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Q&A October 2002

Your Technical Questions Answered
By Various

Q. Should I buy a second-hand tape recorder or a cheap digital multitracker?

I want to start recording music and am looking to buy a four-track recorder. I've heard about using computers for recording, but unfortunately I don't have my own computer. I want to record guitar, some vocals, drum tracks, bass and maybe some keyboards. I've been looking at the recorders in the shops and they all suggest I go for a digital four-track unit, but they all seem to cost around £300. I've seen some second-hand tape-based recorders on web sites like eBay which are far cheaper, such as the Fostex X55.

However, I have no idea what the descriptions on these web sites are telling me — things like XLR and so on mean nothing, and I don't know if the new digital recorders already incorporate this technology and what it does. Is it better in the long run to buy a digital machine? Will this do what the tape recorder does and more? Or would it be better to buy a tape recorder? Could you also possibly suggest which products I should look at?

Jez Williamson

Assistant Editor Tom Flint replies: As a past user of a cassette four-track and a reel-to-reel eight-track, I have certain amount of affection for the qualities of analogue recorders. However, in this day and age I find it hard to recommend an analogue recorder over a digital multitrack.

Foster R8 eight-track tape recorder.Foster R8 eight-track tape recorder.Firstly, let's rule out the reel-to reel option. Something like the Fostex R8, for example, is now quite affordable and gives an acceptable quality sound with many locating and punch-in features that are useful when multitracking. Despite these factors, you have to buy relatively expensive quarter-inch tapes, each of which will only provide 20 minutes recording, and all require spooling on and off the machine before and after each session.

Care must be taken when handling and storing your tape, and there's also the cost of regularly maintaining your recorder. This requires the alignment of transport parts and the replacement of worn contacts, which really needs to be done professionally. A reel-to-reel also requires regular demagnetising and cleaning with Isopropanol and cotton buds. On top of all that you'll need to pair the reel-to-reel with a separate mixer, complete with leads, which obviously adds to the cost.

The Fostex R8 reel-to-reel recorder, Tascam's 414 four-track and Roland's VS880 digital multitracker are all available for a modest price on the second-hand market.The Fostex R8 reel-to-reel recorder, Tascam's 414 four-track and Roland's VS880 digital multitracker are all available for a modest price on the second-hand market.The cassette multitrack is low-maintenance by comparison, but there are two things that need to be checked if you're buying one second-hand. Firstly, the record and playback heads of a four-track are carefully positioned so that they're in exactly the right place in relation to the thin tape. If these are slightly out, your recording or playback may miss part of a track — you can only check this by doing a record and playback test on all four tracks. It's also likely that the quarter-inch jack inputs will be attached directly to the circuit board inside the recorder. If any lead suffers a tug while inserted in an input, the result can be a dodgy connection. Consequently, you will need to check the inputs.

If you're going to consider a cassette recorder, I'd suggest buying new if possible, unless you can try the recorder first. The only other thing to bear in mind is that cassette tape is a noisy format, particularly when used by a four-track machine. This means you'll be forced to use the machine's noise reduction, resulting in a sound that isn't of a professional standard. Unlike a normal stereo recorder, the four-track uses the full width of the tape at once, and to achieve a better signal-to-noise ratio, a cassette multitrack also plays and records faster than a normal stereo machine. Consequently, the faster speed and single 'side' leaves you with about 25 minutes of recording per cassette. On the plus side you at least get a built-in mixer, the cassettes will be cheap, and the maintenance required is minimal.

Q&ASo what about a digital recorder? Well, on the negative side, you may have to pay a little more money, and you must ensure you can back up your data to CD or an external hard disk because digital data can easily be lost. A digital recording may also sound harsher and less flattering than analogue tape, forcing you to improve your recording standards just to get a nice sound. To optimise disk space, many recorders use levels of data compression that compromise the sound quality, but most good products allow you to turn off compression when required.

Those are the main negative points, but now to the positive ones. Most respectable hard disk recorders offer a few megabytes of disk space and the option to install or connect to a CD-RW drive for mastering or archiving. Most provide what are know as 'virtual tracks' that allow you to store different takes, and there are usually levels of undo so you can undo a mistake, or several consecutive mistakes.

A built-in digital mixer is now standard on these all-in-one devices, and most of them also have built-in effects and processing, in addition to digital editing facilities. Digital editing features such as cut, copy, paste, normalise, delete and so on give you a great deal of flexibility, which isn't possible with the above tape formats. One final negative point resulting from the above plus points, however, is that the learning curve for a digital recorder is a little steeper than for an analogue recorder.

You can only get to grips with some of the specifications by reading many reviews, and after a while it will start to make sense. XLR, for example, is a different format to the common quarter-inch jack socket as seen on a guitar amp. An XLR has three pins allowing a 'balanced' signal to be used, and a balanced signal should give a higher level and a better signal-to-noise ratio. You'll find a full explanation of the concept of balancing in the Studio Installation Workshop article in the September issue. Many digital recorders will give you a couple of XLRs that offer what's known as 'phantom power' for use with condenser microphones. If a digital multitracker has XLR connectors and phantom power, therefore, this is a good thing.

