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custom racking

Member for

21 years 2 months
Hello, can anyone recommend a place to rack a couple of Langevin AM16 mic preamps with maybe polarity switching, phanto & input/output controls? Other than Mercenary since they seem very high priced.

Comments

Member for

21 years 2 months

Pro Audio Guest Sat, 01/24/2004 - 09:53
Most any music store or electronics shop can do it for you. The reason to go to a place like Mercenary is that they have done it before, and understand perhaps a little more about it than the typical music store. But if you are looking for the cheapest job short of doing it yourself, take it to your local music store or A/V contractor.

Bill

Member for

20 years 2 months

Tungstengruvsten Sun, 01/25/2004 - 15:15
hmm i'd avoid that route with am-16's....you would want someone familiar with them to rack them. These are amazing sounding pre's if properly done, but lots of things can add up to less than stellar performance. I've seen some pretty sloppy jobs out there and these aren't completely intolerant to placement, shielding, etc.

Do you have the schematics for them?? that would make it easier for someone not familiar with them to work on them, but still...

Some things to consider:
-mu-metal shielding for the units(as they were in the original racks)
-star grounding within the chassis
-internal power supply(orientation of modules and power supply can raise/lower hum/noise floor)
-torroidal tranny for power supply(if internal)
-external power supply if it's a small chassis
-input pad? stepped pad attenuator?
-proper 48v power supply and implementation(am16's are direct coupled, no caps..don't wanna fry that transformer)

These are fixed gain amps, so there are no input/output adjustments. you will have to come up with this yourself. I've seen people use ganged pots but they don't track perfectly and this throws off the CMRR. an input attenuator with .1% resistors, maybe -10,-20,-30 positions would keep this thing sounding beautiful and allow you the flexibility to handle many different mics/instruments...

Member for

21 years 2 months

Pro Audio Guest Sun, 01/25/2004 - 18:58
"hmm i'd avoid that route with am-16's...."

That assumes that there is no one competent in any local shops. I want to point out that -all- shops are local somewhere. I'd have no problems taking anything to Gourmet PA, or Korby Audio, both of whom are local shops. There are also a number of good frelance techs around, like Bob Bell, Mike Mazur, Dave Long... all long-time techs, 2 with major studio experience and one who is a systems designer/engineer. Local doesn't have to mean bad.

Bill

Member for

20 years 2 months

Tungstengruvsten Sun, 01/25/2004 - 19:54
sorry Bill, guess when i think 'local shops' i think consumer audio repair type places...more vcr's and tv's than audio gear like am-16's.

Heck even if they were Siemens/telefunken modules i'd have more confidence in a 'non-pro audio specific' electronics guy racking them, they are at least in mu-metal cassettes and capacitor coupled with most if not all controls already built in...

Not alot of music stores/pro audio retailers etc around here(Toronto) offer the service of racking modules, be it eq's, pre's whatever...there are those that can do it but you gotta look....and know what you are looking for.

Member for

20 years 2 months

Tungstengruvsten Mon, 01/26/2004 - 08:42
I can recommend a tech near here, which isn't too far from NJ but within Canada. His work is some of the best i've seen and he knows the am-16 like the back of his hand. I went through all this a year ago...did my research and after many conversations and meetings with this fellow decided on him. He racked my 4 AM-16's and has done other pair's/quads of them and other modules....really knows his stuff.

Some things i can think of that might help:

-get a torroidal power tranny if the power supply is going to be in the rack....i'm not big on external power supplies as it's one more thing to leave behind(i do alot of work out of town...)but the am-16's are susceptible to hum and a smaller rack could limit your placement options.

-use .1% resistors for the input attenuator-they are expensive but worth it. I had an attenuator that had 6 positions on it...this is because I elected not to do an output control on it(which would be a passive one anyways, no gain increase)

-put the input impedance selection on a switch...it's there!
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