Sonicraft A2DX Lab: Ultimate Multitrack Analog to Digital Transfers
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-- by Steve Puntolillo, Sonicraft A2DX Lab

If you are thinking about getting into multitrack analog tape recording, putting your old analog warhorse back into service or just want to learn more about what it takes to get the best possible quality and reliability from a professional analog multitrack, this article is for you!

I made my first recordings on professional analog multitrack recorders in the early '70's. But, my recent project to build a high-end multitrack analog-to-digital transfer lab (including restoration and enhancements to over a dozen vintage professional analog tape recorders and over twenty head assemblies) has been a crash course in what owning and operating an analog multitrack means in today's reality. It is truly a labor of love to dig deeply into what makes these beasts tick and learn how to squeeze the last bit of performance out of them.

Using an analog multitrack is an amazing experience and choosing, purchasing, restoring and upgrading one can be a real adventure. To help you have a safe journey, I'm going to share a great deal of what I've learned with you. I'll give you advice to help you avoid unpleasant surprises so you can really enjoy your multitrack. And I'm hoping to open up possibilities for you on how you can improve and customize your machine so that it is the best you can make it.

What's This Project Going to Cost Me?

The good news is that, unlike other types of vintage gear, a professional analog multitrack tape recorder will probably cost you a fraction of its original purchase price. The bad news is that repairing or upgrading it typically costs just as much or more than ever. Parts can be expensive and difficult to find. If you are not qualified to repair and maintain your machine, from time to time you will have to hire someone who is. And, you will almost always need to invest in some restoration work to get it back in shape for both optimum sound and reliability.

Your best bet is to figure out what you are willing to spend and see if you can make the project fit your budget. So, come up with your dollar amount and let's go from there.

Choosing Your Analog Multitrack

Each analog multitrack has a personality with its own strengths and weaknesses. You don't want end up in over your head or find yourself pouring your hard-earned cash into the wrong machine. So, start out right by choosing the multitrack that's best for you.

Do you already own an analog multitrack? You should still determine the best machine for your work. There are times when you'd be better off selling yours and investing the money in the "right" machine. Keep reading. Go through the choice process outlined below and hopefully you'll find that you happen to own the right multitrack already.

These first three questions will help you to narrow down the choices:

What kind of work do you want to do with your analog multitrack? Make new analog recordings? Transfer, sample or remix old analog recordings? Make it a giant Pro Tools plug-in? For others to help guide you, you're going to have to explain your needs to them.

Who will fix it when it breaks? No one is manufacturing new analog multitracks anymore. The vast majority of machines available are from 20 to 40 years old. Some of the manufacturers are out of business and the rest no longer maintain field service departments. So, we're on our own.

If there's only one honest and competent tech in your area, you would be wise to buy a make and model of multitrack that tech is qualified to maintain. Otherwise, your tech will be learning on your nickel. Find out who is available and which machines they know how to maintain and repair. Check their reputations. Get their rates. Call them all and explain what you want to do with the multitrack you will be buying. Ask them to recommend the machine they think best suits your objectives and find out the reasons they prefer that make and model. Keep notes on what they say so you can make comparisons between machines.

Where are your spare parts going to come from? While you're talking with prospective technicians and getting recommendations of which multitrack to buy, ask which spare parts you will need to have on hand to keep it running.

Different machines have their Achilles' heels. You want to keep specific backup parts and assemblies at your fingertips in case you need them. If the machine goes down, perhaps you can swap the defective assembly and continue to operate while you arrange to have it repaired. If parts for the machine you are evaluating are scarce, consider an outright purchase of a backup machine as a parts source. A good supply of specific and off-the-shelf spare components can mean the difference between a successful service call and having to pay for the tech to return after the needed part arrives.

By defining your resources and your intended usage you've narrowed your choices down. To make your final decision, here's a list of specific questions to be answered. Not all of them will be of equal importance to you. For example, the bulk of my use of analog multitrack machines is transferring existing tapes into the digital domain. Seamless punch-ins and multi-point auto location are not important to me. But, if you want to do live sessions and overdubs to analog tape, they may be very important to you.

