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T.C. Electronic Effects Boxes


The T.C. Electronic Effects units.


Power Supply



To replace an endless array of PP3 batteries TC Electronics have produced a Power Supply unit, measuring 100 x 60 x 30mm. Finished in matt black with white lettering to compliment their range of effects units, the PSU has four nine volt @ 20mA outputs. Each output has its own 3.5mm jack socket and is fully regulated and short circuit proof. Mains, 240VAC @ 1.6W, is connected via two metres of cable terminated with a 2-pin plug. (A shaver adaptor socket will be required here.) Power on indication is shown by a red LED. The LED extinguishes if any of the four outputs are short circuited and the supply delivers 9.25V at 30mA, well regulated and with low noise. As most effects units require only a few milliamps to work, the supply is obviously generous in its rating, but then one may expect this for a price of £30.30 including VAT.

Integrated Preamp



This unit comes in a die cast aluminium box measuring, once again, 110 x 60 x 30mm; obviously a standard size container used throughout the range. Finished in matt black with a white legend, the controls cover bass and treble boost and cut with an output volume control. Signal input and output are standard 0.25" jack sockets. Power comes from either an internal battery or from a 3.5mm external power socket. Requirements are 9V @ 0.89mA and with this low current, battery life expectancy should be long. The usual output socket doubling up as a switch is incorporated, so that removal of the output jack lead turns off the pre-amp. Measurements taken at 1kHz showed an input sensitivity of 250mV RMS for an output of 1.75V RMS just at the onset of clipping. The pre-amp, adjusted for flat response, has an overall gain of seven from 60Hz to 18kHz, the -3dB points being at 18Hz and 20kHz.

The treble control peaks at 5kHz with boost and cut up to seven times the input level available. The bass control peaks at 60Hz with boost and cut being slightly less; up to four times input level. Both controls offer reasonable control of tone quality, especially for a guitar, as they lie within the most usable range of the instrument. However, the volume control has an effect on the output signal only and not on the input signal level. This allows the pre-amp to be easily overdriven by high output guitars or other effects units and this should be considered when the unit is in use. Background hum and hiss levels were extremely low and no colouration of signals was evident, making the unit pleasant to use even with a price tag of £39.20 inc VAT.

TC VII Emphasible Peak Phaser



Quite a mouthful for a simple device. Again, this effect unit is housed in the standard black and white box. Ins and outs are via 0.25" jack sockets, and external power supply input via a 3.5mm jack. Two controls adjust speed (phasing rate) and peak, or range of phase. A bypass foot switch, for straight signal or effect, is mounted on the box. The switch action is virtually silent, unlike most foot operated switches, and is still mechanical in operation — but electronically actuated. Quite a noticeable difference.

Phasing speed is variable from 0.06Hz up to 10Hz. As the speed is increased, the phase depth decreases, which is usually only a problem with 'cheap' phasers using simple integrator oscillators and all-pass filtering. The peak control alters the depth or degree of phase change during each sweep.

An external potentiometer can be used to alter speed and maximum speed is at the end with minimum resistance. External bypass requires a break action (normally made) switch for control of effect in or out. Current drain is about 2.5mA, low enough to ensure good battery life from the internally mounted PP3.

In use, the phaser gives an effect more like a VCF or auto-wah with bandpass characteristics; the effect lessens with increase in signal frequency, and requires a source rich in harmonics for full appreciation. Although quite a nice result is obtainable I was unable to find a true resemblance to phasing. When the effect is switched in, the sweep ramp always starts at the same point instead of anywhere along the sweep cycle. Quite a novel addition and useful for keyboard players. Finally, calibration of speed control starts from 0.1 to 10 in seven stages and does not match with the true oscillator rate. The same goes for the peak control, calibrated in seven stages from 0 to 6 'somethings'! So, useful as an effect of some sort, but definitely not as a phaser costing £79.30.


Dual Parametric Equaliser



The by now familiar 120 x 90 x 30mm black die cast case, with white legend, shrouds a very interesting signal processing unit. For those unfamiliar with parametric equalisation, conventional broad bandwidth bass, mid and treble controls (eg. Baxandall) offer boost and cut with a gentle 6dB per octave slope. Graphic equalisers offer up to 14dB, usually, of boost and cut with a separate control for each octave (or down to one-third octave) and have a usable bandwidth of 50Hz to 10kHz. The slope characteristic is usually from 6 to 12dB per octave.

This TC dual parametric equaliser has two centre frequency controls, one covering the range 20Hz to 2kHz and the other 100Hz to 10kHz. Together they offer individual control of lower and upper harmonics and dual control of the mid frequencies. Basically, two bandpass filters are used, the centre frequency selected can either be boosted to +16dB or cut to -16dB (measured +16 and -18dB) and the bandwidth control selects either a broad 1 octave band, down to a very narrow 0.1 ( octave) band or notch. Particular frequencies can then be precisely enhanced or removed with very little effect on the rest of the music.

The unit also acts as a pre-amp. With all controls set to unity (flat response) the bandwidth measured 15Hz to 70kHz -3dB. A special treble control is fitted, which can be used to boost or cut up to 18dB of signal at 10kHz, and the overall gain is adjustable +12dB @ 1kHz. Actually, most of these specification figures came out well above on measurement tests and were most impressive. A small slide switch is fitted, which bypasses the equalising circuitry, but leaves in the input and output buffer pre-amps. The high input (1M) and low output (600R) impedance, therefore, remain unaffected.

