preamp | Analog Audio Repair

Archive for preamp

Telefunken V72S Transformer Replacement

Posted in Repaired with tags preamp, Telefunken, transformer, tube, V72, vintage on February 26, 2013 by AnalogAudioRepair

: Removing the transformer takes a lot of disassembling.

: The original and the Sowter replacement.

: Sowter mounted in original frame

: Sowter soldered up and ready to install.

This is a rare Telefunken V72S – the “S” is a higher gain version. Unfortunately this one had a bad input transformer. The frequency response of the transformer looked like this: / A rebuilt original was too costly for my client, but Sowter offers a replacement that works just fine. The hard part is removing the original and mounting the new one!

RCA BA-2C Tube Preamp

Posted in Restored with tags BA-2C, preamp, RCA, tube, vintage on February 26, 2013 by AnalogAudioRepair

: Front view with gain control knob.

: Inside, the original wiring was so nice!

: Here you can see the replaced power transformer.

This vintage RCA vacuum tube preamplifier was missing it’s power transformer. Fortunately I had the schematics and a transformer that would fit the bill. A couple power resistors were required to get the voltages spot on, but in the end it worked out well. The unit got a full re-cap and a fresh set of New Old Stock vacuum tubes. The new owner even received an original manual!

GATES Discrete Microphone Preamps

Posted in Racked Modules, Restored with tags discrete transistor, Gates, preamp, transformer, vintage on December 29, 2012 by AnalogAudioRepair

: Gates Preamps

: Rack, PSU and schematic

: Build in progress

: Testing preamps

This is a pair of Gates broadcast discrete transistor mic pres. These microphone preamplifiers were used in Gates radio boards and have transformer balanced inputs and outputs. They have 37 dB of gain and I racked them with a level control ranging from 20-37db. The position of the level control is immediately after the input transformer so there is no need for a pad on the input unless you are overloading the transformer! These units were re-capped and wired for 150 ohms in and 600 ohms out. This was a super simple and clean rack job so they only have XLR in and out, level control, and a power switch for the outboard +30v power supply.

Universal Audio 1108 & 508

Posted in Racked Modules, Restored with tags 1108, 508, discrete transistor, EQ, equalizer, inductor, microphone, passive, preamp, transformer, UA, Universal Audio, Urei, vintage on October 7, 2012 by AnalogAudioRepair

This is a set of vintage Universal Audio (UA / Urei) 1108 discrete transistor microphone preamplifiers with matching 508 passive equalizers. The preamps are transformer in and out and sound amazing. The EQs use passive capacitors and inductors for simple but smooth EQ. Restored and racked with phantom power and gain pots.

Yamaha PM1000

Posted in Modded, Racked Modules with tags discrete transistor, EQ, equalizer, inductor, microphone, modded, PM1000, preamp, racked, transformer, vintage, Yamaha on September 19, 2012 by AnalogAudioRepair

Yamaha PM1000 discrete transistor console strips cut down, recapped, modded, and racked as mic pres with EQ.

GE 4BA1 Preamp

Posted in Restored with tags 4BA1, GE, General Electric, microphone, preamp, transformer, tube, vintage on August 5, 2012 by AnalogAudioRepair

Vintage GE 4BA1 vacuum tube mic preamp. Recapped (electrolytics inside the old can), re-tubed, and wired up with a restored GenRad regulated power supply.

Neve 5442 Mixer

Posted in Repaired with tags 5442, board, console, EQ, equalizer, microphone, mixer, Neve, preamp, Repaired, vintage on August 5, 2012 by AnalogAudioRepair

Neve 5442 8×2 Mixing Board. Built custom power supply and replaced failed tantalum caps.

Analog Audio Repair