I have to say that some of the really low-budget digital recorders don't particularly fill me with confidence, but for around £300 you'll probably be able to get a fairly decent mid-priced digital multitrack recorder/mixer on the second-hand market.

Reviews Editor Mike Senior adds: I'd suggest that you look at getting a second-hand digital eight-track. You ought to be able to get one for between £200 and £300. Models to consider include Fostex's DMT8 and VF08, Roland's VS880 and VS840, and Korg's D8. The advantages of the digital option is that the sound quality will be good, and you'll be able to bounce (record from one track to another) more often to free up tracks. Check out our May 1999 buyer's guide.

Q. How can I stop my speakers from 'booming'?

I've got a setup in my lounge with some turntables, a mixer and a pair of Soundcraft Absolute 2 monitors positioned on a table. The room has painted walls, no carpet, and no furniture apart from the couch. When I push the volume past a certain level, I get a weird effect where the speakers go crazy and this sort of booming sound comes out. Is this because of the lack of furnishings in the room to absorb the echo or something? What can I do to solve this?

James Smith

Technical Editor Hugh Robjohns replies: I think you are looking too deep for this problem. It sounds far more likely to me that you're getting acoustic feedback from the speakers through to the turntable pickups — a basic howlround situation. The solution? Don't turn the speakers up so loud, and make sure there's no mechanical coupling between the speakers and the turntables by putting the sepakers on stands well isolated from the table on which the turntables are sited, for example.

PC Columnist Martin Walker adds: Any deck will also act like a microphone when subjected to incoming audio from a nearby loudspeaker if the levels are high enough. If the speakers and decks are well decoupled, as Hugh suggests, the only mechanism is via airborne sound. However, if you don't have a solid floor, even after mounting the speakers well away from the deck, you can get low-frequency vibrations travelling from one to the other through the floor — wooden floorboards are bad in this scenario. Sadly, the worst case is yours, where both speakers and decks are sitting on the same table, since the loop is so much smaller, both for airborne and mechanically coupled sound.

The reason for the 'booming' and eventual continuous feedback if you turn levels up even further is because no system has a perfectly flat frequency response, especially one placed in a room that has its own acoustic response. Some frequencies will peak, and as these get louder in the speakers, the output from the deck gets louder at this frequency as well, causing it to get louder in the speakers... First you get a 'booming' sound in time with the music, and if you turn things up any higher the whole system will go into continuous oscillation, or howlround.

Q. Should the earth pin in an XLR plug be soldered to the shell?

I've been tracking down the source of an earth loop and first had my suspicions about my Korg Polysix, even though it's connected to everything else through a 'Reference' DI box from Studiospares, with the earth-lift button activated. With my handy multimeter, I confirmed that no matter whether I tried to lift the earth with the DI box or not, there was still a continuous earth path through it.

At first I began cursing the DI box, but further testing showed that it was fine and it turned out to be the XLR lead that was at fault. I opened up the shell of the plug at the female end and discovered it had been manufactured so that the earth pin had a soldered connection to the shell, which was managing to short out the DI box's attempts to lift the earth. I snipped the connection inside the shell and all was well. The question is: surely this isn't standard manufacturing practice, it it? The XLR lead in question is manufactured by Altai and I bought it in Maplin.

SOS Forum post

Technical Editor Hugh Robjohns replies: Well, this is really about effective screening practice, rather than any particular company's policy on wiring. The link to the XLR shell is there for a reason, and that is to enable the shell to be earthed and so continue to screen the wires contained inside, since they will at that point be outside the cable's own screen, and therefore be more vulnerable to interference. Most people have ignored this issue completely since there are rarely any problems with audio cables if the shells are left 'floating', particularly if you only ever use single-length cable and don't join multiple XLR cables together to form a long lead.

Normally, the shell of the XLR becomes earthed automatically when it's plugged into the equipment because the equipment's chassis is usually earthed for safety. So the bare wires within the shell remain effectively screened (by chassis earth) and all is well. Given this situation, linking the XLR shell to the cable screen internally (connecting pin one to the shell, for example) can actually create earth loops since the audio earth on pin one of the XLR is connected directly to the chassis earth (via the shell) the moment the XLR cable is plugged in. Not good!

However, consider the situation when you have to extend an XLR lead by plugging two or more XLR cables together. If the shells are left unconnected, the exposed wires within the shells now have no effective screening, and are therefore more prone to suffering interference if the cables are in a high-risk environment. In the case of AES-EBU signals, there would also be a much greater degree of interference radiating out from this point, potentially affecting other equipment nearby.

Some people try to overcome this potential problem by linking the shells to the screen at one end of the cable only, but if you think about it, this really doesn't solve the problem. Another concern would be that if the earthed XLR shell should come into contact with some other metalwork (say it ends up resting against a radiator), further earth loops might be created inadvertently.

Personally, I leave all XLR shells floating (ie. not connected to the cable screens), but always try to avoid chaining XLR cables together using a cable of the appropriate length, rather than joining cables to make longer ones whenever possible.

