Signal To Noise: Gain VS Volume

[akaTRENT]

ANSWERED! Thanks.Hi all, excuse my ignorance on this one:

I have a db751 and I was clipping the amp occasionally during harder hits, I was running the gain at 11 oclock and the volume at 11 oclock.

I was informed that If I ran the gain hotter, say at around 1 o clock, and then adjusted the volume to taste I would get a better signal to noise ratio, and higher headroom with less clipping. Can anyone give me some insight to the tech specs behind this?

Thanks.

[Nightlyraider]

Are you sure that you weren't just clipping the preamp signal? In general you want the preamp gain to be set as high as where it sounds good, then increase the volume/poweramp level as needed.

You get a better signal/noise ratio because preamp gain is an increase in signal voltage, and the poweramp is getting a "louder" signal to amplify vs. a low gain signal.

[BassmanPaul]

Any decent amp should have a low noise floor to start out with. There is noise with any high gain stage. I tend to run my Master controls towards full and use the Gain more like a Level control. This gives you the most undistorted headroom out of your power amp.

If your amp has a "clip" light you can advance the Gain until you get the clip light to flash on your loudest peaks and then use the Master to control your level. If you get distortion and don't want it, back off your Gain a bit and bring up the Master to compensate.

Paul

[akaTRENT]

Originally Posted by Nightlyraider

Are you sure that you weren't just clipping the preamp signal? In general you want the preamp gain to be set as high as where it sounds good, then increase the volume/poweramp level as needed.

You get a better signal/noise ratio because preamp gain is an increase in signal voltage, and the poweramp is getting a "louder" signal to amplify vs. a low gain signal.

Im not sure if it's just the preamp, or whether its measuring it after the power section, and the documentation doesnt explain where the clip light is measuring. What I do know is the clip was audible through the speakers.

But in any event, to make sure I have this clear: Since the Preamp signal is louder going into the power section, it gives the power section more to amplify thus allowing for more volume with out clipping aka more Headroom. ?

I need more headroom and I know the amp is capable, I just want to make sure I get the science behind it so to speak, I have to fight with a Vox AC30 haha.

[Nightlyraider]

Yes.

Plug a CD player into the amp with the player volume at 1 and the poweramp on 10.

Then play the cd player with the volume on 25 and the poweramp still on 10.

The second version is much louder and you didn't change a thing on the poweramp's end.

[Munjibunga]

Originally Posted by BassmanPaul

Any decent amp should have a low noise floor to start out with. There is noise with any high gain stage. I tend to run my Master controls towards full and use the Gain more like a Level control. This gives you the most undistorted headroom out of your power amp.

If your amp has a "clip" light you can advance the Gain until you get the clip light to flash on your loudest peaks and then use the Master to control your level. If you get distortion and don't want it, back off your Gain a bit and bring up the Master to compensate.

Paul

The input gain should be set as high as practical. The lower you set it, the closer the signal level is to the noise floor. Then the power amp amplifies both the noise and the signal, and the noise becomes more evident. It's best to get the most gain in the earliest stages of a gain structure.

[akaTRENT]

Originally Posted by Munjibunga

The input gain should be set as high as practical. The lower you set it, the closer the signal level is to the noise floor. Then the power amp amplifies both the noise and the signal, and the noise becomes more evident. It's best to get the most gain in the earliest stages of a gain structure.

Correct me if I am wrong here. When I was using an ampeg svt classic, what paul is saying seemed to ring true?

But whenever I have used a hybrid like my current, it seems that logic has gone at the window when it comes time to play.

[akaTRENT]

Great responses on this btw!, I should also note that I began using a compressor and that is really helping dial down my peaks for even more headroom!

[BassmanPaul]

Originally Posted by Munjibunga

The input gain should be set as high as practical. The lower you set it, the closer the signal level is to the noise floor. Then the power amp amplifies both the noise and the signal, and the noise becomes more evident. It's best to get the most gain in the earliest stages of a gain structure.

I agree Munji, but the actual signal should be so far above the noise floor for the noise to be inaudible on a stage.

