp/hu is clipping besides do amp scoping.

[Zenn]

i can only do it by ear coz i dont have the necessary equipments (oscilloscope, multimeter) in hand.

"turn 3/4 of max HU volume and increase amp gain till hear distortion and back off a little" is common and ive tried it. didnt seem too work.

what do u mean didnt seem to work...?

[xixianlai]

If you don't mind I would like to share my experience regarding this topic.

Items involved
HUs: 4v, 5v & 8v
Amp: 5v & 8v
Comp: Sensitivity: 91db, Recommend power: 150rms

- Amp(8v) below 150rm per channel, which means the comp is underpowering, you'll need to crank up the gain. (Lower sensitivity speaker will need to higher gain)
- Amp(8v) (about 310rms per channel), which now the comp feed well, you'll need 1/4 to 2/4 of the amp gain.

Sorry for my bad explanation, I what I'm trying to say is, the gain is very depends on your system setup. Underpowering/overpowering your speaker make big different at determine the gain. Hope it's help.

[iamkroll]

oh sorry what i meant was the procedure didnt seem "scientific" enough. is there a more "scientific"/logical approach on how to tune the gain level in accordance to the HU?

[Zenn]

yes got, with oscilloscope & sign wave test tone

[iamkroll]

adeii.. dont have the equipment to do that :(

[Zenn]

thats why u end up with non scientific test....

[CSA]

some prefer higher gain in amp vs volume in HU...some prefer vice versa..which one do u guys prefer? both way also can archive level matching right?

[krayden]

Based on the little experience that I have. You should:
O-scope everything to determine clipping level/gain. Mark that level cause it doesn't change.
With low gain set on amp, HU volume up to a few notches below the clipping level. (assuming you have a good HU, this will maximize the HU's sound characteristics in your system.)
If you have EQ, active Xover, line drivers, again set gain a few notches below clip.
Bring up your amp gain till you get your preferred driving volume.

Weather you high gain your HU or amp will depend on which has the characteristic you prefer.

Correct me if I'm wrong or mislead.
 

[Zenn]

always higher volume on HU, lower gain on amp...

coz if u set with low volume on HU and high gain on amp, what if suddenly one day someone accidentally or purposely put full volume on your HU, the amps will be clipping and your speakers will be fried

i remember when i was small, i maxed the volume on my dad's car when the car was off, so next morning when he started the car, the radio was at max volume kaw kaw........kena one good slap.....hehe

[bafukie]

juz sharing my 2 cents opinion

1st installer will scope ur HU see at which volume does the HU clip... say max volume 35.. Hu produce clean non clipping signal even at max. Ok now volume is at 35.

2nd, installler will scope ur amp using diff freq tone.. wat my installer did was use 1k sine wave test tone for front.. at volume 35, adjust the gain till certain point (say 12 oclock) the amp clips..then back down abit on the gain till non clipping (say 11oclock).. that is the gain tat will be on the amp

so even when u blast ur speakers with some lady gaga songs @ full volume which is insanely loud, there will be no clipping therefore no damage to the amp/speakers.

some ppl learn it the hard way of having their speaker cone blast out of the voice coil... or some like zenn... kana one time good... will always remember ...

[iamkroll]

hahahaha got funny story some more 

but sometimes i see ppl purposely lower the volume of the HU so that its not too piercing/fatiguing to listen to. u know sometimes the higher u go with the volume, it becomes very bright sounding. for example my HU's 'comfortable' sound is around 25-28. if i go 30, can hear resonant-like effect on certain frequencies and higher frequencies tend to pierce. so they tune the amp gain to that 'comfortable' volume from the HU.

[mnkh27]

zenn: so notti ha you! if i knew your dad then, I'd ask him to get a mcintosh HU, coz basically if you off the player, the volume is at min. lol.

iamkroll: the main reason why the systems your are referring to sounds bright at loud volumes is simply because it is unable to play loud! and why? because the system is thin sounding and fatiquing. and why fatiquing? because the system has a bad foundation. but why should it sound like that eventhough I have mega expensive equipment? ahhh, perhaps some sifus here can explain...

[cacin]

Hello,
Based on my limited knowledge of DIYing gain using TrueRTA, what Krayden/bafukie said sounds right.
I also refer to alot of forums etc that talks about trueRTA.

This was what I did:

Check HU volume before clipping. I use a 1kHz sine wave that was produced at 0dB. (if you only play Front, Rear and Sub)
once you get the volume. don't go higher than that.

Then, connect your amps, then adjust the gain at amp side until you can see the signal clips. then, lower it down a notch.
Here is where there are different 'ideas' about it. Some people say use 0dB, some say use lower than that. When I'm lazy, I just use 0dB. when I rajin abit, I use -3dB. This would allow a little bit of clipping, on your amp's output, but not on HU side. Unless the song you're going to listen to has a higher digital ceiling than 0dB.
Some people also say must add dummy load (resistors).

the first time I did this, I used:
60Hz, 0dB for sub, 1kHz for mid and 4kHz for tweet. I was having problem getting proper sine wave on the tweeter side. It turns out I did not set the setting of the software properly.

2nd Time I did this:
Since the gain of the amp was high (more than 12o'clock), I only turn the volume on my HU very low (turn more then it'll be too loud and uncomfortable). Then, I notice alternator whine... so, I reset the setting. Used max volume of HU before clipping, then turn amp gain until clips, or my ear hurts, which ever comes first. :)

The hardware/software I used was:
Laptop
voltage divider
trueRTA software
test tone disc (frequencies at 0dB and -3dB)

Disclaimer: This is just the way I did it. the 3/4 rule is still the easiest to do (no need fancy device etc). I am still also learning...

Connection from amp


Connection to laptop (voltage divider in between)


No clip, 1kHz at volume 55


Clip, 1kHz at volume 58