Custom Microphone Preamplifiers

Direct recording preamps that helped make my studio, TRANSIENT SOUND, sound good

For details on a preamp, click on its name or picture above!

While operating my recording studio TRANSIENT SOUND, my biggest advances in recorded sound quality came with direct recording using outboard microphone preamps. Most of the ones that I designed and/or built myself are featured here. I used these mic preamps instead of those in my 16x8 Soundcraft Spirit board (which I modified as a dedicated line mixer on track outputs). My overall setup was somewhat analogous to certain classic British recording consoles, with one side dedicated to input channels (my outboard preamps) and the other to monitoring track returns (my modified Soundcraft board).

I built most of the custom mic preamp channels in pairs. This facilitated easy comparisons while optimizing their designs. The following table gives brief descriptions of each different design. You can follow the links to more detailed descriptions and images. You can also click here to see a summary of their block diagrams.

NAME

NUMBER OF CHANNELS

OVERVIEW OF DESIGN

VIHYB (prototype)

2

Selectable input impedance, transformer- or capacitor-coupled solid-state (Burr-Brown INA103) front-end, directly coupled to vacuum tube (5687 triode) amplifier with cathode follower output. A similar (non-prototype)  version WILL SOON BE AVAILABLE FOR SALE!

HYB

2

Similar to VIHYB, but lacks input transformer and selectable input impedance (i.e., has capacitor input coupling only). Also, uses discontinued Analog Devices SSM2017 instead of the Burr-Brown chip.

SS

2

Capacitor input coupling to Analog Devices SSM2017 chip followed by discrete solid-state output buffer.

TT

2

Transformer-coupled input to two stages of vacuum triode (12AX7 or 12AU7) amplification; IC output buffer.

DTT

1

Transformer input coupling to dual complementary 12AU7 amplifiers, followed by IC differential amplifier/output buffer.

DTS

2

Transformer input coupling to simple discrete (2-transistor) solid state amplifier. Non-buffered output.

DMB

2

Similar to DTS, except battery powered. "Dual Mono," meaning each channel has its own set of four 9-volt batteries in series).

BATTHYB

1

Input transformer-coupled discrete (2-transistor) solid-state stage followed by vacuum tube (12AU7) amplifier and cathode follower output. Battery powered (twenty 9-volt batteries in series!) except for tube heater (external 12 VDC).

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