Making Your Tape Echo Machine Last
Jan 1, 2008 12:00 PM, By Eddie Ciletti
SLAP, LOOPING AND THE FIRST EFFECTS FAMILY
One of the unintentional “features” that results from recording to analog tape is the time delay between the record and play heads. Tape echo — sometimes referred to as tape slap — contributed to some of the high-fidelity era's signature sounds, from pop standards to rock, and rockabilly to R&B.
When musicians wanted to take “that sound” on the road, people like Ray Butts and Mike Battle invented portable versions such as the Echosonic (1952, a guitar amp with a built-in echo unit) and the stand-alone Echoplex. The first 500 Echoplexes were sold to a Chicago dealer in 1959. Battle's is still in business, producing a limited-edition tube version he calls the Tubeplex.
One of the great idiosyncrasies of tape-based echo units is the hint of self-chorusing due to speed variations caused by random friction in the tape path, pinch roller and motor bearings. There is, of course, a limit by which such imperfections can be tolerated, and it's amazing how quickly small frictions can add up and eventually challenge the system. Like many vintage artifacts, tape-based echo boxes have that tactile factor: You can poke and prod the tape with your finger and interact with the device in real time, which is simply not possible in the digital domain, although some of the new touchscreen technologies show that the software side is working on being “tactile.”
Most echo machines are based around a standard, ¼-inch endless-loop audio tape passing over one record head and multiple play heads. One exception is the Binson Echorec, which uses magnetic wire wrapped around a flywheel. The Echoplex and earlier versions of the Roland Space Echo use a proprietary endless-loop tape cartridge that works much like a '60s-era 8-track, where the tape is pulled from a specially designed reel or pulley. For cartridge-based loops, the backside of the tape is impregnated with a graphic lubricant that tolerates the friction of pulling a magnetic rabbit out of a nylon hat.
The cool part about later Space Echo models (like the RE-301) is that they stored the loop in a bin, which means a wider variety of tape stocks could be used. That said, choosing the right tape for the job will maximize tape-to-head contact while minimizing headwear and friction in the process. For this job, I suggest using Quantegy 457 (available at www.totalmedia.com) or any 1-mil tape that's not in danger of shedding. (Professional high-output tapes are typically 1.5 mils thick.) Both the Space Echo and the Echoplex apply back tension to the tape via felt springs, improving tape-to-head contact, and with it treble response.
The Space Echo's heads are fixed in place (Fig. 1); in addition to the space (delay) between the heads, the tape speed is also variable to optimize the delay time — something that was easier to do in the '70s. In the '50s, when the Echoplex was developed, a constant tape speed was the only (easy) choice, and a sliding record head (Fig. 2) changed the delay time.
To get an idea of the relative health of a tape echo unit, you'll need to get a good view of the head area. For these figures, a piece of white paper was laid in front of the head stack to better evaluate its condition. First look for height errors, which are easy to spot by eye — you don't want to see the tape head's “tracks” (pole pieces) above or below the tape. If the heads are in such good condition as to not show any appreciable wear, then the best way to confirm the mechanical head alignment is to draw on the head's face with a Sharpie or dry-erase marker. (Do this with an old tape loop.) The tape will wear away the ink and reveal Zenith errors, hopefully none as bad as shown in Fig. 1, labeled “c” and “d.”
CLEAN THIS, LUBE THAT
As long as the pinch roller isn't gooey or dented, there's probably still some life left in it. (If it's not usable, head over to www.terrysrubberrollers.com and they can make a new one.) Remove the pinch roller (Fig. 3) and wipe it with a cloth dampened with a water-based cleaner such as Windex. If it seems particularly oxide-encrusted, then you can safely soak it (overnight) in a 50/50 mixture of Windex and water, but only after removing the bearing lubricant. (See below.) The pinch-bearing lube in the RE-301 I'm servicing, for example, was stiff like rubber cement, causing the roller to drag the tape speed down.
