BlackSpade Acoustics UM17 Tube Mic, by AMI
In the early 1990's Oliver started to design custom amplifier circuits and transformers around the EF732 tube to "hot rod" Chinese microphones.  His creations were well regarded and ended up in professional studios around the greater Seattle area and gained the nickname of "Oliver's 47-type mod".  Eventually, the design was licensed by Telefunken USA and became the RFT AK47 which received positive reviews.  In September, 2009, the licensing agreement expired and both parties agreed to not renew the license.

Recently, AMI (makers of the TAB Funkenwerk line of pre-amplifiers) was contacted by BlackSpade Acoustics, a company located in Switzerland, to provide them with microphone designs and transformers.  BSA was looking for a quality microphone that could be sold for an affordable price in Europe.  After several discussions, both companies agreed to create a product based on AMI's 47-type microphone mod that would be sold in Europe, Africa and Australia by BlackSpade Acoustics and in the rest of the world by AMI.

With this new partnership, Oliver decided to make improvements to the design based on experimentation and techniques learned since creating the original circuit.  The former transformer used with this circuit, the BV47, used a lamination that was a mixture of iron silicate and nickel which created an artificial distortion.  Oliver has designed a new transformer, the BV8LP, as a low profile version of the historic BV8 in order to fit in the mic body which is smaller than a U47.  Using all nickel lamination, the BV8LP is a higher quality transformer that produces a more detailed output than the BV47 with improved low frequency response and clarity to optimize the EF732 tube.  As the foundation for this mic, we selected the Alctron HST-11a.  The metal work and construction of this microphone is of a high quality and tight quality control.  We then carefully test each capsule to ensure that it meets our level of expectation.  AMI installs every tube and transformer, tests every capsule and tests every unit before they are shipped to BlackSpade Acoustics or to AMI's dealer network.

The finished result is the BlackSpade Acoustics UM17, designed, modified and tested by AMI.

Product Features:

Oliver Archut designed amplifier circuit
Our BV8LP transformer manufactured here in Gaylord, Kansas USA
NOS Telefunken/Sylvania EF732/5840 tubes
Power Supply w/cable
Shock Mount and wind sock
7-pin Connector Cable
Flight Case
Tube and transformer installed, burned in and tested in the US
5-year limited warranty on all components except the tube which has a 6-month warranty, customer pays for shipping
Product Specs:
Type:  Condenser pressure gradient
Capsule:  Alctron K47 dual-sided gold sputtered
Polar Patterns:  Remote 9-position switch from Omni to Figure 8
Frequency Range:  20Hz to 20,000Hz
Impedance:  200?
SPL:  128dB
Sensitivity:  14mV/Pa = -37dB (0dB= 1v/Pa) -10dB
Equivalent Noise:  17 dB, A-weighted
Non-linear Distortion:  1% THD @ 1000 Hz (132dB)
Mic Dimensions:  245mm long, 44mm diameter
Weight:  775g