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Re: Best phono stage $2000 - $3500

"But, we also get a dominating hum (50 Hz and harmonics). Anyone knowing any idea why......?"

Probably a grounding issue. I'm not familiar with your phono stage, but if I understand correctly you have LL9206's built in. I recently built some LL9206's into a very small aluminum box with the inputs and outputs wired to RCA jacks, and this was connected between my turntable and preamp.

I tried various methods of grounding:

1. grounded primary
2. grounded secondary
3. ungrounded primary & secondary

and for each method above I also tried different ways of connecting the turntable arm ground to the SUT ground and to the preamp (built-in phono stage) ground such as:

a. turntable ground to SUT ground, SUT ground to preamp ground
b. turntable ground not connected, SUT ground to preamp ground
c. turntable ground to preamp ground, SUT ground to preamp ground
d. turntable ground to preamp ground, SUT ground disconnected

And I also tried the SUT's with:

i. primary isolated from secondary, and
ii. primary commoned to secondary

The combination that produced the best sound and which was also dead quiet - no hum even with my preamp volume at 9/10 was:
3. ungrounded primary & secondary, c. turntable ground to preamp ground, SUT ground to preamp ground, and ii. primary commoned to secondary.

Now the combination that worked for me may not work for you, as the correct connections will be dependent on the circuits in your turntable and phono stage, such as how the commons and grounds are connected. Hopefully with built-in SUT's it will still be easy enough to get in there and try some different connections.

I definitely agree with going to a SUT ratio of 1:20 and loading at 47K to increase the gain, provided 117.5 ohms is an optimum load for your cartridge. You could try shunting the phono input with an appropriately sized resistor to load your cartridge at 82.5 ohms (as it was previously loaded). Whichever load sounds better to you is the best.


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