Features:

• Two independent channels with 80dB of gain

• Hi-Z instrument inputs

  • Also functions as insert with tip-return, ring-send

• Switchable line-input attenuator

• Vintage UTC input transformers

• Vintage Schumacher output transformers

• Matched NOS tube compliment

  • RCA clear-top 12AU7, Sylvania 6DJ8

Description:

An odd eBay find… turned hi-fi mic pre.

This dual-preamp was salvaged from CBS Records, where it was used as a playback amplifier for an Ampex tape machine in the 60’s. The stock circuit was a little weird! Highs above 2kHz rolled off heavily, resulting in a very muffled sound. In hindsight, this may have been a de-emphasis playback circuit. I spent a lot of time tweaking the circuit, redesigning it a few times over until it sounded great with as many of the original components as possible.

The two channels use the same input transformers as the renowned Universal Audio LA-610, the UTC “Ouncer” O-1’s, which color the sound and give some high-frequency rolloff. A hand-picked 12AU7 tube performs the first stages of amplification and a 6DJ8 drives the output transformer—a Schumacher judging by the serial number. 80 dB of gain is achieved with lots of headroom and a touch of tube and transformer saturation, with dual VU meters to monitor both channels simultaneously.

Line pads make this unit perfect for coloring up stereo mixes, and the Hi-Z input (1 Megohm) is excellent for instruments. As an added bonus, the instrument input is wired as an insert (tip-return/ring-send), allowing you to send your mic/line signal through instrument-level effects.