Another amp gain question.

[Scotnemily]

Hi, I have a question about setting my gain on my amp. I have been out of the car audio world for about 20 years. I decided to hook up some of my old equipment for the heck of it. I forgot how much I used to enjoy doing this. I installed an old PPI ax606.2 with 2 of the old PPI PRO12 subs. I have them on a 2 ohm load on the amp running at 200 rms each. I hooked them up to my factory car audio system using one of the audiocontrol LC2i LOCs. My problem is my old amp has a input voltage of 2.5rms my LC2i is putting out about twice that rms. I need to hook my DMM up to the LC2i and see how the voltage changes as I adjust the gain on it and the bass boost. Right now the output gain is almost all the way down, and the bass boost is slightly under 1/2 way. I was assuming lowering the gain on the LOC would also lower the voltage, but this might not have been the case. I also have the gain on the amp almost all the way down. I was thinking this would make it less sensitive and help with the higher preamp voltage. Though after more reading and trying to remember this stuff I am wondering if this isn't just letting the amp start putting out full power with less voltage. If I turn the amp gain up to 1/2 or 3/4 will this help with the higher preamp voltage? Is there any inline voltage reducer I can use? I was looking at these, Harrison Labs 12 dB RCA Line Level Attenuator Pair https://www.amazon.com/dp/B0006N41B0/ref=cm_sw_r_sms_c_api_Zz9KzbVH4Q97J but now sure if they will do what I need. Thanks for the help.

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[Boomin_tahoe 5,000+ posts]

Always leave the bass boost off. Reason being is because it will cause clipping/distortion. Using bass boost (think of it as bass frequency specific equalization at the amplifier) or excessive EQ or tone control at the head unit will cause your amp's output to clip earlier on the volume dial than it typically would when used normally...this is assuming your gain settings are properly set and your amp isn't putting out full power long before your head unit's volume control is maxed out.

Found a very imformative video for setting gain on your amp(s)....

 

[Scotnemily]

Thanks for the video. I had read that I needed to set the amp gain that way, but the video makes it clear. A few things though. I still need to reduce the voltage going into my amp. Since I have higher voltage is the procedure in the video still the same? I am kind of over driving my amp the way it is now. I still need to hook up my DMM and play with the LOC to see if I can lower the voltage there. if not is there something I can put inline to lower it or am I really going to have a problem putting 4.5vrms into a amp rated for 2.5vrms? thanks

 

[Scotnemily]

Ok so I got my input voltage to the amp lowered to acceptable range. On my LOC my voltage did not change when adjusting the gain on it, so I set it about 1/2 way. That is the suggested starting point for that LOC. I then adjusted the Bass on the LOC. This is what changed the voltage for me. I adjusted it until I got a 2.5v reading with a 40hz test tone. Radio Bass and EQ set to flat. I still have a few problems though. One the DMM never peaked above the 2.5V after I set it to this level. does that mean it is not my RMS volts but my peak? Should I adjust it back to say 4 or 5V Peak with that 40hz tone? Next I moved on to the amp. I unhooked the speakers and connected my leads to the speaker terminals on the amp. I did not get any voltage out of the amp. I hooked up the subs again and they were playing. I hooked the dmm up with the speakers connected to the amp and got a reading but really low like .02V I could not get it any higher than that. I should be getting something like 28.8V if I am pushing 400watts RMS correct? Also this amp is bridged to 2 OHMs when the subs are hooked up but not under a load without them hooked up does this make a difference in what I would get on my DMM? Thanks

 

[Scotnemily]

OMG never mind I am a complete idiot! I hate to explain but feel I need to share my stupidity. I have 2 wires with alligator clips on each side. one side was hooked to a cheap RCA jack. the other is hooked to the test leads on my DMM. Simple way to check my voltage coming from my LOC. Well when I hooked the to the amp, I guess I just unhooked them from my test leads and connected them to my speaker wires. So now I have one end hooked to a RCA that is not connected to anything. the other end is hooked to my speaker wires coming from my amp. The voltage meter is just setting there not hooked up to anything. Hey guess what! It is not reading any voltage!!! I was in a hurry, but still can't believe I did that. I will post my findings later tonight when I get a chance to try it again. my other question about my amp input rms voltage is still Unanswered though, so If someone wants to chime on on that It would help out. Figured the laugh I hope I provided at my expense helps with getting the answer. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[sharkman]

Ok so I got my input voltage to the amp lowered to acceptable range. On my LOC my voltage did not change when adjusting the gain on it, so I set it about 1/2 way. That is the suggested starting point for that LOC. I then adjusted the Bass on the LOC. This is what changed the voltage for me. I adjusted it until I got a 2.5v reading with a 40hz test tone. Radio Bass and EQ set to flat. I still have a few problems though. One the DMM never peaked above the 2.5V after I set it to this level. does that mean it is not my RMS volts but my peak? Should I adjust it back to say 4 or 5V Peak with that 40hz tone? Next I moved on to the amp. I unhooked the speakers and connected my leads to the speaker terminals on the amp. I did not get any voltage out of the amp. I hooked up the subs again and they were playing. I hooked the dmm up with the speakers connected to the amp and got a reading but really low like .02V I could not get it any higher than that. I should be getting something like 28.8V if I am pushing 400watts RMS correct? Also this amp is bridged to 2 OHMs when the subs are hooked up but not under a load without them hooked up does this make a difference in what I would get on my DMM? Thanks

What do you consider the is on the lc2i. The knob labeledbass is the gain. The accubass knob is a boost sure for.at least that's how I see it. And from what I understand the accubass knob controls the main and bass channels. I was wondering if you knew the the lc2i gain range then you can always just eyeball it first to get you started.

 

[Scotnemily]

Thx for the reply. What it appears from playing with it and reading. The Accubass is to keep the bass from lowering to protect the speakers as the volume is increased. A lot of factory radios lower the bass as the volume is raised. The accubass corrects this for the subs. The next is the Main. I thought this was what would control my preamp voltage, but it acts more like the gain on the amp. About 1/2 way up for the accubass and main seem to be pretty good. Next, I have the Bass. Raising and lowering this changes the voltage. Somewhere close to 1/4 sets my preamp voltage to 2.5v. I think this was peek though. As far as the gain range, I think I saw a video were someone said it could put out as much as 14v. I think I read somewhere it could be 9v. Not sure. I could unhook the amp and test it.

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