Sub preouts clipping or clipping inputs?

[yepimonfire]

A couple of times I've noticed some distortion that sounded like hard clipping with loud sounds. After some investigation, I've discovered it's line level. Turning the gain down on the sub does nothing to stop the clipping, only lowers the volume. A majority of the clipping can be avoided by setting the gain on the avr to -15dB and adjusting the volume on the sub except on the very top end of the output signal. Hooking the sub output into an external amp I get the same clipping at the same levels, it also clips the input of my presonus audio box line input at the same level with the gain set on 0. One of two things is happening, either the pre out is pumping out a massive amount of voltage (beyond normal levels) or the output is clipping (less likely). What could cause this?

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[WaynePflughaupt]

Try reducing the level of the sub output itself. It sounds like you have it set too ,to the point that the sub output is clipping before the main channels are.

Have no idea what you’re asking about the Presonus, nor have I any reference for its settings. Not sure why anyone would send a sub output to an audio interface anyway.

Regards,
Wayne A. Pflughaupt

 

[yepimonfire]

Try reducing the level of the sub output itself. It sounds like you have it set too ,to the point that the sub output is clipping before the main channels are.

Have no idea what you’re asking about the Presonus, nor have I any reference for its settings. Not sure why anyone would send a sub output to an audio interface anyway.

Regards,
Wayne A. Pflughaupt

It's already turned down all the way on the receiver end. I only connected it to the interface to diagnose whether the signal was clipping the input or the output was clipping itself. It appears it's sending out too hot of a signal even with the sub gain on the receiver turned all the way down to -15dB and over driving the sub inputs. Perhaps my post wasn't clear.

 

[lovinthehd]

Doesn't sound right that your source clips only on the sub with the level on the sub turned to the lowest level (but where are the speaker and sub levels set during calibration? are all speakers set to use bass management?). What is the source? How are you measuring clipping?

 

[TLS Guy]

It certainly sounds like the receiver output is clipping. Music has such high dynamic range and quite a few devices have insufficient headroom.

What is the receiver?

Your only solution is to turn the sub output down on the receiver and turn the gain up on the sub.

I find that increased headroom tends to be the biggest difference between lower priced and higher priced units.

Peter Walker impressed on me years ago, that you can never design in too much headroom on inputs and line outputs. My Marantz pre/pro has 12 to 13 volts of head room. I don't think you will get that on receivers, except may be the top of the price range.

Reviews always concentrate on the amp power, whereas reviewers should pay as much or more to headroom issues on the inputs and outputs.

 

[yepimonfire]

It certainly sounds like the receiver output is clipping. Music has such high dynamic range and quite a few devices have insufficient headroom.

What is the receiver?

Your only solution is to turn the sub output down on the receiver and turn the gain up on the sub.

I find that increased headroom tends to be the biggest difference between lower priced and higher priced units.

Peter Walker impressed on me years ago, that you can never design in too much headroom on inputs and line outputs. My Marantz pre/pro has 12 to 13 volts of head room. I don't think you will get that on receivers, except may be the top of the price range.

Reviews always concentrate on the amp power, whereas reviewers should pay as much or more to headroom issues on the inputs and outputs.

The gain on my sub is very sensitive. Even with it turned to -15dB turning the knob to 2 o clock gets me to 75dB, it's 100dB turned all the way up. At -15dB the signal still clips about 6dB below full scale, I'm considering placing a 12dB line level attenuator on the preouts like this one http://www.parts-express.com/harrison-labs-12-db-rca-line-level-audio-attenuator-pair--266-244 so that I have enough headroom. Using something like an active DI box would still cause clipping at -15dB. I have a feeling I'm going to have to drop the voltage at the preout.

What's concerning is that with the receiver gain set to 0 on the sub, the output begins clipping at -20dBfs, it appears that something is wrong with the output.

I'm still not positive it's clipping at the output stage rather than clipping the input. That's why I connected it to my presonus interface to diagnose the problem. With the gain set to 0 the signal exceeds 0dBfs at -20dB on the volume control, even with the audio box being set to 24 bit, giving it plenty of headroom, which is why I believe it's the output supplying too much voltage.

I connected the second sub out to an 8ohm resistor, basically wasting some of the power by connecting it in parallel, which immediately stopped the clipping, yet another reason I believe it's supplying too much voltage. Might be time to grab a multimeter and take some measurements.

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[PENG]

A couple of times I've noticed some distortion that sounded like hard clipping with loud sounds. After some investigation, I've discovered it's line level. Turning the gain down on the sub does nothing to stop the clipping, only lowers the volume. A majority of the clipping can be avoided by setting the gain on the avr to -15dB and adjusting the volume on the sub except on the very top end of the output signal. Hooking the sub output into an external amp I get the same clipping at the same levels, it also clips the input of my presonus audio box line input at the same level with the gain set on 0. One of two things is happening, either the pre out is pumping out a massive amount of voltage (beyond normal levels) or the output is clipping (less likely). What could cause this?

Sent from my SM-G360T1 using Tapatalk

Which AVR or prepro?

Your mentioned "gain on avr", did you mean the so called volume setting, or the onscreen "sub level" adjustment that would be between -12 to +12 for D&M and -10 to +10 for Yamaha AVRs, so if it can be set to -15 then I supposed it is the "volume setting" you referred to or it is an AVR that has sub level adjustable from -15 to +15. If it was the avr's volume setting your referred to, then -15 was still quite high.

I have to ask because if you have not tried lowering the AVR's sub level adjustment then you should try that first; and if it still causes the sub to distort, then at least you can narrow the root cause to either the avr/prepro is defective, or the subwoofer is defective.

