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Soundtracs T Series

16:4:2 Mixing Console


The good Dr. Bateson takes time off to put this Soundtracs desk through its paces.


Soundtracs mixers, manufactured by Soundout Laboratories, have established a good name in both the high and mid-price mixer markets. They became Soundtracs in 1981, although the company was first established in 1976 to manufacture Soundout disco equipment. Spotting the demise of the disco phase in 1979 (thank the Lord) they originated the 'Frunt' range of group amplification equipment, which was notable chiefly for its monolithic and indestructible appearance. Since adopting their present guise, they have grown considerably, staff numbers increasing sevenfold in five years. They export 85% of production (indeed I used to think they were American) and last year earned the Queen's Award to Industry for export contributions (and tax, I dare say). They produce a diverse range of mixers and are continually updating; indeed they have five new products coming this year ranging from the small, through the mid-range automated (which could be very interesting) to the vast and fully automated.

This is the 16:4:2 version of the T Series of mid-priced PA or studio mixers, aiming at a similar market to the Yamaha MC1604 reviewed in February's issue. Although similar in purpose, the two differ extensively in approach and detail.

Construction



Just for a change, let us examine in detail the screws that hold the front panel to the base. They are black, 20 in number. 17 self-tappers with nylon washers are spread around the perimeter of the front panel while the others lurk underneath, a point to remember when some perspiring roadie is tearing it apart. (Where most reviews would simply tell you what colour it was, H&SR really gives you value for money.) Incidentally it's grey, but a tasteful grey offset by a multi-coloured array of knobs (Alright, that's enough of that —Ed). The whole front panel is one lump but the inside is entirely modular with IDC connectors on each board. Soundtracs obviously believe in low impedance busses, for no namby-pamby motherboards are found here... more like 6A mains cable.

Since it seems to be in pieces, we may as well loiter a while on it's constructional quality, which is fairly solid without being military in appearance. The front panel looks like 16-gauge steel while the base is folded from 18-gauge material. Structural ABS forms the moulded black surrounds/armrests which although light, are surprisingly strong. Soundtracs' investment in CAD/CAM equipment appears in the form of computer-designed PCB layout and automated assembly, as evidenced by the dummy resistors used as wire links. All the ICs are socketed, which on balance is a good thing in an item liable to device damaging abuse. Components are mainly common or garden types including the Schadow function switches which is good news for the serviceman. The pots, made by Omeg, have narrow (1/8") spindles to fit Soundtracs' custom knobs and would need manufacturer's replacement in the event of failure. The pots also felt a bit wobbly to me, although this has little bearing on their reliability. Similarly, the 100mm faders made by Noble felt a bit lumpy, lacking the silkiness of the better Alps faders. The boards are fairly easy to remove, however, only needing desoldering from the faders and mic XLRs. I imagined the soldered mic input connection to be in the interests of long term reliability under low signal conditions, definitely a laudable practice. Here though, in offering the choice of XLR pin 2 or 3 hot (European or American system) they have used plug/socket jumper links immediately following the carefully soldered input connections!

The other channel input/output sockets are board-mounting jack types, not gold plated so don't install the mixer in a sauna.

At the top right above the group/master boards lies the internal power supply, comprising a large C-core transformer with generous TO3-cased regulators on a separate board and heatsink bracket. Soundout offer the option of an external PSU which they say offers improved noise figures. My trusty scope picked out no particular hum from this version though, even with our lousy domestic mains supply. Perhaps they mean mechanical noise, as there was a slight buzz. However, the console could have been a good 1½" shallower without the transformer. Other options available beside the PSU which can be added without soldering include multicores with multiway connectors for stage use; additional input channels in groups of four up to a maximum of 32 and and additional group module to bring the console to its maximum 32:2:8 configuration.



"Channel tape returns on channels 1-8 would be more useful than group tape returns."


