PCW HC Decoder Help

by Ernst F. Schroeder

Welcome to the Precision Compandor Works HC Audio Decoder help page.
I sincerely hope that the information herein will help you to make better use of
PCW HC Decoder.

These help pages are valid for version 0.9.0 and later

Here you can get information on the following items:

 

PCW HC Decoder. What is it and what is it not?

PCW HC Decoder is a piece of software, written for PCs running the Windows operating system. It allows you to decode audio recordings, specifically audio tape recordings that have previously been recorded while using the compressor part of an audio compander system or noise-reduction system.
Such systems have extensively been used with audio cassette recorders in the 1970s and 1980s, and they were known under such names as Dolby B (*) or HighCom (*).

PCW HC Decoder is designed to decode recordings made with the HighCom compander system. It is not suitable for recordings made with Dolby B and also not suitable for cleaning or for removing noise from any old tape recordings.

This software has been designed with appropriate care, it should not exhibit any harmful side effects. Nevertheless, you use it at your own risk. If you do not agree, then please do not use it.

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How can I obtain this software?

You can download the most recent version of this software in a zipped archive from here. Save the archive file on your computer and remember the location.

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Do I need a license?

When you download and install PCW HC Decoder, you are granted a personal, non-exclusive and unlimited license, completely free of charge.

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How do I install it?

Double-click on the saved archive file. The archive should open and display a single file:

(The version information "x.x.x" reflects the current version.)

Start the installation by double-clicking on the executable file.
A welcome window will open. Click "Next" and the license agreement will be displayed. If you agree to the terms of the license agreement then you should check the "I agree ..." box and click on the "Next" button. Then installation will start.
The installation process is simple, there are no new DLLs, no additions to the registry file, and no changes to your operating system. An entry will be added to the startup menu and an icon will be placed on your desktop. The installation can be reversed without a trace left.

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There is no shortcut icon on my desktop. Why?

On certain installations of Windows 10 the automatic placement of an icon on the desktop may be prohibited. In this case you have to locate the program "PCW-AudioDecoder.exe" on your computer. With a right-click you open the context menu and then chose "shortcut".
In Windows 10 you can as well go to the Start Menu List and locate the entry for PCW HC Decoder. By left-clicking on the icon you can drag it onto your desktop.

dragging the icon
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How do I start the program?

You either double-click on the PCW-AudioDecoder shortcut icon on your desktop or you go to "Start" - "Programs" and locate the "PCW-AudioDecoder" entry. Double-click on "PCW-AudioDecoder", the program will start.

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How do I start working?

It is very easy to actually use this piece of software. But before you can use it, you have to perform a few steps to transfer your analog tape or cassette recordings into a digital version on your computer.
Please read on.

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How do I transfer my analog tape recordings to my PC?

First of all, you need a tape machine or cassette recorder that is able to play the tapes you want to digitize to your PC. Preferably this should be the same tape machine or cassette recorder that has been used to record the tapes or cassettes in the first place. But in many cases these machines will not be available any more. Instead, you can use any suitable and working tape machine, cassette recorder or cassette playback-only machine.
In order to do the actual transfer from analog tape to a digital file on the PC, you have to check a few special items:

Please read on for further information. If that's nothing new for you, then continue here.

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What kind of interface to the PC do I need?

Most table-top PCs do have a "line" audio input. This is the right place to connect to the audio output of your tape playback machine.
But many laptop PCs only have a "Mic" input. In most cases this input will not give good results. Luckily, there are small and cheap alternatives: audio interface boxes with USB connectors, see next picture.
Just plug this interface into an empty USB socket and connect the output of your tape playback machine to the "L" and "R" "Input" (cinch) sockets of the adapter.
You have to make sure that the interface is able to digitize audio signals with one of the higher sampling frequencies like 88.2 kHz or 96 kHz. More on that further on.

USB audio interface

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And what kind of software do I need?

Next you need a piece of software that lets you actually record the analog audio signals in digital form and store them as a ".WAV"-File onto your PC.

A powerful and free piece of software suitable for this task is "Audacity", that you can get from here:
https://www.audacityteam.org

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How do I work with Audacity?

Download and install, then start the program.
As a first step you should identify your audio input device. There is a drop-down menu, and in this case we use the device with something like "USB" in the name.

Audacity, select input device

Next you should adjust the quality preferences. Select Edit/Preferences/Quality and adjust the Default Sample Rate to 96000 Hz and the Default Sample Format to 24 bit. These values are not mandatory but help preserve the over-all quality.

Audacity, quality preferences

Now go to the top row where it says "click to start monitoring"
When everything is OK, you should now see some reaction on any input signal you have connected. In this example there was a 400 Hz signal with level 10 dB below digital maximum.

Audacity, recording level

OK, hit the red button - and recording should start.
Then, after a few seconds, hit the "stop" button, the one with the black square.
With a constant signal like above you will probably get something like this:

Audacity, recording level

Finally you need to save the digital recording to your hard disc storage system.
Select File/Export/Export as WAV
Now you have to decide where to store the recording and what name it should have. Don't forget to select the correct format under "Save as type":
From the drop-down menu select "WAV (Microsoft) signed 24-bit PCM".

Audacity, export as WAV

That's it - you have successfully created a digital audio file from the analog audio input.

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How do I establish a certain reference level?

