Issue with my AMP

[madhurshankar]

Hi,
Upon playing tracks with high volume, the sound coming out of my amp breaks. This issue is very inconsistent because this happens occasionally and even if the sound breaks upon continuous playing the sound break goes off. I took my unit to a local tech but problem was not reproducing in his place. I'm pissed off and not sure how to sort this out.

Do you guys have a clue on what could be the issue? I also can live with it for now and take it to tech if it gets worsen(when it is easily reproducible), Will you guys recommend this?

Regards,
Madhur

 

[Shivam]

First identify if the problem is with the amp itself.
Use another source and speakers. change the input. Next check if the problem is in both the speakers.
Try exchanging the left and right speaker connections to identify which channel is affected.

 

[Thtpro]

When the problem occurs what is the complete setup in terms of equipment and settings?

Do the problem repeat with the same set of equipment and settings?

Open the cover of the speakers and see if you have any woofer damage-- It may be the speakers

 

[sandeepmohan]

To me, this sounds like the amplifier is clipping. Can you reproduce the problem at lower volume levels?

 

[Flash]

Have you tried a different electrical socket. It could be the case of the Amp not being able to draw enough current to make it sing at higher volumes.

That could be the reason why the Amp stutters at higher volumes in your rig and the problem was not replicated at the local tech's place

You could try turning off other devices in the room or house when you notice the amp acting up to see if it solves the problem

 

[hifipal4all]

I strongly suspect a mis-match ... your amplifier is under-powered to drive your speakers. Your HK AVR 4500's wattage is 55 watts @ 8 ohms (peak) and your speakers are 130 watts (peak). Moreover your speaker's sensitivity is also very low (88 db).

With this matching, listening at lower volumes will not cause any problem ... you can listen for hours and hours of music but when you try to increase to higher volumes the speakers will start demanding more power and since your amp is under-powered it is not able meet the demand and clipping occurs. Even though the KEF IQ5s amplifier Requirements mentions: 15-130W, low powered amps can be used only for low/moderate volume level. If you want to listen high volume on your KEFs you need a powerful amp (atleast 90-150 watts amplifiers).

Try two options:
1) Make sure your 'FRONT' speakers are set to 'LARGE' in the AVRs speaker config settings.
Get a pair of low powered speakers (may be from 75-100 watts with 8 ohms impedence) from any of your friends and check it with you AVR.

2) Try your IQ5s with some other AVR which is a bit more powerful (90-150 watts range).

 

[square_wave]

Agree with the rest of the folks. Looks like the amp is clipping. If this is indeed the case, there is nothing technically wrong with the amp. The amp and speaker are wrongly matched. I had the exact same problem a decade ago when I bought wharfedale speakers are tried to match it to a pioneer stereo amp. The amp started clipping like mad when the volume was turned up.

A nad amp solved the problem.

The old pioneer amp is still running fine at a vintage lover friends home powering a sansui three way

 

[madhurshankar]

All,
Thanks for your inputs. Please find my response below

First identify if the problem is with the amp itself.
Use another source and speakers. change the input. Next check if the problem is in both the speakers.
Try exchanging the left and right speaker connections to identify which channel is affected.

I'll definitely try with other speaker. BTW, The problem occurs in both the channels.

When the problem occurs what is the complete setup in terms of equipment and settings?

Do the problem repeat with the same set of equipment and settings?

Open the cover of the speakers and see if you have any woofer damage-- It may be the speakers

Yes. The problem does reproduce with same equipment and settings, The only difference is I just raise the volume the tricky part is this problem happens ocassionally and even if it reproduces it goes off upon continuous playing.

To me, this sounds like the amplifier is clipping. Can you reproduce the problem at lower volume levels?

No, This problem does not happen at lower sound levels.

Have you tried a different electrical socket. It could be the case of the Amp not being able to draw enough current to make it sing at higher volumes.

That could be the reason why the Amp stutters at higher volumes in your rig and the problem was not replicated at the local tech's place

You could try turning off other devices in the room or house when you notice the amp acting up to see if it solves the problem

No, I did not try a different socket but I tried to connect my amp to an UPS. I deliberately switched off the main supply of UPS to make my amp run from back up power of UPS(assuming the output will be constant). But the problem still persisted. Can I trust my UPS power output in this regard?

I strongly suspect a mis-match ... your amplifier is under-powered to drive your speakers. Your HK AVR 4500's wattage is 55 watts @ 8 ohms (peak) and your speakers are 130 watts (peak). Moreover your speaker's sensitivity is also very low (88 db).

