Why do amps clip?

[bassmonkey]

I hadn't really noticed this with my Stingrays, but with the Bongos, especially the HH, if I dial in a fair amount of bass, for a reggae style number, then the yellow "clipping" light on my GK rig lights up loads. Why?

Also I can visibly see the 4X10 speakers moving, this is only with volume on 4. Is this damaging for them.

Powerful things these Bongos.

 

[Psycho Ward]

Bongo’s use flux capacitors.



The Bongo has an already strong output, by dialing in more bass you are also increasing the overall output too, just back the volume down a little any time you boost any thing in the eq. Your yellow light is telling you are overdriving the input of your amp.

Yellow is just a warning, but if you see the dreaded ultraviolet light… RUN FOR YOUR LIFE!!!!

 

[bassmonkey]

Fantastic!

I knew I could rely on Psycho "Lefty" Ward for an answer.

Cheers mate.

How about the visibly moving speakers?

 

[Bill]

My 2 12s move continuously at every gig due to the sound my Stingrays pump out...haven't had any trouble with the speakers crapping out yet. Just lovin' the tone!

 

[Big Poppa]

speakers are supposed to move

 

[bassmonkey]

speakers are supposed to move

LOL!

I know, call me a dumb limey!

It's just I've never seen speakers move as noticeably as these do. I guess I've never had a 5 string before either.

 

[kompressaur]

nothin like watching (and hearing )air being moved

especially dub with an 18.

komp

 

[adouglas]

Clip lights, power amp clipping and visibly moving speaker cones...all different things.

The more prevalent the low frequency component of a given signal is, the more energy it takes to produce the same perceived output. The speakers have to pump a lot more air. So you can see them move more. If they bottom out they can (and probably will) get damaged...the voice coil physically whacks into the frame of the speaker and gets bent, or the spider tears, or the surround tears.... This is marked by nasty farting noises in my experience. (Yes, experience. Do not do what I did.)

When you turn up the bass, you're changing the frequency profile (adding more low frequency component) and are in effect asking the amp to put out a whole lot more power even if you don't turn up the volume. This is going to push the power amp closer to clipping. The bassier the signal, the more headroom it's going to soak up. If you really want to go BOOM BOOM, seriously consider joining the Kilowatt Klub.

Low frequencies using a lot of power is why bass amps have to be so much more powerful than guitar amps.

I have an anecdote about this that is pertinent but I won't waste your time with it unless you're interested.

Your yellow light is telling you that your preamp is clipping, which means your input signal is too hot. Since the Bongo has a face-melting 18v preamp, then you need to turn down your input gain on the amp, and turn up the master to compensate.

 

[bassmonkey]

Clip lights, power amp clipping and visibly moving speaker cones...all different things.

The more prevalent the low frequency component of a given signal is, the more energy it takes to produce the same perceived output. The speakers have to pump a lot more air. So you can see them move more. If they bottom out they can (and probably will) get damaged...the voice coil physically whacks into the frame of the speaker and gets bent, or the spider tears, or the surround tears.... This is marked by nasty farting noises in my experience. (Yes, experience. Do not do what I did.)

When you turn up the bass, you're changing the frequency profile (adding more low frequency component) and are in effect asking the amp to put out a whole lot more power even if you don't turn up the volume. This is going to push the power amp closer to clipping. The bassier the signal, the more headroom it's going to soak up. If you really want to go BOOM BOOM, seriously consider joining the Kilowatt Klub.

Low frequencies using a lot of power is why bass amps have to be so much more powerful than guitar amps.

I have an anecdote about this that is pertinent but I won't waste your time with it unless you're interested.

Your yellow light is telling you that your preamp is clipping, which means your input signal is too hot. Since the Bongo has a face-melting 18v preamp, then you need to turn down your input gain on the amp, and turn up the master to compensate.

Thanks.

Sage advice from a man who knows.

Problem with turning the input gain down is that it will lower the overall volume, won't it? Or am I just showing my ignorance? I have a GK RB1001, and to be honest I find the controls and the manual a little confusing.

I'd be interested in the anecdote, PM me if you don't think it is appropriate for the forum in general.

 

[adouglas]

You've got two controls that are related. On your amp I think they're called VOLUME and MASTER. VOLUME controls what goes into the preamp, and MASTER controls what comes out of the power amp. Turn one up and the other down, and the overall output remains the same. So, to get rid of your clipping, turn your VOLUME down and your MASTER up.

I'll send you an email about the anecdote. It's about non-traditional amplification (Bose) and most here couldn't care less.

