Mic/Eq Modules

[newguy12]

I know this is a really newbie question but can somebody explain what these mic and eq modules are, how are they different from regular outboard mic pres and rack mounted eq units and how does one go about installing them in a rack and using them. Also I was just curious, what exactly makes certain mic pre units so much more expensive than others and how difficult is it to make a mic pre? Thanks in advance for your patience and help.

[Professor]

Ah you have been searching the dreaded eBeast for recording gear. Or perhaps other places but either way you have discovered that lots of folks are selling lots of old crap in little pieces that don't seem like they can plug into anything. Well, way back in the glorious 'old days' people built mixing consoles that were dirty, noisy, unreliable pieces of - you get the idea. Truthfully many of these consoles were the very height of their period technology, but they were unreliable as much old electronics was. The consoles would be used nearly twenty four hours a day for years until they broke down. Conveniently, they were modular so you could send off a few channels to be repaired and still have a functioning console. Some were so modular that you could choose how many channels had mic inputs, liine inputs, equalizers, aux busses, etc. to get the exact right fit for your needs and budget. As a studio would outgrow its console, or the breakdowns became more frequent they would replace with a new console and sell the old one off to another smaller studio. That smaller studio would use the hand-me-down until it no longer suited them and sell it off again. The cycle would continue until the console was beyond repair as a single unit and the console would be sold off for spare parts - well off studio could then have spare modules for their boards incase of failure.
Today we have wonderful boards with all IC designed circuits that are distortion free with frequency ranges that are flat from DC to light. But as is the case people pine for the 'sound' of the old consoles. But an old console cost $100,000 when it was new and the price hasn't dropped if it is still in prime working order - it has probably gone up. So, the industrious engineer can purchase the modules desired from a particular mixing console and add on a power supply, and some connectors to create a stand-alone preamp, equalizer, compressor, line amplifier, etc. It's not the same as an old console, but you are not confined to the old 'character' all the time. You can use a newer console that is clean and distortion free and choose to apply the 'vintage' 'character' to any particular track when it is needed and or appropriate. So, with a couple of different modules you can have your cake, your pie, your chocolate mousse and eat them all whenever you feel inclined. Pretty sweet. (sorry I had to)
If you are just starting out into the world of equipment, you are probably not ready to pick up any used modules. You should have other gears like mics, mixer and recorder first. You can do a lot more with an $800 Soundcraft mixer than you can with an $1800 Neve 1272 module. Sure the module has a vintage sound, but that is all it has, and it can't mix or equalize or feed a headphone mix for overdubs without a console. When you are ready for them it is great to get some nice modules just like it is nice to get other outboard processing equipment.
As for why some are more expensive than others, well it is like anything else. In cars there are Porsches, and Benzs, and then there are Lamborghinis, and Bugattis. In audio there are vintage Sound Workshop boards and there are vintage Neve, or Studer or API or Telefunken, or any of a whole host of other brands. Some cost more because they sound fantastic. Some cost more because there were very few made and even fewer still around. Some cost alot because they are rare and desirable. It all depends. Don't feel compelled to get any modules now for fear of not being able to get them later - they will be around, and the prices will rise and fall with their popularity and demand.

Hope that helps explain that little quirk in the business.

-Jeremy

[newguy12]

Thanks Jeremy that really cleared up a lot of confusion for me. The one remaining question I have is, how difficult is it to make a microphone preamp (not that I'm going to attempt to build one anytime in the near future). Thanks again.

[Professor]

Not to belittle the art of electronics design or anything, but it really shouldn't be too hard at all. I wanted to build a headphone amplifier about a two years ago, so I searched on the internet for headphone amplifier schematics and found a couple websites with verious designs. I printed them out, read through a few and worked out a design that wanted to attempt that drew from a couple sources. I used a basic single opamp per channel, added one more opamp per channel to unbalance the balanced inputs and then I built a little power supply board to provide balanced power (positive, negative and ground) from a 9-volt supply. I had trouble with the gain control and didn't want to compromise the circuit, so I left it out and just used the stereo out on the mixer to control the level. I've learned a lot more about circuit design since then and may revisit the project someday, but for now the amp still works.
You'll need to do some research and make some decisions on the design before starting. Things like balanced inputs? phantom power? transformer coupled? input impedence? range of gain control? and other issues. The neat thing is that you can start with a little circuit and keep changing the design as your knowledge progresses. I did a quick search and found lots of pages when searching hotbot.com for 'microphone preamplifier schematic'. Here are a few:

This looks like a really simple circuit and I might try this one out sometime, though I would add a balanced input circuit for obvious reasons.
http://home.new.rr.com/trumpetb/audio/micamp.html

This one is a tube preamp, though the page is less detailed and it is based on a 12AX7 which can turn microphonic itself in some designs. but still...
http://www.geocities.com/d_zeman/Projec ... cpream.htm

And here is a complete diagram of the commercially available Rane MS1 preamp which sells for around $200 per channel. It might cost you $250 to make your first one, but if you make 4 and sell two to a friend, who knows...
http://www.rane.com/pdf/ms1bsch.pdf

That should get you started. Perhaps in 50 years all the young engineers will be searching for those vintage newguy12 preamps.

-Jeremy
http://www.geocities.com/d_zeman/Projec ... cpream.htm