Technical specifications
Supply voltage: 10-14 V stab.
Supply currents: 20 mA
Audio input: impedance 20 kOhm, optional preemphasis
Output voltage: 0,4 V rms
Dynamic range: >50 dB
Parts list
Resistors:
R1 - 68 k
R2 - 22 k
R3 - 180 k
R4 - 10 M
R5 - 10 k
R6 - 47 R
R7 - 240 k
R8 - 1,5 k
R9 - 820 R
Capacitors:
C1 - 100 p (ceramic)
C2 - 1 n (plastic)
C3, C6, C12 - 100 n (ceramic)
C4, C11, C13 - 100 u (electrolytic)
C5 - 0,33 u (tantalum)
C7, C8 - 10 u (electrolytic)
C9 - 220 n (plastic)
C10 - 47 n (ceramic)
C14 - 470 n (plastic)
Misc.:
T1 - BF245C
T2 - BC556B, BC307
IC1 - LM386
Don't place the C8 if you don't want to use whole dynamic range. Then you will get much better S/N ratio.
You may adjust release time by C7 and R4 values.
PCB layout
Original from : http://pira.cz/enlter.htm