Gain Setting Tutorial

[mastadulog 10+ year member]

should i just set it at normal listening levels, because thats the only way i can get the voltage down to the range i need to set it at

 

[eFertLIS 10+ year member]

I have a Sony XM-3001SXD Class D amp running at 1 ohm. I dug up an old issue of Auto Sound and Security and it tested as following -

"We adjusted the input voltage to 6 volts (max the amp is rated to handle) then added 5 db overlap to account for the average levels of music. Here's what we measured playing tracks, not test tones -

Rated/Measured

4 Ohms - 300/462.25

2 Ohms - 600/838.86

1 Ohms - 1000/ UNTESTED - FILL IN THE BLANK FOR ME!

83.7% Efficiency"

So I am trying to see what voltage I should shoot at for my 1 ohm set up.

1000 - 31.62

1200 - 34.64

1400 - 37.41

1600 - 40

1800 - 42.42

I always assumed that the amp is pushing about 1200 watts into 1 ohm but the tests suggest the possibility of more power.

I have ran this amp to a 12" HCCA 12D and now and Orion H2 12.2 and personally hate Sony but this amp has treated me well over the years. What do you think?

 

[txred0810 10+ year member]

I have been trying to set my amp correctly for some time now. I have a JBL 300.1 and it is rated for 150 watts at 4 ohms and 300 at 2 ohms. Right now I am running two JL W0 8 ohm single VC speakers wired in series to produce a 4 ohm load. Using the tutorial this means i should set my amp channel to measure 24.5 ACvolts (sqrt of 150*4). I put in a test tone cd at -6db at 50hz for about a 2:1 ratio. turned the volume up to 26 out of 32 subwoofer level at 0 bass at 0 etc etc. I then proceeded to check the voltage and it was around 22 volts with the gain all the way up to 250mV. I can't ever get the voltage to reach anywhere near 24.5 volts. Am i doing something wrong?? I followed all the directions... im pretty sure my preouts are 4.5v so that would generally mean to barely turn the gain up since the the highest volts are 4 on my amp. Anyways im lost!! I can set it well by ear but i want it to be perfect...

 

[NiteScort 10+ year member]

i have a PPI PCX2200(2x200@4ohms) powering a single JL 12w6v2 set in series(8ohm) and bridged. is it (400*8)sqrt? i come up with 56.56v that way. or (400*4)sqrt? 40v that way.

Thanks for any help!

 

[squeak9798 5,000+ posts]

sqrt(400*8) = 56.56V

 

[NiteScort 10+ year member]

sqrt(400*8) = 56.56V

well i set the amp with my dmm according to the 56.56v setting and it sounds pathetically wimpy. my gain winds up being set at about 1/4. if i turn my comps amp down to match the the sub the whole system sounds like its powered off a headunit. back the way it was. thanks anyway squeak!

 

[Mr. Opportunist 10+ year member]

Thanks to this forum and this thread i will never let someone install anything else for me ever again, I just went through this for a couple hours due to the fact that it was my first time ever and that all the digital shit on the amp complicated it a little, When i checked the volts how the shop had it they were 72.x i believe but they are suppose to be at 44.72 so now that i have them at the correct settings they sound incredible, the only problem i have now is that my components(stock) and my 6x9's(stock) are trying to reproduce some low notes and i cant get them to stop i have the pioneer 860mp headunit does anyone have any suggestions?

 

[60ndown 10+ year member]

you can put 'caps' (capacitors)? on your stock speakers to stop them playing to low. dont know which (value capacitors)ones tho,im sure someone here does.

 

[Nikuk 5,000+ posts]

....nothing to see here....

 

[anders213 10+ year member]

I am running active. What freq. test tone should i use for my tweeters?

Cheers

Anders

 

[aek 10+ year member]

I have a Profile AP1200 powering 2 RF punch stage 1 subs, one sub connected to each channel @ 200 watts rms(4 ohms). However, the subs RMS is rated at 150 watts. How would I go about making the formula for this? Would it be sqrt(200*4) ; sqrt(400*4) ; sqrt(150*4) ; or sqrt(300*4)

Thanks

 

[Decipha 10+ year member]

sqrt (150*4) = 24.5 volts AC

^^thats per channel on the amp

I have the same exact subs just be careful not to push them they will blow fairly easy

i blew one, the other one is still go tho has about a week and da half play on it... if your interested i can get it out to you just PM me

 

[ElCaudillo]

First of all I want to thank everyone who has contributed to this thread, amazing help.

My question is, I understand how to do all these calculations, but what about setting the voltage to the sub's power rating rather than the amps? Specifically, a (slightly) underpowered sub.

Numbers to make things clearer:

Amp does 280watts RMS at 2 ohms, so I'm looking for 23.6643 volts

However, sub is rated at 300 watts RMS (presents a 2 ohm load of course), so when calculating for the sub's power rating, I get 24.4949 volts.

So what are the consequences of setting the amp to this higher gain level, I mean this can't magically make the amp produce 300 RMS watts when it's only rated at 280, right? So does this automatically introduce distortion/clipping?

Thanks in advance.

 

[ruckus]

sqrt (150*4) = 24.5 volts AC
^^thats per channel on the amp

I have the same exact subs just be careful not to push them they will blow fairly easy

i blew one, the other one is still go tho has about a week and da half play on it... if your interested i can get it out to you just PM me

and I have that amp and it can blow subs with higher RMS than their output if not set correctly on gains //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[fatryan 5,000+ posts]

i need to set my gains on my amp today and i dont get this formula. how does 100*4= 20? thats not my formula anyways though. i have a JL 300/4 4 channel amp and MBQ 4ohm comps. so thats 75wrms @ 4ohms per channel. My deck is a Pioneer deh-550MP (2V pre-outs i believe)what V should i set mine to? TIA