New Amp for Fronts purchased - What is gain strategy for the amp ?

[timetohunt]

I bought an amp to power my front speakers. My receiver (which I like) was not up to the task and I wanted to relieve it of the front duties, thereby being more stable for my surrounds and center. Thats a whole different story, but trust me, the fronts needed separate amplification. So using my receiver as a pre-amp, I now have the new amp connected. I got some initial recommendations on Amps, but when I checked them out, my eyes popped out once I saw the prices (musical fidelity and so forth). It seemed that the best solution was a pro-audio style amp. I got a Peavey 900 for under $300. It sounds good and meets my needs for now. Yea, the fan make some noise, but I play loud, and don't notice when the music is on.

Here is the question: I noticed that when I set the gains on the new amp higher, the amps distortion detection kicked in. I set them low, and could get plenty loud by using the volume on the receiver without any distortion detected. So, I can get loud either way. Its just that the Distortion Detection LEDs dont come on set with gains low, and receiver volume high.

So, Is the strategy to keep the gains on the amp as low as possible, yet high enough to get the volume I want ? Ofcourse I just pretty much want to leave those gains set where I want and use the receiver volume. Any notes on your experiences with this would be helpful.

 

[lmarc78]

I'm pretty sure there is something wrong with the amp you should be able to have your gains all the way up. In the owners Manuel it should tell you to turn your gains to max, the reason I not to sure about but my two Integra amp's are maxed per say the Manuel.

 

[timetohunt]

I'm pretty sure there is something wrong with the amp you should be able to have your gains all the way up. In the owners Manuel it should tell you to turn your gains to max, the reason I not to sure about but my two Integra amp's are maxed per say the Manuel.

No, I don't think there is any wrong with this amp out the box. Gains to the max seems weird to me. But what do I know, I'm just getting back into the hobby.

 

[markw]

you have to match it's gain to the other amps in the system.

IOW, play those test tones. but, you're gonna have to do this a little different than usual.

First, turn the gain controls on the Peavy all the way down.

now, play those test tones and adjust the other three speakers. Ignore the R/L for now.

Get the other three to sound pretty equal (or use a SPL meter, whatever)

Odds are they will all show about the same db reading.

Now, set the channels going to the external amp to about the same db reading.

Now, bring up the gain on those channels up just so their level matches that of the other channels. You might have to go back and forth a few times, but try to get the level readings (and the levels themselves) for these channels about the same as for your center.

Once this is done, they should be pretty balanced and all your volume control should be on the receiver from now on. If the distortion lights still come on, I dunno what to tell ya.

If it DOES work out, you might want to put some kind of mark (your girl's red nail polish?) on the Peavy so you know where to set the gain controls should they get moved, and they will, trust me.

 

[agarwalro]

All amps have a max input signal level above which the output distorts.

So receiver pre-out max output level < Pevey max input to prevent distortion.

In your case the max output voltage from the pre-outs on the receiver is most probably higher than the max input voltage allowed on the Pevey. You should try a setting where you are not reaching the max limit on the receiver output or Pevey input.

To answer your question, the aim is that on the receiver all channels trims be near the mid level. You should start by keep the Pevey at 50 - 70% of max and then calibrate the system to level match all speakers at 75dB. If the center and surround channel trims have to be adjusted way above or below the center point, you will need to adjust the Pevey's gain to compensate. If receiver trims are high, increase the gain, conversely, if receiver trims are low, decrease gain.

It sounds confusing... but it should give you the optimal setting.

 

[timetohunt]

Thanks, that a good start to play with. I also realized that I might need to be careful with my 'Zone B'. I have the surround back channels set to Zone B which goes upstairs to my second level (the speakers are nothing as robust as my main fronts, yet use receiver power, not separate amp), so if I have both zones on - I might stand the chance of blasting out the ones on the second level. I guess I need to figure that in as well.

 

[zildjian]

set preamp output signal to the amp's input sensitivity rating

You need to check the level at which the output from the preamp to the amp. An amp is designed to perform ideally with a certain signal input level, obviously if it's too low, then you have to turn the gain up on the amp beyond what it should be to achieve a certain volume, and conversely over driving the preamp wouldn't be good either. Look at the specs for the amp, find the input sensitivity for the type of input (either balanced or unbalanced/direct) and there should be a voltage value such as... 0.6V rms (just an example value! look for your amp's specific value). That means your amp is designed to perform ideally with an input signal of 0.6V. Play a pink noise source through your preamp and measure with a sensitive voltmeter at the outputs the voltage level with the volume set on the preamp set to it's reference, "0 dB" or whatever it is on your amp, it would be turned up loud if playing music! Adjust your preamp's gain for each channel so that it's 0.6V.
After you do that, THEN you worry about the level at which your amp gain is set, and then, it's whatever volume you want out of it (of course within it's capabilities...).
Hope this helps,
Brad