Buying a Tape Machine: An 11-Point Checklist

Author: Hou

Sep. 09, 2024

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Buying a Tape Machine: An 11-Point Checklist

Tape is still in high style in the audio world. Like a Corvette or a standup Pac Man machine, some technical pleasures never go out of fashion.

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Although 99% of today&#;s audio facilities have a DAW as the center of operations, an element of analog tape processing remains a welcome element in a large number of studios.

While many engineers are content to approximate the sound with the wide array of tape-emulating plugins currently available, there&#;s no shortage of recordists willing to go hard-core with an actual tape machine on hand.

The problem for engineers, producers, studio owners, and archivists who have their heart set on obtaining a tape machine &#; whether it&#;s their first or is complementing one or more machines already in-house &#; is that there are virtually no new models on the market. Save for the Otari Mx MKiii, which is still being made on a limited but costly basis, people who want/need tape will have to obtain a used machine.

So how do you know if that shiny Studer A827 24-track 2&#; machine that you&#;ve just discovered for sale on Craig&#;s List is your dream machine, or a lemon?

One man who can tell quickly is &#;Midnight Bob&#; Shuster of Long Island-based Shuster Sound, who stands among the country&#;s most experienced audio techs. A professional maintenance engineer since , Shuster kept all the gear humming at top NYC facilities including the Power Station, Media Sound, Record Plant, Electric Lady, Sony Studios, Pomann Sound, Avatar, NBC, and many more.

Today, Shuster&#;s clientele has grown to include an ever-expanding list of solo studio operators and engineers, as well as radio stations, who count on him to keep their analog gear running strong. Tape machine repair and maintenance can account for several of Shuster&#;s house calls each week, and while some of the newly-obtained Ampex, Otari, Studer, MCI and Scully machines he sees are running clean, others would be more useful as retro coffee tables.

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Re-lapping is obviously the most economical choice, and most headstacks can be relapped between one and three times (depending on the amount of wear on the heads each time). A good test for a worn head is to take your fingernail and run it along the upper or bottom edge of the head &#; if you can feel a ridge or your nail catches on a ridge, it is a good idea to have it inspected for possible relapping. The exception to this would be an &#;undercut head&#; which actually has grooves cut just above the top and bottom of the head cores to help reduce edge wear and protect the tape.

To those unfamiliar with headstacks, it is difficult to explain the differences between head wear and intentionally undercut heads, but it is most easily explained that the undercut head has wide machined grooves which is easy to see. If the head is not undercut, it should have a completely smooth surface and your nail should not catch on ridges. You may also see uneven patterns across the face of the head. Badly worn heads will have grooves at the top and bottom where the tape has travelled and causes level inconsistencies and can even damage the tape.

Another indication of bad heads is that they may not play or record at all and they may be worn beyond what relapping can repair. If you&#;re not sure about you&#;re seeing, call somebody in to do an evaluation. If you&#;ve purchased the deck already, have the heads taken off the machine and send them down to John French of JRF Magnetics in New Jersey &#; he&#;s the legend as far as saving tape heads. For illustrations and further information about heads and relapping, visit JRF Magnets at http://www.jrfmagnetics.com.

If it&#;s too late for relapping, then replacement heads are the ultimate step, but that&#;s considerably more expensive.

The Tape Path

Next, take a look at the tape path: the reel spindles, incoming guides, impedance rollers, capstans, tach roller, tension arms/rollers, lifters and pinch roller.

Reel Spindles: hold and secure the reels of tape on the machine

Incoming and Outgoing Tape Guides: provide proper positioning of the tape across the heads

Impedence Roller: smooths the tape as it comes off the reel before reaching the heads (See &#;Image 1&#; in the gallery following the article)

Lifters: guides that pull the tape away from the heads in fast wind modes to prevent unnecessary wear on the heads. Lifters can also be released for fast wind audible cue. (See &#;Images 2 & 3&#; below)

