Gain staging question

[rickryan.com]

For the past few years, I've mostly run in mono. Here's my normal path:

Laptop (90% volume, player putting out mono) > Behringer USB card > Denon X500 (master 75%, channel gain 25%, switch set to mono output, slider 50% up) > Peavey IPR3000 amp (subs 100%, tops %80). I've begun to notice that on a few specific tracks; BEP "Boom Boom Pow", Barry White "Can't Get Enough of Your Love" that the tops channel was clipping. Now the meters on the Denon are cool, no hint of being overdriven. I'd have to dial the volume way back to get out of clipping at the amp.

Fast forward to this past weekend, I switched the tops over to run in stereo and now, not even a hint of clipping. Comparable volume to normal. I'm assuming it's a matter of summing the signal to mono but thought I'd pose it here for discussion. It only seemed to happen on a handful of tracks. I'm now wondering if this might've been the cause of me burning out the crossover on those Carvin neo12s. Any thoughts?

 

[ahoustondj]

For the past few years, I've mostly run in mono. Here's my normal path:

Laptop (90% volume, player putting out mono) > Behringer USB card > Denon X500 (master 75%, channel gain 25%, switch set to mono output, slider 50% up) > Peavey IPR3000 amp (subs 100%, tops %80). I've begun to notice that on a few specific tracks; BEP "Boom Boom Pow", Barry White "Can't Get Enough of Your Love" that the tops channel was clipping. Now the meters on the Denon are cool, no hint of being overdriven. I'd have to dial the volume way back to get out of clipping at the amp.

Fast forward to this past weekend, I switched the tops over to run in stereo and now, not even a hint of clipping. Comparable volume to normal. I'm assuming it's a matter of summing the signal to mono but thought I'd pose it here for discussion. It only seemed to happen on a handful of tracks. I'm now wondering if this might've been the cause of me burning out the crossover on those Carvin neo12s. Any thoughts?

You lazy bum! Do some research, we have covered that subject many times here.

 

[steve149]

Summing shouldn't so that unless the mixer is doing something funky .. the signal should be the max of either channel, not a sum of the 2. If you're Y-cabling the outputs, then you'll get a sum .. that's a no-no.

Start at the beginning of the chain. Cue a channel with something playing and set the gain for the channel so the input peaks minimally .. that'll be the max INTO the mixer and the best way to increase gain without increasing noise. Once the channel gains are set for a device/mic, they really shouldn't be touched.

Setting the channel slider to unity (usually marked 0, and the master fader to unity, slowly raise the sensitivity on the amp channel(s) so the amp peaks only minimally. That should be the max you should run the system (assuming your speakers can take the power). If your speakers can't take the full power, set the sensitivity low, bring the 2 faders (channel/main) up to unity and slowly bring up the sensitivity control on the amp to the point of desired loudness.

The reason you normally set the 2 faders to unity before setting the amp sensitivity, is because it's too easy for someone to walk over a slide a fader up to make it louder and having the 2 faders near max travel minimizes the ability to damage the equipment (as the amp controls will be / should be much below 100%). Always look to maximize the signal early in the chain, not later to get the best of of the system.

 

[rickryan.com]

Summing shouldn't so that unless the mixer is doing something funky .. the signal should be the max of either channel, not a sum of the 2. If you're Y-cabling the outputs, then you'll get a sum .. that's a no-no.

Start at the beginning of the chain. Cue a channel with something playing and set the gain for the channel so the input peaks minimally .. that'll be the max INTO the mixer and the best way to increase gain without increasing noise. Once the channel gains are set for a device/mic, they really shouldn't be touched.

Setting the channel slider to unity (usually marked 0, and the master fader to unity, slowly raise the sensitivity on the amp channel(s) so the amp peaks only minimally. That should be the max you should run the system (assuming your speakers can take the power). If your speakers can't take the full power, set the sensitivity low, bring the 2 faders (channel/main) up to unity and slowly bring up the sensitivity control on the amp to the point of desired loudness.

The reason you normally set the 2 faders to unity before setting the amp sensitivity, is because it's too easy for someone to walk over a slide a fader up to make it louder and having the 2 faders near max travel minimizes the ability to damage the equipment (as the amp controls will be / should be much below 100%). Always look to maximize the signal early in the chain, not later to get the best of of the system.

