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KEF Ref 107 KUBE forces my power amp close.

I have bought a KEF Ref 107-1 in a very very good condition last month. Then I bought a SS power amp (Audionet Amp 1) and drive it from preamp out of my Primare I30 SS integrated amplifier. Everything was OK and also I was using KUBE without any problem. Then I decided to buy a tube preamp and problems started. When I connect whatever tube preamp then my power amp gives a strange noise and closes itself. From the signals, it says "high frequency oscillation error".

I tried many things and the only solution is NOT to connect KUBE. Without KUBE the system works flawlessly but if I connect the KUBE into the system then power amp closes itself again. I also tried many different tube preamps but the problem didn't change. As I said my SS integrated amp's pre out doesn't cause such a problem and I use both KUBE and my power amp with pleasure.

I'll greatly appreciate if you can say why KUBE might cause this error and what I should do to use KUBE without problem.

Thanks and Regards
airnotas
8 responses Add your response
airnotas OP
3 posts
 
I think, as many other people do, tube preamps sounds better and sweeter than SS preamps. That's why I insist on the tube gadget. I've found a very clean CJ premier 17 LS2 with NOS tubes and I don't want to miss it. Finally I omitted the KUBE from the pre-power chain and that's just fine.

My technician who is also a very good music lover and audiophile, offered to put a capacitor in the KUBE and claims that it will resolve the issue but I didn't prefer this way.

Thanks for all your attention for the issue.
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dbphd
1,628 posts
 
That the KUBE works fine with the SS preamp and the tube preamp works fine without the KUBE suggests some sort of interaction, so I doubt checking either out separately will solve the problem. There are a number of fine SS preamps to choose among, so why fight the problem?

db
brf
1,715 posts
 
You need to take the KUBE to someone who can test it for you to ensure that it is working properly.
airnotas OP
3 posts
 
I tried the tape monitor loop and btw source & preamp but both ways failed and power amp closed.
brf
1,715 posts
 
You can also try the kube between your source and preamp, or as previously mentioned in the tape loop. Either way the kube will be buffered the output section of the pre.
airnotas OP
3 posts
 
Nice idea. I'll try it. Thanks.
brf
1,715 posts
 
Have you tried placing the KUBE in the tape monitor loop?
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dbphd
1,628 posts
 
I suspect the problem is a distortion generated by tubes. When we tested tubes, we used to thumb them to check for ringing, a common failing of tubes. But that was in the late 50s when I was a grad student.

I'd use a good solid state preamp or processor, unless you need the warmth distortion tubes can provide. According to the KEF manual, the 107 KUBE is integral to the design of the 107 and required for accurate sound. It provides active equalization for the crossover transitions that a passive R/C network would provide at the cost of lower efficiency. You can bypass the HF and LF tweaking controls, as I do with my 107/2.

db
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