Multi-Pattern Condenser Microphone

The FC 3 is a side-address, 3-pattern FET condenser with a transformer-coupled output circuit.

Although previously reported here (based on statements from GAP) to use a 34mm, 3-micron capsule, the sample FC3 microphone we purchased contained a 32mm capsule. This capsule almost certainly has a 6-micron diaphragm. It is a center-terminated K67 type.

Three switches on the mic body enable pattern selection (Cardioid, Omni, Figure-8), a switchable pad (-10dB), and a switchable high-pass filter (cutoff at ~80Hz).

The circuit is a two-stage transistor design, with an emitter follower driving a low-ratio output transformer. This circuit is linear — it does not apply any frequency-dependent corrective filtering to the capsule’s signal, unless the high-pass filter is engaged.

The DC circuit board contains a voltage multiplier that is capable of polarizing the capsule at +60VDC. Individual samples we’ve seen vary from 50–63VDC. Note that in Figure-8, the rear diaphragm is at double this voltage (+120V), while the backplate is at +60.

The FC3 is nearly identical to the CAD GXL3000, although the GXL3000 comes with a higher-quality, larger capsule (35mm O.D., 6 micron diaphragms).

The Golden Age Project FC 3 is also known as: FC 3.

Specifications

Golden Age Project FC3 Mods

The GAP FC3 combines a linear circuit with a peaky 32mm K67 capsule type. The result is a not flattering to most sources, creating sibilance on vocals and fatigue on most everything else.

We offer two modification options for this mic.

#1: Capsule Replacement

The stock GAP capsule is a typical 32mm K67 type, found in just about every inexpensive large-diaphragm condenser microphone on the market. It has a peaky and uneven response that is not very musical, and tends to require EQ to fit into a mix.

We recommend replacing it with a K47 type, which will give a more neutral top-end response, with rich midrange detail. Our favorite capsule for this mic (assuming the stock circuit is retained) is the RK-47.

Another option is our RK-12. The voicing of this capsule is bright, but it sounds different than the stock GAP capsule; it has a smoother top-end response and warmer lows. It excels for female vocals.

#2: Circuit Replacement

The FC 3 circuit is a 2-stage transistor circuit with an "emitter follower" and a low-ratio output transformer. We don't care much for the design; the 2nd stage transistor seems to clip under moderate SPL, and the transformer is not adding any sonic value.

We've developed a version of the KM84 circuit, which is a linear single-stage JFET design with a very high-quality output transformer. We designed custom circuit boards for this circuit, to make room for the best-quality parts we could find. Customers say the results more than justify the cost.