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Rackmounting Mixer Channel Strips

Is It Worth Your Time And Expense?
By Sam Inglis

Rackmounting Mixer Channel Strips

We all love vintage mixer EQs and preamps, but it takes a lot of work to rack them up for use in today's studios. Is it worth your time and expense?

Some people base their buying decisions on a carefully considered assessment of their needs. I usually base mine on whether something looks like a bargain. This can be fun, but it's possibly not the most effective way to put together a studio! I've certainly made a few bad choices over the years, and it's especially easy to get carried away in the bargain-spotting stakes with things that need work to make them work.

"Just rack these up and you'll have X channels of vintage preamplification and EQ!", the sellers say, and it's a tempting prospect. From the '70s onward, most professional analogue consoles have had channel strips with preamps, several bands of EQ, and sometimes dynamics. Those consoles cost tens or hundreds of thousands back in the day, and represented the pinnacle of British, European and American engineering. If you can pick up one or two of the important bits for a few hundred quid, surely that's a better option than paying a couple of thousand for a new high-end channel-strip-in-a-rack?

Having recently dived down this rabbit hole myself, I can report that it's not as simple as it sounds. Sellers are always keen to tell you about the audio Nirvana that awaits once you've "just racked up" your modules, but they tend to gloss over what's involved in actually doing this. After all, if it was that easy, the sellers would do it themselves

When Is A Mic Preamp Not A Mic Preamp?

One thing to be aware of is that not all mixer modules are quite what they seem. For example, circuits are sometimes misrepresented as mic preamps when that was never their original role. The classic cases are the Neve 1272 and the Telefunken V72, both of which were originally line amplifiers. These particular units can successfully be modified for use as mic preamps, and often are, but the same doesn't apply to every line amp, headphone amp, talkback amp or other little grey box. Input stages from reel-to-reel recorders are sometimes resold as 'preamps', too, though they may need a lot of work and extra circuitry to fulfil this function, and once you start looking into modules made for broadcast, you get into a maze of almost-identical model numbers that can be pretty hard to navigate. It's also not unknown for unscrupulous dealers to sell modules missing vital components such as input or output transformers.

Modules from older professional mixing consoles usually plugged into multi-pin connectors, often mounted on a  backplane like this. Make sure you can find the right connectors, and that you know which pin carries which signal!Modules from older professional mixing consoles usually plugged into multi-pin connectors, often mounted on a backplane like this. Make sure you can find the right connectors, and that you know which pin carries which signal!Even if your modules really are true 'channel strips' with a mic preamp and EQ and so on, they will have output stages designed to feed the mixer's internal bus architecture. These may not be capable of delivering a line-level output when the module is used stand-alone, and if not, extra circuitry will be necessary. Finally, don't forget that mixer modules usually talk to the rest of the console via multi-pin edge connectors; these come in a variety of shapes and sizes, and mating examples can be hard to track down if they're not supplied.

Then there's the question of condition. Most second-hand mixer modules will...

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Published February 2020