What cmot the mechanical dimensions you used to make the PCB fit so well? Great job JDS Labs! Add to watch pcn Add to wish list. We specialize in fun and easy to use electronic gadgets.
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Main feature is that the new PCB fits exactly to the classic Altoids tin-can. This new CMoy incorporates moreover bass-boost circuit and constant current charger for 9V battery. C2 is coupling capacitor. R2 defines the input impedance of opamp. R3 and R4 define the gain of the amplifier 5x in this case. Rb and Cb form bass-boost circuit. These components increase the gain for low frequencies. For the low frequencies the gain is By increasing the Rb resistors you can increase the gain for low frequencies and vice verse.
You can decrease the cutting frequency by increasing the Cb capacitors. Bass-boost can be deactivated by shorting out Rb resistors. R5 is optional, but to avoid some bouncing at the output the value should be around 22 ohms. V1 is a Rail Splitter which creates virtual ground. C1 is high quality blocking capacitor with low ESR. Resistor R1 limits the current through LED. The value should be modify according the type of LED. D2 limits the maximum voltage in the input to 12V.
U2 together with resistor R0 create constant current source for charging the 9V battery. In my case the R0 has value 47 ohms and then the current is around 25mA. Cin is tantalum blocking capacitor for U2. D1 is Schottky diode for avoiding any damage when the voltage with opposite polarity is connected. Realization: I designed the PCB with two rounded corners. The PCB fits exactly to the Altoids tin see pictures below.
On the PCB are also nice pictures of input jack and headphones. The resistors and diodes must be assembled vertically to reduce occupied space. Assembly diagram top side.
CMoy Headphone Amp PCB