MCI 428B Tricks and Hacks

There is a joke amongst studio techs that MCI stands for "Most Contacts Intermittent", and it's basically true. It's great sounding, solid, workmanlike gear once you've got it going but there can be so many bad contacts and solder joints the chase out along the way. 

Here we have a 428B console where the issue was certain channel and buss signals disappearing. The culprit ended up being solder joints which cracked due to flexing at the seam between two sections of motherboard PCB. Had MCI used flexible jumper wire like some other manufacturers this might not have happened, but it did so we desoldered the intermittent jumper wire and replaced it. That's what was bring down the busses. The intermittent channels were due to cracked solder joints at the base of the male molex pins soldered to the underside of these motherboards, presumably also from flexing.

Another issue with these consoles is that they use a proprietary MCI op amp (2001 or 2003) which (is arguably not very good and) sometimes fails and it can be rather difficult and expensive to source spares. Normally we would just replace it with something else, but the TO-99 footprint and +/-24VDC power supplies make that rather difficult. Eisen Audio solved the problem by replacing the stock MCI power supplies (which have loud fans and make for lousy sound quality) with a pair of Acopian GoldBox A Series which not only sounds a lot better but allowed us to lower the supply voltage to +/-21.5VDC by placing a couple resistors in the sense lines. Now, using our TO-99 to DIP-8 adaptor PCB we can use any sort of generic IC op amp as replacement or upgrade.

Neve BCM10 Better Summing

This is one of the better BCM10 consoles from 1974, with direct output wiring already installed, which makes for a great way to house and use a set of Neve 10xx series channel amplifiers. Unfortunately, the summing quality is not on par with larger Neve models from this era. In order to improve the situation, and seeing as how this particular console is being used as a sidecar to our modified 8014, for additional inputs at mixdown, Eisen Audio did the following:

  1. Re-calibrated the input router modules for 5dB lower operating level
  2. Disconnected all misc and additional feeds to the mix buss in order to lower crosstalk
  3. Re-terminated the 1272 summing amp inputs in order to decrease buss source impedance for lower crosstalk and better bass response.
  4. Re-terminated the 1272 summing amp gain and calibration settings in order to restore proper operating level, for best THD+N and max output.

The next logical step would be a replacement  B106 card containing a “ballsier” amplifier with which to drive the faders and 2-mix feed on each channel.

Trident Series 70 Rebuild and Upgrades

This 30-year-old desk had suffered catastrophic and repeated failure of stock Trident power supplies which was the straw that broke the camel’s back after decades of wear and tear. In an effort to make this console behave like new again (if not better), Eisen Audio - under the supervision of Tech Mecca - carried out the typical array of procedures which included:

  • replacing all of the electrolytic capacitors
  • replacing all of the failed Audiofad faders with P&G 3000 series
  • replacing all of the potentiometers which could not be revitalized via cleaning with equivalent spares
  • replacing the crucial and worn out pushbutton switches which could not be revitalized via cleaning with brand new gold plated equivalents
  • A more transparent control room monitoring path including new volume control
  • terminating switches and draining caps for less audible "clicking"
  • strategic upgrade of the most crucial IC op amps for lower noise, without replacing the majority channel strip op amps which help makeup the "Trident character"
  • reinforcing the power and ground distribution all along the underside of the console motherboards and rear of frame which helps lower noise, crosstalk
  • tying the new power/ground distribution to a new array of Acopian Gold Box A Series power supplies which, aside from having adequate protection against failure, also tend to sound a lot better.

Spectra Sonics 1024 Rebuild

This console had been purportedly reassembled by a third-party from a disparate collection of modules and spare parts and was delivered to client with a new power supply, recapped, cleaned, with multipin connectors reterminated, and many IC sockets replaced but nevertheless barely working and entirely unreliable. Evidently, two fatal mistakes had been made: 1. powering the console with +/-24VDC which greatly exceeded the Safe Operating Area of and thereby damaging nearly all of its IC op amps and logic switches, and 2. attempting to spray clean sealed conductive plastic potentiometers which had been damaged by the DC offset from failed ICs. 

Eisen Audio was hired to subsequently rebuild said console according to client needs.

