How do you properly adjust LOC with DMM?

[TT52]

I've been searching around and all I can find is how to properly set the gain on an amp with a DMM. I just purchased one and I'm trying to get everything wired up properly.

If I understand correctly..the output from the LOC should be around 3-4V (my amp's input sensitivity is .5 - 5V). I just don't know how/where to measure that?

Any help is appreciated. Thanks!

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[Side Show 10+ year member]

huh?

 

[TT52]

I have a 2-channel LOC that allows you to adjust the input. I'm trying to figure out how to properly adjust it?

I can max it out then set the gain on the amp to match or I can turn the LOC up just slightly which will require me to turn the gain up a bit more on the amp.

This is what I have..

Axxess 2Channel Differential Converter AX-ADCT2 - Best Buy

 

[moneypit]

Why not crank it up all the way to get a strong signal to the RCA's then just adjust the gains? Not understanding why you woild want less than 4-5 volts if you could get it. I look for H.U.'s with a min. of 4 so....? Bare in mind i have never used one of these line convertors so im not 100% on there use.

 

[TT52]

That's what I originally did but then decided to set it at half because the thought of maxing something out just doesn't seem like the right thing to do...ha. Right now I have it sitting at about half and adjusted the gain on the amp with my DMM. I just don't know if this is the correct way to do it? Maybe I should max out the LOC? I just can't find a definite answer.

 

[phemps 10+ year member]

In theory if your input sensitivity is matched with the output of the LOC then everything should be where it needs to be. Thats what gains are designed to do anyway. Theres debate as to whether having high pre-out voltage makes a difference. Seems like the only real reason it may be better is that your gain on your amp will be lower reducing noise floor. Whether or not your LOC introduces and noise into the system if cranked i do not know. oscilloscopes are handy for such a thing

 

[phemps 10+ year member]

If you want to measure its output use a multimeter and probe the center plug with positive and the outside of the connector with negative and measure voltage

 

[moneypit]

If you want to measure its output use a multimeter and probe the center plug with positive and the outside of the connector with negative and measure voltage

I thought you hax to run it threw a resistor to check voltage on a rca?

 

[phemps 10+ year member]

I thought you hax to run it threw a resistor to check voltage on a rca?

Theres no reason i can think of you need to, why do you think that? just measure AC voltage and play some tones. The best way to do this would be to use an O-scope and see your voltage and whether your clipping at the same time

 

[moneypit]

Theres no reason i can think of you need to, why do you think that? just measure AC voltage and play some tones. The best way to do this would be to use an O-scope and see your voltage and whether your clipping at the same time

I could have swore that i read something stateing that. It had to do with haveing a load on the rca's to mimic a amp. Could be wrong though. I have never actualy measured any rca output before. Only amp when settibg gains.

 

[Jepalan]

O-Scope is the right way to do this. I made a female to female RCA adapter by soldering two RCA panel jacks back to back. This way I can probe the signal with the o-scope while it is plugged into the actual amp that will be loading it.

1) Turn amp gains all the way down, or disconnect speakers.

I typically check for RCA voltage clipping separately using a low, then mid, then high 0dB test tone.

2) With LOC gain set very low, turn up HU volume to see if there is any point the HU clips using the o-scope and adapter at amp input.

Leave the HU at highest non-clipping volume (typically around 3/4, but I back off just a little from the clipping point for good measure)

3) Now slowly increase LOC gain to see if it clips - leave it at highest gain that doesn't clip on all three tones. (I back it off just a bit)

Now remove test adapter and set amp gains as normal.