Build a microphone preamplifier

So you’re back from holidays spent somewhere in a hot and sunny place, enjoying the a hotel or beach resort with organized activities like morning aerobics in the swimming pool and loud parties at night and where you karaokeed your lungs out of your body, and now you are missing that festive ambience? Then it is time to build this great all-analog, all-through-hole microphone amplifier and impress your friends and family once again with your vocal capabilities.

Here is an all-analog, all-through-hole, cheap & cheerful preamplifier for that perennial problem of getting the microphone amplification just right.

Now available in the Elektor Store is the May & June Edition of Elektor Magazine. Packed with the usual array of articles, projects and reviews it’s definitely not one to miss. As always, you can get a printed copy sent straight to your door with no shipping costs at all.

To be able to listen to bats you need to have a special detector that translates the high frequency signals (20 to 100 kHz) to sounds that are audible to humans. Elektor’s recent ‘Bat DetectorPLUS ‘ uses a special microphone that is suitable for these high frequencies. But the device package is so small and difficult to solder that this requires a considerable amount of care.

High performance microphone preamplifier with phantom power for use with line-level audio inputs as found on todays computers. Gain can be set in six steps from 20 to 70 dB, 20 dB by 1: 10 input transformer.

For no particular reason I was looking at the Wikipedia article on microphones, and I noted in the 2nd paragraph a trivial but relevant detail: « Microphones are used in many applications such as telephones, hearing aids, public address systems etc. ». The first application mentioned, the telephone, seems logical to me: if humans talk to each other more than ever, they surely make massive use of the microphone in their phone?

The preamplifier is intended for use with dynamic (moving coil – MC) microphones with an impedance up to 200 ? and balanced terminals. It is a fairly simple design, which may also be considered as a single stage instrument amplifier based on a Type NE5534 op amp.

To many hi-fi enthusiasts and musicians, the thermionic valve (electron tube), the sound of a valve amplifier cannot be bettered by that of a solid-state amplifier. To satisfy that conviction, here is a microphone preamplifier based on valves. The circuit in the diagram is intended for use with a studio microphone with or without phantom supply.

In this article we answer the questions of our readers.

There are occasions when it is desirable or even essential for a stereo microphone to be connected to a personal computer. Unfortunately, the microphone input of most sound cards used in PCs is monophonic. This article describes a simple adaptor to convert the mono(phonic) input into a stereo(phonic) input. It may also be used to provide a cassette deck with a stereo(phonic) microphone input.