It's as if some rf is removed making the sound cleaner but it's subtle.Any body else notice this?
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I have the X2.5 which is similar to the X1. From my experience, there is very little difference (if at all) between dimming the lights and leaving it on. Perhaps psychologically my eyes get to relax a little more instead of staring straight at a bright florescent display. Without any lighting, it gives me the impression of a slightly quiet and blacker background. However to answer your question the digital circuits are seperated and isolated from the analog supply. The display circuitry would be isolated from injecting any noises back into the pre-amp. Of course like everything else, any energy that is taken is still energy and so I wouldn't be surprised if the sound does improve with it off. The X1 has an even more isolated circuitry on all levels.
Yet it may be better to ask Nelson Pass or any others out there in the Pass forum:
If you noticed a difference, that is a bonus. I don't believe the lighting option is for sonic purposes but just a convenient way like many other designs to give a choice for those who may be distracted by a brighter display or who like to have different display levels. The Noritake display used in all the Pass amps is designed to have brightness control automatically. The Noritake company if I can recall correctly are the inventors of the vacuum flourescent display and basically have many products out there for the PC,gaming, and electronic displays. You can check their site out at : http://noritake-elec.com/
Hope the above helps.
I hear a slight edge off the top removed with the dimmer down. I know the digital circuitry is seperate from the analogue and the difference I hear is very subtle yet it is there. Not enough to have me dimming down the display all the time however. The difference is slight. A very touch more snap in the highs.
Sonically, I think the X2.5 and the X-1 are outstanding pre-amps at least with my line conditioners attached to them.
What I do not care for is their somewhat crude remote control interface and the lack of incremental attenuation for fine-tuning volume levels.
But still outstanding products and company.
They are near identical in sonics. However, I enjoy the egonomics, the lights, and the overall visual appeal of the Chapter quite a bit more. It is one cool looking component.
But I certainly do not want to take anything away from the performance and simplicity in design of the X2.5 and X1 preamps.
I have no experience with the X1 Preamp, but as a long-time ham radio operator and having built some clocks and digital displays, and working a lot with computers (display drivers are basically a small compter of sorts), I would suggest that in a less than perfect design the digital display drivers could generate noise or "hash" that could get into the D and A circuits at some point. There are also small caps around the chip or chips that make up the display driver hardware that could be missing (factory defect) or have failed and now be letting some noise out that otherwise wouldn't be a problem.
Hence I'm not surprised that you are hearing the display in the preamp output. If you can live without the display while doing serious listening, I would turn it off.
The difference I may be hearing with the display off may warrant it being dimmed off if doing some extremely careful critical listening.
I still say there is a difference psychoachioustical or not. I notice a slight touch of noise dissappear like just the very edge of a snap of a cymbol. With the disply on the snap has more bite but with the disply off it is a tad more natural. That being said, it wouldn't be the first time my mind played tricks on me, but I know what I hear.
The difference isn't worthy of switching the display on and off.
I leave it on to see the volume and know which function I'm on. I love my X1.