To clean the heads (and pinch bearing), use 99-percent (or denatured) alcohol and cotton swabs. Clean the capstan shaft and the pinch roller's mounting post with a cloth dampened (not soaked) with the same alcohol. Don't let any cleaning solvent drip into the capstan bearing as this will dissolve the lubrication, increasing friction and causing heat that could possibly damage either the capstan or the motor bearings.
The Echoplex uses a belt to link the AC motor to its flywheel, the other end of which is the capstan. The Space Echo uses a direct-drive motor. (Neither the heads nor the motor are available, so be nice to them.) In both cases, a solenoid engages the pinch roller. The capstan and pinch roller should be perpendicular to the tape path and the deck plate (surface). If this is not the case, then the tape will drag on the tape guide edges, creating a “mound” of oxide dust below. (If you remove the pinch-roller screw, it, too, may attempt to ride up or down, another sign of poor mechanical alignment.)
For the Echoplex in Fig. 2, either the machine was left on continuous duty (for perhaps a decade) or more likely a certain “someone” (not me) increased pinch-roller pressure to compensate for perhaps what might have been the wrong tape type — or bad tape. The excessive pressure on the capstan shaft was enough to visibly elongate its bearing, which is riveted into place, messing up the tape path in the process (a complicated fix).
FALL INTO THE GAP
The business part of the head that creates the sound stripe or track comprises two mirror-image pole pieces that nearly meet. You may be able to see this “gap” in Fig. 2; if not, a good magnifying lens will do the trick. The gap should be perpendicular (at a right angle) to the tape. The adjustment to get it there is called azimuth. The “Az” and “H” designations (in green in Fig. 1) are screws that affect the azimuth and height adjustments, respectively, on the Space Echo.
Getting the azimuth right will maximize the high-frequency response. The best way to judge the HF response is with pink noise from a signal generator or FM static. In this case, you would inject and record pink noise, and listen to one head at a time while adjusting azimuth (side-to-side head tilt) for the clearest signal. All tools and heads should be demagnetized. The Space Echo heads are “stereo” wired for mono, making azimuth more critical than on the Echoplex.
AZIMUTH, HEIGHT and ZENITH
Endlessly looping tape creates noticeable horizontal wear lines across the upper and lower head face (the edges of ¼-inch tape travel) as shown in Figs. 1a, b and g. There are multiple lines because the tape height wasn't consistent. (More on that in a moment.) For the Space Echo, the rear height-adjustment screw (not shown) when combined with the front height-adjustment, affects zenith — the poorly aligned, front-to-back tilt that caused the uneven “c” and “d” wear pattern (Fig. 1). The top “e” area of all the heads is worn more than the bottom “f” area — bummer.
Figure 2 shows the combo erase/record head, which is on a slider that increases the distance — and delay — between it and the play head. A separate play head allows sound-on-sound/looping on both the Space Echo and the Echoplex. The black arrow indicates the “lip” created by the bottom edge of the tape, above which is the wear pattern. From just looking at it, it looks like the amount of wear is equal to at least the tape thickness, which is not a good thing.
A yellow-ish green glue has been applied — in the annotated area — to lock the head in place. The glue will likely crack off when the head is moved. To adjust azimuth, a nut behind the head assembly must first be loosened, after which a wrench can be used to ever-so-slightly rotate the head. I will say (somewhat squeamishly) that zenith is “adjusted” by bending the head-mounting brackets.
THE MAINTENANCE FACTOR
(BIRTH OF THE COOL)
No matter which tape-based echo unit is within your field of vision, there's a symbiotic relationship between the “investment” required to be in possession of vintage coolness and the maintenance factor required to preserve it. Even if you can't D.I.Y., you might now know how to recognize and avoid doing further damage to something that could be older than you are. If your beloved does need more than D.I.Y. help, then send the entire unit in for lapping and mechanical alignment. Treat it well afterward, and it can give you a lifetime of service.
Eddie Ciletti is an educator, engineer and electronics techncian based in St. Paul, Minn. Visit him online at www.tangible-technology.com.
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