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In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage

Post Subject: Beats and pieces.Posted by Romy the Cat on: 11/16/2011

rogier wrote:
It could be dirt (dust) in the aircaps..

Hm, a good point, I never consider how dust in aircaps might sound. I presume that it will be no difference as dialectic is air anyhow, it is beside the point that there. Still, the sonic difference between “clean” air caps and dirty is certainly not know to me. Nevertheless, I do not think that it is due to dirt in air caps as it would be developing slowly. My problem appears all of the sudden. Well, it might be a single piece of dirt all of the sudden shorted two aircaps sheets? In this care it would be juts drop in capacitance with change of RIAA cure. Sure, it is not hard to blow the aircaps. Juts to be on the save side I will run tonight inverted RIAA sweep and see if I am still flat. Subjectively I do not recognize any in frequency response in the records I know and I am very sensitive to it. The anti-RIAA sweep sill would be a good indicator…

Markus wrote:
... but did you clean your needles? And does this happen on all records or just specific ones?

I always clean needles. I even removed the headshells and inspected the needle and cantilevers as I thought that some metal dust was somehow attacked in my room and jammed suspension. Nope it was not the case and my cartridges are fine. The effect is happening on all records.

N-set wrote:
Yes, I understand all your points. I don't think I have any ground loops though--I tried your ground bypass technique and it didn't change anything so far.

Try to short the signal to ground at different points of the corrector and see how noise disappears. Literally go over the circuit from front to the end before and after each element and see if shoring it this specific location affects noise. If the specific location cares DC then use cap to short the signal. Does the corrector have noise without the transformer? If not then you need to find a proper interface between transformer and corrector. Most common problem (if your transformer is properly shielded that most likely not be the case) is that people use dual mono transformer with stereo correctors. I think it is what you do, I do it as well. So, to deal with it you need to connect grounds of your transformer together. Where to connect them and how to connect them to corrector is a big subject but for beginning to short the grounds of RCAs would be a good start. I do not know what Pieter use for shielding if it is one layer of mu-metal then it is not enough. BTW, a transformer has to have some room in the shielding can and some empty space around itself. The shielding layer must be separated by air and do not lay over each other. Anyhow, I am sure you will find the problems. It is impossible to remotely debug ham….

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