 

[bassmonkey]

You've got two controls that are related. On your amp I think they're called VOLUME and MASTER. VOLUME controls what goes into the preamp, and MASTER controls what comes out of the power amp. Turn one up and the other down, and the overall output remains the same. So, to get rid of your clipping, turn your VOLUME down and your MASTER up.

I'll send you an email about the anecdote. It's about non-traditional amplification (Bose) and most here couldn't care less.

Cheers, I'll check it out when I get home.

I think GK don't call it master, but have a couple of knobs which control the output gain, this is what confuses me. I'll sit down with the manual again and try to figure it out.

 

[Oldtoe]

I have been known to fry a few voice coils.

I'm thinking seriously of adding a second cabinet soon.

 

[dlb1001]

Did some checking of the owner's manual that GK has online...there is a -14dB input pad that could be used to deal with hot output from the bass. These days, I think, more amp mfrs are adding these pads to deal with active basses.

 

[bassmonkey]

Did some checking of the owner's manual that GK has online...there is a -14dB input pad that could be used to deal with hot output from the bass. These days, I think, more amp mfrs are adding these pads to deal with active basses.

Yeah, I've used that, but it just turns the volume down. Not sure I understand how to dial in this amp properly.

 

[Bill]

On your GK, try turning down the leftmost volume knob--that's the input gain--until it doesn't clip. Then turn up the woofer volume on the right. I never use the input pad since I can just turn down the input enough to eliminate any unpleasant overdrive noises.

 

[adouglas]

Yeah, I've used that, but it just turns the volume down. Not sure I understand how to dial in this amp properly.

Uh, yeah. That's the point. It reduces the sensitivity of the input so you can't drive it into clipping so easily.

BTW...I went to the GK website. Your master is indeed labeled MASTER. Look below the last knob to the right.

It seems you're not quite clear on what these controls do.
Your GK head. like all bass amps, has two basic components inside: A preamp and a power amp. The preamp is what all of the tone controls are attached to, and its job is to massage your instrument's signal before feeding it to the power amp. The power amp's job is simply to take that signal and boost it to speaker levels without coloring any further.

Your GK's VOLUME knob, which some amps have labeled as GAIN, controls how much signal gets into the preamp. The more signal going into the preamp, the more it distorts (which gives you that characteristic gritty "drive" that you sometimes want). Too much signal and it clips, which sounds nasty.

Which is why you've got a 14 db pad available. If the input signal is so hot in the first place that you can barely move the VOLUME knob without driving it into clipping, you need to knock down that signal a bit so the controls will be useful to you.

Since the power amp's job is only to boost what the preamp feeds it, there's only one control attached to it: MASTER. It does nothing but control how much signal comes out of the power amp. Small signal in (from the preamp), MASTER up, big signal out.

It might help to think of the VOLUME knob as a "sensitivity" control, and the MASTER knob as the "volume" control.

So: Adjust VOLUME (preamp) to get the tone and level of drive (grit, fuzz, whatever you want to call it) you want, then use the MASTER (power amp) to adjust the overall output of your rig.

Make sense?

 

[Oldtoe]

Make sure you're playing as loud as the loudest note you play while adjusting the input gain to just below clipping. This will ensure it doesn't clip when you slap a low "B" or similar.

 

[bassmonkey]

It seems you're not quite clear on what these controls do.

You are spot on with that observation.

Very helpful post. Thanks.

The problem is, this GK rig is the first decent bit of kit I have ever owned. Prior to this my amps have only had volume, bass, mid and treble controls. I think I need to experiment a little, using the points you make as a reference.

 

[adouglas]

Go to school on that amp. You'll be glad you did.

There's a real problem with most musical gear IMHO...a lot of it has too many controls. That gives musicians too much to play with. If you understand what's really going on that can be very powerful...but if not, you're just as likely to flail about randomly and never get the most that the gear can give you. Worse, if you really don't know what the controls actually do you can make your high-end fantastic gear sound like a garbage truck with a bad transmission.

The EBMM folks know this very well. It is the exact reason, we are told, why the Bongo has "only" a four-band EQ. The prototype had many more controls...too many.

We all tend to wind up finding a setting we like and leaving the thing alone anyway.

 

[Ken Baker]

Go to school on that amp. You'll be glad you did.

Excellent explanations.

You gonna go into power amp clipping and why little amps can destroy big speakers? I wanna watch! There's always someone whose head ends up spinning around. He said. Having been there. Head spinning.

Ken...