Rate these questions according to their importance to you and go through them for each machine you are considering:

  1. Is this machine reliable, or can it be made reliable within my budget?
  2. How do its repair costs compare with other machines I'm considering?
  3. Can I do some of the maintenance myself or is it too complex for me?
  4. Does it support the tape width and track formats I need?
  5. Can I or my clients afford the width and/or speed at which it consumes tape?
  6. Does it have a remote? Which features does the remote have?
  7. How quickly and seamlessly can it punch in and out?
  8. Does it auto-locate? How many locate points can it store in memory?
  9. Can it lock to time code? How is this done?
  10. Can it be aligned to take advantage of the newer tape formulations?
  11. Can it "remember" more than one alignment? How many? Can it self-align?
  12. Which speeds (7.5 ips, 15 ips, 30 ips) can it run?
  13. Which EQ curves ( NAB , IEC1, AES , etc.) does it support?
  14. Does it have varispeed (variable pitch control)?
  15. Does it have built-in noise reduction? Which type?
  16. How does this machine sound?
  17. How gentle is the transport on tape?
  18. How much ambient noise does it make?
  19. How good is the sync response?
  20. What are the specs for frequency response, signal-to-noise, speed consistency and wow and flutter? (Be sure to look at what operating level and tape type the signal-to-noise specs were referenced to when making comparisons. Also, pay attention to whether or not measurements are weighted. Weighted measurements always look better than unweighted measurements. In some cases, there is more than one kind of weighting. For all specifications, you want to make absolutely sure you are comparing apples to apples.
  21. What will it cost to make the overall repairs and improvements I want? See the section on Restoration below.
  22. Which components in the machine can be updated or upgraded to something better? See the section on Upgrades below.
  23. Can this machine be easily and cost effectively modified to meet my requirements? If a machine is very close to ideal, but doesn't quite serve your purpose, you may be able to close the gap. Some examples of reasonable modifications might include making a 7.5/15 ips machine run 15/ 30 ips, changing a machine from NAB EQ to IEC1/ CCIR EQ at 15ips, outfitting a 2-inch 24-track machine to run 2-inch 16-track, adding support for time code, etc. See the section on Upgrades below.

So, now that you have selected the make and model of analog multitrack that best meets your needs, you are ready to start the hunt to purchase one, right? Well, almost. There's just one more thing. Check your budget and get pricing on which accessories you are going to need. Here's a checklist of candidates:

  • Service and operations manual(s)
  • Editing supplies: splicing block(s), leader tape, razor blades, etc.
  • Tape path care: demagnetizer, head & pinch roller cleaners, etc.
  • Spare reels, hubs and boxes
  • Shop tape(s) for alignment and testing
  • Patch bays, connectors and wiring
  • Outboard Varispeed
  • Time code synchronizer
  • Noise reduction system
  • If you are going to align or maintain the machine yourself, the minimum requirement is:
    • Alignment tape (for each tape width)
    • Oscillator
    • Oscilloscope
    • Alignment tools
    • Tape tension gauge (Tentelometer)
  • You may also wish to consider some or all of the following shop gear:
    • Soldering iron or "station"
    • Desoldering tool or station
    • Tools for wiring and mechanical repairs
    • AC Voltmeter
    • Wow and Flutter meter
    • Spectrum Analyzer
    • Distortion Analyzer

Purchasing Your Analog Multitrack

In a perfect world, your tech finds you a cream puff machine that's been sitting mostly idle in a rich entrepreneur's smoke-free home studio ever since it was manufactured. Mr. Success now wants to recycle his studio into a home theater and just wants a few bucks for the machine so he can get it out of his way. Hey, it does happen. Just not to me .

