checking PAM8403 noise strength. no sound. silent

lm4880 stereo amp :RK-297

Using LM386 with the differential circuit of op amp 741d.

NJM2073D stereo amp

triple LM386 :stereo amp

TDA7268 stereo amp : 1 chip for stereo

LMC555で変調テスト

3 tubes wireless-mic(no,90). D.I.Y : using p.c.b

cw training unit on FM radio .

melody IC SM6201-2L sound D.I.Y

TDA7267 stereo amp with D.I.Y supply

TDA7267 stereo amplifier D.I.Y

first testing about sm6201 melody IC

JF1OZL style .Emitter-follower-power-amplifier type2. RK-284v2 with AC supply.

JF1OZL style .Emitter-follower-power-amplifier　type2. RK-284v2

TDA7052 single amp ; frequency characteristic flat to 400kHz

melody ic um3512 , checking my p.c.b on may 10th

JF1OZL style .Emitter-follower-power-amplifier. test2. This model is RK-284.

D,I,Y. three tube wireless mic( one board wireless mic ) :testing at apr/30/2024

D,I,Y. three tube wireless mic( one board wireless mic ) :testing.

JF1OZL style .Emitter-follower-power-amplifier.

Emitter-follower-power-amplifier. JF1OZL style.

sepp amp d.i.y : Imitating chriskit p-35. A1359/C3422

twin 6EW6 radio ( RK-283 ) :d.i.y 2024/april/13

melody IC :SVM7993　sound

melody IC : HK322-6 sound

sepp amp d.i.y : Imitating chriskit p-35:max out put 125mW (9V supply) d.i.y

kp-12a checking audio freq response (no sound)

Searching for the optimal resistance value for osc strength. 22.00MHz

cascaded OP AMP + booster (2sa1394+2sc3422)