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Biscuit

Possible Khorn Wiring Issue - Please advise.

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My father bought Khorns as a second owner 2.5 years ago and was told they were 2 years old.  So I think they should be in the 2014 range for age, give or take a year or two. He bought a new generation McIntosh 275 tube amplifier and it would go into a fault protection if he turned it up too loud.

 

Given his level of listening is lower than mine, and they didn't actually sound more than ~ 100db sound levels, I thought that something was probably wrong with the 275. Fast foward 2 years and after a few more faults at levels that I would not consider super loud, it blew a channel.  Right channel stopped working. The unit was still under warranty and went to get repaired for free from McIntosh. Unit comes back, sounds great.  He turns it up again, and it blows out.  Best Buy Magnolia says, sorry, we'll order you a new one. That one should come Thursday.

 

It got me to wondering if perhaps the 3 speakers on the Khorn weren't hooked up or bridged correctly for single amplification.  I had him take the following pics, to see if one of you could verify that they were correct or incorrect. Serial number too.

 

Thanks for the help. I would hate to have him lose another 275 for wiring his Khorns wrong!  The input comes in on LF IN from the Amp via a bananna plug.

 

 

 

 

 

 

 

2019-08-05 (1).jpg

2019-08-05 (2).jpg

2019-08-05.jpg

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It is hard to tell from the pictures. What one would be worried about is if the "plus" was seeing the "minus". If that was the case, then the amp would have choked immediately. Did you get a more specific diagnosis from the technicians?

 

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Posted (edited)

I was able to finally find this:  https://f072605def1c9a5ef179-a0bc3fbf1884fc0965506ae2b946e1cd.ssl.cf2.rackcdn.com/product-manuals/Klipschorn-2019_Manual_p04.pdf

Looks like slightly different version of posts, where they weren't aligned on the same horizontal.  But...it looks like single ampflications needs to come in on the HF in, not LF in?

 

That shouldn't matter right?   They are bridged.

Edited by Biscuit

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24 minutes ago, PrestonTom said:

It is hard to tell from the pictures. What one would be worried about is if the "plus" was seeing the "minus". If that was the case, then the amp would have choked immediately. Did you get a more specific diagnosis from the technicians?

 

I'll check.

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When using the jumpers for LF and HF input then which ones you connect the amplifier to doesn’t matter because they would be in parallel electrically speaking. 

 

Which version of the MC275 does he have..?

 

It has power sentry monitors so even if he has a shorted speaker cable its not supposed to damage the amplifier. 

 

I would suggest you inspect the speaker wires running from amplifier connection to the speakers for any loose strands of wire touching the wrong terminal or possible pinched or damaged insulation which might also lead to a somewhat resistive short (ie:not a dead short which would cause an instant shutdown) which could lead to premature shutdowns as volume is raised as you have described. 

 

miketn

 

 

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38 minutes ago, mikebse2a3 said:

When using the jumpers for LF and HF input then which ones you connect the amplifier to doesn’t matter because they would be in parallel electrically speaking. 

 

Which version of the MC275 does he have..?

 

 

It is the new one re-leased 3-4 years ago.

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I agree with the above comments, that the wire connections and the jumper wires in your pictures look correct. 

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I would strongly suggest you use the 4 ohm output terminals on the McIntosh.  The K-Horn goes down to that impedance in the bass and using 8 ohm or 16 ohm output terminals could very well cause the protection circuit to trip.

 

WMcD

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13 minutes ago, WMcD said:

 

 

I would strongly suggest you use the 4 ohm output terminals on the McIntosh.  The K-Horn goes down to that impedance in the bass and using 8 ohm or 16 ohm output terminals could very well cause the protection circuit to trip.

 

WMcD

 

Thanks WMcD.  Can other Khorn owners chime in with whether they hook them up in 4 ohm?

 

 

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Let me add that using the 4 ohm tap will reduce the output voltage.  But you've got power to spare.  It will reduce the amps electrical noise output and reduce distortion (very likely  Addition by Edit: See below quote from Stereophile review).  It certainly will not hurt anything.

 

My guess is that the power trip circuit is a new addition to the 275 series and thus you might well be a pioneer in this area.  It is probably true that other folk using 275's without the power trip circuit have used the 8 ohm tap successfully.

 

Maybe you can see what there is to be seen on a McIntosh forum.

 

Best,

 

WMcD

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These graphs show that the distortion remains well below 0.1% as long as the nominal tap value is equal to or less than the load impedance. (Ignore in some of these traces the sawtooth effects, which are due to the Audio Precision's gain-ranging switching.) But when the load impedance is significantly below the tap value, the distortion quickly rises above 0.1%, even at low powers. 
Read more at https://www.stereophile.com/content/mcintosh-mc275-power-amplifier-measurements#UlTw3WpRfhM11jft.99

 

Addition by Edit:  Ann Landers famously said: "All generalization are false -- including this one."  We don't have data on all amps. 

 

Applying what Stereophile reports, use of the 4 ohm tap gives the best performance as far as distortion because the actual impedance of the K-horn does go down to about 4 ohms and is certainly below 8 ohms in ranges.  This is true of many other Klipsch speakers even though they claim to be "8 ohm compatible."  [Get the yellow button, please.]

 

So I'll generalize and recommend that the 4 ohm tap be used with all speakers unless you have some compelling reason to do otherwise.

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