Unless you have (1) a deep commitment to restoring one of these machines and (2) a track record of finishing-a-project-no-matter-what, spend as much as you must in order to buy the most pristine, ready-to-use machine you can find. In the process of cleaning up and restoring a beat machine, you are going to spend the difference between what it and the pristine machine costs anyway. Maybe more. You might as well buy the better machine and save yourself a lot of time and hassle.

But, you can't always find the ideal machine in your budget or time frame. Most of the machines you will be offered will have seen from moderate to heavy usage and will look that way. Typically, a used mulitrack's owner has been contemplating selling it for quite a while. He long ago stopped investing in it and began working around its problems instead of fixing them. Heads are worn. Brakes are worn. The pinch roller is getting gooey. Bearings are noisy. Fans are noisy. Filters are clogged. Bulbs are out. Switches don't always switch. Relays are frozen. Meter lenses are broken. Some channels don't erase or record or play. Some make crunchy noises that come and go. Some don't make any noise at all. Maybe the machine is out cold and won't even turn on. If you're not a tech, before you buy a machine like this one, you'd better get a tech. Have the tech go through the machine with you. Together, you can evaluate the following:

Look at the head assembly very carefully. The heads are the heart and soul of the machine. If the heads don't deliver 100% of the signal, nothing else in the machine or your studio will recover the loss. Are these heads original, upgraded from the originals or are they cheaper replacements? Make sure every track of each head is working. If a multitrack head has one dead track, the entire head is worthless. See if you can persuade the machine's owner to ship the head assembly (or assemblies) to one of the handful of qualified head experts for evaluation. They can tell you what quality the heads are and how much life is left in them.

A quick word about head life. Being told a head assembly has thirty to fifty percent remaining life (after relapping) may sound like a problem to you, but it probably isn't. Considering that professional analog recorders were built to run 24 hours a day, seven days a week, for years , it is unlikely you will ever burn through them. However, make sure you find out what it will cost to put the assembly in shape before you buy the machine.

Manufacturers of multitracks often performed or recommended field upgrades. Like a "recall" on an automobile, some field upgrades are essential. Before you buy the machine, find out what the upgrades are and see if the machine has them. Go through every printed circuit card and verify that it is the original or a suitable upgrade. Also, look at cards for changed components, modifications, areas toasted from overheating, signs of repair soldering, etc.

Doing a full alignment on the machine will tell you a lot in a comparatively short time. Be sure to try every function. List the defects that you find as well as broken or missing parts you will have to replace. Then, estimate what it will cost for repairs and replacement parts.

Are you getting everything you need? Make a list of options offered for that particular multitrack and see which ones the machine is equipped with. Remember, an option included in a package deal for a machine will almost always cost you less than it will purchased on its own.

If any spare parts and accessories come with the machine, take an inventory of them. A seller who is "throwing in" a good usable 2-inch 15/30 ips alignment tape could save you hundreds of dollars off of your accessories budget. Or, perhaps he is including some or all of the backup parts you need.

OK, it's time to do some math. The seller's price for the machine, plus cost of repairs, plus cost of missing options or accessories, minus the value of desirable or saleable extras included in the deal tells you what you are really paying for a complete and operable machine. If you are planning to do cosmetic restoration, upgrades, modifications or need to have the machine moved or shipped, add these costs in now. At this point, you should be looking at a number that's reasonably close to your total cost. The transaction should leave room in your budget for the unexpected. If that is the case, and you feel the deal makes sense, you are good to go.

What if the machine is too far away to inspect? Try to track down an honest qualified tech in the area where the machine is located and have him check the machine out for you. Otherwise, you have little choice but to assume the worst and make your decision (and offer) from that standpoint.

Most people selling large multitrack recorders (typically from 400-800 lbs) do not want to deal with shipping. I have had very good success with hiring national moving companies to bring the machine to me. It is hassle-free for both you and the seller. The moving company sends a truck to the seller's location, where the movers wrap the machine in plastic and moving blankets, roll it into their moving truck and bring it right to your door. A typical price to have this done is generally from $350 - $600. Your results may vary.


