Microphone adapter - IPRS Baneasa - Prospect 8103

Microphone adapter - IPRS Baneasa - Prospect 8103

Reading time: 2 minute

What does the project present?

This vintage DIY electronic kit features a microphone preamplifier. The assembly ensures a uniform amplification in the 30Hz - 30kHz band of a signal received from a microphone. The scheme includes 2 BC 172B transistors, resistors and capacitors.

How does the assembly work?

The input impedance is high. The two floors amplify in voltage the audio-frequency signal provided by a microphone. The signal thus amplified can be applied to the input of an amplifier with an input signal of 100 mV.

The power supply of the scheme is made from a stabilized voltage source. To better understand how and what to use this adapter, we recommend reading the article here.

Technical characteristics of the assembly

  • Input signal amplitude: 2 mV
  • Output signal amplitude: 100 mV
  • Supply voltage: approx. 20 Vdc
  • Input impedance: approx. 50 KOhm
  • Output impedance: approx. 10 KOhm

List of required components (with recent equivalents):

  • T1, T2 - transistors BC 172B or BC 547C
  • C1 - 2.2uF capacitor (min. 25V)
  • C2 - 47uF capacitor (min. 10V)
  • C3 - 100uF capacitor (min. 6.3V)
  • C4 - 330pF capacitor (min. 25V)
  • C5, C6 - 4.7uF capacitors (min. 10V)
  • R1 - resistor 390 KOhm (min. 0.25W)
  • R2, R7 - resistors 220 KOhm (min. 0.25W)
  • R3 - 680 Ohm resistor (min. 0.25W)
  • R4 - resistor 39 KOhm (min. 0.25W)
  • R5 - resistor 10 KOhm (min. 0.25W)
  • R6 - resistor 1 KOhm (min. 0.25W)
  • printed wiring or breadboard test board
  • tin or connecting threads

Download the original IPRS leaflet Baneasa 8103

For a better understanding of the operation of the circuit we will need electronic scheme presented below:

In order to carry out this project in our own laboratory, we will also need printed wiring PCB layout From lower:

Many of you are probably wondering how this DIY electronic kit was packaged or distributed. Below I have attached a picture with packaged product (new). Thanks Mr. Marius Balauta!

The image below shows the electronic kit in another variant, having the same prospectus number (8103).




  1. I didn't catch them in stores, I had leaflets at the children's club. So I built them after the leaflet, and they all worked 🙂

  2. Yes, all will be uploaded to the site. In the meantime ... are we waiting for more information about the manufacturing section of these kits?

  3. Yeah Al that sounds pretty crap to me, Looks like BT aint for me either. But out of their hands came electronic products appreciated by both children and adults. On the production side, there were 4-channel light organs, 5-way stereo equalizers, 3W amplifiers, 10x30W with TDA 2, even electric gas pumps for the Lastun car. And more and more were being made. The atmosphere was extraordinary - there was no boss, no subordinate. We were all friends! Too bad the business went downhill on Saturday!

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