Input Channels



These follow the time-tested 'balanced input:EQ:routing and auxiliaries' formula executed in an attractive and usable way. I was impressed with the way the controls fell easily to hand. Starting at the top with Soundtracs' characteristically shallow rear-sloping panel, we have an electronically balanced mic input on XLR, supplied with pin 2 hot. Phantom powering is available on all mic inputs controlled by a single switch on the master section but it is not available to remote microphones via a stage multicore, very wise. Remaining inputs and outputs are unbalanced but use stereo jack sockets. Line input and post-fade output are available on each channel. These are dual level, wired tip +4dBm, ring (or half-inserted jack!) -10dBm. The post-EQ inject socket is wired ring send, tip return and operates at +4dBm which is probably too high considering the type of studio effects likely to apply in this price range, but is valid for live work. In practice, since there is post-fader gain available (see below) you could easily run low level effects from the insert points. The provision of individual channel outputs is unusual in this price range but potentially very useful.

The controls start with a 30dB mic pad switch and a mic/line input selector. No tape return input or switch is available on input channels, though they are provided on the groups. A red-pointered gain control provides a nominal gain range of 20 to 60dB. Following this comes a 3-band EQ section.

A single sweep mid-range control can be centered anywhere between 250Hz and 5kHz, while the High and Low controls are supplemented by switches enabling them to shelve at 6 or 12 kHz, or 60 or 120 Hz, respectively. A Wein type circuit is used in the mid-range control, as in the majority of mixers. I always seem to find their implementation (ie, choice of filter Q) makes them sound a little hard and 'peaky' but this, of course is a matter of taste. Again, circuit restrictions usually prevent a single sweep control from covering a really wide frequency range. This one manages a 20:1 ratio, which is wider than most but maybe a range switch would have been worthwhile.

Below comes the EQ in/out button, followed by Auxiliary Send controls. Four are provided; 3 and 4 are dedicated post-fade while 1 and 2 are switchable pre- or post-fade. Internal links and simple instructions are given to make the pre-fade position pre- rather than post-EQ if you should so desire. All knobs are appropriately colour-coded; grey for EQ (white to differentiate the mid-frequency) red for gain and green for auxiliary.



"The whole front panel is one lump but the inside is entirely modular."


Next we come to the four routing buttons. The first assigns that channel to groups 1-4 or 5-8 (ie. nowhere in the unexpanded version, a point to remember if you seem to have lost a channel). Two white buttons select groups 1-2 (5-6) and 3-4 (7-8), odd and even groups corresponding to left and right on the Pan control. A further, blue button permits direct routing to the L-R master group. The flow is briefly interrupted by the yellow Pan control (a proper dual-pot type) before resuming with a white channel mute button which operates post-insert, pre-fader and auxiliaries. A red Solo button lies above the channel fader; I shall come to its mode of operation in awhile.

The final channel facility is a small oblong Peak LED, which operates in a slightly unexpected way. The fader nominal unity gain, 0dB point lies 75% of the way up the mechanical scale, while full scale represents 10dB post-fader gain. Because of this, the peak indicator turns on 4dB before clipping only when the fader indicates unity gain. Flat out, you could be 6dB into clipping before the LED lit at all, by which time someone might have noticed! And since the group and master mixing stages are unity gain for each channel, the problem worsens with many channels in use. The word is, don't ever let the Peak LEDs light, or change R67 in each input channel (680R) to 2k2 to make the LEDs light 10dB earlier. Remember, this does not imply any headroom problem in the mixer, just that the LEDs are unhelpful in their present state.

Sub-Groups



The four subgroups lie to the right of the console and combine various auxiliary and tape return functions. Each auxiliary buss terminates at a group board, is virtual earth amplified and sent to an Aux Master send control, this being the topmost of the group controls. Following this the signal is buffered and sent to an Aux Output socket, again a split-level +4/-10dB device. Just above the Aux Master control is a switch marked Aux AFL, which allows you to solo monitor whatever is going out. No Aux returns as such are provided, so you must use input channels for this. This is not so bad in a typical 4-track system and you can add extra channels if necessary as the system grows.

Group functions proper begin with buss amplification, followed by a Group Inject socket similar to the Channel Injects. From here, the signal can go to the group output socket (and thence, typically, to the tape machine) in one of two ways, defined by the position of the Fader Reverse switch fitted above the group fader. In normal mode the fader directly controls the group output level, while the Mon Level knob taps off a portion of the prevailing group output and sends it (indirectly, see below) to the L-R master groups. In Fader Reverse mode, they perform each other's functions, allowing convenient (fader) monitoring of the group outputs.

