Archive for the ‘tape machines’ Category

Digitising Audio Tape – Process, Time & Cost

Monday, June 10th, 2013

Last week we wrote about the person time involved in transferring magnetic tape to digital files, and we want to tell you more about the processes involved in digitisation work.

While in theory the work of migrating media from one format to another can be simple, even the humble domestic cassette can take a substantial amount of time to transfer effectively.

Doing transfers quickly would potentially keep the costs of our work down, but there are substantial risks involved in mass migrations of tape-based material.

Problems with digital transfers can occur at two points: the quality of the playback machine and the quality of the tape.

First, lets focus on the playback machine.

Each time a cassette is transferred we have to ensure that the cassette deck is calibrated to the technical specification appropriate to that machine. Calibration is a testing procedure where a standard test tape is used to set the levels for tape to be digitised. The calibration process allows us to check tapes are played back at the correct speed and audio levels, that wow and flutter levels are set and the azimuth is aligned.

Azimuth refers to the angle between the tape head(s) and tape. Differences in Azimuth alignment arise from the azimuth of the original recording. You cannot know this information from just looking at a tape and you will get a sub-optimal transfer unless you adjust your machine’s azimuth to match the original recording.

sony-apr-5003-headblock-azimuth

Regularly checking the Wow and Flutter on the tape machine is also very important for doing quality transfers. Wow and flutter refer to fluctuations in speed on the playback mechanism, flutter being a higher rate version of wow. If you have listened to a tape you will probably be familiar with the sound of warped and woozy tape – this is the presence of wow. All tape machines have wow and flutter, but as components in the mechanisms stretch there is the potential for wow and flutter to increase. It is therefore essential to know what level the wow and flutter are set on your tape deck –less than 0.08% Weighted Peak on our Nakamichi 680 machines – to ensure optimal transfer quality.

Not all cassette machines were made equal either, and the quality of playback is absolutely dependent on the type of machine you have. There is a massive difference between the cheap domestic cassette machines made by Amstrad, to the cassette decks we use at Great Bear. Nakamichi machines were designed to squeeze the most out of the cassette, and their performance is way above the standard ‘two head’ cheap domestic machines.

Even with a Nakamichi deck, however, they have to be regularly checked because they are fragile electromagnetic machines that will drift out of specification over time. When machines drift they slip out of alignment, therefore effecting their operating capacity. This can occur through subtle knocks, everyday wear and tear and general ageing of mechanical and electrical components. For example, with extended use the grease in the components dries up and goes hard, and therefore affects the movement of the mechanisms.

Wow-and-flutter-monitor

Problems can also arise with the tapes themselves.

Most issues arise from tapes not being played back in well calibrated machines.

With audio cassettes the potential for azimuth error is increased because the speed the tape moves pasts the head is very slow. The tape therefore needs to be assessed to see if it is in a playable condition. It is played back in mono because it is easier to hear if there are problems with the azimuth, and then the azimuth is manually adjusted on the machine.

Migrating tape is unquestionably a ‘real time’ process. You need to listen and monitor what’s on the tape and the digitised version to ensure that problems with the transfer are detected as it is happening. It is a very hands on activity, that cannot be done without time, care and attention.

Nakamichi 680 Discrete Head Cassette Deck and Music & Liberation

Tuesday, January 8th, 2013

In 2012 Great Bear digitised a selection of audio and audio-visual tape for the Heritage Lottery Funded exhibition, Music & Liberation.

The first job was to migrate a short film by a feminist film making collective called Women in Moving Pictures who were based in Bristol in the early 1980s. The film shows how the Bristol Women’s Music Collective were using feminism to politicise music making and includes footage music workshops, group performances interspersed with self-defence classes and intimate conversations.

Film still in colour. Woman playing a saxophone.

Film still from ‘In Our Own Time’

Several copies of the film had been stored in the Feminist Archive South, including the master copies. Out of curiosity the u matic copy was initially digitised, before the original was migrated to high definition digital format.

Picture of a group women singing and playing guitar

Film Still from ‘In Our Own Time’

Another job digitsed a series of rare recordings on tape, donated by Maggie Nicols. This included rare footage of the pioneering Feminist Improvising Group, whose members included Sally Potter, Georgina Born and Lindsay Cooper. One of the tapes was originally recorded at half speed, a technique used to get more recording time. We used the Nakamichi 680 Discrete Head Cassette Deck to play back the tapes at the correct speed to ensure the highest quality transfer.

We also digitised a series of tapes from the open improvisation collective Maggie co-founded in 1980, Contradictions. This included the performance ‘Madness in a Circle’ and many other creative experiments.

Music & Liberation re-opens at Space Station Sixty-Five in London for the last four days of its UK-wide tour on 10 January, so if you want to listen to the music or watch the films make sure you catch it.

 

reel to reel tape transfer of rim drive or capstan free recordings

Tuesday, February 22nd, 2011

The capstan drive tape recorder is (or was) very common and was used in a huge range of cassette tape audio, video and open reel machines from cheap domestic to very expensive broadcast tape machines.

Occasionally we receive quarter inch tapes, always be on small 3 inch spools, that reproduce on our capstan drive machines with terrible speed variation. They start off very fast then gradually slow down over the duration of the recording to around normal speed.

These reels must have been recorded on rim drive machines. These type of open reel tape recorders didn’t use a capstan and pinch roller to save space and more often cost. As there is no capstan, as the supply reel gets smaller the tape recording speed increases. When replayed on a rim drive machine the speed, while not likely to be ‘Studer stable’ will be pretty stable and the recording sound OK.

It’s not feasible or desirable for us to own unlimited machines of all types due to the time to service and repair them, find parts and storage space therefore we use a small range of carefully picked high quality tape machines that with care can replay most tapes, speeds and track formats. This is the problem with rim drive recordings and an analogue or digital solution must be found.

The tapes we received were 15 reels of family recordings from the Welsh Valleys. Others apparently had tried to transfer these tapes but gave up finding no material. This was easily solved as the tapes were wound the opposite way to normal so the oxide was facing out not in. This is the same as in audio cassettes. The original tape machine must have had it’s heads in a similar position to a cassette machine.

Replace Tascam BR 20 Capstan Belt

Monday, May 10th, 2010

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.

Tascam / Teac BR 20 rear panel removed

  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.Tascam BR 20 capstan motor board with cables removed
  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.
    Tascam BR 20 capstan motor board unclipped from assembly
  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!
    New Teac capstan belt for Tascam BR20 reel to reel tape machine

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greatbear analogue and digital media ltd, 0117 985 0500
Unit 26, The Coach House, 2 Upper York Street, Bristol, BS2 8QN, UK


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