But that's the weird part of this equation Steve. I'm not running the channel gain, channel slider or master output hot at all. The mixer never comes even close to yellow, much less red, yet, the amp peaks on a handful of songs (they have not been gain-adjusted via an editor either) and only if run in mono. And no, I'm not running a y-cable. USB to the sound card then RCAs into the mixer (L-R). It's got me stumped.

 

[The Wizard Of OZ]

Running in mono is good. That way everyone regardless of where they're located in the room, hears the same thing. Summing the inputs works fine I've been doing it for years.

The problem is that the laptop volume is way too high-you're sending a too hot signal. I found this out by trial and error. Now, I never go above 50% volume at the laptop. Try it, you'll be surprised.

 

[rickryan.com]

Running in mono is good. That way everyone regardless of where they're located in the room, hears the same thing. Summing the inputs works fine I've been doing it for years.

The problem is that the laptop volume is way too high-you're sending a too hot signal. I found this out by trial and error. Now, I never go above 50% volume at the laptop. Try it, you'll be surprised.

You're probably right but 50% seems kinda low. I remember Cap suggesting 80%-90%. He mentioned (and I noticed the same thing) artifacts (crap signal) if the level was too low. It struck me as strange that the amp would be peaking (not the mixer) on mono but not stereo. What kind of soundcard are you using?

 

[ahoustondj]

Some additional reading: http://www.rane.com/note135.html

 

[drzinc]

Lots of people like to run in mono for many reasons but if the track was recorded in stereo it is better to reproduce that way. Even bass notes are sometimes recorded in stereo. Some funky stuff happens when some songs are summed, weird phase shifs lost of some frequencies and distortion. If running in mono was the norm then the recording engineers would have recorded most tracks in mono. Go to a concert and even though part of the crowd on either side will hear mostly one stack of speakers they still do a stereo mix to the audience. Like I said before we have two ears and our brain can pick up stereo (spacial) cues even if they (speakers) are very far apart or even if they are placed right next to each other. I can see someone running in mono if they have only one amp and want to run their tops on one channel and the sub on the other but if you have two amps and a crossover run your tops in stereo.

 

[ahoustondj]

I agree with what David said above. If the stereo is big enough for the room there is no reason why one should not run in stereo. One song that comes to mind is Hank Williams - Family Tradition. Listen to it in Stereo first and then play it in Mono, you will quickly notice a lot of the dynamics and separation is lost in Mono. If the scale of sound is correct, Stereophonic effect can be achieved in any room. I use a summed stereo only in my Monitor as I only want to deal with one speaker. Again, the size and power of the sound system has to be adequate for the room so natural sound can be realized.

 

[The Wizard Of OZ]

I use several different sound cards, but I also use the same Behringer that you mentioned. You have nothing to lose by trying what I suggested and have been using for a long time with great results. The signal isn't too weak. It allows me to run my amps with both attenuators at full blast. I control the rest using channel gain knobs and the main and channel faders. This way I have very good visual monitoring of levels at both the mixer and at the front of the amp showing me whether I am near peak levels or just at the center or at low levels. I've never blown a driver and rarely if ever have ffedback. This is without using a separate EQ, separate crossover, dbx driverack, feedback destroyer, compressor or any type of signal processing-just the built in crossover on the amp.

I discovered running the laptop at 50% by getting low rumble. I tried adjusting the sound level on the playback program and then I tried instead to adjust the sound output on the laptop to 50%. Since then this is how I always run and it has eliminated any priblems caused by a signal that's too hot.

 

[ahoustondj]

Rick,
Are you running a full range signal to your tops?

 

[rickryan.com]

Rick,
Are you running a full range signal to your tops?

Nope. I use the hi/low pass on the amp to separate the signals. I believe on the IPR3000 the crossover point is 100hz. I use xlr to the amp (when running mono) then use balanced 1/4" to jump the two sides together.

 

[ahoustondj]

Nope. I use the hi/low pass on the amp to separate the signals. I believe on the IPR3000 the crossover point is 100hz. I use xlr to the amp (when running mono) then use balanced 1/4" to jump the two sides together.

Give me more specific details on this hookup.

 

[rickryan.com]

I agree with what David said above. If the stereo is big enough for the room there is no reason why one should not run in stereo. One song that comes to mind is Hank Williams - Family Tradition. Listen to it in Stereo first and then play it in Mono, you will quickly notice a lot of the dynamics and separation is lost in Mono. If the scale of sound is correct, Stereophonic effect can be achieved in any room. I use a summed stereo only in my Monitor as I only want to deal with one speaker. Again, the size and power of the sound system has to be adequate for the room so natural sound can be realized.