The problem I see with adding controls whether to a pre-amp, gain, or to a power amp, bias, is that someone is going to use them inappropriately. They are also going to worry about them.

Some folks dislike the noise of the cooling fans some of them have even disconnected them and wondered why their amps have failed.

OK I'm going to stop here otherwise I'm going to be on my soapbox all day!

Paul

[akaTRENT]

Originally Posted by BassmanPaul

I agree Munji, but the actual signal should be so far above the noise floor for the noise to be inaudible on a stage.

The problem I see with adding controls whether to a pre-amp, gain, or to a power amp, bias, is that someone is going to use them inappropriately. They are also going to worry about them.

Some folks dislike the noise of the cooling fans some of them have even disconnected them and wondered why their amps have failed.

OK I'm going to stop here otherwise I'm going to be on my soapbox all day!



Paul

I actually find your soap boxes very informative... Seriously.

[BassmanPaul]

Well there's an unexpected compliment! I thank you Sir!

Paul

[naturalkinds]

Munji is right. Gain first, then power amp.

Think about studio recording. You don't max out the gain on the compressor output and minimize it on the mic preamp! That generates a ridiculously high amount of noise in comparison to adjusting the gain on the preamp appropriately, and then adjusting the compressor output to achieve unity gain.

And it's not always about what noise you hear on the gig, Paul! Some of us, myself included, are interested in optimizing the signal-to-noise ratio in settings outside of bars and stadiums.Frankly, very little hi-fidelity nuance gets transmitted in a mix off the floor. I couldn't really tell the difference between playing Markbass and Glockenklang on a gig, but you'd better believe that the Markbass was hiss-city in comparison to the Glock in a quieter setting.

Honestly, if you are clipping a DB751, something might be wrong. For one, a tube preamp isn't like a solid state preamp. You don't max it out and hear digital clipping; it just distorts. Moreover, If correct gain staging -- a la Munji -- doesn't help, then call Aguilar. Your settings sound pretty modest to me, but, then again, your bass and playing might be fairly aggressive, which I can't relate to.

[naturalkinds]

Also, you really shouldn't need a compressor to get more headroom out of that amp. If you do, then you're probably playing to crowds big enough where you can afford another DB751 or DB412, and would have more fun using that instead.

[akaTRENT]

Originally Posted by naturalkinds

Also, you really shouldn't need a compressor to get more headroom out of that amp. If you do, then you're probably playing to crowds big enough where you can afford another DB751 or DB412, and would have more fun using that instead.

I am playing Nokia Theatre Times Square on friday with Level 42. So yes, I do play crowds that big... Sometimes. But no I cant afford another one. haha.

[babebambi]

Originally Posted by Nightlyraider

You get a better signal/noise ratio because preamp gain is an increase in signal voltage, and the poweramp is getting a "louder" signal to amplify vs. a low gain signal.

How do you get a "louder" signal without higher voltage?

Originally Posted by Munjibunga

The input gain should be set as high as practical. The lower you set it, the closer the signal level is to the noise floor. Then the power amp amplifies both the noise and the signal, and the noise becomes more evident. It's best to get the most gain in the earliest stages of a gain structure.

This.

Originally Posted by naturalkinds

Honestly, if you are clipping a DB751, something might be wrong. For one, a tube preamp isn't like a solid state preamp. You don't max it out and hear digital clipping; it just distorts. Moreover, If correct gain staging -- a la Munji -- doesn't help, then call Aguilar. Your settings sound pretty modest to me, but, then again, your bass and playing might be fairly aggressive, which I can't relate to.

I too think it's nuts to actually clip the power stage of the DB750/751.

[babebambi]

Originally Posted by akaTRENT

I am playing Nokia Theatre Times Square on friday with Level 42. So yes, I do play crowds that big... Sometimes. But no I cant afford another one. haha.

Well, perhaps just add another DB412 then

[akaTRENT]

Originally Posted by babebambi

Well, perhaps just add another DB412 then

Lol, when a label wisks me away maybe an 8x10 thats my dream rig! 412/810

[akaTRENT]

Hey guys. seriously thanks for all the help on this one. I feel dumb for having to ask to begin with but I feel well informed once again thanks to my friends at TB.