ok, i bought a sperry dm350a


im trying to tune my amp and i cant figure out how to work this damn thing

my amp says it needs 44.7v on a 4 ohm load while running a 50hz sine wave

i run the sine wave hook it up and the numbers are all over the place... nothing consistant it goes from like 25-150


anybody know how to set these damn things up, i read the instructions but they help about as much as helen keller at a spelling bee

 

i have been installing for 5 years and puchasing and using amps and speakers for 20 + years

i have never used a DMM to set my gains

i have never blown a sub woofer or mid ever


but if you feel you need to use post on caraudio.com

 

Could you can post a picture of how you are measuring this, and what exactly you are measuring (the input to your amp?, the output to your amp?, etc.)

 

I think you are way in over your head. The reason you use a DMM is to adjust your amplifer input gain to your headunits ouput voltage. This voltage is usually between .5volts for a low end head unit to 8 volts for a high end unit. I have never heard of an amplifier being able to accept 44.7 volts. as there is no head unit in the world that sends out that much voltage on the preouts. Most amplifers are made to accept between .05 volts and 5 volts. I also do not understand how you get into the 4Ohm load, this is usually the resistance an amplifer can handle on the output side not the input side. There is no reason to use a DMM on the output side of an amplifer unless you are trying to see how much watts you are producing, but this has nothing to do with the tuning of the amplifer. Tuning of an amplifer consist of matching the gains with the ouput of the headunit.

 

same here. ive been installing for 4 years and never used a multimeter to set gains. if i need to, i have a cd that detects clipping for subs and speakers. it actually works pretty good, but im pretty good that i can tune by ear

 

If you're talking about setting the output you need to disconnect your speaker(s) from the amp, set your head unit volume to 75% of max, play the 50hz sine wave, then measure and adjust your amp's gain to get the recommended output for the amp for the ohms.

JL's site explains it pretty well if you need more detail.

 

I've worked electronics since the tube days, it's sounds as if they want you to set the max voltage your system will create based on the input to avoid clipping. So you'll need a 4 ohm load rated at the wattage of the amp or more. You measure across the resistor for the voltage with the desired input. The meter needs to be in the 200 scale on the red V~.

 

no, the output of the amp needs to be 44.7 http://mobile.jlaudio.com/pdfs/gainSetting.pdf

 

Actually the best way to adjust the gain is the one they have given him, head unit @ 3/4 volume and adjust the gain for the output voltage. Only problem is, he needs a 4 ohm load, something that not everyone has laying around. You could use the speaker itself as the load, but I think you'll have trouble setting the gain because of other electrical noise produced by the speaker. A non-inductive load is the best thing to use something like this. Two in parallel will give you 400 watts of load and being non-inductive, it'll be easier to get a good solid reading.