PA:CE MP175 12 Channel Mixer
TEST ON: PA:CE MP175 12 Channel Mixer
DATE November 1975
PRICE £250 Ex VAT
In the last year or so, many of the more affluent bands and groups have changed policy from one of having separate amplifiers for each musician to one of distributing a mixed sound. This change involves buying a mixer with a large number of input channels, many facilities, and which must also be built to quite a high standard in order to ensure adequate reliability.
The cost of such a mixer has, until now, been out of reach of all but the very top bands. The MP175 changes that.
The MP175 is a compact, high performance, but very inexpensive 12 channel mixer.
Each input channel has a main fader, foldback level, echo level, four channel equalisation, pan and input gain controls. The input is via a jack socket and there is also a switch to select high or low input impedance.
The output facilities are: left and right output channels with separate master faders and meters; echo mixer with a master send control; foldback mixer with master foldback level; and a stereo headphone output which is driven from the two main channels. An interesting feature is the provision of separate echo return controls for the left and right hand channels.
The unit is powered from standard 240 V AC mains and it consumes only five or six watts. There is no mains voltage selector but an illuminated on/off switch and fuse are provided.
The construction is very simple and tidy and obviously the result of a lot of careful planning. All of the electronics, including the input socket, are mounted in the top part of a two part steel case, the lower part being just a cover. The bright blue control panel has all the control workings (silk screen) printed in dark blue and sports an array of over 100 expensive collet knobs. The lower part is finished in a grey paint which has a peculiar simulated rexine appearance. The finishing touch is added with two teak veneered wooden end plates.
Equally well considered is the construction of the electronics. Each input channel has its own printed circuit board on which all the components for that channel, including the control pots, are mounted. Two further P.C. boards carry the components for the mixing stages and output channels. These 14 circuit boards are then interconnected with copper bus bars which are soldered into slots in the boards. Apart from these bus bars there is hardly any other wiring.
The quality of components and workmanship and the accessibility for maintenance are all very good.
A feature of the engineering which stands head and shoulders above the competition is the sophistication of the circuit and the number of components. Each input board has six transistors and two integrated circuits and the output boast three transistors and four integrated circuits. Most manufacturers try to squeeze the performance out of half the number of components — and usually fail.
Many details, like the use of long travel slider pots and jack sockets with gold plated contacts, together with the small physical size of the unit, indicate that the designers clearly understand band's priorities and problems.
|Maximum gain||Hi. i.p. 31.5dB.||Flat frequency response -||A little on the low side|
|Lo. i.p. 58.9dB.||all gains - maximum|
|Input saturation level||Hi. i.p. -4.8dBm.||(450 mV.) input gain||Good|
|Lo. i.p. -32.3dBm.||(19 mV.) at maximum|
|Noise referred to signal||Hi. i.p. -93.2dBm.||Wide band measurement with||These figures would have|
|Lo. i.p. -120.8dBm.||inputs open circuit||been a little better if a|
|measurement had been done.|
|Residual noise||—65.2dBm.||Noise at output with all||Quite good|
|channels at minimum o.p., at max.|
|Distortion||0.015%||T.H.D. at 1 KHz. with||Excellent|
|Tone control||+13.2dB.||Treble at 10KHz.||Excellent range|
|+10.3dB.||Mid 1 at 2KHz.||Nice and symmetrical|
|+10.8dB.||Mid 2 at 600Hz.||Good square wave|
|-10.2dB.||response with tone control.|
|+11.2dB.||Bass at 100 Hz.||Control.|
|Maximum output||+22.7dBm.||10.5 V. r.m.s.||Very good|
|Output meters||0VU= +12.2dBm.||Left meter||Rather high levels and not|
|0VU= +13.2dBm.||Right meter||accurately balanced.|
Of all the equipment we have tested, this is the first item which has given a performance as good as the best — at a price found only among the least expensive.
The noise level we measured is slightly outside the manufacturer's specification because there is mains hum present. The manufacturers know about this and are going to correct it. But even so, the background noise level is very low.
The bright blue front panel and meters with yellow dials, in my opinion, give the unit a cold and not too attractive finish. This is a pity because a prospective customer will make a first assessment on the basis of appearance and may not fully appreciate the gem of engineering behind that bright blue front panel.
The facilities provided are the same as all the expensive mixers except the MP175 does not provide pre-fade listen. Four channel equalisation is provided. The extra middle control is an unexpected but useful luxury. A slightly strange feature is that the output meters monitor the mixer levels before the output faders. There are, however, advantages in doing it this way.
I do not know how MM can produce such a sophisticated machine for this price but this really has to be "the best buy".
Review by Bruce Gibbs
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