In addition to epic amounts of troubleshooting, reflowing bad solder joints, bulk replacing failed ICs, chasing out intermittent signal via cleaning and reseating or outright replacement of moving parts…

The quad pan pots had failed irreparably and were replaced with new stereo pan pots utilizing the front LR busses and disabling the rear LR busses.

The solo system and control room monitoring section did not make sense and were never going to work correctly. Eisen Audio first constructed a new passive control room monitoring section complete with talkback and solo relays, installed all new solo switches, and tied the existing solo busses to the new hardware.

There was no 2-mix insert loop, so one was added. Additional 2-mix direct inject points were also brought out for calibration purposes and for use as additional parallel processing returns.

The correct master logic module for VU meter and overdub mode switching could not be located, so a module from a different Spectra Console was painstakingly hacked.

Maintenance is ongoing.

An excellent harness and patchbay system was constructed by Coral Sound.

Neve 8014 Advanced Modifications

This is a classic 4-track recording console which is beautifully constructed and sounds fantastic but which was not designed for a modern mixing workflow.

Two upgrades which can make this console more useful during mixdown are to bypass most of the passive matrix and control room monitoring circuitry for greater playback accuracy, and to reroute the “jukebox” passive return section so that it can serve as 8 additional inputs at mixdown instead. 

Taking over for a colleague who abandoned this client and desk, Eisen Audio finished the job properly by adding some discrete fader buffer amplifiers, installing the equivalent of four more 1272 summing amplifiers inside the frame, adding 8 NOS Neve pan pots, adding relays for reliable source select, and carrying out some substantial internal rewiring. This was all done on-site without flipping over or disassembling the console, and with a minimum of studio downtime.

We have continued to service this desk through periodic recapping, cleaning, power supply replacement, calibration.

New patch bays were built and installed by our friends at Coral Sound. Phantom power switching was added by Carl Farrugia.

Sony MXP-3000 Upgrades

Seaside Lounge hired Eisen Audio to help upgrade their mixing situation in Studio A.

First we recapped, recopied, cleaned, and replaced the volume pot in their Control Room monitor module for more accurate listening.

Then we installed one of our NonLinearAudio™ Candy Buss cards as shown. This replaces the following stereo mix signal paths:

  • summing amps
  • insert send, return, and bypass
  • master fader buffering
  • main outputs
  • monitor outputs

The console still operates as before, with the same gain structure, patch points, and metering  and patch points in effect. The stock SONY modules have had only minor modifications done which are easily reversible. All of the associated wiring has been connectorizedz for easy troubleshooting and reversing in case they want to keep the CB2 card and sell the console as stock. For now the card lives on a rack shelf beneath the integral console patch bays.

Whereas the stock Sony signal path was comprised of more or less generic IC op amps and capacitors alone, the CB2 card contains premium discrete op amps, transformers, and more carefully selected capacitors which has resulted in a subjectively superior soundstage.

Extra attention was paid to grounding, helping make for a shockingly quiet 2-buss.

Neve 8058 Switch Replacement and Advanced Cleaning

Through continuous use since the 1970s some of the isostat pushbutton switches in this console had altogether worn out and needed to be replaced. Being that it’s rather cost-prohibitive to obtain new isostat switches with the large minimum order requirement and that they’re made with the same inferior point-contact design and silver plating, we decided to replace them with superior gold plated shadow pushbutton switches instead. An adaptor PCB with right angle brackets had to be constructed.

In other parts of the console it made more sense to replace old isostat with new isostat as shown.

In the case of some blore edwards rotary switches no longer passing signal we had to disassemble the wafers to scrub them with harsh chemicals and then flush it all out. This was a last resort after trying repeated spray cleaning, ultrasonic tank cleaning failed to produce lasting results. A replacement rotary switch was sourced but deemed too expensive.

Upon reassembly we replaced the worn out pan pots with new parts.

Langevin AM4 Additional Summing

A client purchased this AM4 10x4 mixer already recapped, cleaned, with a new power supply, and generally working quite well.

Wishing for greater functionality, he asked Eisen Audio to install some additional summing. First we wired some drop-on resistors and cable so that eight unused pots and toggle switches could be activated as an 8-channel monitor return for listening to 8-track playback. Then we added a transformer-based passive network and insert loop so that busses 3 and 4 could dump into busses 1 and 2 for subgrouping and parallel processing. While we had the frame emptied, we also fortified the grounding and power supply decoupling in order to lower the overall noise floor.