You also mentioned "hooking the sub output into an external amp", did you mean the sub output on the AVR? If it is, then is that external amp an integrated amp or power amp, and did you use it to power the sub? Maybe it is just me, at this point I am not clear if I understand exactly what those input/outputs you referred to and until then it is hard to troubleshoot.

 

[WaynePflughaupt]

I have to ask because if you have not tried lowering the AVR's sub level adjustment then you should try that first; and if it still causes the sub to distort, then at least you can narrow the root cause to either the avr/prepro is defective, or the subwoofer is defective.

+1

Regards,
Wayne A. Pflughaupt

 

[yepimonfire]

+1

Regards,
Wayne A. Pflughaupt

Yes, as I've mentioned, it's at -15dB in the level calibration menu.

 

[yepimonfire]

Which AVR or prepro?

Your mentioned "gain on avr", did you mean the so called volume setting, or the onscreen "sub level" adjustment that would be between -12 to +12 for D&M and -10 to +10 for Yamaha AVRs, so if it can be set to -15 then I supposed it is the "volume setting" you referred to or it is an AVR that has sub level adjustable from -15 to +15. If it was the avr's volume setting your referred to, then -15 was still quite high.

I have to ask because if you have not tried lowering the AVR's sub level adjustment then you should try that first; and if it still causes the sub to distort, then at least you can narrow the root cause to either the avr/prepro is defective, or the subwoofer is defective.

You also mentioned "hooking the sub output into an external amp", did you mean the sub output on the AVR? If it is, then is that external amp an integrated amp or power amp, and did you use it to power the sub? Maybe it is just me, at this point I am not clear if I understand exactly what those input/outputs you referred to and until then it is hard to troubleshoot.

It clips the input section of my sub and the input section of an external amp. I was checking to see if the sub was defective. Hooking it up to my PC and looking at it via an oscilloscope I don't see any clipping at all, although it's possible the sound card's line in isn't presenting the same load to the pre amp as the sub's input.

 

[PENG]

It clips the input section of my sub and the input section of an external amp. I was checking to see if the sub was defective. Hooking it up to my PC and looking at it via an oscilloscope I don't see any clipping at all, although it's possible the sound card's line in isn't presenting the same load to the pre amp as the sub's input.

I am surprised there is so much -ve adjustment to subwoofer output level. What do you mean by "it clips the input section of your sub and the input section of your external amplifier"? Sorry, still not clear, but am very curiously to know what's going on. It shouldn't be hard to find the culprit even just by process of elimination.

 

[lovinthehd]

It clips the input section of my sub and the input section of an external amp. I was checking to see if the sub was defective. Hooking it up to my PC and looking at it via an oscilloscope I don't see any clipping at all, although it's possible the sound card's line in isn't presenting the same load to the pre amp as the sub's input.

The output voltage of the avr would change depending on what you're connecting it to? I'm not an EE but that doesn't sound right I don't think you've got clipping at this point.

 

[yepimonfire]

I am surprised there is so much -ve adjustment to subwoofer output level. What do you mean by "it clips the input section of your sub and the input section of your external amplifier"? Sorry, still not clear, but am very curiously to know what's going on. It shouldn't be hard to find the culprit even just by process of elimination.

I mean there is clipping on everything I plug the
sub out into. I don't even know if it's relevant whether or not the output is too hot or is clipping, if something like that is wrong with it it's probably a matter of time before it gets worse.

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[yepimonfire]

The output voltage of the avr would change depending on what you're connecting it to? I'm not an EE but that doesn't sound right I don't think you've got clipping at this point.

Then what is it? There's no reason I should have to set the gain in the avr to -15dB to avoid clipping at normal volume levels. I get clipping at 0dbfs on the LFE channel when set to a gain of zero in the avr menu at a volume level of -20dB. For movies, -15dB is the lowest volume setting in order for all listening positions to get intelligible dialogue. I generally listen at about -10dB, which means I could experience clipping if an LFE peak comes through.

At -15 in the AVR menu, the subs knob only has to be turned to about 1 o'clock, which is why I'm assuming the clipping is at the subs input stage because the output is too hot. The sub isn't defective, because the clipping happens with another subwoofer.

 

[PENG]

Then what is it? There's no reason I should have to set the gain in the avr to -15dB to avoid clipping at normal volume levels. I get clipping at 0dbfs on the LFE channel when set to a gain of zero in the avr menu at a volume level of -20dB. For movies, -15dB is the lowest volume setting in order for all listening positions to get intelligible dialogue. I generally listen at about -10dB, which means I could experience clipping if an LFE peak comes through.

At -15 in the AVR menu, the subs knob only has to be turned to about 1 o'clock, which is why I'm assuming the clipping is at the subs input stage because the output is too hot. The sub isn't defective, because the clipping happens with another subwoofer.

Now that you mentioned the clipping happened with another subwoofer (previously you just mentioned it clipped the input of an external amp too), then the odds are great that it is your AVR. Somehow it's sub out circuit is failing if not completely, could be the Op amp.

 

[lovinthehd]

Then what is it? There's no reason I should have to set the gain in the avr to -15dB to avoid clipping at normal volume levels. I get clipping at 0dbfs on the LFE channel when set to a gain of zero in the avr menu at a volume level of -20dB. For movies, -15dB is the lowest volume setting in order for all listening positions to get intelligible dialogue. I generally listen at about -10dB, which means I could experience clipping if an LFE peak comes through.

At -15 in the AVR menu, the subs knob only has to be turned to about 1 o'clock, which is why I'm assuming the clipping is at the subs input stage because the output is too hot. The sub isn't defective, because the clipping happens with another subwoofer.

What avr is it? Did you run a calibration? What were speaker and sub levels set by this? What source/type of signal are you using to test for clipping? Why wouldn't the oscilloscope show clipping if it is?

Maybe you have a problem with the sub channel in the avr, do you have another or can borrow one to test with?