With this matching, listening at lower volumes will not cause any problem ... you can listen for hours and hours of music but when you try to increase to higher volumes the speakers will start demanding more power and since your amp is under-powered it is not able meet the demand and clipping occurs. Even though the KEF IQ5s amplifier Requirements mentions: 15-130W, low powered amps can be used only for low/moderate volume level. If you want to listen high volume on your KEFs you need a powerful amp (atleast 90-150 watts amplifiers).

Try two options:
1) Make sure your 'FRONT' speakers are set to 'LARGE' in the AVRs speaker config settings.
Get a pair of low powered speakers (may be from 75-100 watts with 8 ohms impedence) from any of your friends and check it with you AVR.

2) Try your IQ5s with some other AVR which is a bit more powerful (90-150 watts range).

I'm really sorry for not mentioning my setup. I have a pair of PSB Alpha SE powered with vintage Luxman lv-113. I'm not convinced this could be speaker mismatch because sound break occurs ocassionally and inspite of occurance it goes off after playing continuously for a while. It is due to this inconsistency I cannot determine the actual problem.

 

[sandeepmohan]

No, This problem does not happen at lower sound levels.

There you go. Clearly; the amplifier is being over driven. You will also notice that it will be running extremely hot if it has been clipping for some time. This is highly dangerous for the speaker system. I suggest a more power matched amplifier to the speakers impedance, sensitivity and power rating.

An alternate option to keen going with your existing amplifier is to turn down the bass, loudness or any other feature that increases bass.

 

[sandeepmohan]

But the problem still persisted. Can I trust my UPS power output in this regard?

This cannot have anything to do with your UPS. However; I would not route my stereo through a UPS as the current draw for spikes could be limited by the UPS and this could lead to clipping at peaks.

 

[madhurshankar]

There you go. Clearly; the amplifier is being over driven. You will also notice that it will be running extremely hot if it has been clipping for some time. This is highly dangerous for the speaker system. I suggest a more power matched amplifier to the speakers impedance, sensitivity and power rating.

An alternate option to keen going with your existing amplifier is to turn down the bass, loudness or any other feature that increases bass.

Hi Sandeep,
The sound was not too loud for sure, It was slightly above the normal hearing level(Volume dial was slightly above 9'0 clock). Anyway, I have my speakers connected to Speaker A outlet and subwoofer connected to Speaker B outlet. Will this be a contributing factor for this issue(Is my sub extracting more out of my amp)?

Alternately, I have a provision to connect my subwoofer to either Speaker A/Speaker B outlet and connect my speakers to high level output terminal of my subwoofer. Will this make any difference in reducing the amplifier stress?

Thanks,
Madhur

 

[hifipal4all]

I'm really sorry for not mentioning my setup. I have a pair of PSB Alpha SE powered with vintage Luxman lv-113. I'm not convinced this could be speaker mismatch because sound break occurs ocassionally and inspite of occurance it goes off after playing continuously for a while. It is due to this inconsistency I cannot determine the actual problem.

Try a different amplifier with your PSBs and try a different speakers with your amplifier. It is a simple way to confirm if there is a mis-match.

The sound was not too loud for sure, It was slightly above the normal hearing level(Volume dial was slightly above 9'0 clock). Anyway, I have my speakers connected to Speaker A outlet and subwoofer connected to Speaker B outlet. Will this be a contributing factor for this issue(Is my sub extracting more out of my amp)?

Quite possible. Disconnect the subwoofer and try listening at high volume level.

Alternately, I have a provision to connect my subwoofer to either Speaker A/Speaker B outlet and connect my speakers to high level output terminal of my subwoofer. Will this make any difference in reducing the amplifier stress?

This is method is better than connecting the subwoofer directly to speaker B. This method will filter out the low frequencies and pass only the mid/high frequencies to the PSBs. Comparatively, stress to the amp is less and the overall output will be more cleaner and musical.

 

[madhurshankar]

This is method is better than connecting the subwoofer directly to speaker B. This method will filter out the low frequencies and pass only the mid/high frequencies to the PSBs. Comparatively, stress to the amp is less and the overall output will be more cleaner and musical.

Thanks Hifi4allpal,
My issue got resolved upon connecting my speakers to high level output of my sub :yahoo:. Sorry for the delayed post.

Also, Thanks all for your suggestions hyeah:

Regards,
Madhur