Q. How reliable is the word clock on Yamaha's SW1000XG?

How does the word clock on Yamaha's SW1000XG soundcard compare to the word clock on other soundcards and other hardware? Do you know how good the clock is on Yamaha's DS2416? Is that the same as the SW1000XG or would it be better? The reason I ask is that I have my whole setup running from the SW1000XG clock, via the DS2416 with AX16 ADAT card. Is this compromising the quality of any outboard gear that's connected to the ADAT card?

Yamaha's SW1000XG is still a popular soundcard, but can its word clock be trusted?Yamaha's SW1000XG is still a popular soundcard, but can its word clock be trusted?My other digital gear includes a Korg 168RC desk, TC Electronic M*One and a Tascam CDRW700. I guess none of these have brilliant word clocks, but are they better than the SW1000XG? Am I better off using the internal word clocks and using analogue connections? I'm more concerned about the CD recorder since the clock signal it receives has passed through three other devices first.

SOS Forum post

PC Columnist Martin Walker replies: This is a tricky question to answer since very few manufacturers quote the jitter level of their word-clock generators. The only specifications you're ever likely to see are those of high-end (and therefore very expensive) word clocks, so in the absence of this information you'll have to use your ears.

Leave the SW1000XG's digital output connected to each others device's digital input and audition some material with lots of high-frequency transient information such as delicate percussion. While listening carefully to the position and focus of these instruments, switch between the internal and external clock on your other device and see if you can hear any difference. If you can't, there's little point in rejigging your connections. However, if using one clock tightens up the top end and makes an instrument easier to place in the stereo image, you've found the clock with the lowest jitter.

To be honest, I've only really noticed improvements over my Mia's internal clock when replacing it with that of rather expensive soundcards, including Aardvark's Q10 and the Lynx Two, which cost far more than the Mia.

Q. Can you advise me about connecting a classic Leslie to a VK8?

In Gordon Reid's review of the Roland VK8 organ in the September 2002 issue, he mentioned the possibility of hooking up a classic Leslie 122RV or 147. I'm interested in doing this and wondered if you could provide any additional information?

SOS Forum post

Technical Editor Hugh Robjohns replies: Hooking up Leslie cabinets isn't a task for the unwary amateur, particularly when dealing with some of the older models of Leslie.

The Roland VK8: you don't want to hook it up with just any old Leslie...The Roland VK8: you don't want to hook it up with just any old Leslie...There are three basic Leslie interfaces: two variants on a six-pin plug, a multitude of variants on a nine-pin plug, and the more modern 11-pin version as fitted to the VK8 and most other Hammond-esque keyboards and modules. All but the 11-pin carry a live mains supply to power the Leslie, and one carries a 310V HT supply for early Leslie valve amplifiers — so lethal voltages are kicking about. To make matters worse, the standard Leslie cables have plugs at both ends with exposed pins; so if one end is plugged into the organ, the other potentially has lethal voltages within easy grasp! This isn't the case with the 11-pin variety, fortunately, and many rental companies and bands have changed the type of plugs used in their rigs to overcome this rather dangerous design flaw.

The classic Leslie 122 uses a six-pin connector type and carries a balanced audio signal on which is superimposed a phantom voltage to switch Leslie speed. A mains supply is also carried in the cable and, depending on the organ, there may be an HT supply too. This is the kind of system you would expect to find on classic Hammond B3s, C3s and A100s.

The Leslie 147 was designed to interface with non-Hammond organs but uses the same six-pin connector. However, it's wired differently and carries different signals, so mixing these two interfaces up will kill the Leslie with a loud bang and a wisp of smoke! Although the Leslie's mains supply and earth use the same three pins as the 122 interface, the 147's audio signal is unbalanced and a second mains supply is used to switch the speed control relay. If you plug a 147 into a 122 outlet you'll blow up the preamp, which isn't conducive to a happy Leslie. Conversely, if you plug a 122 into a 147 outlet, you'll have a very nasty sound and no speed control.

The nine-pin interface was used on popular models like the Leslie 760, but the wiring tended to vary slightly according to the specification of the speaker. While the Leslie's mains supply always occupied the last pair of pins, the rest provided various low voltage control signals to change speed or switch the reverb or an auxiliary channel on and off. The audio input was unbalanced again.

The 11-pin connector is the safest interface, used on all modern keyboards and modules, and thankfully no longer carries the Leslie cabinet's mains supply. Depending on product specification it can incorporate up to three unbalanced audio inputs: one for the rotary speakers, one for a static main channel and one auxiliary input. The rest of the interface provides low-voltage switching for cabinet on/off and speed control, including an off or 'brake' position.

As I said, this is definitely not an area in which to perform plug-and-play experiments. Get the Leslie interfacing wrong and you stand a good chance of killing the Leslie, and maybe even yourself! While there are some suitable Leslie interface conversion kits, they can be very hard to track down and don't cover all the possible permutations anyway. However, a good electronics engineer should be able to design suitable converters given sufficient technical details, and the best information source I have found is on the web at: https://theatreorgans.com/hammond/faq/all_leslies.html. But good though this information is, it may not apply to your own equipment. Many Leslies and Hammonds have been 'modified' over the years, so always check carefully that what you think should be on each connector pin is really there!

Published October 2002