setting gain with dmm

[aLCHeMiST45 10+ year member]

I am having a great deal of difficulty when trying to set my gain using a DMM. I have a Directed D2400 powering (2) 4 ohm DVC Kicker CVR. I am planning on wiring the subs to a 1 ohm load. Each sub RMS is 400 watts; a total of 800 watts needed to power both.

When using the formula to calculate desired voltage:

Sqrt(Power*Resistance) = Voltage

Sqrt(800*1) = 28.28 volts

Regardless of how high the gain is set, the AC output never measures anywhere near 28.28 volts. I am testing using a 50Hz test tone @ 0dB with volume set to maximum for listening. I have actually turned the gain to the maximum and it still does not measure near 28.28 volts.

As far as bass boost is concerned, I have tested with bass boost on along with the gain set to maximum. The voltage does not come close to 28.28 volts.

Another thing I am questioning is the fact that I have no voltage reading from the speaker outputs until the gain is above half.

I do not have my gain set at maximum, I was testing for different speaker output readings.

Could someone please help me?

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[xluben 10+ year member]

check the fuse in the DMM, same thing happened to me. just second in current (Amps) mode can blow it, and it doesn't actually tell you the fuse is blown (on mine), just gives wierd readings.

 

[luvinthebass 5,000+ posts]

either that or your amp is overrated, try it at 3/4 volume and see if you get more voltage

 

[Symon_say 10+ year member]

Check your RCA's i have had the same problem last week, the amp was reading about 1.0-3.0 volts. i check all over and dont found anything and for the last try i check in the radio and bingo the rca in the radio was little unplug, problem fixed.

 

[GrnEydDvl 10+ year member]

Yes, check your wiring.

Also, what is the max voltage you are measuring? And what is the fuse rating on that amp?

 

[2loud4u 10+ year member]

What deck do you have?

What are the settings on the deck?

Are you using a LOC?

 

[aLCHeMiST45 10+ year member]

check the fuse in the DMM, same thing happened to me. just second in current (Amps) mode can blow it, and it doesn't actually tell you the fuse is blown (on mine), just gives wierd readings.

I have checked the fuse and the battery in the DMM and both are properly working.

either that or your amp is overrated, try it at 3/4 volume and see if you get more voltage

I tried to turn up the volume past what I would normally set the maximum volume to and I didn't get much of a change.

Check your RCA's i have had the same problem last week, the amp was reading about 1.0-3.0 volts. i check all over and dont found anything and for the last try i check in the radio and bingo the rca in the radio was little unplug, problem fixed.

I have checked the RCA connection to the back of the HU and everything is plugged in.

Yes, check your wiring.
Also, what is the max voltage you are measuring? And what is the fuse rating on that amp?

I have checked my wiring numerous times. The max voltage that I am measuring at the speaker outputs on the amp is 20.8 volts. This is with to gain set to max and the bass boost on.

What deck do you have?What are the settings on the deck?

Are you using a LOC?

The HU is an Alpine CDA-9856. The settings are:

volume: 21/35

bass: -7

BBE: 2

subwoofer: +15

subwoofer system: 2

I am not using a LOC.

 

[xluben 10+ year member]

how do you know the fuse is working correctly?

try testing a 9V battery and see if it reads something near 9V.

i have the same head unit.

try this:

bass :0

bbe: off

subwoofer :+15

subwoofer system: 1

if the fuse i working correctly i think that should fix all your problems.

 

[aLCHeMiST45 10+ year member]

I do not know for sure that the fuse in the DMM is working. Having the DMM set on ACV 200, the readings of a 9V battery are 20.0. Having the DMM set on DCV 20, the readings are 9.47.

 

[GrnEydDvl 10+ year member]

You only answered half of my question. What is the fuse rating on that amp?

 

[aLCHeMiST45 10+ year member]

I just tested the voltage with the following:

bass: 0

BBE: off

subwoofer: +15

sub sys 1

The max voltage was 23.9 volts with the gain set to max and bass boost on.

The amp has (3) 40 amp fuses.

 

[GrnEydDvl 10+ year member]

try this:

bass :0

bbe: off

subwoofer :+15

subwoofer system: 1

if the fuse i working correctly i think that should fix all your problems.

Sounds like the dmm is ok. Try these settings. Having the bass set that low on the HU cannot be good for output voltage at 50hz.

 

[xluben 10+ year member]

what do you have the settings of the amp at?

subsonic filter: ?

low pass filter: ?

what dB level test tone and at what frequency?

 

[aLCHeMiST45 10+ year member]

One other thing that I am unsure about is the way my speaker wire is going from the box to the amp. I am currently using a pre-fab box that has 2 terminal cups. The voice coils are wired to 1 ohm. The amp has (2) positives and (2) negatives; they parallel internally. I have each sub positive and negative going to the individual positives and negatives on the amp. Is this the proper way to wire to run at 1 ohm?

 

[aLCHeMiST45 10+ year member]

what do you have the settings of the amp at?
subsonic filter: ?

low pass filter: ?

what dB level test tone and at what frequency?

The settings of the amp are:

subsonic filter: on

LPF: 90Hz

The test tone is 0dB @ 50Hz. I got all of my test tones from http://www.realmofexcursion.com.