Studio recording mixer
An attractively finished recording mixer from Yamaha, examined by David Strange
The RM804 has eight identical input channels and these are arranged in a linear fashion on the left of the console. The output controls appear on the right along with the controls dealing with monitoring and to the rear are mounted six meters, four for group monitoring and two for L/R stereo monitoring. Input and output sockets can be found on the back plate of the console except for a stereo headphone monitoring jack which is placed on the right hand upper control surface, and each channel has a MIC/LINE balanced input which is via XLR type socket. The range of level that can be handled by the input stage (-60dB to -20dB) is perhaps not wide enough for the description MIC/LINE to be strictly true, especially as this is followed by an equalisation stage which can add another 15dB of gain. However, these basic facilities gave a good indication of things to come.
The equalisation is in three bands with a maximum boost and cut of 15dB in each (characteristics are shown in Fig 1). A switch is placed ahead of the equalisation to enable its input to be taken either from the MIC/LINE input stage or direct from a -10dB tape insert point. After the equalisation a break jack, made up from two phono plugs linked by a metal U-link, is provided as an insert point for various effects units such as compressors, special Eq, delays etc. The insert point, electrically also the top of the channel fader, is then monitored by an overload indicator and this flashes an LED if clipping, due to too large a signal, is imminent — a neat and concise layout.
The output of the channel fader is fed to a buffer amplifier whose output provides both a -10dB direct channel output, via a phono socket, for an eight track tape recorder and a source for internal routing. Part of the routing is to a panning potentiometer whose outputs go to the four PGM bus matrix switches. The channel signal may therefore, by means of the switches, be applied up to all four of the buses and panned, and since the panning works between odd and even numbers so the signal can, for instance, be panned between number one and two or number three and four buses, the complete network providing every desired combination.
Signal from the buffer amplifier is taken to a two pole two way switch which selects the signal to be sent to the L-R stereo buses.
This switch is labelled POST/TAPE and in the POST position, signal from the buffer is selected to be applied via the echo mix potentiometer to the echo bus and via the stereo mix potentiometer to another buffer amplifier and on to a stereo pan potentiometer. From the stereo pan potentiometer the signal finally ends up on the stereo L-R channel buses, and when the TAPE position is selected for the switch, as in mix down from eight track, signal is applied direct from the IN phono socket into the stereo mix and echo mix potentiometers.
There are seven mixing buses within the mixer, four concerned with four track outputs, two for L-R stereo outputs and one for echo send. The four track buses are connected to the eight input amplifiers by the matrix switches that have already been described.
The only switches on the stereo buses address it to the echo return inputs, though there is a fader between each of the mixing amplifiers on the buses and the final output amplifiers.
All the mixing buses except the echo send, are monitored by a meter connected across the final output amplifier. Aural monitoring from the mixer is achieved from two amplifiers whose inputs can be addressed to any of the mixing buses and a two track direct input for monitoring stereo tape. There is sufficient drive from the monitoring amplifiers to cope with both high and low impedance headphones and the headphone jack is mounted on the control surface of the mixer.
The four track mixing buses each have a direct input for expansion of the mixer, but there are no such expansion facilities for the stereo buses, something that would be quite useful in practice.
The quality of the mechanics and general assembly of the RM804 is excellent both internally and externally. The printed circuit boards and associated components are well up to industrial standards and should be very reliable in service. However, bearing in mind the controls will receive tens of thousands of adjustments during the life of the mixer, the faders especially and also other potentiometers, do seem to be lightweight and might be subject to premature wear.
One thing sadly lacking from the mixer is a source of tone. This is very surprising considering the number of interfaces that can be made to external tape machines and yet there is no way of ensuring that the mixer meters are aligned with those in the tape machine. A tone source would also be a useful aid to sorting out routings, especially when the mixer is used to its full potential. Ideally, if tone could be injected into each of the input channels separately, not only could an eight track machine be aligned, but also, through the normal routing of the mixer, so could two and four track recorders (a possible project here — Ed).
Returning to a point made earlier related to the MIC/LINE input, the addition of a switchable 20dB attenuator on this input would make it truly a MIC/LINE input, especially useful to interface with professional equipment.
Operationally the RM804 mixer is a joy to use and anyone who works with the mixer will find they hardly have to leave the desk because all in/out levels are so conveniently to hand. Also, the matrix of switches make reconfiguration from record to mixdown a simple operation. Indeed, the Yamaha RM804 is literally packed with features that anyone who is looking to set up a small eight or four track studio would want. Even including the criticisms mentioned, there is a lot of very good mixer for a RRP of £738. This is a surprisingly low price to pay for a mixer of such extraordinarily high quality, and it is thoroughly recommended.
Review by David Strange
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