Sony MX510
A five-into-two portable mixer that turns up in the oddest places — including the stock lists of a London pro-audio dealer.
Overview
The MX510 is a compact active mixer that combines up to five channels of input and delivers two channels of output, with a variable pan pot for placing sources in the stereo field. Sony built it as a stereo/mono unit, and in the United States it was distributed by Superscope, Inc.
The channel count tells you what it was for. Five inputs summed to a stereo pair is a small-ensemble or location-recording topology — enough for a few microphones or a couple of stereo sources plus a spare, without the bulk of a proper console. Modern Recording (February 1977, p.31) described the MX510 as a new portable stereo/mono mixer built around that variable pan pot, which is the detail that separates it from the fixed-pan budget mixers of the period. Being able to steer a source continuously across the image, rather than just hard-left or hard-right, is the difference between a utility summer and something you can actually mix on.
The feature set, as catalogued in the period press, points to a box designed for real work rather than hi-fi shelf duty: an active circuit, a slide-type master volume control, an input selector, and — notably — switchable filters. There are high-cut filters at 5 kHz or 10 kHz and low-cut filters at 100 Hz or 200 Hz, which is a genuinely useful pair of choices for a small mixer. The high-cut options let an operator tame hiss or roll off a bright source without gutting the top end, while the two low-cut settings handle rumble, handling noise, or proximity boom depending on how aggressive you need to be. Four aux outputs run in parallel with four line outputs, so the same signal can feed a monitor path and a record path simultaneously without repatching.
Power is where the MX510 gets interesting for anyone intending to use it away from a wall socket. It runs on a.c. or d.c., with an optional AC-12 power adapter for mains operation. That d.c. capability is the whole point of calling a mixer "portable" — it means the unit can go where the session is, whether that's a remote recording or a stage side-fill, rather than being chained to a rack. Collectors should note that the AC-12 adapter is an accessory, not a built-in supply, so a secondhand MX510 without its adapter is a battery-only proposition until one turns up.
What the documentary record makes clear is that the MX510 was sold into the professional and semi-professional channel rather than the consumer hi-fi trade. The British pro-audio dealer REW listed the Sony MX510 repeatedly in its Studio Sound advertising through the late 1970s, alongside the MX8 and the MX650, in a mixer range that ran from £35 to £2500 and shared shelf space with Soundcraft, HH, Canary, Hill, Allen & Heath, JVC and Uher. That's a meaningful piece of context: the MX510 was being pitched to the same buyers as proper small-format British consoles, not to someone shopping for a home stereo. REW's listings through 1977, 1978, 1979 and into 1980 place it in the five-input/two-output slot of that range, with the MX650 sitting above it at six inputs and two outputs. Anyone trying to date a unit or reconstruct a period rig now has a fairly firm anchor — the MX510 was an off-the-shelf item in the UK pro channel for at least a few years running.
Where the record goes quiet is the frustrating part. There is no confirmed production span, no original retail price for the unit itself, no dimensions or weight, and no published distortion, noise or frequency-response figures in the material available. The five-in/two-out topology, the pan pot, the filters and the a.c./d.c. operation are solid; the deeper bench specs are not documented here, and it would be a mistake to assume them from sibling Sony mixers. The MX8 and MX650 shared a dealer shelf with the MX510, but sharing a shelf is not sharing a circuit, and nothing in the available material establishes that their specifications transfer.
For a working owner, the practical picture is a small active mixer with a sensible filter section, four parallel aux and line outputs, and the option of battery operation — a combination that made it useful in the field and makes it interesting now to anyone putting together a period location-recording kit. The caveats are the usual ones for gear of this age and this class: the optional AC-12 adapter is a separate item and often missing, the slide master and the input selector are the kind of mechanical parts that accumulate wear, and there is no spare-parts documentation in the available record. Buyers should expect to verify filter switching and pan-pot travel before committing, and should not assume a mains supply is included. Beyond that, the MX510 stands as a tidy example of Sony's late-1970s pro-audio reach — a mixer that turned up in London dealer stock lists next to the British consoles, which is not a bad place for a small Japanese five-channel to be found.
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