Mix It Up

Mix It Up

REWIRE YOURSELF

by

Ball Kanner

Last year we talked about setting up a basement recording studio. One of the elements involved was the Teac Model 2 mixer which was a relatively inexpensive and versatile unit. Since that time, Teac has taken the Model 2 off the market and replaced it with an improved version, the Model 2A, and upped the price to $450. Supposing you’d like to work with a mixer but not spend that kind of money—can you find something that will allow you to balance a variety of sources and place them pleasingly?

The answer, as you know, is a resounding yes, if you are willing to spend around eight hours assembling a mixer and soldering components. In short, AudioMarketing of Stamford, CT, is offering the AudioKit 62. It’s a 6-in/2-out mixer complete with faders, gain, cue, echo, bass, treble and panning controls for each input. The 62 also features two VU meters and a set of aux outputs so you can put your product through a separate amp and monitor your results. While it’s not exactly a Model 2A, its price of $265 including power supply does not beg to be compared to the Teac’s. However, the quality of performance compares quite favorably to anything on the market remotely in the same price range.

While the kit is a bargain for anyone who likes to putter ground wifh a soldering iron, I would not advise it as a first kit. Its manual, while complete, is not quite as~ step-by-step as the Heath and Dynakit manuals we are used to. The manual tells you how to do it without holding your hand while you’re doing it. Also, since both the kit and instructions are British imports, you may find yourself confused at first by such terms as: “leave it proud,” meaning “let it stick out.” In the color code description (for resistors), the British “mauve” replaces the more common American “lavehder.” An American manual would say “Phillips” screvv driver, while the AudioKit 62 advises you to use a “pozi-drive.”

However, for the more experienced kit builder, these anomalies become interesting variations,rather than stumbling blocks. The kit itself is easy to construct and the instructions are rather easy to follow,

The 62’s basic complement is six input boards and two output boards. One of each has been prewired to give you a model and the boards are marked indicating the value and type of each component to be placed. All you do is follow the model as given. My only mistake was inserting one 1C backwards but a careful check of the board after testing showed that one up.

Both inputs and outputs are phone type jacks, rather than the RCA/phono jacks more common to American gear. However, phone plugs and adaptors are readily available to turn one end of your standard phono cables ipto phone plug terminations. >•

If the builder encounters any real difficulty at all, it’s likely to be in positioning the phone jacks. The manual indicates that the washer should be removed. I found that if the washer was removed, it was bloody difficult to solder the jack tabs which disappeared under the chassis flange. I kept them in, mounted them on the inside, and was able to angle my iron tip to snag the tab.

The 62 took the promised eight hours to complete pnd I followed the test procedures outlined in the manual. The IC reversal problem showed up relatively quickand was just as quickly corrected. Once it was properly assembled, the mixer worked well. The two VU meters gave me $ good relative indication of levels and, after,plugging in several microphones, I was ready to record. The pan pots worked easily and again, the meters gave me a good indication of the balance I was puffing ort each output channel. My first setup was a simple two microphone job going directly to each output channel. I then added a third microphone whose signal would be distributed equally. Once again, the mixer allowed me to mix and pan and fade, boost or cut treble" and/ bass with ease and accuracy. It introduced no noise of its own and pny tapes ended up sounding just about as good as the original performance with the added fillip of source movement.

My only complaint of the AudioKit 62 is that it dotes not have an adequate “operating” manual for the novice recording engineer. The company assumes that if you want to build a mixer, you’re familiar with its use. Other than that, thi£ unit is a fine mixing board and an excellent value. Incidentally, the company can supply the unit with what it calls a “high performance option” (sounds more like a GT than a piece of studio equipment). The “option” is a set of ICs with lower distortion figures, which goes for an additional $20.

Mighty Microphones

One of the reasons I was so pleased with the mixer was the performance of the three microphones used for this project. I had a pair of Audio Technica AT 813 electret condensers and a Marlboro M-500. Both are uni-directional in pickup pattern and both gave excellent results.

Microphones have different pickup patterns. Most are either omni-directional or uni-directional. The omnis pick up sound evenly in a spherical pattern 360° ground the microphone element. The uni-directional models have a pattern looking like an imploded sphere with the caved-in section at, the base or, rear, of the microphone (toward the handle). This does not mean that a uni-directional microphone picks up its sound on/y from the front, but its sensitivity is highly skewed in that direction.

I chose uni directional microphones so that I could limit the input within my makeshift studio. I wanted as little of the street noise as possible to leak into the recording.

The Marlboro M-500 is one of the company’s Professional Series models. It’s recommended for use with acoustic guitars, keyboards, basses, and drums. I used it with both acoustic guitar and voice—the results were very good.