Your multitrack has arrived in your studio or shop and it's time to make it fit for service. If you are planning to do any modifications or upgrades to your machine, don't start them yet. First, you should make all of the necessary repairs to get it running properly as it is. Why? If you make an improvement or modification to a fully operational machine and something stops working, you will know exactly where to start looking for the problem.

Resist the temptation to turn the machine on until your tech arrives. It has been moved, so someone must go through it, find all of the plug-in components and re-seat them. If this is not done before you apply power, you run the risk of anything from minor to catastrophic damage. If the machine has not been run in a long period of time, it might be best to "bring it up" the first time using a Variac® - a device that allows you to ramp up the power gradually.

Dirt is an enemy. It clogs airflow causing components to overheat and finds its way into electrical connections causing transport malfunction, noisy controls, audio signal degradation or loss, etc. So, you might want to do some cleaning. Pull the covers and remove as much dust and dirt from the inside of the machine as possible. Some techs say vacuuming pulls dirt into places you don't want it. Some say compressed air blows dirt into places you don't want it. Be mindful of this when choosing which to use. Clean or replace all air filters.

Contacts including edge connectors, plug-in connectors, switches, pots, and relays should be carefully cleaned. Heads, guides and rollers need to be cleaned and demagnetized. There are correct ways to do these things. Do your research!

Once your tech has gone through the machine and gotten it running, here are some things you might want to do:

Recapping. There are a lot of opinions about recapping varying from "replace anything over 10 years old" to "if it ain't broke, don't fix it". My personal experience is, if the cap is non-polar, you can probably leave it alone. Some old tantalum capacitors should be replaced for reliability. There are some nice tantalum replacements being made today that are worth considering. Old electrolytic capacitors invariably dry out and become slow and weak. They should be replaced to restore the machine's performance and sonic integrity. In some cases, changing an electrolytic or tantalum capacitor before it fails can also protect other circuits from damage.

It's always safe to replace an electrolytic cap with one of the same specs. However, today's caps can be significantly better performers than their older counterparts. Capacitors in older machines were sometimes chosen based on available space on the circuit board. Since newer capacitors take less space and do the job better, you might be able to choose new caps with better specs and higher capacity. Often, you can not find a replacement that is the exact value of the original. Your tech should be able to tell you which current unit will be a safe or even beneficial substitute.

Bearing replacement. Multitrack machines are full of bearings. They are in reeling motors, capstan motors, roller guides, tension sensors, flutter idlers, and counters. Any bad bearing will cause malfunction, stoppage, or vibration which ultimately turns up in the signal as flutter. Good bearings should be virtually noiseless. If you can put a very light finger touch to the top of any rolling part and feel vibration, chances are good it's time to change the bearings. Bearings go by classes. Use the highest class replacement you can find and certainly no lower class than the stock unit.

Pinch roller replacement. If your multitrack uses a pinch roller, be sure it's in good shape. It should never be sticky. The surface should not be excessively soft or hard. There should be no cracks, pincushioning or bowing. Most old pinch rollers need to be replaced.

Capstan resurfacing . Different machines use different capstan surfaces. If your capstan is metal and has a shiny band where it touches the tape, it is probably getting slippery from wear. Have the surface bead blasted and it will look and perform like new. If your capstan is polyurethane coated, replacement capstans are generally available.

Repainting. Computerized paint matching systems can be found in the better paint stores, departments of major home improvement centers and body shops. If you're just doing touch-ups, be sure to match the finish (flat, satin, gloss, etc.) as well as the color. It should look as great as it sounds, right? With a little patience and finesse, you can make remarkable improvements to the appearance of your machine.

Upgrading: Going Beyond Restoration

You've done your homework, selected and purchased your multitrack and restored it to full working condition. Hang onto your wallet! We're ready to get into upgrades.

Working quietly in the background for the past two decades or more, analog diehards have been slowly but surely advancing the performance of analog tape recording. If you wish to squeak every bit of wonderfulness out of your multitrack, here are some areas you can explore to improve its performance:

Heads. No single component in your multitrack is more important. For some multitracks there are replacement heads available that will improve performance, sometimes dramatically. Consult a head expert before purchasing or installing replacement heads.

