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Professional Feature:

Vinyl Transfer - Some Basic Guidelines

Ian Hippell -
Mantra sound restoration
Mantra vinyl transfer

The following notes are guidelines intended for use in the professional studio - this process is not recommended for those with no prior experience of sound restoration! Mantra CDs and Recording cannot take responsibility for unsatisfactory results obtained by following these instructions, and advise those with limited knowledge of this technique to seek professional assistance in transferring their materials.

Cleaning and Preparation

Clean vinyl as effectively as possible.

Some vinyl will withstand a wash with warm, soapy water. It should be carefully dried using a lint free cloth.

Care should be taken not to damage the label (it is possible to mask it with tape and plastic sheeting if critical.

Proprietory cleaners can be effective - particularly the "Pixall Roller" available from some audiophile shops - it takes the form of a masking tape type of material on a 4 inch wide roller. If used by pulling it across the vinyl from centre to the edge, it picks up most (if not all detectable) foreign matter off the surface of the disk. Regular replacement of the cleaning surface is necessary so as not to "pit" the vinyl from harmful matter attached to the paper.

Some soft cloths and liquid solutions may be effective but take care that the vinyl is of a suitable chemical make up so as not to be damaged by the liquid (particularly 78's made of Shellac).

The Record Deck

Once cleaned, the record deck should be checked out.

Obviously Direct Drive turntables offer the most stable speeds but well cared for belt drives can be just as effective. Try to avoid cruder, rim drive turntables which do inherently suffer from speed variation.

The turntable should be mounted on a flat surface (use a spirit level if critical to the make of turntable) and should be placed away from any devices that may induce interference (e.g. Computers, power amps, loudspeakers etc.)

Pick up arms should be set up according to the original manufacturers' instructions. It is most important that correct weightings for the type of cartridge and stylus are observed as this can have a dramatic effect both upon the reproduction of the programme material and upon the residual condition of the vinyl (rare and valuable records should not be damaged by the "lathe effect" of using too greater weight upon the grooves of the vinyl). Furthermore pick up drop onto the vinyl can cause unnecessary pitting if the cartridge weight is too heavy. Styli also wear out quicker if the weight is too great.

On belt drive decks (particularly those that are not used frequently) should be allowed to rotate for a few minutes prior to making the transfer so as to properly align any natural belt slippage and to maintain as near constant speeds as possible. It is also wise to use a test tone disc to check for wow if available.

Cartridges come in two flavours, moving magnet and moving coil. The output voltages of the two systems are different 5mv for the former, 0.5mv for the latter.
Moving coil cartridges are considered by most (including audiophiles) to be the more sensitive and most accurate in the reproduction of sound.

Connection of the deck output should either be via a phono pre amp circuit (as found on older hifi systems) or via a suitable microphone preamp or direct injection box. It is obviously better to use stereo inputs unless the source material is mono in which case a mono input may be sufficient although not recommended as a stereo image of a mono source can give you the opportunity to either choose the cleaner channel or combine the two channels in a wave editor which can reduce background noise and increase the level of the programme material. If this method is used, you must take care to not introduce phasing errors between the channels which may be difficult to compensate for.

There are a few proprietory phono preamps available which do offer an improvement over using mic pre's or DI's as they are set up to allow for RIAA de-emphasis (see RIAA below).

Steinberg sell a package called "Clean Pro" which includes such a preamp. Terratec also produce a similar device. There are other offerings from other companies as well as user installable boards available for modern hifi pre-power amplifiers.

RIAA (Recording Industries Association of America)

This is a system of equalisation as defined by the RIAA. It is an internationally recognised standard of Pre-emphasis - de-emphasis which is used both at the cutting lathe stage and the phono preamp stage of reproduction equipment to allow for greater accuracy, particularly in the low and high end frequency output of the reproduction system.

Use of a mic pre or DI system does not allow for the RIAA equalisation system and requires further eq filtering at the wave editing stage if used.

For 33/45 rpm discs a shelf bass boost at 500 Hz sloping at 6db per octave with a peak of 17db at 50 Hz is required.

Additionally, a shelf high frequency slope is required at 2.1 kHz with a peak of 13.6 db at 10 kHz.

For 78rpm a shelf bass boost at 250 Hz with a peak of 12db at 50 Hz is required. The top end can usually be left alone due to the low high frequency content; although a shelf at 3 or 6 kHz with a peak of 12db at 10 kHz may give better results (it is obviously highly subjective and dependent on the age and state of recording present).