Capstans: provides the precise speed to drive the tape past the heads. Rotational speed and diameter of capstan shaft determines the speed. Most capstans shafts have a dull finish. When they become too polished or shiny, they may cause tape slippage and speed errors. The capstan should be able to be rebuilt or refinished by a specialized motor rebuilding service. One such company is MDI Precision Motor Works, visit at http://www.precisionmotorworks. (See &#;Image 4 & 5&#; below)

NOTE: There are two disclaimers to the polished finish &#;rule&#; about capstans. There ARE some designed to be polished or shiny. The best way to determine if your machine&#;s parts were designed as such is to check the entire length of the shaft. If it is uniformly polished, it is probably designed to be so. Other capstan shafts are made from ceramic material and wear out very slowly, if at all. They are white in color.

Pinch Roller: rubber roller that provides proper tension to the tape against the capstan, permitting tape to draw off the supply reel and past the heads at a constant speed. If the pinch roller becomes gummy or cracks, it should be replaced or rebuilt. One of the rebuilding companies I use is Terry Rubber Rollers, at http://www.terryrubberrollers.com.

Tach Roller: (found on more advanced machines) Used for tape read-out/time counter and also monitors the direction of the tape and its speed for transport control. (See &#;Image 6&#; below)

Rotating components in the tape path (guides, impedence rollers, tac rollers, lifter rollers) can have noisy bearings. To test for this problem, you should put a recorded tape on the machine and listen. If you detect noisy bearings, they may need to be replaced. Luckily, many of these parts are shared by a wide range of machines, so they are readily available through many companies that make bearings.

The Motors

In a tape machine, you&#;ve got the capstan motor, supply motor, and takeup motor.

Reel Motors (Supply & Take Up Motors): controls the reel play out of each reel and provides proper tension across the tape path and heads. It&#;s easy to tell if you have problems here. They either work or they don&#;t. If you encounter motors that do not work, they could have worn out or burned out. Either case, they need to be replaced or rebuilt. On newer decks, the motors are driven by a motor drive amplifier (MDA, for short) and this amplifier can fail, preventing the motor from operating. The only way to make this determination is through component level troubleshooting by a skilled technician.

Capstan Motor: the most critical motor in the machine. If it is not working properly, the tape will not move properly across the heads, you may hear flutter or other unusual noises when listening to a tape. The best tests include using an alignment tape to distinguish if the tones are steady. Using a piano recording is also a critical way to test for flutter.

Keep in mind that if one of the motors isn&#;t turning, the motor itself may not be bad &#; it may be the circuitry. The drive electronics may not be happy. The only way to test for this is through component level trouble shooting performed by a skilled technician.

Other Rubber Parts

Rubber parts are prone to stretching, drying out and crumbling or even turning into a liquid black goo, depending on how they were treated. Urethane parts can turn into a white-colored liquid goo. This is particularly of note to those tape machines using the indirect drive of capstan. In other words, a machine that uses a motor to drive a belt/flywheel containing the capstan shaft. The belts are made of rubber and should be replaced if any of the conditions described above are present.

Some Ampex and Otari multitracks use a servo system that employs capstans only and no pinch roller. On these machines, the capstan rollers are made out of rubber or urethane and can experience the same problems described above. However, they can be rebuilt in most cases.

There are also some parts of braking that use rubber which should be checked, as well. Most machines do NOT use rubber brakes, but those that apply can be found under the deck plate by the reel spindles or motors.

Speed

Just to review the basics, tape machines record at different speeds, the higher the speed, the better the quality of the recording. The measure is IPS or inches per second of tape that passes across the record head. Obviously, the faster the tape speed, the more tape that is used to record the performance, so there are financial considerations in determining the speed at which you want to record.

Speeds range from 15/16ths IPS (which is only used for low quality voice recordings and logging) up to 30 IPS for the highest quality analog music recording and mastering. If you are doing any serious recording or mastering you will only want to record at 15 IPS or 30 IPS.

7 ½ IPS is the lowest speed considered for &#;professional&#; use, but it was limited in use. In the past, radio stations used it as a way to save tape and it was considered the top speed for home recording use. However, it was only used in professional audio recording for making dubs to give to clients to play at home or for radio station use.

