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K2: Ch 1 overloads w/same input as Ch 2


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#1 noah Katz

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Posted 13 August 2005 - 05:06 PM

Hi,

With both a Y'ed input from my receiver sub output, and also with a single input using the K2's Y function, the Channel 1 input IOC and clip input lights illuminate with bass-heavy transients (dino footstomps and so forth), while the Channel 2 lights do not.

I just replaced my JBL 2226 subwoofer drivers with Avalanche 12's and re-ran the EQ on my HK635 receiver. The Av 12's are less efficient, which would presumaby result in higher drive levels to the sub amp from the receiver, but that still doesn't explain why the K2 channels behave differently.

I don't hear the clipping, but then there's a lot of other sound happening too, and I don't want to fry my new drivers.

Thanks

Noah

#2 noah Katz

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Posted 14 August 2005 - 03:57 PM

Something else occurred to me - is it possible to overload the  K2's input stage before driving the output to clipping?

During setup my receiver sends sweeps to all the speakers; at the K2's initial front panel level settings, the subwoofer sweep was making something in the room vibrate.

I turned the levels down about a quarter turn so this wouldn't happen, figuring the receiver would compensate. The sub level after setup was +5 dB.

#3 DGlass

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Posted 15 August 2005 - 08:49 AM

If the clip light is flashing it is indicating distortion has become audible in the amplifier output.
If you could provide a little more information it would greatly help to decide if it is the amp or a system issue.

Was the amplifier acting the same way with the JBL sub woofers?

If you change inputs does the Clip light change to the other channel?

If you swap loads to the other output channel does the clip light follow the load?

What position is the amplifiers Bridge-Mono switch in?

Is the IOC light also flashing?

Are both Input sensitivity switches of the amplifier in the same position?
What are their settings?
When in the 1.4v setting the input voltage to get full output with the attenuators turned all the way up is 1.4 volts. If you can put a tone or Pink Noise on both channels and slowly ramp up the drive voltage both channels of the amp should clip at about the same time.

You say you turned down the amplifiers because something in the room was vibrating and the speakers are less efficient. Itís possible the system is trying to compensate for the speakers lower efficiency and the amplifier being turned down by raising the drive level to the amp to achieve system balance. You may be clipping the input to the amp. If you switch inputs and the clip light follows the input source then there would be an imbalance in the signal source.

#4 noah Katz

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Posted 15 August 2005 - 11:51 PM

Hi David,

Sorry, I should have included more info.

> Was the amplifier acting the same way with the JBL sub woofers?

No

> If you change inputs does the Clip light change to the other channel?

Both channels received the same signal two different ways - Y'ing from the sub output, and using a single input with the K2's Y input function.

> If you swap loads to the other output channel does the clip light follow the load?

see above

> What position is the amplifiers Bridge-Mono switch in?

"out"

> Is the IOC light also flashing?

yes

> Are both Input sensitivity switches of the amplifier in the same position?
What are their settings?

yes; 1.4 V

> If you can put a tone or Pink Noise on both channels and slowly ramp up the drive voltage both channels of the amp should clip at about the same time.

The Ch 1 IOC and clip lights illuminate with transients, the Ch2 lights don't turn on at all

> If you switch inputs and the clip light follows the input source then there would be an imbalance in the signal source.

Per above, the signal source is the same for both channels.

Perhaps I can get the clipping to stop by fussing with input/output levels despite there being an imbalance that shouldn't be there.

If not, can you hazard a guess as to the repair cost?

Thanks

Noah

#5 DGlass

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Posted 16 August 2005 - 08:22 AM

QUOTE(noah Katz @ Aug 15 2005, 11:51 PM)
Hi David,

Sorry, I should have included more info.

> Was the amplifier acting the same way with the JBL sub woofers?

No

> If you change inputs does the Clip light change to the other channel?

Both channels received the same signal two different ways - Y'ing from the sub output, and using a single input with the K2's Y input function.

> If you swap loads to the other output channel does the clip light follow the load?

see above

> What position is the amplifiers Bridge-Mono switch in?

"out"

> Is the IOC light also flashing?

yes

> Are both Input sensitivity switches of the amplifier in the same position?
What are their settings?

yes; 1.4 V

> If you can put a tone or Pink Noise on both channels and slowly ramp up the drive voltage both channels of the amp should clip at about the same time.

The Ch 1 IOC and clip lights illuminate with transients, the Ch2 lights don't turn on at all

> If you switch inputs and the clip light follows the input source then there would be an imbalance in the signal source.

Per above, the signal source is the same for both channels.

Perhaps I can get the clipping to stop by fussing with input/output levels despite there being an imbalance that shouldn't be there.

If not, can you hazard a guess as to the repair cost?

Thanks

Noah
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If you swap the speakers from one side to the other does the problem go to the other side? This will tell if it is load (speaker) related or not since you say it wasn't happening with the JBL Subs.

If the amp is under three years old than it would be covered under warranty if it is older our service rate is $70/hr plus parts. If you would like to send it in for service a Service Return Authorization (SRA) can be obtained at: http://www.crownaudio.com/support/factserv.htm