Studio Projects C3 Circuit Upgrade Kit

$ 69.00

This circuit mod kit will give your Studio Projects C3 the same frequency response curve as a $3300 Neumann U87 -- although with fuller bass! Better still, the high-frequency response of the circuit is adjustable, so you can dial in as much filtering/attenuation as you like.

Linear Circuit, No More

The Studio Projects C3 is nicely built, but in our opinion is too brightly voiced for many sources. It's great for sources that need to cut through a dense mix, but can be fatiguing, especially when layered.

We have created an add-on EQ circuit that reproduces the corrective high-frequency attenuation built into the Neumann U87. It gives the C3 a sound very very close to that of a U87, although with fuller low-frequency response.

The kit includes additional upgrades as well, to reduce microphonics, lower the mic's self-noise, and increase sensitivity.

Here is a frequency sweep showing the response of the C1 circuit (which is substantially the same as the C3's). This is not an acoustic test of the microphone, but an electronic test of the circuit by itself. The stock circuit is rolled off in the low bass, but linear out beyond 20kHz. This is a poor match for the K67 capsule, which can be thin in the bass but hyped in the 8-12kHz range.

C1 Circuit Sweep

The green trace shows the modified circuit: flat in the lowest bass frequencies, but rolled off above 1kHz. This is exactly the sort of complementary EQ that the K67 capsule needs and expects. This is called "preemphasis/deemphasis;" the capsule pre-emphasizes high frequency information, and the circuit attenuates it. The Neumann U87 uses precisely this same approach, with the same HF rolloff seen here.

What's in the box?

The new EQ circuit is housed on a US-made, custom PCB. You'll also get a pair of significantly upgraded, US-made signal capacitors, plus a handful of other components.

You will not need to change the C3's capsule for this mod. It is a very nice K67 type.

(If you have already changed the capsule for our RK-87 or RK-12 types, you could still use this mod kit. If you have installed a K47 capsule, we do not recommend this mod kit, as the circuit mod would cause the microphone to be too dark-sounding.)

Audio Sample

We recorded a U87 Ai and a modded C1 side by side. The audio tracks are practically indistinguishable. Listen via the MP3 players embedded below.

Here's a frequency analysis of these two audio tracks. The response of the two mics is nearly identical above 80Hz. Below 80Hz, the modded C1 has better response. (If you don't want the lows, just switch on the mic's high-pass filter.)

Modified C1 vs U87 Frequency Graph

Note: the graph above is not a sweep test of either microphone, but an averaged frequency response of the voice recordings included below. The point of the graph is that the U87 Ai and modded C1 capture almost exactly the same frequencies (above 80Hz).

Compatibility

We have two versions of this mod kit; please be certain that you order the appropriate model. The following notes describe the two C3 models that are compatible with this mod kit:

The first-generation C3 is identified by:

  • PCB as pictured on the left side of this C3 circuit board photo
  • Two switches: pattern (O/C/8); pad/filter
  • "797 Audio" branding
  • Offset XLR jack (not centered)

The second-generation C3 is identified by:

  • PCB as pictured on the right side of this C3 circuit board photo
  • Red triangle "SP" logo badge
  • Centered XLR jack
  • 3-position pattern switch (O, C, 8)
  • 3-position pad switch (0, -10, -20)
  • 3-position HPF switch (75 Hz, 0, 150Hz)


C3 Mod Service

We now offer a mod service for US residents. If you're not able to solder, or don't wish to risk damaging your microphone, we can perform this modification for you.

The mod service includes:

  • Modification of your mic by an experienced professional technician
  • 24-hr burn in and testing
  • Return shipping (domestic US only)
  • 30-day warranty

 Read more about the C1/C3 Mod Service. (The mod service price includes the cost of the parts kit.)

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