If you can improve your erase head you can potentially get deeper erasure and less crosstalk between channels. Double-gapped erase heads perform better than single-gapped erase heads. Erase head gaps that overlap each other in the guard band between tracks reduce crosstalk by erasing whatever signal bled out beyond the gap during recording.

Improving your machine's record head can help you make a quieter and more accurate recording, but the biggest potential gain comes with improving the playback head. In almost any given analog recorder, record performance exceeds that of playback. There's almost always more information going onto the tape than the machine is able to reproduce .

It's like playing your favorite CD through a better monitoring system. You hear things you never heard before, but the recording hasn't changed. The "improvement" was always there waiting to be revealed. Likewise, there is usually detail recorded onto the tape that your stock machine can not reproduce. So, make better playback performance the initial focus of your improvements. In particular, the playback head is ultra-critical because whatever it fails to retrieve from the tape will never be heard in your mix.

Another way to upgrade your multitrack is to increase your track width by lowering your track count. It's pretty ironic to suggest that decreasing your track count might be an upgrade, but depending upon your priorities, it may be for you. This is because wider tracks sound and perform better.

Because the guard bands between tracks must be sufficient to prevent crosstalk, when track counts go up, track widths suffer more than you would expect. For instance, a lowly quarter-track consumer tape deck has tracks roughly the same width as a professional 2-inch 24-track machine. Both are only about half the track width of 2-inch 16-track. Increase your track width and you will hear a significant drop in tape noise and a healthy increase in punch. It's not subtle.

Two easy and relatively inexpensive track conversions are to drop down from 2-inch 24-track to 2-inch 16-track and from 1-inch 16-track to 1-inch 8-track. If you have a 2-inch machine and a bigger budget, you can look into 2-inch 8-track heads. Before you make a purchase, be sure your machine can handle the higher bias, record and erase levels required to support these wider track heads. Also, since wider tracks increase your exposure to signal loss from misalignment, make sure your machine's transport is capable of very precise tape handling.

How can you improve your mulitrack's transport? Some transports are already either thoroughly optimized or don't lend themselves to improvement. Other, usually older transports are wide open for some very nice enhancements.

An upgrade that decreases scrape flutter will actually produce an audible improvement in your mulitrack's clarity of reproduction. Scrape flutter is the vibration of the tape caused by friction between the tape and the surface it is passing over. The frequency of this vibration is a function of tape speed (the higher the speed the higher the resonance frequency) and the distance between the points that the tape is contacting (the longer the distance the lower the frequency).

In general, upgrades that use precision rolling guides to replace static (non-rotating) guides in the tape path will tend to reduce scrape flutter with a resulting improvement in signal clarity. Some multitrack head assemblies are machined and ready for extra optional scrape flutter idlers (rollers). These "damp" the vibration of the tape and can be very helpful in reducing scrape flutter. Remember that any time you replace a static component in the tape path with one that rolls, you must be sure it is of ultra high quality and precision or it may add flutter instead of reducing it.

How about a speed change? If your transport came equipped for 7.5 / 15 ips operation, you might want to outfit it for 15 / 30 ips operation instead. For 30 ips operation, your record and play heads, record and play equalizers and capstan drive must all be compatible. After the changeover, your transport tensions may require a complete readjustment.

Doubling the speed of the tape from 15 ips to 30 ips changes the frequency response of the machine enhancing your high frequency response at the expense of the lowest frequencies. Find out if your multitrack supports one of the playback heads designed to extend and recover lost low frequency response at 30 ips so you can enjoy the best of both worlds.

Sometimes, you can upgrade the sonic performance of your multitrack by updating or upgrading individual components. Some likely candidates for upgrades are capacitors, transistors, resistors, opamps, and other audio-related integrated circuits. This gets controversial, so I'll keep it simple. You want to track down devices that affect the audio signal path or cleanliness of the power delivered to them and replace them with ones of higher quality.