There are machines that record at 1 7/8ths IPS and 3 ¾ IPS. Besides reel-to-reel machines, cassettes were recorded at 1 7/8ths IPS. The much maligned 8-track cartridge was recorded at 3 ¾ IPS and this speed was considered to be a good voice recording and background music recording speed for home reel-to-reel use.

Track Width

The wider the track, the quieter the tape and the hotter the signal that can be recorded onto the tape. The tape width determines the amount of tracks you can record on a tape and still maintain excellent quality.

Two-track recordings are stereo mix-downs and should be recording on either ¼&#; or 1/2&#; formats, depending on your budget.

If you are doing multi-track recording on an analog professional format, there are the following choices:

=1/2&#; four track
=1&#; eight track
=2&#; sixteen or twenty-four track

There are also semi-professional formats as follows:
=1/4&#; four track
=1/4&#; eight track
=1/2&#; eight track
=1/2&#; sixteen track
=1&#; sixteen track
=1&#; twenty-four track

There are some 1&#; two track machines used for mastering, but they are very exotic and extremely expensive to operate. They are specially modified headstacks installed on professional two track machines.

So, the faster the tape speed and the wider the tape, in general, the better the quality of the recording, but, also, the more expensive the cost of tape. At 30 IPS, a standard foot reel of tape will only provide a little over 16 minutes of record time. Depending on the width of the tape, the tape costs range from $50-300 per reel, or more. (Note: Tape costs fluctuate greatly).

Updates

On professional studio machines, manufacturers generally released updates to improve performance. Some lesser quality machines might also have upgrades if the original owner turned in the warranty card and paid attention to service update advisories.

For example, if you purchased a Studer A80 made in , there were manufacturer updates up until the late s, which included things as important as changing the heads, so you may be lucky enough to find a machine that has been updated on a regular basis.

At the big studios, such as Power Station, we would get calls in the Technical Maintenance Department from Studer, Sony, and Ampex letting us know of updates, &#;We have an update. Can we send a tech over to update all of your machines?&#; Everything would be kept in their files and the manufacturer kept track of which machines were eligible for updates and when. The update could be something as simple as a resistor value where they would say, &#;This update will make your deck sound better.&#;

You can check to see if a machine has been upgraded by looking for a little sticker in the machine which indicated the version. If it&#;s a later machine with microprocessors, then you can look in the service manual and it will say that this microprocessor was put in from &#;x&#; serial number to &#;y&#; serial number. Or you can check online, there are still websites that cater to these machines.

Some decks, like the Studer A820 (pictured) will provide the software version in the menu display when powering up.

Service records for machines are a rare commodity. The largest facilities kept logs for all of their equipment, but most of the analog reel-to-reel machines were taken out of service some time ago and most of those records are no longer available. Plus, many of the machines have changed hands a number of times and the current owners never thought to request any of the past service records or notes.

On rare occasions, you may be lucky enough to find that meticulous owner. I actually knew the Media Sound and Power Station machines individually, and have recognized one or two of the Media Sound machines when we&#;ve met again in a different studio, but that only comes from spending many years with my hands inside the guts of the machine.

Rebuilding/Restoration

Due to the nature of electrolytic capacitors, there is a tendency for them to dry out, resulting in degraded audio quality due to the fact that their values shift. Therefore, one of the currently popular topics is replacing these capacitors (&#;recapping&#;) in audio electronics and power supplies. I doubt that the manufacturers ever thought we would be still using some of this equipment over a period of more than 40 years, so the capacitors are just plain getting old.

Old microphone pre-amplifiers and consoles are very popular purchases today, and I spend a lot of time recapping them and the same thing applies to the electronics on analog reel-to-reel tape decks. These older workhorses are often in need of new electrolytic caps. So, when you are investigating the purchase of a machine, ask questions about whether they replaced any of the capacitors during routine or emergency maintenance. If not, you should budget for this expense.

Capacitors are components found on the circuit board inside the tape machine. Most people cannot check out the condition of the caps themselves because it requires test equipment to measure the value of each component.