The M-500 is a dynamic, dual-impedance microphone. That means that its transducer element is similar to that of a conventional cone speaker. While a speaker cone is vibrated by the voice coil, the reverse process happens in a dynamic, microphone. Sound pressure causes the diaphragm to move which, in turn, causes changes in the voic^ coil. Dual-Impedance means that the M-500 can be used with either high impedance or low impedance equipment, simply by changing a connection located beneath the microphone head. Snap the connectors together one way and you’ve^ got a high impedance (20kOhms) microphone for tape decks requiring them, and snap the connectors the other way and you’ve got a microphone with an impedance of 200 ohms for low impedance inputs. . The microphone also has-'-an on/off switch on the handle. It comes with a detachable 16 ft. cable and XLR connector and has a frequency rtenge of 50-16,000 Hz.

I found that the M-500 gave excellent results and sounded natural. I could vary the sound by easing off on the position, which produced an intimate, sexy quality when cbse to the performer. A good and exciting microphone at a price of $97:

While^ Audio Techniea’s. AT-813 is also a unidirectional (or cardiod) microphone, it is an electret condenser rather than a dynamic type. That means that it’s more closely akin to electrostatic speakers than to conventional cone types. The condenser (or capacitor) microphone has a charged diaphragm and a perforated plate held apart by spacers. These elements act as a capacitor. When sound pressure hits the diaphragm, the capacitance and the electrical output change. An electret condenser uses a polarizing voltage imbedded in the diaphragm during its manufacture and only requires a low voltage battery to power an FET impedance matching circuit, while a conventional condenser microphone requires an external power source.

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REWIRE YOURSELF

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The advantage of the condenser design in a microphone is ]thc same as the electrostatic design in a speaker. High end performance is increased and the overall sound is well balanced and natural. The AT-813, for example, boasts a frequency range of 20-20,000 Hz.

I used my pair of 813s on both vocal and acoustic guitar and found that what is claimed for the condenser design is true to my ears. The vocal quality is sensational. The presence and brilliance of a female voice is captured well by this microphone while the resonance of a guitar is also well represented.

The AT-813 is a low impedance (600 ohms) microphone only, but Audio Technica has a line matching transformer (AT-8201) that will give you a high impedance output. The microphone comes with a I6V2’ cable, A3F plug on the microphone end and V4” phone plug on the equipment end. It carries a suggested list of $95.

Super Duper Deck

Technics, which is quickly becoming “Numero Uno” in Audioland, has recently introduced the latest in its “Professional Series” of open reel tape decks. The 1520 is a truly versatile, high quality machine for the audiophile or semi-pro market.

Let’s start by looking at its speeds: 15, IVi and 33A ips and, of course,' it takes IOV2 NAB reels. The 1520 offers a number of features for the studio. Variable equalization (NAB or IEC) is available at the flick of a switch. Cannon connectors and balanced or unbalanced input and output connections are standard. Meter sensitivity is variable and both equalization and bias can be fine tuned from the front panel. Those fine tuning adjustments /ire in addition to the three way toggle switches for standard adjustments for both bias and equalization.

, ' Other unusual features include an oscillator which produces a test tone to optimize bias and „equalization, a pitch control which gives a* + 6% variation in speed from the 1520’s direct drive transport system, and a real time counter rather than the standard turns counter. The figures that appear on the four digit counter represent time at V 15 ips (for 7V2, multiply by two and for 33/4, multiply by four). A strobe system is also included. 1 ,V '

The transport is Technics’ “Isolated Loop.” The loop starts and finishes on opposite sides of an oversized capstan. The path and the pinch rollers keep the tape virtually immune to any outside influences itself is controlled by solenoids with full IC logic. The user can go from any mode to any other with no strain on the tape. Both reels are driven by independent direct drive motors while the capstan’s direct drive motor is quartz-locked to assure proper spedd unless the pitch adjustment control is employed.

An indication of the use Technics has in mind for this unit is the fact that it’s a two-track or half-track record machine. Rather than the conventional quarter-track design, which allows you to record two track in one direction and then come back with two the other, way (each track utilizing one-quarter of the tape’s width), the 1520 will record two tracks (utilizing half the tape’s width) in one direction only. Go back the other way and you erase what you had. The half-track design makes for better fidelity, as the 1520’s frequency response of 40 to 22,000 Hz+ 2 dB at 15 ips makes cleair^ However, you’ve got a switch on the headblock that allows quarter-track (or conventional) playback for pre-recorded tapes or tapes recorded on standard machines.

The edit function is also unusual and designed for professional use. An edit lever allows you to have sound via the monitor and playback head while freewheeling the reels. A system of markings and dials allows you to mark the exact spot on the tape where any sound occurs.

■ I’ve already given the frequency response at 15 ips, but at 7 V2 the 1520 shows a remarkable 30 to 20,000 Hz + 2 dB. Wow and flutter are listed at 0.018% WRMS at 15 ips, 0.03% at 7Va' and tf.06% at33/i. Signal-to-noise is listed at 68 dB for an A-weighted signal at 1kHz 65 On Wb/m. at both 15 and 7 Vi ips.

To get to the nitty gritty, the 1520 works like a charm and sounds like the real (reel?) thing. It’s optimised for Scotch 207 (I used Scotch Master with a virtually identical formulation).

The sound is full and complete and the controls allowed me all the precision I needed. While the $2000 price tag of the 1520 is not small, if you’ve got a need for this honey, you won’t be disappointed.