Better specs don't always equal better sounding, so make one change at a time and listen to the results. Don't let your hopes or your imagination get the best of you. You must observe the rules of doing meaningful A/B comparisons and make your decisions based on them.

For record or playback electronics, try changing just two channels, record some music with lots of listening cues and then listen critically to see if your improvement is both audible and desirable. If so, you can go ahead and do the rest of the channels. Remember, a lot of very small gains can eventually combine to make a significant overall improvement, especially when multiplied by many channels.

Be sure you're delivering good clean power to your machine before you tackle any in-depth critical listening tests. Your grounding system for both power and audio must be right. And, be sure to invest in a good grade of wiring with clean solid connections in and out. Once you've taken care of that, remember that audio circuits turn the power from the machine's power supply into the audio signal. So, upgrades to the power supply are potentially upgrades to all of the audio circuitry.

Audio transformers are a subject that deserves particular attention. If your multitrack uses them, you may find them on mic inputs, line inputs, line outputs or between the repro head and playback electronics. Depending upon how transformers are used in the circuit they can sometimes be bypassed, replaced with active circuitry, upgraded to a more modern equivalent or left in place for their unique sonic signature.

For a more vintage sound, you probably want vintage transformers. If you are looking for less coloration, you could find you have to upgrade or bypass them. Do some listening tests. You may discover you are a lover of the sound of a particular transformer or transformers in general, or you might be thrilled with the change you get by bypassing a transformer. The differences can be significant and it's worth the effort to do what it takes to find out for yourself.

Some engineers love the sound of analog tape recording, but object to tape noise. Before you consider purchasing a noise reduction system, there are alternative ways of reducing noise you should investigate.

Let's talk first about tape speed and your machine's record/ play EQ curve. If you plan to run at 30 ips, you will likely be using the AES EQ curve. This is a decent curve and many engineers feel that if you combine 30 ips AES EQ with the best of the modern high output / low noise tapes and some skill with setting record levels, you can operate very happily without noise reduction.

If you must operate at 15 ips, and your machine is set up and aligned for NAB EQ you might want to consider a switch to the IEC1 (also called CCIR) curve. The 15 ips NAB curve was developed in the 1950s for very early tape formulations and does not take advantage of the improved performance of modern tapes. Neither AES or IEC1 curves are optimized for today's tapes either, but they are both far better performers than the NAB curve.

You may or may not need to make some component changes in your EQ circuitry to change your machine's 15 ips curve from NAB to IEC1. Again, try a pair of channels and make comparisons. Different curves sound different and you should take a listen first.

Another way to lower your noise floor without using noise reduction is to use a tape formulation that is inherently quieter and / or allows you to record at a higher level (thus improving signal to noise ratio). Note that different tape formulations also have different sonic characteristics, so be prepared to do some more comparisons to determine what you like best.

If you've chosen your combination of tape speed, EQ curve and tape formulation and still feel there is more noise than you can live with, perhaps you can try going to wider tracks to take you the rest of the way.

If not, you can always use a noise reduction system. There are four professional noise reduction systems to choose from: Dolby A, Dolby SR, dbx Type I and Telcom C4. To a greater or lesser extent, they all reduce the noise added by the tape recorder and each has its individual strengths and weaknesses.

The best way to evaluate noise reduction systems is to borrow or rent a two-channel unit of each type and conduct careful listening tests. Try some stereo program material as well as solo electric bass, solo piano and a single tambourine or hi-hat to get a good handle on how effective each system is at reducing noise, how it changes the sound of your recordings and what audible mishaps might occur if it mistracks.

So there you have it. You're now prepared to tackle choosing, purchasing, restoring and upgrading a professional analog multitrack recorder. I hope you enjoy each step on the way to your ultimate analog experience. May the music you record be as wonderful as your finished machine sounds.

More questions? We're here to help. Feel free to call us at (732) 303-8559 or email Steve at

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