PSU for High end audio without electrolytic capacitors
Electrolytic capacitors are constant part of power supply of audio devices, but in terms of sound he does not bring anything good, dispersion of sound quality-type of electrolytic capacitor is very large. Sonically the best types of electrolytic caps are Nichicon KZ, FG, Panasonic Pureism, Black Gate FK, NX, Elna Cerafine, Silmic II, Silmic,but the attempt to eliminate from PSU electrolytic capacitors was very successful, instead is used “electronic capacitor” (right side of the circuit).
All NFB regulators have inductive output impedance, placing electrolytic capacitor especially low-esr types creates a resonanses in output impedance (if the is yet a film or ceramic capacitor we will have more and stronger resonances). Impulse response to change the load current especially with low noise regs (M5230, M5290 etc) is very bad (one solution to this problem is use after regulator CRC filter,but it has its drawbacks), and output impedance and noise is a function of load current, as load changes noise and output impedance will be correlated with load changes (correlated to our music). Proposed schematic completely eliminates all problems with regulators and capacitors, and have stable resistive output impedance at frequencies up to 500-1000Khz (then the capacitive). Stability of the output impedance at audio frequencies is a very important thing for sound quality and tonal balance.
Scheme is shown in Figure 1, it is global negative feedback free electronic substitutes, that has a low and stable impedance 0,1…0,2Ohm (equivalent to cap 40000u) in the band to megahertz shunting NP0 0,1 microfarads Murata GRM31 in close to chips, it completely detach regulator (317\337) from load, therefore we have the ideal transient response when load “changes”, and dont have noise and output impedance modulation. Output capacitors 0.1-10u SMD NP0/X7R is needed for HF bypass (>1Mhz), caps on 317/337 out (not less than 1u) is needed for 317/337 stability. R1-C3, R9-C7 forms LPF that eliminates HF noise produced by switching of diodes working on capacitor filter.
Calculation of this schematic is not difficult, according to the desired output voltage and maximum output current calculate values of resistors R4, R6 and R2, R10, respectively, from the formulas below
R4=240*(Uout-Ueb) / 1.25
R2=(1,25-Ueb) / ((0.3/Uout)+Iload)
where Uout-output voltage V, Ueb-emitter-base voltage VT1, VT4 V, Iload- load current А.
This structure of regulator-”electronic capacitor”(follower) provides in a comparison with the best series audio electrolytic capacitors significantly better results.
Original article is here
“Directly or indirectly, all questions connected with this subject must come for decision to the ear, as the organ of hearing; and from it there can be no appeal.” Lord Rayleigh