As I said, the L-R routing is not direct, and in fact further EQ and auxiliary functions are available. Remember the mixed signal presented to the group outputs? This is routed to a switch just below the Aux Master knob, entitled Tape Return. From here, either the group signal or one from the dual +4/-10dBm Tape Return socket (naturally!) can be selected. Metering is taken from this point, in the form of a 10-segment LED bar-graph reading from -28dB to +8dB. Next in line for the signal comes a rather spurious non-defeatable 'bass and treble' type tone control. (I'd rather have auxiliary returns). All four auxiliary busses can be sent to, post EQ, on each group: two pre-fader and two post-fader (which can be the fader or the monitor control, depending on the fader reverse switch). Phew! Explanation over.

Master Groups



This is where it all happens of course. Three main functions are found here, covering master mixing, monitoring and talkback/test tone generation. The latter consists of four pushbuttons, a level control and a microphone socket. A 1kHz test tone oscillator can be activated by the top switch and either this or the pre-amplified talkback mic signal is selected by the PTT (press to talk) switch mounted directly above the master faders. The chosen signal then goes via an uncalibrated level control to two further switches, permitting signal injection into all the Aux busses and all the Subgroup busses, respectively. This is a simple arrangement which must cover the majority of applications, though I would have liked to assign the talkback to just one Aux or Group buss.

Monitoring arrangements are quite comprehensive. With no Solo buttons depressed, monitor outputs are fed either from the post-fade main output or from the stereo return sockets, according to the position of the mix/mon switch. On pressing one or more of the Solo buttons, the solo relay operates, a 'Solo On' light appears and the solo buss is connected to the monitor system. One additional switch lives round here. This is 'L-R meter' which when activated reconnects the meters above groups 1 and 2 to the left and right monitor system outputs.



"I was pleased to see no significant noise contribution in the EQ circuitry."


Performance



It's time to dig out ears, scope and meters. No specifications are actually given in the manual, so no cheating is possible. Many mixers are based on TL074 BIFET op-amps which without excessive loading produce about 0.02% THD, so no worries there. Bypass-type listening tests revealed no audible degradation at all.

Noise figures depend principally on the input stage. Here I found perfectly standard 2N2222 NPN transistors which returned a perfectly standard -124.5dB equivalent input noise (20kHz bandwidth, unweighted, 150R input load). This is fine for most of the live and semi-professional applications at which the desk is aimed. Input impedance is quite low, at 1.6K (mic) and about 10K (line). On the output end, the high supply voltage (±17V) gives a maximum output level of +21 dBm, ie. 17dBm nominal headroom. Maximum gain from mic input to main outputs is nearly 80dB. Output stage noise is minimal and I was pleased to see no significant noise contribution in the EQ circuitry. Rise time, at 8μS, is faster than my eardrums will go but this is not at the expense of stability, well I couldn't provoke any misbehaviour. This is at least partly due to careful earthing. Soundtracs have a central earth which is also a chassis earth and a binding post for external earthing.

The bargraph meters are quite accurate, half-wave peak reading types with a 0.5mS attack time... full wave would be better but no problem. They also look nice.

Conclusions



In use the mixer proved a well thought out and logical design, and if typical it's easy to see why Soundtracs are successful. I have a few comments of course; channel tape returns on channels 1-8 would be more useful than group tape returns (although in practice you could easily devote 8 line inputs to this function) while auxiliary inputs could supplant the group EQs. I thought the desk deserved non-stick faders but the remaining controls operated very smoothly and predictably. It appears to be primarily aimed at the small studio and in that respect I particularly liked the expansion idea. This makes it an excellent upgrade in a 4-track system which remains as useful when Gran buys you that Tascam 38. At £1516.50, the price is about par for the size. I'll take one. (But do fix the peak indicators, chaps.)

The retail price is £1516.50, and further details can be obtained from: Soundout Laboratories, (Contact Details)



Previous Article in this issue

At Home in the Studio

Next article in this issue

TOA 280-ME


Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.

 

Home & Studio Recording - Jun 1986

Donated & scanned by: Mike Gorman

Gear in this article:

Mixer > Soundtracs > T Series

Review by Simon Bateson

Previous article in this issue:

> At Home in the Studio

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> TOA 280-ME


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