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Claudio Hi-end Phono        
 1  st , 2012 - working in progress ......


This project born to create a good and simple phono preamplifier for my friend Claudio to connect to the TACT 2.2x digital preamplifier with dynamic room correction.
The original design by Walter G. Jung, presented on AES and on OPA606 datasheet, has been implemented with some little changes.
It use the TI Burr-Brown ultra-low noise, high-precision monolithic operational amplifiers OPA37 and OPA606.
Any resistor in the schematic has been  replaced with a parallel for two or tree Vishay MRS25 1% metal resistors to match the right value and to reduce the parasitic inductance, all the RIAA capacitors are Vishay MKP1837 100V 0.1uF 1% (cod. MKP1837-410-011 - cod.  RS166-6487).
To get a very low noise the power supply use a virtual battery operation, invendted by Technics, and a virtual ground configuration.
There is no electrolytic capacitors on the signal path and in the power supply after the regulator has been used 15uF 250V MKP Solen.
The output capacitors are 2.2uF 250V MKP Solen bypassed by a 0.22uF Audyn Cap. PLUS.

values   2x totale err %   3x totale err %
49.9   100 50 0.20        
2490   4870 2435 -2.21   7500 2500 0.40
47000   97600 48800 3.83   140000 46666.67 -0.71
7320   14700 7350 0.41   22000 7333.333 0.18
1050   2100 1050 0.00        
200   402 201 0.50        
3740   7320 3660 -2.14   11300 3766.667 0.71
50000   100000 50000 0.00        

The virtual battery has been implemented using the IRF620 mosfet but any other model can be used without problems.
For the virtual ground I have used a strong solution TLE2426CLP (TO92) followed by a BUF634T (TO220-5pin).