There were some pieces of electronic gear that were known to have bad capacitors from the time they were new. But most of those capacitors will have already been replaced by the time you would acquire it second-hand, unless it was barely used.

Unfortunately, there are not many resources available to provide in-depth technical information about these vintage tape decks, consoles or other pieces of great gear since so many of the manufacturers are out of business, the machines were often custom-made for the purchasing studio, and they were often not widely produced. However, you can check out a few of the online discussion groups that people have created for individual brands: Studer, Ampex, Otari, Scully, and others.

If you know that a piece of electronic gear has not received any maintenance in the past 20 years, you should count on having to replace capacitors.

Basic Maintenance

Say you take the plunge and buy a tape machine, or you&#;ve already got one, there&#;s day-to-day maintenance you should do. I don&#;t mean pulling out the test equipment and doing an overhaul &#; just regular maintenance associated with normal usage.

For keeping the tape heads and the tape path clean, use 91% or better isopropyl alcohol with Qtips &#; either wooden stick Qtips or regular Qtips. Dip your Qtip in the alcohol, clean the guides, the heads, the capstan. You want to keep your machine clean! Especially if you&#;re playing back a lot of old tapes with sticky shed problems. But then you may want to be baking tapes, which is a topic for a whole other conversation.

The heads should be demagnetized once a week if you are using the deck regularly. I recommend one made by R.B. Annis called the &#;Han-D-Mag&#;. You can find them on eBay or a Pro-Audio vendor like Sweetwater or John French at JRF Magnetics. The last time I looked they were less than $100 new. The instructions are on the package. It&#;s an easy DIY procedure.

The motors should be oiled from time to time&#;.once a year or every six months, depending on use, using what the manufacturer specifies. DO NOT USE 3 In 1 Oil!!

Keep the outside of the machine clean as well. Use a damp cloth to remove dirt, dust, and grime. Cover the machine when not in use, but only when the power is off.

You should also purchase a MRL (Magnetic Reference Lab) Calibration Test Tape. This tape with tones on it allows you to setup your recorder to standard operating levels. If your tape is played on other machines that were setup with the test tape, it will playback correctly. You should record test tones on the beginning of your masters if you send them out for mastering, 1khz, 10khz, 15khz, 100hz and 50hz.

Tape Costs and Tape Types

One of the most frustrating things about analog recording in the past five or so years has been the lack of availability of magnetic tape, and the tape that is available is expensive. Right now, we only have two companies manufacturing magnetic tape. RMG, which is really now known as Zonal, is a company located in Holland, but manufacturing their tape in France. The other company is ATR, which is located right in the U.S. of A. in Pennsylvania, and is owned by Mike Sptiz.

The quality of the two manufacturers is similar, both are professional grade. But be aware that, historically, magnetic tape has been known to have a &#;bad batch&#; now and then. Most manufacturers will exchange bad product for new if you make them aware of the situation.

Tape can be reused multiple times unless it has been damaged or spliced. However, you do not want to re-record on tape that is sticky or shedding, which is a problem found with certain brands of tape. Some include Ampex 456 and 406 (the Quantegy 456 was generally OK), Scotch 226 was also notoriously bad for sticking and shedding.

Professional Support

How is recycled quartz sand produced?

Tape machines are complicated electromagnetic devices, which require servicing. Unless you know what&#;s going on in the machine, it&#;s best to call a pro. If you want something aligned, just call us. We&#;re here to keep the machines going, because no one is making them anymore.

If you are looking for more details, kindly visit Goodi.

Additional resources:
The Advantages of Utilizing Recycled Quartz Sand

Maintenance is a necessary evil &#; there&#;s not that much stuff out there that&#;s 20 years old that people want to use, but if it sounds good you&#;ve got to keep it going. Guitar amps are a great example of ancient technology still being made today.

So you need a tech guy to check out a machine beforehand and after you acquire one, and nine times out of ten the guys working on your tape machines can fix the rest of your equipment too. For mixers, Pultecs, limiters, you&#;re tapping into a lot of knowledge from these people. There&#;s not a lot of us, but we&#;re still around and brave enough to stay in this business!

