Studio Microphones of 1954

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• Any ideas on how to get schematic for capps tube condenser microphone?

  • I own 2 Capps CM2250's and have the paperwork.
    I will be glad to send you a scan of the mic and p/s schematics. If you don't have the power supply, it isn't be hard to "homebrew" one if you are familiar with vacuum tube gear and respect the voltages involved. The tube in the Capps is either a 6AK4 or a 5703. 5703's are fairly easy to find. The Belden p/s to mic cable is hard to find, but the Gotham (Bethlehem, PA) cable should work. PM me on FB and mention the CM2250 schematic.
    The power supply furnishes 225 v dc plate and 6 v dc for the heater. The heater voltage must be elevated above ground to avoid exceeding the tube heater/cathode voltage rating, and for low noise.

    • Hi RM, A friend recently gifted me a capps cm2250 microphone with the power supply. It is not working at all. Fortunately I came upon your post on Preservation of sound mentioning you have a schematic for the microphone and power supply. I you could scan and email it to me, I will be very indebted.
      Many Thanks in Advance
      John Charette

    • Did you ever get your mic going? I just picked up a pile of them and wanted to get your thoughts?

    • I too am interested to get a schematic since I just picked up a pile of Capps condenser mics. Thanks.

• I have an old capps p/s and microphone body with a tube pre in it. Someone modifyied it to use an M7 capsule in a U87 head. Would love to have schematics to document the mic.

  Thanks,

  Mark

• Bought a Capps mic back in 1959 when I was 20 yrs old. Traded it for a BSA motorcycle in 1963. Should've kept the Capps! Got another Capps a few years ago from a collector in San Diego. We did a trade: my RCA 44BX for his Capps. He said he paid $900 for the Capps! I paid $200 for the 44! In 1959 I met the guy who worked for the Capps company. He designed the mic! Frank Capps died around 1946. I think wife Isabel was running the company after 1946. The original designer was Roy Ruth. He's still alive; lives in Wisconsin. I have his phone number. He was a friend of Emory Cook. I still have my Capps mic. Beautiful antique! My first quality mic! Roger Murray/Chief Tinkerer.

  • I have Emory Cook's Capps mic but no power supply. The mic came with the Cook Collection to Smithsonian Folkways Recordings.

    • Pete,

      if you were so inclined, it should be pretty easy for a tech to build a power supply. by opening the unit and reverse-engineering it based on the plate and cathode resistors of the tube it should be easy to get the correct plate voltage by just looking at the tube data sheet. similarly, the heater voltage is easily determined once you know the tube type. c.

• I have two Capps CM2250 mics and the paperwork. The power supply is a straightforward 6X4 full wave circuit furnishing 225 volts for the anode; the heater for the 5703 is 6.3 v DC and is floated above ground. Shouldn't be difficult to build a power supply to run it. The aluminum element in the capsule tended to collapse with time and render the mic inoperative; reskinning with sputtered mylar holds up better.

• I believe I have an extra power supply should you need and want an original one. Think I have an extra cable for it as well. Will check when I get up to the lab tomorrow. Feel free to contact me if interested.

  • Hi Larry, I’m reading this long after the fact. Do you still have that power supply and cable? I found a Capps 2250 at a yard sale. No power or cable but heck it was free?!?! I sure would appreciate any help in finding what I need to get it working.
    Thanks G

• The Modern Jazz Quartet recording "No Sun In Venice" was recorded by Tom Dowd with a pair of Capps condenser mics. He had a battery power supply for the mics. The 2 mics went straight into an Ampex 350 2 track. It is a great sounding recording with amazing top end.

• Dear sirs

  I have a CM2011A CAPPS condenser microphone.could you tell me what it's worth.

  JACK MAC
  Thank you

• I would appreciate any help I can get

  Jack Mac

• Was the Turner 57 considered a high end mic at the time? IIs it worth having at a studio?