4
« on: November 19, 2008, 09:51:18 AM »
For what it is worth, just a few personal thoughts from my own limited experience of Dolby A and the 361 series unit in particular.
I think it is fair to say that any form of processing will be a balance of good and bad. Dolby A was the first virtually transparent form of audio noise reduction, and probably single handed gave rise to the (once) modern multitrack recording industry. Sure there were other and rather later devices from people such as DBX and Telex (their telcom system even plugged into a 361 frame) but they were thought at the time to be less transparent or have fairly obvious artefacts.
The problem, was that it was becoming increasingly obvious that the cumulative build up of noise (both in decrease of S/N ratio and in the increase in modulation noise) was making the newly developed multitrack tape formats of the early 1970?s almost unusable. But Ray Dolby?s new system almost by chance made multutrack workable enough to become the new way of manufacturing popular music. No longer need a group of musicians come together to make a recording, but various bits of a ?track? could be stuck together and at various times like the components of a motor car to make complete the end ?product?. Backing track, lead and vocals all recorded at different times and sometimes even on different continents could be glued together (during the reduction as it was known) to make a seamless whole. And all this mostly because of Dolby A, which was probably the most significant innovation in the audio business since the invention of the tape machine itself. Later the different though still analogue Dolby SR system was developed to combat the then up and coming digital formats. By then though virtually all analogue master tapes would have been Dolby A encoded, and every disk cutting suite would have had a pair of 361s in the playback mastering chain.
Now while U47 is of course correct about Decca using the first A-301 systems they did however change over to their own digital mastering system (for classical music) in the late 1970s. Interesting that the 361/Cat 22 is thought to be a step down in sonics to the 301, certainly when I was a trainee recording engineer (tape op) in a minor London studio in the early 70?s, racks of 361s working with Ampex or Studer machines were thought to be the last word in quality back then, and were to become the de-facto standard for years to come. I do however remember that Angus Mackenzie wrote in his review of the 301 that one could by removing certain boards use it to clean up old 78 recordings(!). Which you can?t do that with a Cat 22 module.
The fully interchangeable Cat 22 modules in their 1U 361 rack units were a much more convenient package than the first Dolby 301s once it became obvious that the multitrack studio was to be Dolby A?s true home. Partly because they were much smaller (though surprisingly heavy) but more importantly that they had remote control of record and replay switching, so that a single signal from say the tape machine?s control panel could switch a whole bank of (8, 16, 24) Dolbys from record to replay mode. The Dolby 301 units contained a stereo pair of record/replay channels (and separate boards for the 4 individually processed frequency bands) while the 361 was an integrated single channel of record and replay processing with one Cat 22 module. Later, Cat 22 modules would be fitted to even more compact multiple rack mounts. I am not sure how many of those Tant beads were used in the signal lines as the circuit was pretty secret but naturally they may have had some detrimental effect. (I found that the much more expensive metal cased tantalums could sound even worse). But of course professional audio equipment was never designed as hi-fi equipment in the first place, it just had to work reliably day in and day out.
My own personal experience of the A-361 system was with a pair bought from the BBC some years ago. Once used in their Mada Vale studios, I used them with both my Stellavox SU8 and an Akai GX77 for mostly recording Jazz FM broadcasts from a Yamaha CT7000 tuner. Interfacing was a pain as they had balanced (of course) ins and outs, no gain controls (only fine trimmers) and needed a healthy input signal at something like + 4dBm. They were of after all designed to work from the output of a professional mixing desk. Once set up and working though the most obvious effect was a considerable reduction of tape noise with none of the treble and transient problems of Dolby B (or C), but there were other more subtle effects in that these units reduced crosstalk, modulation noise and made the recordings (even at 3 ? IPS) sound cleaner and ?nicer?. While of course daft, taped Dolby A recordings of Lps seemed to sound rather better than the originals?
I don?t use them now for in this world of exotic cables and connectors having a couple of transformer coupled audio processors in the signal path seems to be a bit of a problem philosophically. And anyway for simple ? track recording with a slight amount of tape noise seems not a problem.
Sorry to go on.
Show Posts