Golden Age Premier GA-47
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Mic body and grille
The mic body is made of brass, the grille is made of iron.
The grille, which is a critical component affecting the sound character, is similar to the one in the U47.
The capsule for the GA-47 is designed to provide the requirements of modern day recordings by mixing the character between a vintage K47 capsule and the one from a K67-style capsule with a wide frequency response and high sensitivity. The result is a truly great sound.
Being a dual-sided one, it provides the GA-47 with both cardioid and omni polar patterns.
In order to get a good consistency between units, for each production run of 50 pcs GA-47 units, approximately 200 capsules is evaluated in order to find 50 capsules with specifications that lie within the tight tolerances.
- Backplate material: brass
- Capsule diameter: 35mm
- Membrane diameter: 27mm
- Membrane material:6 micron gold-coated mylar.
- The capsule is mounted on a 7 mm thick aluminium plate in a special way to minimize the effect from physical vibrations.
- The sensitivity of the front and back side of the capsule do not differ more than 0,3 dB. The sensitivity between different capsules do not differ more than 0,5 dB.
- The tight manufacturing tolerance will lead to a very good consistency between different GA-47 units.
- The capsule is specially designed to complement the electronic circuit of the GA-47 to achieve a frequency response curve with a nice balance between the high, middle and low frequencies.
The GA-47 uses a NOS Telefunken 800 series super low noise pentode tube connected in triode mode in order to decrease distorsion and noise. This tube is modern glass derivative of the VF14M used in the vintage U-47.
The GA-47 transformer is especially designed with a 6.5:1 dual bobbin transformer by a reputed transformer factory. It is a replica of the BV8 transformer used in the vintage U47. It uses a high quality core material.
Capacitors and resistors
The coupling capacitor is made in United Kingdom, the brand is Ciarit, the same type used in the famous and very expensive B&W Nautilus loudspeaker. It is an axial capacitor made from MKP material with copper pins.It has a delicate, full sound and a wide frequency response.
Other used capacitors are MIAL polystyrene film capacitors with very low loss. The resistors are ALLEN BRADLEY carbon film resistors made in the USA with vintage and warm sound.
Mic interior and cabling
The electronic circuit is mainly built with point-to point wiring and the ground connections are tied together using an insulated soldering.
Teflon insulated, silver-plated copper wire is used for the internal connections.
Power supply transformer and electrolytic capacitors
The vintage style power supply PSU uses a high power R-style transformer with a low noise level and a minimal stray field. The electrolytic capacitors are of a high quality audio style type.
A simple but effective circuit uses dual-stage filtering for the filament voltage. The high voltage is precisely filtered and stabilized using an ON semiconductor zener diode.
The cable is specially produced using 99,99% pure oxygen-free copper, teflon insulation, tin foil and 98% kitmesh, ie with a very high braided density of the cable shield. It has a very open and smooth sound.
The connectors are gold plated.
Mic and psu circuit in relation to the original mics
The circuit used in the GA-47 is similar to the U-47 but the component values has been adjusted to fit the EF800 tube.
In order to achieve the best sound quality, no coupling capacitor is used between the capsule and the tube, just like in the classic U-47 microphone. Even the highest quality capacitor will affect the sound.
The small price to pay is that it´s then not possible to achieve a Figure-8 polar pattern. For users who would prefer to accept that sound quality degradation, the GA-47 can be modified to have a Cardioid and Figure-8 pattern.
The polar pattern switch is located on the power supply allowing for easy sound comparisons.
The circuit used for the power supply is also similar except for adding a zener diode to assure the voltage and current stable.
The connectors are gold plated. All three connectors are placed on one side to facilitate handling and placement.
Frequency Response: 20Hz〜20KHz