[Photo] Dynamic audio preamplifier

This is a 3 stage discrete amplifier with gain control. AlternaTIve transistors such as BC109C, BC548, BC549, BC549C may be used with little change in performance. The first stage built around Q1 operates in common base configuraTIon. This is unusuable in audio stages, but in this case, it allows Q1 to operate at low noise levels and improves overall signal to noise raTIo. Q2 and Q3 form a direct coupled amplifier, similar to my earlier mic preamp.
Input and Output Impedance:
As the signal from a dynamic microphone is low typically much less than 10mV, then there is little to be gained by setTIng the collector voltage voltage of Q1 to half the supply voltage. In power amplifiers, biasing to half the supply voltage allows for maximum voltage swing, and highest overload margin, but where input levels are low, any value in the linear part of the operating characteristics will suffice. Here Q1 operates with a collector voltage of 2.4V and a low collector current of around 200uA. This low collector current ensures low noise performance and also raises the input impedance of the stage to around 400 ohms. This is a good match for any dynamic microphone having an impedances between 200 and 600 ohms.

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USB Charger Socket

Function description

The socket is ordinary converter,with two output 5V2A power USB power supply at the same time,can be very convenient in use electrical appliances and recharge the equipment at the same time,such as digital products like Iphone Ipad,MP3,MP4 etc.The charge apply to full range of international AC output,no-load power consumption less than 0.3W,with short circuit,overload,over-voltage protection,can be convenient for your life and save more energy


Timer Control Time Adgustment

1.Press the power switch 1 time,the 1HOUR LED will light on.The Timer into ON mode,USB and control socket output ON .

2.Continuously press the power switch the LED light on,the Countdown mode and LED light on will cycle change from 1HR,2HR,4HR,6HR,8HR,10HR.

3.Choose you need countdown time mode,the mode LED will lighto on,start countdown until countdown time finish,the control output and USB change to OFF

4.Then the countdown is start,The Time indicate LED will from high to low auto change until Countdown finish off.

Failure analysis:

1.check whether the power supply connection is good

2.check whether the USB cable is loosen

Warning Note:

1.Use indoor and dry location ONLY

2.The load max does not exceed 15A 3600W

3.This product does not convert voltage please do not miss use DO NOT exceed the maximum loading of 3600 Watts 15A

4.Always have earth connection for safety reason

5.If in doubt please consult with a qualified electrician

USB Charger Socket, Fast Charge USB Wall Socket, USB Plug Socket, USB Socket Charger, Socket USB charger

NINGBO COWELL ELECTRONICS & TECHNOLOGY CO., LTD , https://www.cowellsockets.com