In the analog world on your cassette recorder and on the tape there is a certain "reference level", which can be marked in different ways, e.g. as "0 dB", "0 VU" or simply as the border between differently colored parts of the level indicator.
When you want to transfer an anlog recording into a digital file on your computer, you have to establish a correspondence between this "reference level" on tape and a certain "digital value". For this it is customary to relate "0 dB analog" with a digital level of about 10 dB below absolute digital maximum.

To establish this relation you should take the following steps:

  • Start Audacity software (you should have set quality preferences to 96 kHz and 24 bit before)
  • Create a new stereo track: Tracks > Add New > Stereo Track
  • Create a new signal: Generate > Tone.. > Waveform: Sine, Frequency (Hz) = 320, Amplitude = 0.316, Duration 00h00m10.000s, i.e. 10 seconds long
  • Hit the Fast-Forward button (>|) or letter "K" on the keyboard to position the cursor at the end of the current signal
  • Add another signal, this time with a bit larger amplitude and shorter duration: Generate > Tone.. > Amplitude 0.398, Duration 00h00m01.000s, i.e. 1 second long
  • Repeat the last two steps 4 times, with increasing amplitude values: 0.5, 0.629, 0.792, 0.998
  • Now you have a signal with 10 seconds of reference level, followed by a string of short pieces with amplitudes increasing in steps of 2 dB each. Save this file to your PC with a proper name for further use: File > Export > Export as WAV > save as type: WAV (Microsoft) signed 24-bit PCM (just click <OK> when asked to enter metadata tags)
  • Hit letter <J> on the keyboard to position the cursor at the start of the signal. Then hit <blank> and listen to the signal while watching the level indicator on top right to stay at -10 dB for a while, then go up in steps of 2 dB each.
  • Connect the audio line output or headphones output of your PC to the line input of your cassette or tape recorder. Start the analog recording, then again hit <J> and <blank> and at the same time try to adjust the level controls on your recorder in a way to record the 10 seconds long part of the signal from Audacity as "0 dB" on the analog tape.
  • Rewind the recorder and play this recording, actually listen to it. Make sure that there is no gross distortion during recording or playback. Rewind and repeat until you have a stable recording. Note the settings of the controls for recording level on the recorder for later use.
  • Close Audacity, hit <No> when asked for "Save project ...?"
  • Start Audacity again and create a new empty stereo track like above.
  • Now connect the line output of the analog recoder to the line input of your PC and use the input to Audacity you have established before. Start playback on the analog recorder and hit the red button in Audacity to start recording. Your cassette recorder may have a control to adjust output level and Audacity has a control to adjust input level. Adjust these controls in a way to finally obtain as close a replica as possible of the signal you have generated before.
  • Note the details of the connection between analog recorder and Audacity and of all the level settings. You have now established the reference settings and you will need exactly these settings for all further transfers from tape or cassette to your PC.
  • Done

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    Now, knowing all this, how do I actually work with PCW HC Decoder?

    OK, you have a digital audio file in .WAV format that contains an audio signal. And this audio signal has previously been compressed by the High Com compander system. Now you want to decode it, digitally.

    OK, simply launch PCW HC Decoder. You will see this work area:

    PCW HC Decoder work area

    You'll notice that three different modes of operation can be selected, and that "HighCom (later version)" Decode Mode is preselected. (More on these different modes is here)

    Now, click the top left icon to find and select the name of your input .WAV file. Then click the output file icon below. The name of the output file is preset with the name of your input file with "_dec" appended. You can select any suitable directory or name for the output file.

    When you have selected both files, the Start button becomes active. And after pressing this, processing will start. While processing is going on, the gain gauges will show the gains applied in each of the two channels. The Start button changes into an Abort button that enables you to stop the processing before it ends automatically.

    After processing is done, the elapsed processing time is shown on the bottom.

    Please note, that you cannot immediately start the same process again. When you want to do just that, you first have to select the input and output files again. This is easy, as the previously selected file names are remembered and shown in the file selection windows.

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    What do these three different modes of operation mean?

    When the HighCom compander system was first introduced, it was based on the Telefunken integrated circuit U401B. So in the earliest cassette recorders equipped with HighCom you will find this IC or one of its variants U401BG and U401BR. Shortly after its introduction, an additional circuit was used that you can actually see as a piggy-back circuit on top of the IC.

    In case that you do not know which version may have been used to generate your analog recordings, just start with "HighCom (later version)". When you get unsatisfactory results, you should alternatively try "HighCom (early version)".

    There has been a third and very different version of the HighCom compander system. This was the version used by the Japanese high-end company Nakamichi in their separate compander device, named HighCom II. If you are certain that your recordings have been made with this version of HighCom, then please use this option.

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    How do I get further help?

    If you encounter a problem not covered on this help page, then please send an EMail with a clear description of your problem.
    Please allow for a reasonable response time.

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    How can I give feedback?

    Any feedback is highly appreciated. Please send an EMail and describe what is missing or what you have found out. And if just in case you find this software helpful and supportive for your work, why not send a short message?

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    I have received a new version. What shall I do?

    If you want to install a newer version of PCW Fistcheck, then you do not have to uninstall any older version. Just install the new version over the older version.

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    How do I get rid of it all?

    That's easy: select "Start" - "Programs" from your task panel, then identify the entry for PCW HC Decoder. Within this folder you will find a shortcut with the name Uninstall. Double-click and follow any instructions. Voilá, PCW HC Decoder is removed from your system, very probably without a trace.

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    (*) Trademarks are property of their respective owners.

     

     


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