Midnight Bob Shuster is located in Metro New York and can be found at http://www.shustersound.com.

Please note: When you buy products through links on this page, we may earn an affiliate commission.

Tape operating level aka 'reference fluxivity': what's it all ...

So, I&#;ve been investigating the subject of tape operating levels. Or, to use the more technical-sounding term, reference fluxivity.

I actually started looking into it a few months ago but it&#;s taken me this long to get my thoughts into enough of a semblance of order to write something vaguely coherent! Why? Well, it turns out that reference fluxivity is a veritable curate&#;s egg, a can of worms&#; a seemingly simple concept and yet the more you research it, the more variables, differing terms, different units of measurement and contrasting yet strongly held beliefs you find. And, as I eventually worked out, some of these beliefs are simply wrong. Others, meanwhile, are just different opinions and preferences. Some people consider tape operating levels to be all-important while others take little notice of them. Of those in the former camp, some support a view of &#;the higher the level, the better&#; whereas others stick resolutely to decades-old standards. As for me, my starting point was when Ed Pong of UltraAnalogue Records brought it to my attention, and so off I went exploring (as ramblers tend to).

I&#;ll admit that this hasn&#;t been the easiest of explorations. I think I now understand the rudiments and the key implications of reference fluxivity, but whether I can then explain it in a remotely useful way remains to be seen! In the spirit of reel-to-reel rambling, let&#;s give it a shot&#; but first I must re-emphasize that I&#;m not claiming to be any kind of expert here, just a journeyman sharing his tales from the road, as it were. So if there&#;s something here that strikes you as being off the mark, please do drop me a line and steer me back towards the righteous way.

What the devil is/are &#;reference fluxivity&#; and/or &#;tape operating levels&#;?

Before we dive into the detail (and there&#;s lots of it) let&#;s start with a quick précis of what we&#;re talking about here. To the recording engineer, the studio and the record label, the choice of reference fluxivity, or tape operating level, is made to minimize tape hiss and maximize dynamic range and resolution, ultimately to achieve the highest level of realism in the recording. In practice it&#;s something that a studio would have decided upon and then stuck with, perhaps changing once or twice over the course of a few decades (as tape formulations evolved and audio electronics became more advanced).

So, what does the beginner need to know? Tape operating level, or reference fluxivity, is a term used to describe the strength at which the record head &#;prints&#; the signal on to the tape. However, this does not directly relate to the level of the signal that your tape machine outputs to your amplifier, nor does it directly relate to the recording level&#;

Say, what? (Good question). Usually I&#;m a fan of straight-talking and plain English, but in this case I find the more complex term &#;reference fluxivity&#; to be slightly more useful to my understanding than the simpler &#;tape operating level&#;, which is why I&#;m switching between the two here. &#;Level&#; is a broad term that could potentially mean all manner of different things and so it&#;s easy to confuse it with other parameters. &#;Reference fluxivity&#;, on the other hand, is quite specific so let&#;s kick off with that as our starting point.

So, &#;flux&#;&#; magnetic flux is a measure of the strength of a magnetic field at a particular location, so in the case of R2R tape, we&#;re talking about the strength (or level) of the signal that the recording head &#;prints&#; onto the tape. The tape is said to be recorded at a certain level, which is measured in Nano-Webers per meter (nWb/m or 10-9 Wb/m) &#; hence the term, &#;tape operating level&#;.

Reference fluxivity, then, is a given magnitude of magnetic flux (for example 250nWb/m, typically measured at 1kHz) that is used to calibrate the input and output circuits of a tape machine such that the signal level meters (VU or PPM) indicate 0VU (or PPM5), when a reference level signal is recorded or played back. These settings are applied to your tape recorder using laboratory-recorded reference tapes specifically made to calibrate tape deck recording and playback levels. A recorder calibrated to, say, a higher fluxivity will record at a higher level of magnetisation on the tape, but will play back at a lower level, thus producing the same output level. So, for example, a machine calibrated to 320nWb/m will record at approximately 2dB higher level on the tape compared with a machine calibrated to 250nWb/m but will play back at -2dB level and so produce the same output level. Whatever your deck is calibrated to, the key point is that a level of 0VU in will give a level of 0VU out, whether recording or playing back.