Sampling rates / bit definition

For most transfers a sample rate of 441.khz at 16 bit depth is sufficient to comfortably contain the dynamic range of the programme material and allow sufficient headroom for processing of the file. Some engineers prefer using a bit depth of 24, allowing for greater resolution in the wave processing stages. The file is then dithered to 16 bit at the final stage before cutting to CD (noise shaping or UV22 dither can also offer greater resolution or dynamic range).

It may be more desirable for audiophiles who wish to keep the high harmonic content of some half speed mastered recordings (or other high quality offering) to use a sample rate of 88.2 kHz.

It is always best to stay with at least a multiple of 44.1 kHz since this is the final frequency used on CD and resampling from any other rate may cause antaliasing or quantisation errors.

Transferring of the recording

With 33 and 45rpm recordings it is a straight forward matter of setting the sample rate (44.1 or 88.2khz, 16 or 24 bit depth) and commencing recording.

Monitoring should be kept to an absolute minimum so as to remove any risk of feedback between the pickup and the monitors.

Critical monitoring of the whole source should take place after the wave file has been recorded. This allows for checks that the entire programme had been accurately transferred. There are two main reasons for this;

Firstly, there is always a risk of stylus jump, or groove stick, especially with poor condition vinyl or where weighting on the cartridge is insufficient for the type of grooves (fine grooves can cause skating - larger grooves such as those found on 78rpm discs or loud DJ cuts on 12 inch singles can sometimes throw the stylus out of the groove if the stylus is not sufficiently weighted;

Secondly, there is also the possibility of background tasks, hard drive contention or some other housekeeping or internal function causing the computer to hesitate in the recording process which may then cause dropouts or stuttered takes of the audio material. Properly set up audio PC's should be less prone to this type of problem but long recordings of this nature (less often performed than shorter multitrack takes) often show up deficiencies in PC set up and can help in determining the setup health of your system.

78rpm recordings provide a different problem; If, assuming you do not have a turntable capable of rotating at 78rpm, it is necessary to repitch the material to the appropriate recorded speed. This can be achieved by one of two methods;

Use a transfer speed of 45rpm in all cases as this is nearest to the required 78rpm and thus allows for less "bending" in the processing and a more accurate result.

Some systems (particularly sound cards) are capable of recording at user set sample frequencies. By carrying out the following calculation 44,100 X 45 / 78 a sample rate of 25442 Hz is determined. If the disc is sampled at this rate, it can then be played back at 44,100 Hz to restore it to its correct playing speed.

The other more commonly used method is to sample the disc at 44,100 Hz and then carry out a pitch shifting routine. 45 / 78 equates to 57.692% expressed as a percentage. Using the pitch shift routine found in most common Wave editing packages produces the recording at correct playback speed. The highest quality setting should be used when carrying out the shift.

It should also be borne in mind that 78rpm discs were recorded on very crude equipment with rotation speeds anywhere between 60 and 90 rpm, depending upon the age and quality of the equipment used. In this case it may be necessary to determine the key of the original recording and make the necessary calculations to return the transfer to that original key. Again, if the key is not known or cannot be calculated, use your ears to determine the most appropriate speed by listening to both the playing style and the natural attack / decay and tone expected from the instruments used in the material.

Tape based transfers

The two most likely formats to be transferred are open reel or cassette, although there are a few lesser known formats such as Eight track, micro cassette etc. which may be presented for transfer (in the early days of recording, Wire recorders were used prior to the invention of tape). These more rare formats can be treated in broadly the same way as open reel and cassette decks, providing you have the means to reproduce the sound in the first place. In the case of very rare formats such as Wire, it is most likely that you would need to contact a private collector or working museum to obtain the use of a playback machine (the BBC is always a good place to start your search).

Cassette decks usually have a consumer output of around -10dbu, open reel usually use the pro level of +4dbu. There are however a number of exceptions to this (in the form of professional cassette decks or consumer reel to reel machines) and inspection or measurement or even the owner's manual (if available) should provide the necessary output value.

Both cassette and open reel use a number of different tape technologies and noise reduction processes as well as playback equalisations, so it is important to identify the appropriate settings for the job in hand.

Cassette tapes come in ferrous, chrome, pseudo chrome, ferrochrome or metal brands. They require different playback switching (where available) on the playback machine. Open reel have used similar tape formats, although the most common has been ferrous based tape. Occasionally, you are presented with a playback bias control on the deck, this should be used with care to reproduce the most natural sounding programme.

