Krell amp out of phase

Heliac_swe

Heliac_swe

Member
A few months ago i bought a Krell Ksa100. According to the seller it has been for service just before i bought it. It took some days before i hooked it up, but i heard directly that something was wrong. I thougt i had swapped +/- on one speaker but i had not.

If i swap phase on one speaker the amp sounds fantastic, no hum or noise and it can run for hours. I believe it sounds a little better with the left side swapped but i could be wrong.

So my question is..could something been hooked up wrong when it was at service? Some wires inside thats been swapped? Where should i start to look..

I swap amps all the time so i know that my cables are allright...if put another amp in the rig the problem is gone.
 
I'm not saying it's the cause of your issue. But, my Krells take jumpers like this to short pins 1 and 3 of the xlr connectors when using the single ended inputs. I'm pretty sure this is standard for all Krell amplifiers. Check the manual to be sure.

krellshortingpins_zps7f1897e8.jpg
 
Ok, i will hook it back up after work and test. I cant find the manual for just my amp (KSA 100 EUR) but it seems like its pin 1 and 3 that should be togehther.

Another Krell manual says something about those pins.

1 Ground
2 Non-inverting
3 Inverting

But if i do the same thing on both channels im pretty sure it still will be out of phase..:(
 
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I agree, logic suggests there is something else wrong for one channel to be inverted.

I would get it in the hands of a competent tech with a good track record with Krell gear. It is certainly worth getting sorted out properly.
 
For myself its no big deal with having the speakercables crossed, but im thinkin about selling it so i want to be in order.

Maybe some of the tech gurus here on AK have some clue :)
 
For me, i would have to get it sorted out. At least to the extent of determining where the inversion is taking place. If it's simple, and at the input or output connections, i'd do it myself.

But, if i ruled out the simple, effectively suggesting that the inversion is taking place within the amplifier circuitry, i'd want a competent Krell expert to go thru my amp and see what else has been mucked with.

Whomever worked on this amp prior to your ownership is not qualified or competent to do so, don't let it go back there. Krells are worth fixing right.
 
I know a good tech guy, some miles away but..

At first i will try myself, it might be an easy solution like you say.

The amp is very clean inside, looks like new no dust. So i think it has been opened recently and at least cleaned...and maybe serviced if the seller dont lie.
 
bowtie427ss said:
For me, i would have to get it sorted out. At least to the extent of determining where the inversion is taking place. If it's simple, and at the input or output connections, i'd do it myself.
Click to expand...

I don't know about this amp, but for most amps it would be impossible to invert only one channel at the input connections. Usually the shield between the two channels is common so if one channel is inverted then that channel is essentially shorted to ground via the shield for the other channel.
 
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Just left field - but the tech may have switched the inverting and non inverting input wires on one channel. YMMV
 
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sregor said:
Just left field - but the tech may have switched the inverting and non inverting input wires on one channel. YMMV
Click to expand...

Please explain that.. :)

I remove the top plate last night, not much space but its easy to see the wiring inside.

And damn...this is well built.
 
My thoughts exactly!

sregor said:
Just left field - but the tech may have switched the inverting and non inverting input wires on one channel. YMMV
Click to expand...

If the unit has balanced connections with XLR, there is a good possibility that the polarity of one channel was accidentally swapped (maybe not at the XLR itself but maybe at the PCB end of a cable leading to the XLR?) :scratch2:

Mark T. :music:
 
Yes it has balanced connections. The xlr-jacks looks correct from what i can see. Down on the pcb i cant see without taking it apart.
 
Thanks. Just spoke to him. There is a big chance that this is an internal wiring problem he said.

I found this pic and my amp has the same driver boards.

These boards are mounted along the sides of the amp with the eight caps pointing at the front of the amp. As you can see the signal wires is placed the same on both cards. But when putting the boards inside the amp the red wire will be in top position on one side, and in bottom position on the other side. Right?

In my amp the white wire is on top on both sides. Could this be the solution?
 

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I just wonder if i can damage anything by changing place on the white/red signal wire? The black in the middle is ground i suppose.

Anyone?
 
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