One of our recent and ongoing jobs is a very large, over 2000, NAB 10.5 inch reel to reel archive of quarter inch professional tape recordings.

To fit into the budget but maintain quality we needed to find a way to streamline our workflow in converting the high resolution 24 bit 96 Khz master .wav  files to CD quality (16 bit / 44 Khz) and MP3 (320 kbps) audio files.

Typically this would be done manually with 2 track audio software such as Audacity, Peak Audio Tools, Wavelab, etc with a Graphic User Interface (GUI). For such a large amount of individual files this is time consuming, expensive and unnecessary. While many audio editors have batch processing tools, Amadeus Pro being one of our favourites, they are still not as flexible as combining command line tools with a Bash script.

SoX is a powerful command line audio tool that can be used to edit, convert, process, record and play a wide range of digital audio files. It also has a very high quality resampling algorithm which we are using here.

Once the tape reels have been digitised they are split into individual .wav files which are then renamed with artist and track details using a php script that accesses a .csv file. These 24/96 resolution files are then converted to lower, CD resolution using SoX and to 320 kb/s MP3′s using LAME. The script also uses sed, the stream editor, to add the text _16_44.wav or _mp3.mp3 to the filename for ease of identification. The script finds all files with the suffix _24_96.wav in all the subdirectories of it’s working directory and processes these.

At the moment this script is running under Mac OS X 10.5.8 using the MacPorts project but will, in time, be moved to one of our Apple G4 servers running the PowerPC version of Debian GNU/Linux 5.05 ‘Lenny’.

We have two of these excellent machines in addition to our Sony APR 5003 and Studer A80′s. The Tascam BR-20 was Tascam’s last and top of the range 1/4 inch reel to reel tape machine and available in two track stereo and stereo with centre timecode option.

The capstan drive in the BR20 is belt driven by a wide belt. Both belts in our machines looked OK but we’ve replaced all roller bearings, belts and pinch rollers in both of our machines anyway as a matter of course. These parts are still available from Teac UK via Acoustic Services on 01-844-347600.

Below is a simple explanation of how to change the capstan belt.

1. Unplug machine from mains power and move to a strong stable base.
2. Remove cross head screws from the rear panel and lift plate off. Depending on the type of plug in your country you may not be able to remove it completely.
3. You’ll now be able to see the capstan motor and it’s control board attached to it.
4. Remove the 4 cross head screws and gently lift the analogue audio output board away from the machine as in the picture above.
5. We now need to remove the whole capstan motor assembly with the control board still attached. Remove the 4 cross head screws right at the front of the assembly, NOT the six nearest to you when looking at this image. 
6. Carefully unclip the 4 cable connectors from the motor control board. The other connector cannot be removed from the board and must be removed where it connects to the other board.
7. The whole assembly can now be lifted out from the machine. Be careful to not snag any cables and remember to unclip the black cable ties.
8. You’ll now be able to unclip the control board from the assembly by carefully compressing the black clips with some needle nose pliers.
   
9. Now remove the six cross head screws holding the capstan motor assembly together. This is the only way to remove and refit the capstan belt. There’s not enough room to do it any other way!
10. Now you can remove the old belt and capstan shaft. It’s a good idea to clean the capstan with IPA where the old belt has run and reapply a little grease to the bearing end of the capstan.
11. Fit your new belt and reassembly is the reverse of dissasembly! Be careful though to not drop the screws into regions you can’t get them out of – luckily there aren’t that many on this machine but a long magnetic screwdriver is very useful.. just don’t get it anywhere near the headblock and heads!