Of course, if you are playing back a tape that has been recorded with a higher fluxivity than your machine has been calibrated with, the output signal will be higher. For example, if your machine is calibrated to 250nWb/m and you are playing back a tape recorded at 320nWb/m, the resulting output signal will be 2dB higher, and show +2VU on your level meters.

The name of the game: signal vs. noise

In very crude layman&#;s terms, the reference fluxivity, or the tape operating level (to use the simpler term from here forwards), of a R2R tape is a measure of &#;how magnetized&#; the tape is. And so, as in almost all things audio, there&#;s a push-pull between ideals. &#;More&#; magnetization has the potential to offer more musical desirables &#; information, detail, dynamic range, shifting the recorded musical signal further away from the inherent noise floor of the tape itself. But then as you move up the scale, the arch enemy of distortion creeps in until, ultimately, you reach a tape&#;s saturation point &#; the point at which it&#;s so magnetized it&#;s kind of &#;whited-out&#;.

What we&#;re talking about, then, is that all-important ratio of signal-to-noise. Or in this case perhaps we could say, finding the optimum sweet spot in a scale of noise&#;to-signal-to-saturation.

Sounds simple enough &#; so where&#;s the rub?

So far, so graspable. But the complications that then arise are due to the fact that (as with all things analogue) standard or common practice in the world of tape has evolved with time, experience and technology. Therefore, tapes from different eras were recorded at different levels. What&#;s more, different decks intended for studio or domestic use were calibrated for different tape operating levels. And even now, recording engineers have varying preferences and practices and so modern master tape copies also differ in their levels.

To help make sense of all these variations, let&#;s take a very brief tour from the good old days to modern practice.

Tape variations

First off, the physical quality of magnetic tape has improved over time. Older tapes had lower saturation levels than many modern tape formulations. By recording at a higher level, any tape hiss will relatively be lessened. So different tape recordings may have different operating levels depending on when they were recorded, reflecting the quality of magnetic tape being manufactured at the time.

Studio/recording preferences & deck variations

Typical vintage consumer tape machines, which were obviously designed for home rather than studio use, were either calibrated to 160nWb/m, which was known as the NAB Broadcast Cartridge Standard (not to be confused with NAB equalisation), or to 185nWb/m (@ 700Hz, it&#;s actually 180nWb/m @1kHz), which was known as the Ampex Operating Level. Either of these was considered to be a sensible tape recording and playback level at the time (from around the s). The Ampex Operating Level became the de-facto standard reference point for recording studios and so from here forward we&#;ll refer to it as the 185nWb/m reference, or &#;0db&#;.

Over time, as tape manufacturing improved, many studios changed to using a higher recording level. As a result, by the s and s many professional studios had calibrated their decks at 250nWb/m (it&#;s a logarithmic scale, so that&#;s nearly 3dB &#;louder&#; than 185nWb/m). So a steady test tone recorded at 0dB on such a studio machine would replay as a steady +3dB tone, well into the red, on your vintage consumer machine.

As tape manufacturing continued to improve, studios began to raise their operating levels accordingly. In the United States, 250nWb/m remained the norm for most of the analogue era, but in much of Europe it was increased to 320nWb/m. 320nWb/m is nearly 5dB over the old 185nWb/m standard, and 2dB higher than 250nWb/m.

These days, some tape formulations, such as Recording The Masters SM900, can comfortably be recorded at +9dB above that 185nWb/m baseline, therefore some users (studios and consumers alike) choose to calibrate their machines even higher in order to achieve even lower tape noise and greater dynamic range. It&#;s certainly not uncommon to find machines calibrated to 516nWb/m (+9dB relative to 185dB).

What does this mean for me as a listener / occasional recorder?

