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Rotel RIAA Module
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Old 12th July 2018, 07:54 PM   #11
analog_sa is offline analog_sa  Europe
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Rotel RIAA Module
Quite a few low-offset opamps will allow dc coupling at output. As for the MKS caps beating all lytics i am not convinced at all. Perhaps they will be an improvement over the stock caps.
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Old 12th July 2018, 08:15 PM   #12
schillg11 is offline schillg11  Germany
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I didn't argue , that they will beat all electrolytics. There will be a sonic improvement against the orginal equipped one and longterm stability will also be improved. A further improvement may be replacing the 1206 resistors with Mini-melf resistors, as suzyj showed in her investigations (better THD).


@ merlin el mago
The lowest voltage available is 50V and the maximum capacity is 10F with pin spacing of 5mm (acc. https://www.wima.de/wp-content/uploa...WIMA_MKS_2.pdf).

Last edited by schillg11; 12th July 2018 at 08:21 PM. Reason: adding sth
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Old 12th July 2018, 09:25 PM   #13
Salas is offline Salas  Greece
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Maybe try with Nichicon ES bipolar electrolytics first. In terms of distortion these caps are extremely clean.
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Old 16th July 2018, 04:34 PM   #14
seeyou is offline seeyou  Greece
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Ok here is what I did with the phono module:

I drilled some holes for the leads of the WIMA 0.1uf

1.jpg

2.jpg

Put the opamps (OPA827) and the caps in place

3.jpg

4.jpg

5.jpg
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Old 16th July 2018, 04:54 PM   #15
seeyou is offline seeyou  Greece
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Bipolar Output caps C451 & C452 changed to Elna Silmic II in following way:

Each cap should be 4.7uf. I soldered 2x 10uf back to back (+-|-+).
The resulting cap measured 4.8uf. I would keep it if you think it is ok this way

6.jpg


Thank you very much!
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Old 18th July 2018, 02:02 PM   #16
sgrossklass is offline sgrossklass  Germany
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Is there any particular reason why nobody has pointed out the main shortcomings of this circuit yet?
1. Input impedance is nonstandard, at ~68k || 250p. Check requirements of cartridge used and capacitance of existing cabling. This might work well with a Shure M97xE but most any AT cartridge is going to be a bit unhappy.
2. Feedback network impedance has been kept high so that capacitor values could remain small. Noise levels thus are, in all likelihood, not as low as they could be. (A 2k2 series resistor in the input CRC filter is not helping matters either.) The OPA827 may help a bit but I wouldn't expect a night and day difference either. Improving upon an NE5534 (especially 5534A) in a phono pre application is not a trivial task.

Last edited by sgrossklass; 18th July 2018 at 02:06 PM.
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Old 18th July 2018, 10:57 PM   #17
seeyou is offline seeyou  Greece
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So what should be done?
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