Core components: gold seal, field tube input, good audible single op amp OPA445BM, low frequency strength and treble extension are in place
Power supply voltage: ± 35-- ± 45v high voltage power supply (recommended ± 40v, OPA445BM without radiator, favorite temperature)
Circuit characteristics: DC servo circuit is adopted, input / output capacitance is eliminated, the midpoint is always below 0.5mV, and the sound is super transparent
Ultra-low noise: the noise is about 0.2mV, more than 110DB
Large dynamic, high level output: when ± 40v power supply, the effective value of the output audio reaches 25v
Size: 84 * 76mm
Magnification: 10 times, can increase the resistance of 18k on the board to increase the magnification
Recommended potentiometer: 50kA
Recommend low internal resistance, large dynamic, class A parallel regulated power supply board
Recommended transformer (use 2 AC36V in series)
OPA445BM parameters
Working voltage: ± 10V-± 45V; netizen destructive test to ± 60v, working normally, output Vp-p: 110v
Output current: ± 15mA, short circuit output 26mA
Distortion THD%: 0.00003
Common mode rejection ratio: 95DB
Voltage conversion speed: 15V / μs
Broadband gain product: 2MHZ
Input offset voltage: ± 1MV
Voltage noise density: 15nV / √Hz
The finished boards are all commissioned, tested, and sounded OK.