Documents and sketches

Ribbon Microphone Patents

Thu, 26 Aug 2010 10:28:51 +0100

Harry Olson, Marconi, July1932.
Improved ribbon mic with tube amp and better housing. Possibly the first tube ribbon mic!
GB391340.pdf

Olson, Marconi, May 1933.
Directional microphone with velocity and pressure components connected in series.
GB405497.pdf

Otto Kolb, September 1933.
Ribbon mic with 1 to 1.5 micron ribbon and holes in the pole pieces for improved air way.
GB414907.pdf

Andrew Swickard, Bell Telephone Labs. July 1936.
Ribbon microphone with both velocity & pressure sections
US2141420.pdf

Thomas Julian, GEC, March 1944.
Improvements in ribbon microphones.
GB592492.pdf

Horace Duffell, Radio Gramaphone Development, June 1947
Adustable magnet pole pieces.
GB641897.pdf

William Cragg, Standard Electric Corp. December 1945.
Velocity microphone with ribbon supported along its edges
US2510079.pdf

Helumth Eckardt, Bell Telephone Labs, May 1949.
Describes a 3-zone ribbon to eliminate distortion and improve frequency response.
US2608265.pdf

Donovan Shorter & Hugh Harwood, BBC, March 1953
Improved ribbon microphone design. Looks very much like the STC / Coles 4038!
GB738864.pdf

Cadenza Ribbon mic manual

Wed, 18 Aug 2010 10:30:45 +0100

Scanned documents for a ribbon microphone from Cadenza, including wiring arrangements for high and low impedance use.

Lomo 19a9 manual

Sun, 13 Jun 2010 14:27:47 +0100

Here is a scan of the original Russian manual for the LOMO 19a19 tube microphone.
Lomo19a9.pdf
To download, right click and save etc.
The full schematics for the 19a9 have been hard to find, particularly the power supply. I’ve saved those schematics as separate files. Click here to see them.

I’ve combined the key components for the microphone circuit in the figure below.

There’s a discussion about the microphone here at prodigy pro.

Thiele Brochure

Tue, 8 Jun 2010 12:39:04 +0100

Here’s a scan of a short advertising document for Thiele M4 and M5 (photo to the left) tube microphones.

Note how expensive the microphones were at the time - 500 and 600 Deutchmarks. For reference, between 1950 and 1960, 4 Deutchmarks approximately equalled 1 US dollar.

Neumann-Gefell documents

Tue, 4 May 2010 10:06:13 +0100

Click on the images to view them at higher quality.

CMV563 brochure UM57 document M582 document

CMV 563 Flyer

Telefunken ELA M251 brochure

Wed, 17 Feb 2010 09:39:38 +0000

Click on the thumbnails to view the full brochure (16 Mb) and schematic for Telefunken ELA M250 / 251 microphones.

Handy Calculators

Tue, 16 Feb 2010 07:06:12 +0000

Pentode Express have some useful on line tools for calculating components and behaviour of simple tube amp circuits. These seem to be intended for guitar amp use, but they work just as well for tube microphones.

Cathode Bypass Capacitor Calculator

Plate Amplifier Output Impedence Calculator

Cathode Follower Output Impedence Calculator

Other electronics calculators for audio

Attenuator calculators for audio

Impedance matching calculator with lots of networks

Simple RC filter calculator at muzique.com

RLC frequency calculator 1

RLC resonant frequency calculator 2

Acoustics calculators

Bob Gould’s Room mode calculator - design your control room or live room.

Similar room mode / standing wave calculators from marktaw.com and mcsquared.com

An Eigen-mode calculator with a nice graphical display of your room.

And here are some discussion on how to apply these results.

Schematics and manuals

Mon, 8 Feb 2010 14:14:14 +0000

Altec 438A compressor (pdf)
BBC LL228 transformer
Gretsch Atkins SuperAxe
Maplin Mic preamp kit & Modifications
Gardner Transformer data sheet
Klein & Hummel UE100 equalizer (pdf)
Whiteface Omnipressor (pdf)
Beyer transformer data (pdf)

AKG brochures

Thu, 4 Feb 2010 10:25:24 +0000

Click on the images to view them at higher quality.