Open reels often offer either NAB or IEC equalisation (pre-emphasis / de-emphasis circuits). NAB is more commonly used in Europe whereas IEC is more common in America. More sophisticated decks allow you to switch between the two formats.

Noise Reduction

Noise reduction can also present a number of options to the engineer. There have been a number of different systems used over the years; Dolby A, Dolby B, Dolby C, Dolby S, DBX, Bell and several other proprietory brands. In the case of cassette, Dolby C was introduced in the late eighties, any recordings prior to that are likely to have used Dolby B although some decks have used DBX circuitry and in rare cases, no reduction at all.

Open reel have tended to be recorded without noise reduction because of the extended dynamic range of the format. Some tapes however, particularly consumer recorded hifi tapes, use DBX, Dolby A or Bell noise reduction.

Where there are no obvious markings on the tape as to the process used, a certain amount of detective work has to be carried out;

Dolby A, DBX, Bell and Dolby C use a pre-emphasis - de-emphasis system which produces a certain amount of "pumping" when played back without noise reduction. These tapes are best reproduced with the appropriate noise reduction switched in. In the case of some of these systems, it is necessary to adjust the amount of effect produced by using the supplied sensitivity controls. In the case of Dolby B, pumping is less obvious and it is the author's preference, often to make the transfer without the noise reduction circuits switched in, relying upon modern "noise print" based algorithms to remove the effects of the process and the inherent noise of the medium. This is of course subjective and depends very much on the effectiveness of the Dolby circuitry in use.

Playback checks

Another vital aspect in the reproduction of the programme material is to check the condition of the playback circuits of the machine itself. Open reel machines, particularly go out of adjustment in terms of playback equalisation on an almost daily basis. Now, almost a forgotten art, is the line up procedures followed by engineers of the past in analogue recording studios. Professional reel to reel machines are fitted with a number of potentiometers to allow strict alignment of recording and playback equalisation and bias. To carry out these procedures varies from machine to machine but he principal is broadly the same. It is necessary to apply a metered input of test tones of 100 Hz, 1 kHz and 10 kHz at 0dbu to the input circuitry of the machine. The record amplifiers are then aligned to produce 0dbu at the playback meters of the deck. The tones should then be recorded to tape and the playback circuitry realigned to reproduce those tones at 0dbu. Allowances should be made if noise reduction circuits are used so as to produce the 0dbu levels when the noise reduction circuit is switched in.

In the case of pre-recorded masters which have been professionally recorded, the tape should contain a set of the appropriate tones either at the beginning or the end of the reel. The playback circuitry should then be aligned to produce those frequencies at 0dbu as to ensure accurate playback of the frequencies of the programme material. Some engineers use different frequencies and line up levels, these should be noted on the reel box and should be used where appropriate.

For critical transfers, head alignment should also be check to determine whether the azimuth (head alignment to tape path) is correct. This procedure should detailed in the maintenance manual / procedures for the machine in question. It is particularly important to check head alignment where there appears to be a loss of high frequency from either of the playback channels as the tape may have been recorded on a misaligned deck, or the playback machine may be misaligned. Adjustment of the height and angle of approach of the head to the tape path may be necessary to ensure accurate playback of the programme material.

Cassette decks can suffer broadly from the same problems although are usually less critical as the dynamics of the physical design of the machine make it less likely for the heads to wander too far out of alignment. However, cheaper machines may have never been aligned correctly and should be checked in any event to take the problem out of the equation.

Because of the inability of cassette media to accurately reproduce the kind of levels produce by open reel machines, test tones are often checked at around -10dbu.

Transfer to computer then follows the same principles as that of vinyl although monitoring levels are not critical as feed back should not occur from the playback heads at normal listening levels.

Once transferred it is then of course necessary to check the whole programme for dropouts, tape folds etc.

The same rules again apply to overall eq to account for de-emphasis where a noise reduction system has been used and is switched out or unavailable for the purposes of the transfer. The actual values of the filter slopes will depend upon the de-emphasis characteristics of the system in operation.

Repairing dropouts or other damage

The first stage in processing the wave files for transfer to CD is to ensure that you have continuous programme material. There are a number of processes depending upon whether the source programme came from vinyl or tape and whether there has been any computing error in the recording of the material.