As a listener and occasional recorder (say, making back-up copies of your tapes), your concern is essentially twofold. First, when having your tape deck calibrated during initial set-up and subsequent servicing, to what reference fluxivity should you calibrate your machine? And second, there&#;s the tape-by-tape basis to consider. If you&#;re lucky enough to have a deck with adjustable operating levels, it&#;s a simple question of checking the tape&#;s cover information to identify the level, or playing the test tone if there is one, and adjusting the output level so that reads at the 0VU mark. But if your deck doesn&#;t offer that option, then you&#;re stuck with the level to which your deck&#;s been calibrated, and so you might want to have a quick check of the fluxivity of a tape before buying it.

Not that getting it wrong, or paying little or no attention to it, is likely to blow up your deck or anything! In fact you could happily ignore the whole issue if you wanted to. But if you&#;re an audiophile, you&#;re unlikely to want to, since it&#;s all about optimizing the signal-noise ratio of your deck and tapes, and hence your musical pleasure. Let&#;s face it, if you&#;re paying several hundred pounds to hear the ultimate copy master of an album, then you&#;ll probably want that &#;ultimate&#; to be, well, ultimate!

Deck calibration and adjustment of output levels

As if all this wasn&#;t complicated enough, R2R decks can be fitted with either volume unit (VU) meters, peak programme meters (PPM), or no meter at all.

A VU meter is a simple galvanometer and uses the physical inertia of the movement to average out the reading. A PPM is more sophisticated and has a very fast rise time and slow decay. PPM is favoured by the BBC as it shows peaks that exceed a certain duration that could overmodulate a tape (or even blow a radio transmitter!). These peaks are not shown by VU meters. However, VU meters have simpler circuits and are easy to use for most domestic applications.

When the deck is calibrated, which is done at the point of manufacture and then in subsequent servicing, the reference point of the VU or PPM meter is set at a given level. This is the deck&#;s calibrated operating level.

So when you&#;re listening to a tape on an optimally calibrated deck, the baseline of a recording &#; say, the backing track average or the main vocal &#; will be at or slightly below this 0VU point (i.e. the position on your VU meter where it changes from black to red, with peaks perhaps overshooting very slightly into the red).

So how do you know what reference fluxivity / tape operating level your deck&#;s been calibrated to? And what are the implications of having it calibrated at any one of the various possible levels? You can find out by playing a calibration tape to see where the reference level is set. Undoubtedly the most reliable source of reference calibration tapes is Magnetic Reference Laboratory Inc (abbreviated to MRL, and based in San Jose, California).

It doesn&#;t matter if you don&#;t have a calibration tape recorded at your required fluxivity as you can easily convert from one to the other. For example, if you have a calibration tape for 250mWb/m and you want to set up your machine for 320nWb/m, simply set the repro levels at -2VU (-2dB from your reference 0VU). Then when you set up the record levels, you record a tone at 0VU in and get 0VU out, but the tone will be recorded 2dB higher on the tape than one recorded at 250nWb/m &#; simple!

MRL calibration tapes are specifically made for calibrating tape machines. My personal preference is to calibrate my Studers, which were both pro machines, at 355nWb/m. That&#;s +6dB over the old standard of 185 nWb/m, and +3dB above the later studio standard of 250nWb/m. My Technics, on the hand, which was a consumer machine, is calibrated to 185nWb/m. Note: While I would always have my decks calibrated by a professional, you can find a useful technical guides at www.mrltapes.com

Now, in addition to your engineer-set calibration level, you should also be able to manually adjust the output level &#; assuming that your particular deck has output level controls. On most (but not all) decks, you&#;ll have an output knob so that you can adjust that level above or below the calibrated setting. The one on my Technics has a small dot adjacent to the &#;8&#; position to indicate that&#;s where the calibrated level is (see image left). So at position 8 it&#;s playing exactly to its 185nWb/m calibration. But I can adjust above and below that, giving a little room to accommodate replay of higher or lower level recordings.

On a studio/pro deck these controls might not be so obvious &#; it&#;s just as likely to be labelled &#;repro&#; than &#;output&#;, and on Studers you select these controls by pressing the &#;UNCAL&#; button.

