Remember the Portastudio ?
I bought a Portastudio 4 track tape recorder in the early eighties. This allowed me to record 4 tracks of audio on a compact cassette tape. The tape spooled at twice the normal speed to increase fidelity. It also had a 4 track mixer and basic studio facilities. The main drawback with this system was that it only allowed a maximum of two tracks to be recorded at any one time. It allowed 4 tracks to be mixed into a stereo output but it had no facilities to output 4 separate tracks at once.
At the time it was the bee’s knees and was very popular with bedroom musicians. I used it in conjunction with a Polysynth that I built and a very basic drum machine. The vocals were questionable !
Wind on thirty years….. I wanted to preserve all my earlier creations and I wanted to get them digitised as the tape deteriorates and the machine will stop working soon. There have been so many advances in digital audio engineering and I have the facilities to edit, improve, add effects etc.etc.
My first attempt was to output two channels (1 & 2) and record them to my PC using a stereo ADC interface, and then record the other two channels (3 & 4). This required two passes of the tape and when I tried to match up the two recordings there were quite serious synchronisation problems.
I then decided to hack the machine and get access to the 4 channels at the mixer. I bought a 4 channel ADC USB interface and hooked this up to my PC.
I used a superb, cheap DAW (digital audio workstation) application called “Reaper” on my PC and this allowed me to record 4 channels at once. Each track can then be saved as a WAV file.
The Portastudio hack involved the following:-
- Take a stereo phono lead and cut in half so that you have 4 phone connectors.
- Take the back off the portastudio.
- Solder the signal wires to test point connectors on the Mixer part of the exposed PCB.
- Attach the screen wires to the chassis.
- Plug the phonos into the MAYA 44 USB analog inputs.
Notice the connector labelled “T.P. (TRK 2)” in the centre. Connect a signal lead to it. (actually shown as white). The phone cable screen is connected to the blue/white stripey wire.
Continue with Tracks 1 to 4.
The screen wires (connected to blue/white stripey wire) are connected to the chassis.
The Portastudio back is stuck back temporarily and there are 4 phono leads available.
I have managed to transcribe all my old Portastudio tapes to individual WAV files. I have managed to do various tasks, for example I have taken off the old drum machine track and replaced it with a more realistic track, I have managed to add extra tracks of instruments, Vocal tracks. I have also managed to edit the tape to duplicate choruses, take out bum notes – that sort of thing.
In order to add extra drum tracks or MIDI sequences it helps to make sure that the tracks are all synchronised to a standard beats-per-minute. I play the tracks together using Reaper and press a key to generate a marker on every bar start. I can then get the average BPM and set up a grid with this figure. I then manually adjust each marker to the grid using the time expand /compress feature to get the start of each bar to line up with the grid. The adjustments required are very small (if required at all) and do not affect the fidelity. If a track includes a drum machine it is easy to check that the manually generated marker is actually the start of the bar.
Once this has been done, it is easy to run a drum machine along side or add a MIDI track.
I used to bounce 3 tracks into one track in order to free up more recording tracks, unfortunately this cannot be undone and the tracks need to be transcribed by ear and re-played on a MIDI instrument.
I shall show a tutorial for processing the tracks on a later blog entry.