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Fostex 350 Mixer

The new range of Fostex recording machines, highlighted by the superb and innovative eight track A-8 using ¼" tape, is complimented by a very useful and compact mixer — the Fostex 350.

It is a versatile 8x4x2 mixer designed for recording, mixdown and PA applications and uses unbalanced input/outputs, as well as a routing system that offers maximum scope from this unit priced at £401.87 ex. VAT. The 350 follows the style and smart grey/orange presentation of the companion tape recorders, measuring only 3¾"(h) x 18½"(w)x 16"(d) and weighing 18 lbs. An optional meter bridge is available (£97.50 ex. VAT) that mounts across the top rear of the mixer, with six VU meters for monitoring the four main output lines (ABCD) and the two auxiliary outputs. The bridge is linked and powered by direct multicable connection to the rear of the mixer and its side screw supports allow angling to suit the user.

Rear connection panel.

Apart from two stereo headphone sockets mounted on the front, all connections are compactly located on the rear panel. The mic/line inputs use standard ¼" jack sockets with all other connections made via RCA phono sockets.

There are eight input channels (impedance 50kΩ) with an adjustable level range for mic/line inputs from 0.5mV to 4V. Each channel has a tape input socket as well as a patching wire link across the signal path at this point that can be removed to 'send' and 'receive' effects and other signal processors.

Thus mixdown is made easy from the eight track by simply flicking the switch for 'mic/line, off, or tape'. There's also a red LED situated above each input fader that flashes warning of likely overload of the input stages.

Whilst the channel fader then feeds an EQ section, the signal is also routed to the auxiliary (L/R) stereo output buss sockets. A switch allows selection of the signal before or after the channel fader, or from the tape input (i.e. pre, post, tape), with gain and pan controls provided for each channel. So the aux buss is very useful as a stereo foldback (or two mono), as a reverb/echo buss, or as a tape monitor during recording.

The EQ section replaces the normal bass (mid) treble controls and offers lower and upper centre-band frequency control from 80Hz to 1.2kHz, and 800Hz to 12kHz, with boost and cut of 12dB using the gain controls. At first, the section is a little awkward to use, but soon becomes an attractive alternative because of the increased control it allows in tailoring the frequency response. Hums and hisses are easily removed and large tonal changes to the input signal can be made.

The EQ output is split to feed a direct output socket, useful for further sub-routing (to another mixer or recorder), and a pan pot that is routed (via an 'A/B, off, C/D' switch) to either pair of output groups. The A/B, C/D references for the output lines match the A-8 recorder's input routing system and both group outputs are controlled on the mixer by ganged faders, before buffer amps send the signals to 'line out' sockets.

The metal chassis supporting controls.

Additional 'Buss In' sockets with gain control are provided on each of the group lines (A, B, C, D) and also on the Aux buss, but with no level controls unfortunately.

The stereo monitoring system is unusual in that it is done through five switches with level controls prior to its L/R output sockets. Nevertheless, it is very easy to use and offers not only A/B and/or C/D monitoring in stereo, but a mono (centred) signal for A or B, and/or C or D — all done by pressing switches A, B, C, D appropriately. If the fifth switch is pressed, the Aux buss (L/R) is heard instead.

Normally, the monitor sockets would go to your amp/speaker system and would require level adjustment from the amp with this mixer. There is also a stereo headphone amp with level controls that allows direct headphone monitoring via two ¼" stereo jack sockets. The quality is exceptionally good, with little background noise and high gain (maximum 100mW to 8Ω).

Finally, two good quality stereo RIAA preamps are built into the 350 mixer and accessed by dual input and output phono sockets on the rear panel. These will appeal not only to disco users, but to electromusicians who often refer to records during their studio work but don't have room for a separate hi-fi system.

Internal view showing the main RCB.


The 350 mixer is very well made and despite its 'plastic' feel, is built to last, on a rigid metal frame internally, with one large PCB holding most of the circuitry. Even input sockets feed directly to this board. Phono preamps and Monitor Select switches each have their own PCBs, and the transformer (not toroidal) is screened, with PSU fuses located next to it. Servicing is quite straightforward as the whole chassis lifts out, once fader knobs and four long screws are removed. Knobs and switches are all well made and the only point was some stiffness at the top of the end of the faders (only apparent on my review model, it appears).

The rear connections certainly allow much of the routing you'll require to be prewired, but once the meter bridge is attached to the mixer, there is quite a hassle accessing the jack and phono sockets, especially if you use short connecting leads to your A-8 tape recorder, etc. One answer, of course, is to use a separate junction box linked to the mixer from which access can be made more easily. Incidentally, no leads (except for a fixed mains lead and bridge multi-way lead) are provided; and the medium impedance of the system limits lead length to under 10ft before hum and high frequency losses may occur.

The bridge also has very little angle to manoeuvre once all connections are made. But it's still an advantage to have, particularly for its large illuminated VU meters.

What you have to weight this against is that for a small outlay by today's prices you can make this mixer do virtually everything you want in a small 8-track/4-track stereo studio situation and that alone makes the problem of fiddling with connections at the rear worth it. And, of course, it's so small that it fits in any situation. I would have liked a built-in oscillator, although with plenty of synthesisers in my studio, it is easy to line up meters using one of these as an external source. A second foldback and monitor level control would have been useful, but Fostex have obviously kept their design to a sensible minimum.

Operation of the mixer is quite straightforward, with overdubbing, tape mixdown, foldbacks all easily done. A small but comprehensive manual explains the alternative ways of using the 350. Fader attenuation is good with no breakthrough at minimum, and cross talk is claimed to be 65dB at 1kHz.

The most important features of this instrument are not only its versatile routing, but its good low noise operation plus — now that CB is here to stay — its minimum RF pickup, yet still giving plenty of gain at the input stages. If you need a small mixer that will maintain your off-tape quality, the 350 is highly recommended.

The Fostex 350 Mixer is distributed in the U.K. by Bandive Ltd, (Contact Details).

Figure 1. 350 Mixer block diagram.
(Click image for higher resolution version)

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


Electronics & Music Maker - Apr 1982

Scanned by: Stewart Lawler

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Mixer > Fostex > 350

Review by Mike Beecher

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