Solved the Noise on Tape Recorder Caused by Frequency Converter

Case: I am restoring a 1960s analog audio tape recorder for high quality audio use, the tape recorder is a USA model operating on 120VAC at 60Hz, the mains voltage in Singapore where the machine will be operated is 230VAC but 50Hz. Other converters that convert 230VAC/50Hz to 120VAC/60Hz have been unsuitable -- I hear high distortion and square wave noise to break through in to the audio in both recording and replay modes causing noise and high distortion and making the tape recorder unusable.

Do you have a product that can give me the right voltage conversion (230VAC to 120VAC), with mains frequency conversion of 50Hz to 60Hz that gives professional studio grade audio, no distortion or DC square wave break through into the audio.

Solved: Take an example of 1kVA frequency converter for the tape recorder.
1. Open the top cover of the frequency converter
Frequency converter keypad
2. Power on the frequency converter, wait for approx. 1 minute, then press the “SET” button
Frequency converter display menu
3. The display will show as above picture
Frequency converter PCB
4. Find this "button 1" in the frequency converter (near the display), press one time.
Frequency converter kHZ
5. The display will show as above picture
Frequency Converter 8kHZ
6. Press the button once again, until the display shows as above picture.
CBB capacitor
7. Parallel a CBB capacitor at the output of the frequency converter(the capacitor is 3-12UF), one end of the capacitor connect to the Neutral (N) of the output, the other end connect to the Ground(G).


  1. Connecting a filter to the output of the frequency converter
  2. Adjusting the frequency converter as above 1-6 steps
  3. Adding the capacitor to the output of the frequency converter


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