AKG BX-20 reverb AKG C28 series AKG C422 mic AKG C422 controller

Tubes for microphones

Sat, 30 Jan 2010 10:17:29 +0000

Data sheets for tubes often found in microphones...

6AU6.pdf
6AU6A.pdf (Sony C800, C37)
12AU6.pdf
6bq5.pdf
6sj7.pdf
408A.pdf
5840.pdf (Royer)
6111.pdf (Neumann M147 & 149)
6205.pdf
EC92.pdf (Neumann Gefell UM57 , CMV563 etc)
ECC88-1.pdf
EF12.pdf
EF86.pdf
EF806S.pdf
PF86.pdf

Soviet tubes - Oktava and Lomo mics
6Z1P.pdf
6Z3P.pdf

Inside Neumann Mics

Fri, 29 Jan 2010 22:12:10 +0000

The youtube clip shows a Neumann U87 being machined and assembled. Well worth a watch.

Also, there are some great internal shots of vintage Neumann tube microphones over at Jogi’s. The descriptions are in German but there is some good information there. Microphones studied include Neumann U47 and CMV3, and the East German (now Gefell) UM57 and CMV563.

http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Neumann-Mikro/Neumann.htm

Another great website with lots of microphone information and internal photos is Saturn Sound.

josephson C720

Sat, 9 Jan 2010 19:10:43 +0000

The first thing you notice about the C720 is its size - this is one big mic, U47-big, and makes a big bold statement in the live room or vocal booth - it’s built like a tank and it definitely has that ‘wow’ factor which gets the artists talking.

The next thing that grabs your attention is its radical aluminium metal-foam headbasket, which looks like something you could scrub your pots and pans with. The non-periodic headbasket is actually designed to eliminate internal acoustic reflections and refraction of soundwaves, avoiding comb-filtering effects and so giving a more realistic recording.

The third thing you notice is that it has two XLR outputs. Like many condenser microphones, the capsule has dual diaphragms which can be combined in different combinations to give cardioid, omni, figure of eight patterns. Unlike most microphones, the two transducers have separate head amplifiers and separate outputs which means that the signals from opposite sides of the microphone can be recorded separately and mixed together, either in phase or with the polarity reversed, at a later stage. What this innovation means in practice is that you can pick the polar pattern after recording, which might be used to eliminate unwanted sound sources by rotating the null point of the microphone. Also, and more importantly in our studio use, with close-mic’ed sources such as vocals you can dial in more or less proximity effect, making a singer seem bigger, darker or lighter and brighter.

So what does it sound like? Possibly because of the lack of head basket comb filtering, and the facility to tune the pattern and proximity effect, this is a very versatile microphone. The one word that sprang to my mind in describing the sound, whichever pattern you pick, is ‘solid’.*

Another thing we’ve noticed is it sounds pretty damned good on pretty much anything you can throw at it. Because of it’s ability to handle high sound pressure levels and become a go-to mic for low end stuff, and is rock-solid on bass guitar and front of kick drum, but it’s just as handy on both male and female vocals - especially those with a tendency to get loud when they belt it out. Vocal recordings are up front, sound as they should, but without the top end brightness of, say, our TLM49.

Furthermore, it can be used for more radical effects by compressing or reverberating one side of the capsule only. For example, I had some interesting results on a male rock vocal by compressing the signal from the front capsule, mixing together with the phase reversed rear capsule, then compressing the sum of these. The effect was that as the vocals push harder, the relative amount of rear capsule included becomes greater giving it more of a hypercardioid pattern, balancing the tendency of the vocalist to step back from the mic when belting it out. With a bit of creativity the possibilities are endless.

Overall this is a brilliant, radical piece of thinking and and one of those bits of gear that comes into your life and is there to stay.

*After writing this I read another review of this mic which used exactly the same word - ‘solid’ - to sum up the sound.