I like running in stereo for most setups. There are times where mono makes sense (distributed systems) so it'd be nice to get this little gem debugged. My hunch is that it's at the source. While running in mono, I have the player in mono then also have the switch on the Denon set to mono as well. Perhaps it'd be better to send stereo out and switch it only on the mixer when needed?

 

[ahoustondj]

I like running in stereo for most setups. There are times where mono makes sense (distributed systems) so it'd be nice to get this little gem debugged. My hunch is that it's at the source. While running in mono, I have the player in mono then also have the switch on the Denon set to mono as well. Perhaps it'd be better to send stereo out and switch it only on the mixer when needed?

Are you using only one amp (One Channel to tops and the other to the subs?)? Again to give you the best answer, I will need to know exactly what equipment you are using, the setting of each, how each is hooked up to the other especially the cables, ins and outs.

I have a strong feeling that your tops are being underpowered. What is the total ohms of each of the tops and its ratings?

 

[rickryan.com]

Are you using only one amp (One Channel to tops and the other to the subs?)? Again to give you the best answer, I will need to know exactly what equipment you are using, the setting of each, how each is hooked up to the other especially the cables, ins and outs.

Thought I did.

Laptop > Behry USB Soundcard (both sides) > Denon x500 (mono switch engaged) > Peavey IPR3000 (low/hi split to individual channels, set to 0db sensitivity)

Windows volume at 90%, player (winamp set to output mono) at 90%. While in mono, if I play a track that clips, it does not clip at the mixer. It still clips at the amp, even if I back it way off on the sensitivity (25%). If I take this exact same setup and run stereo tops, I can hit the same volume level with zero clipping at the amp. This is not a prevalent problem and only seems to happen on a handful of specific tracks.

 

[ahoustondj]

If you have a Mono switch on your Mixer like I do, then you should hook up everything as though you are running stereo. If you want mono, then just engage the switch, very easy. Also if you are only using one amp for both tops and subs, you are playing with fire. If a channel goes then you are screwed. Use two amps that way you can always make that adjustment in the case of an emergency.

 

[rickryan.com]

If you have a Mono switch on your Mixer like I do, then you should hook up everything as though you are running stereo. If you want mono, then just engage the switch, very easy. Also if you are only using one amp for both tops and subs, you are playing with fire. If a channel goes then you are screwed. Use two amps that way you can always make that adjustment in the case of an emergency.

I have 2 amps in the rack but in the past I did run bi-amp off the single amp. I was keeping the 2nd amp completely disconnected in case I got a lightning strike or something that smoked the first amp. I figured I could always just hookup the 2nd amp and keep going. The way I'm running it now is to have tops off one amp then subs coming off individual channels from the 2nd amp (4-ohm cabs). BTW, it's dual IPR3000s. For giggles, I think I'll try just switching the denon to mono and see if I can replicate the same problem.

 

[ahoustondj]

Thought I did.

Laptop > Behry USB Soundcard (both sides) > Denon x500 (mono switch engaged) >One cable or two cables? Peavey IPR3000 (low/hi split to individual channels, set to 0db sensitivity)How are you going to the Speakers?

Windows volume at 90%, player (winamp set to output mono) at 90%. While in mono, if I play a track that clips, it does not clip at the mixer. It still clips at the amp, even if I back it way off on the sensitivity (25%). If I take this exact same setup and run stereo tops, I can hit the same volume level with zero clipping at the amp. This is not a prevalent problem and only seems to happen on a handful of specific tracks.

See above in red. Again my first thought is not enough amp for the speakers.

 

[ahoustondj]

What I don't understand is how you can set the crossover setting on ONE amp to only affect one side. If you are coming in with a full range left and right to the amp and the setting on the amp is set for your subs, then by using the "Throught" 1/4 to the tops, you are actually sending full range to the tops. Full range will include bass which will in turn put more demands on that amplifier channel = high probability of early peaking if the speakers are being under powered.

You don't even have an Equalizer to control the side you want to control. Shortcuts to proper sound deployment will bring about problems like you are experiencing. For the kind of Gigs that you do my recommendation is that you get a two way crossover & EQ or a Driverrack plus two amps, one for tops and the other for subs. Put the damn thing in a rolling rack and ditch the friggin table.

The following statement is not meant to belittle you but this is the exact reason why they started making powered speakers. Each speaker has its own crossover and amp so there is less change of mismatching. Even then , some DJs still do screwy things.