With vinyl, the most common problems are those of jumping or groove sticking.
It is not always necessary to repeat the record process and this sometimes leads to an identical replication of the original problem.

If there are a large number of jumps, it may however be necessary to repeat the take and experiment with the pick up arm and cleaning. Sometimes there may be dirt stuck in grooves which can be easily repaired. Damaged grooves can sometimes be repaired (especially wider grooves) by analysing the damaged disk under a magnifying glass or low power microscope. A sharp pointed tool can be used to reconstruct the wall of the groove although a very steady hand and well placed confidence in what you are undertaking are necessary.

Where there are only a small number of jumps or sticks it is possible to record the areas leading up to the jump and then place the stylus immediately after and carry out the repair manually. It is then necessary to reedit the repair into the main track. Competent editing is required to carry out this procedure. It is also possible (in the case of some material) to find an identical passage elsewhere within the track for example, a chorus and edit it into the place of the damaged material. Once corrected, any remaining clicks can be removed from the Wave file using methods described below.

With tape, the most common problems occur from tape drop out (where the oxide has been shed), tape folding or shredding or print through where the tape has transferred its data onto the adjacent tape through poor storage or as a result of poor media in the first place. Thinner tape formats tend to suffer from this more so.

If a tape is shedding oxide and has become brittle, there is a danger that it might not survive more than one pass through a tape machine there are specialist methods of "tape baking" etc. which are not covered within the scope of this document.

Dropouts can often be dealt with by using the wave editor to lift the level of the affected passages. It may be necessary to use level slopes and negative fades where the material demonstrates a reduction of level over time. Again, editing an identical passage from elsewhere in the material can often be the simplest repair.

Folded or shredded tape is difficult to deal with and often requires manual winding and flattening of the affected tape. Care must be taken not to remove any more oxide than has been loosened by the damage. Again edits from elsewhere are often the best solution.

If areas cannot be repaired sufficiently then it may be necessary to discuss the job with the commissioner to see if they want you to accurately reproduce what is there or whether they wish you to carry out some "creative editing" to mask the damage.

It is also worth asking whether it is the only copy of the source material as reconstruction even from an inferior copy can sometimes be made acceptable by the use of copy cat equalisation tools such as Steinberg's Freefilter.

Print through only really causes problems on lead ins and quiet passages. If the print through appears before the start of a track, it can simply be removed by editing or fading the prematerial leader. On fade outs, it may be possible to introduce an earlier fade so as to mask the print through. In quiet passages, eq and expansion are often the best tools, (print through is composed mainly of mid and low frequencies, it may be possible to lift the high frequencies so as to again reduce the effect of the print through. This does not always work and again, discussion with the commissioner of the job may need to be called in to determine the most acceptable result for their purposes.

Computer related dropouts and stutters can only be effectively dealt with by sorting out the computer hardware or software problem and retaking the material or the affected section. Again, this is not covered within the scope of this document.

Processing the Wave file.

There are a number of distinct artefacts and problems apparent in the file whether transferred from vinyl or tape which now have to be addressed. Since some of the problems are common to both sources this section will cover the subject of file processing as a whole.
The principle artefacts are:

Noise (including hiss, hum, motor noise), damage (including pops, clicks, vinyl scratches ,crackles), programme quality (including equalisation, tape dropout, dynamics).

The first stage after checking the integrity of the transferred file is to address any dropouts, jump, sticks or other artefacts that spoil the continuity of the file. These have been dealt with previously.

The next stage is to remove any unwanted general noise from the material.

NB. It is appropriate at this stage to discuss automation and batch processing.

Since, in a commercial environment it is necessary to carry out these procedures as efficiently and as automatically as possible certain workarounds should be considered so that the files are dealt with on a production line basis.

Loading vinyl will often give you two files of approximately 20 minutes duration. Cassette and reel will depend upon the track format and the length and speed of the tape. The largest file most commonly met will most likely be created from one side of a C90 audio cassette giving a length of approximately 45 minutes.

With modern processors, most procedures now take a few seconds rather than minutes and are best dealt with in batch processing format or continuous long file format as loading and unloading of separate tracks is both time consuming and relies heavily on manual intervention - the computer carries out more i/o than processing.

Some wave editors such as Wavelab and Soundforge offer the facility to place region markers within a continuous file. Processes such as noise reduction, equalisation and declicking can be applied to the whole file in one pass. Separating the file into individual tracks need only take place at the point of preparing for burning to CD.