I have many analogue records, but could not hear them after breakdown of my vacuum tube amplifier. I do not care about quality of sound so much now. So I wanted to make RRIA equalisers using operational amplifiers. I looked around the net and found a simple circuit as this. I took the circuit as master and designed a circuit as below. I used my favourite operational amplifiers MC33178P (33179 with four amps). These amps convenient with high slew-rate, large output swing and large output current of 50mA.

The circuit was very simple and finished in two nights.

簡単な回路なので二晩で完成。

I pushed the PCB in to a box in hand and connected input, output and power supply. I found the noise was large if the earth wire from the turn table was floating. So I connected the earth wire to the common of the PCB. The hum noise level was acceptable and the equaliser seemed work well.

ありあわせの箱に入れて、入出力、電源をつなぎます。ターンテーブルからのアース線は浮かしておくとノイズがやたら出るので基盤のコモンに接続しました。ハムノイズもほとんど気にならないし、充分使い物になりそうです。

Now I can listen of records connecting the equaliser to a main amplifier. Anyway I want to digitise the analogue records. A/D converters built-in computers may have large noise. So I use a USB video capture unit I bought to convert 8mm video tapes to DVD. Capture files may be large with this, but not a problem at all. Then I extract the sound part from captured .mp2 files using a freeware “AoA Audio Extractor.”

これでアンプにつなげれば聞こえるわけですが、アナログレコードもデジタル化しておきたい。コンピュータ内臓のA/Dコンバータはノイズだらけのことが多いので、以前8mmビデオをDVD化した時に買ったUSB Video Captureユニットを使うことにしました。何にも映っていない画像も同時にデジタイズしてしまうのでファイルが大きくなってしまいますが、大した問題ではありません。キャプチャーした.mp2ファイルから、 AoA Audio Extractorというソフト（フリーウェア）で.mp3に変換します。