Berning ZH270 help

Thanks for the hint Tubegroover, actually Iàve already contacted Allan for the that. Living in Italy doesn help this.
Anyway I ve found what I consider the best option for cables: Sublima an italian manufacturer, He's cables are mervelous to preserve harmonic richness and correct timbre reproduction. So sooner or later I'll have my ZH270 cabled by Alessandro Cereda of Sublima.
Another thing I'm thinking to is to get rid of the potentiometer an switches. A friend of mine has done it with the Berning Siegrfried I sold him and the results were quite big.

By the way, the noise on the left channel came out again, I definetely need to service it. Even if my suspect is onot on components but maybe a soldering point no more good or a signal path on the audio board with breaks.

Paolo

Paolo.
Switch the input interconnects to the amp from left to right and right to left, see if the noise stays in the same channel.

The ZH-270 is different from the Siegfried, as is has different feedback settings, if you remove the pot, then you will have problems with sensitivity in low and maybe medium feedback, you will most likely hear pre-amp noise.

You might be able to do it if you are running a CD player direct but there are few pre-amps made, especially tubes ones that the ZH-270 will not pick up the noise without having to reduce the sensitivity of the input to the amp, the only other alternative is to find the exact resistance needed to which feedback you use and put a fixed resistor.

Thanks again Allan,
The noise on left channel appears even without anything connected to input, definetely not dependent on pre o input cables.
The way it disapear it make me thing about a cap that cannot full charge properly, with a quick turn off/on it probably doesn't discharge much and get the current peak again to force him charging full. Just an idea.

Yea I agree, it is not easy to mod ZH270 without loose its great flexibility. In real I seldom use other tha 12dB feedback, it is the setting better delivering bass performance and best highs extension (I've Tannoy monitor golds 15" drivers, and dumping is a matter of quality here even at 94dB efficency).

The 25K pot in the signal path does indeed effect the quality of sound. Maybe inprove it with a switch matrix of very good carbon resistors.