However, some studio machines didn&#;t have them at all. The machines were calibrated internally by a technician and then left at the calibrated level. So, if that&#;s your scenario (or if an engineer has bypassed your output controls in the interests of improved hi-fidelity), it pays to think carefully about your calibration level, according to the types of tape you want to buy and play &#; since you&#;ll need to ensure that you&#;re buying tapes that are at least close to the level of your machine. But to be honest, your best bet is to make sure you buy a deck that does have adjustable output.

Buying and playing tapes

If you&#;re buying vintage consumer tapes, they&#;re likely to have been recorded at 185nWb/m or lower. Vintage master tapes, meanwhile, are most likely to be 185nWb/m or 250nWb/m.

What&#;s more, a good number of contemporary master tape copies are also recorded at this level. The Tape Project, for example, records at 250nWb/m giving them plenty of headroom so they&#;re never going to overload the tape. But there are others who favour higher levels. Open Reel Records records onto SM900 tape at 320nWb/m, which being a &#;+9dB tape&#; still leaves bags of headroom but lowers the noise floor to 3dB less than it would be at 250nWb/m. UltraAnalogue Recordings uses the highest level I&#;ve come across in contemporary recordings, at 396nWb/m, further lowering the noise floor and increasing the dynamic range. Sensibly, recording at this level, they include a 1kHz test tone (also, very sensibly separated &#; before the leader tape, so that you can check and set your repro level accordingly). For example, if your machine is calibrated to 250nWb/m the 1kHz tone on an UltraAnalogue Recording tape would read +4 on your VU meter and so you should turn down the output level accordingly. Can&#;t adjust your output levels? Don&#;t worry, on request UltraAnalogue will make 250nWb/m copies for those that can&#;t handle these levels. Still, my advice (again) would always be to invest in a machine with an easily adjustable output level.

Pros and cons of high / low levels

At this point you might be thinking, if recording at a higher level means a lower noise floor and a greater dynamic range, then why not always record at the highest possible level?

Because you have to balance this against saturation, the point where the tape is &#;full&#; and begins to distort.

Secondly, well before you get to the saturation point, increasing the tape operating level increases the potential for print-through: the recorded signal imprinting a copy of itself on top of the adjacent layer of tape (kind of like a magnetic brass rubbing). The stronger the imprint, the greater the likelihood of this transferral of information between successive layers. So, I&#;ve come to the conclusion that there&#;s a sweet spot.

Summing up

Well, several pages of rambling later, does this explain or simplify anything? Or are you more confused than ever?!

The basic rule of thumb is this:

Know what operating level (reference fluxivity) your tape machine is calibrated to.
Know the operating level of your recordings on tape and adjust your repro level to make sure the VU meter reads &#;0&#; at the reference test tone. If there are no tones (not unusual) then find out what operating level the tape is and adjust the output accordingly, or adjust so that the VU needle just flicks into the red on the loudest sections of the music.

Of course, in the business of replay only, none of this is that critical. If a tape sounds really loud, lower the repro level. If it seems quiet, raise it.

It&#;s only when recording that you really need to get het up with all this stuff. But that&#;s a whole other ramble!

Here&#;s a quick reference guide for getting your head around the logarithmic nature of the numbers, or how increases in nWb/m relate to loudness in decibels:

Reference fluxivity nWb/m @1kHz

* 185 nWb/m @700Hz

Relative level (dB) referenced to 185nWb/m (to nearest 1dB) 185* 0 250 +3 320 +5 355 +6 396 +7 520 +9

Note that the oft-used reference of 185nWb/m is actually measured at 700Hz which equates to 180nWb/m if measured at 1kHz. Throughout this article, to save confusion we&#;ve referred to 185nWb/m. Similarly the other figures are approximate.

Right, now I&#;m off for a lie down (you may feel the same way after reading all of this!). But not before I offer my sincere thanks to Ed Pong of UltraAnalogue Recordings and hi-fi journalist Neville Roberts for allowing me to pick their brains and therefore helping me to make sense (I hope) of this mind-boggling subject.

Buying a Tape Machine: An 11-Point Checklist