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Old 27th June 2018, 01:06 AM   #2901
Eric is offline Eric  United States
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Depending on output level of the cartridge you are using, you may need to degenerate the jFets in the first gain stage as well. My AudioTechnica 150MLX has 5.0mV output and even after fiddling with R14/R16, it was still overloading and distorting on some LPs. Increasing R21-R24 from 10R to ~22R reduced the gain of the first stage and removed the overload I was getting. I just lifted one leg of the original resistors and added another resistor to the empty hole and connected them in series. A quick jumper will return things back to the original state.
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Old 27th June 2018, 05:02 PM   #2902
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Quote:
Originally Posted by Eric View Post
Depending on output level of the cartridge you are using, you may need to degenerate the jFets in the first gain stage as well. My AudioTechnica 150MLX has 5.0mV output and even after fiddling with R14/R16, it was still overloading and distorting on some LPs. Increasing R21-R24 from 10R to ~22R reduced the gain of the first stage and removed the overload I was getting. I just lifted one leg of the original resistors and added another resistor to the empty hole and connected them in series. A quick jumper will return things back to the original state.
Reducing the first gain By increasing resistor values impairs noise performance. Bedides, the problem is in the second gain stage.
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Old 27th June 2018, 05:31 PM   #2903
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This is interesting to know, Jack. With a 5mV output MM cartridge, I was unable to avoid overload distortion through adjustments to the second gain stage alone. Perhaps I need to experiment further. Of course, the other solution is to get a moving coil cartridge as was intended
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Old 7th July 2018, 05:48 PM   #2904
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This is interesting to know, Jack. With a 5mV output MM cartridge, I was unable to avoid overload distortion through adjustments to the second gain stage alone. Perhaps I need to experiment further. Of course, the other solution is to get a moving coil cartridge as was intended
If you’re clever you can skip the passive RIAA and incorporate it in the second stage feedback loop.
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Old 8th July 2018, 03:21 AM   #2905
Eric is offline Eric  United States
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Sadly, I need to learn more before I consider myself to be clever...
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Old 9th July 2018, 12:48 AM   #2906
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Am I correct to assume that using a LPS will be better than a SMPS/wall wart?
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Old 9th July 2018, 12:57 AM   #2907
6L6 is online now 6L6  United States
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Perhaps...?

One thing is sure, a bipolar SMPS of the proper voltage will be a challenge to find.
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Old 12th July 2018, 03:24 AM   #2908
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One thing is sure, a bipolar SMPS of the proper voltage will be a challenge to find.

Perhaps I should stop searching for one then. LOL.
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Old 13th July 2018, 10:38 PM   #2909
jackinnj is offline jackinnj  United States
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Perhaps...?

One thing is sure, a bipolar SMPS of the proper voltage will be a challenge to find.
DK shows 52 (dual) +/-24V SMPS in stock.

Unfortunately, you'll need a bit more than that if you plan to use the LMxxx regulators on Wayne's boards.
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Old 13th July 2018, 11:05 PM   #2910
6L6 is online now 6L6  United States
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Yup. That's the issue.

I'd love to try a switcher feeding this, the newer ones really are getting quite good.
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