T84-55 Circuit Kit

The T84-55 is a premium transformer-coupled microphone circuit kit, designed as a drop-in upgrade for popular donor microphones from Groove Tubes, Sterling Audio, and M Audio. The circuit design is similar to what you'd find in high-end microphones such as the Mojave Audio MA-201/MA-301 FET. Read more about the genesis of this circuit design on the T-84 Circuit Kit page. Why upgrade the circuit? Although the stock circuit in these microphones is not deeply flawed, it leaves room for improvement. Compared to the original circuit, the T84-55 offers: 3–8dB higher output (the sensitivity of the various Luna, ST55, and GT55 mics we measured varies by 5dB, but the T84-55 has higher output than all of them) 8dB lower self-noise higher levels of second harmonic content The last point above is the critical one. Vintage microphones sound the way they do in part due to 2nd harmonic distortion. Modern transformerless electronics lack this sound. People who use the words "warm" and "vintage" when