The internal PP3 battery supply is very low current and is replaceable with a 3.5mm jack external power socket. Supply switching is via the signal input jack, and output comes from a standard jack socket.

In use, I found the unit extremely versatile, from removing mains hum and acoustic feedback to enhancing the tonal qualities of my guitar. Noise, hiss and hum levels were extremely low, as one comes to expect with TC products, and at £65 this is good value for such an impressive parametric system.

Booster + Line Driver & Distortion



Generally, distortion units have been well exploited, and just about everyone either owns or makes them (or both). For those unacquainted, distortion is usually achieved by driving a pre-amp stage into clipping and then applying boost or cut to the upper harmonics to mellow the effect or sharpen it.

Unfortunately, high gain input stages mean that all signals, including hum and noise etc are amplified, producing a lot of noise in the absence of an input signal.

The booster-distortion unit under test has two separate modes of operation. Firstly, as a boost pre-amp with volume, bass and treble controls; and secondly, as a distortion driver producing soft clipping, with depth control from normal boost to maximum distortion.

The two effects are switched in and out of circuit with a foot operated bypass switch. The effect mode is selected with a slide switch and a noise suppressor control protrudes through the front panel. The electronics are housed in a (dare I repeat?) 120 x 90 x 30mm die-cast case, finished in matt black with white lettering. There are standard jack sockets for signal input (also controlling supply on/off) and signal outputs. 3.5mm jacks cater for an external power supply and external bypass switch.

I must mention the electronic switching. The foot switch (bypass) is very light in operation and electronically selects the effect in or out of circuit. The switch appears to work as a latching flip-flop toggle, making external switching simple and not dependent on the internal switch. A miniature red LED comes on for about 10 secs, indicating that the effect has been selected.

With boost effect selected, the unit acts as a pre-amp with a flat 20Hz to 18kHz response. Bass and treble boost of ±18dB @ 60Hz and 8kHz respectively is available and an input of 70mV RMS produces an output of 2.25V RMS @ 1kHz.

A noise suppressor ensures that any input signals below 5mV in amplitude, are not amplified and the threshold control is adjusted so that output noise signals are at a minimum. This 'noise gate' effects the dynamic range of instrument signals, but can be adjusted for minimum interference and is a useful addition.

In the distortion mode, the usual clipping of the signal waveform is apparent and upper or lower harmonics can be processed using the bass and treble controls. Used in conjunction with the distortion depth control, quite nice soft clipping effects can be produced and background noise and mush is just not there. A line output Cannon plug is fitted for remote mixer/PA applications making £77 worth of electronics nicely presented, and effective.


TC XII and XII B/K Programmable Phaser



I found this unit similar in effect to the emphasible peak phaser and have to admit that I am not sold on the effect created. Phasing, generally, is produced by changing the degree of phase shift between all pass filters, and a 'notch' is generated after every 360° of phase change. The more filter stages available, the more notches are produced at 720°, 1440°, 2880° etc known as a 'comb' response. Similar effects are created using delay line devices which have an added bonus of echo or reverb depth added to the phasing. The filters are swept or voltage controlled using a slow oscillator, producing the familiar 'phasing' effect, sounding much like a passing prop plane on a hot summers' day.

This unit has a speed control, varying the phasing rate from 0.06Hz to 10Hz, and sweeping the filters with a triangle wave form. The total number of filters (or notches) are selected with a three position toggle switch connecting 4, 8 or 12 filters into circuit, and the function control varies the phasing intensity from 'peak' through 'linear' to 'notch'. The effect of this control is to produce a normal phasing effect in the 'Linear' position, with decreased filter response producing a shallower phase towards the 'notch' position, and increased filter response producing a deeper, richer phase towards the 'peak' position. The 'Q' of the filter can thus be varied for best effect.

The sweep width is varied with the width control, which increases the upper and lower sweep limits when turned from 0 to 6. The working range of the phase effect can be shifted up or down, using the colour coded jack plugs provided, when inserted into the 'program' jack socket. The blue jack shifts the phasing range up above normal, and the red jack shifts the range down. A volume (or swell) pedal could also be used for manual (pedal?) control of sweep when connected to this socket.

Standard input and output jack sockets are fitted, with supply switching on the input jack. A 3.5mm external power supply jack allows a low noise PSU to be connected, or an internal PP3 can be used to drive the phaser which has low current requirements. The usual silent bypass switching is fitted and can be integral, with a foot switch, or external via a 3.5mm jack. Used either way, a miniature red LED lights up for five seconds, indicating that the effect has been selected.

All electronics are housed in a 120 x 90 x 30mm die cast case, finished in matt black with a white legend and looking thoroughly presentable.

Sound effects from very deep phasing and close to flanging can be set up, also a useful slow to fast rotor/vibrato simulation. The TCXII B/K is intended for bass guitar and keyboard use and has an extended frequency response and slightly different phasing characteristics. Both units are priced at £96 (inc VAT).

T.C. Electronic Effects are distributed by Gigsville, (Contact Details).



Previous Article in this issue

Tempo-Check

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A History Of Electronic Music


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Jan 1982

Review by Dave Goodman

Previous article in this issue:

> Tempo-Check

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> A History Of Electronic Musi...


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