Guitar to AV Receiver Interface

Have you ever wanted to amplify your electric guitar by plugging into an AV Receiver (home stereo)? Ever tried rigging up a 1/4" mono instrument plug to RCA patch cable? If so you most likely were disappointed when it didn't work. Most modern consumer grade AV equipment only has output power amplification which has to be fed with Line-Level Pre-Amplified signals. Musical instruments with passive pick-ups have a high impedance low signal level output that has to to be gradually stepped up with pre-amplification.

Article Features:
Simple two transistor stage pre-amplifier circuit, with a high impedance input stage suitable for musical instruments with passive pick-ups and an output stage with enough signal level to feed AV equipment. A brief description of the processes I used to fabricate the clear acrylic case I made. The input stage of this amplifier circuit is a Common Collector amplifier which has high input impedance, low output impedance, and high current gain. The output stage is a Common Emitter amplifier which has medium input and output impedance, and high power gain. The input and output is decoupled from the 3V DC supply power by C1, C2 & C3, R1 & R3 control the base current of Q1 & Q2, and R2 & R4 control the output current of each transistor stage respectively.

I used point-to-point construction for this circuit, however it could be built on a PC board if desired. I used aluminum duct tape to form power rails on the inside of the acrylic case. Since the tape can't be soldered I used small pieces of tape to fasten the connection points to the components. It was challenging to make reliable connections with this method. Alternatively copper tape, or wire could be used.

Parts List:

I used male RCA plugs as the output termination because I wanted a compact inline connection, alternatively female RCA jacks could be used with patch cables. I connected the RCA output plugs in parallel to feed both the left and right channels of the AV receiver.

Standard AV RCA phono plug on center spacing is 13mm with a 10mm panel mount hole.

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