Neve 34128 modules are a pretty straight forward job to rack if you are handy with some tools and a soldering iron. Doing so will allow you to use the microphone preamplifier and three band EQ as a channel strip while tracking and mixing. This modification can also be applied internally within the Neve 542 series mixer as to provide direct outputs from each channel. The input of these modules uses a Belclare transformer which is present in the signal path in both line and mic modes. The “MIC” switch simply drops a pad in and out of the signal path just prior to the transformer to prevent clipping the circuit when using it at line level.
The 34128 uses a standard 15-pin EDAC edge connection. It is identical to the blue 15-pin EDAC connector used for API 500 modules, but does use a different pinout. Each module runs on +/- 15volts, and requires some thought to implement +48volt for phantom power as well as establishing a balanced line level output for the module as it cannot adequately drive such loads as standard.
Direct Output Mod
The best way to add a direct output from a Neve 34128 module is to tap the signal directly from junction 22 as shown on the schematic and indicated on the PCB ledgering. This point in the signal path is directly before the pan pot. Placing it here means the direct output is post fader, and also has the added advantage of providing a neat little stand-off on the PCB (marked “22”) to solder your connection to.
You can take the signal directly from here and run it through a balancing amplifier or buffer circuit to obtain your direct output if you want. This will hardwire your modules in place, unless you place an additional connector inline with your junction 22 and your buffer amplifier wiring. The neatest way by far, as suggested by Geoff Tanner of Aurora Audio, is to isolate PIN D on the edge connector and use it for the direct output. PIN D is simply tied to ground at PIN C. Using a dremel or similar cutting tool, just cut the trace directly between these two pins. All you need to do then is run a shielded jumper from junction 22 to PIN D, grounding the shield to PIN C and you can then access the direct output from PIN D on the EDAC connector.
You can balance or buffer the output through any number of methods, but you must do it. Don’t be tempted to do a hack job and simply tap the signal at junction 22 and connect it to an XLR or TRS connector. You can use a discrete opamp and transformer, a 5534 or THAT Corp 1646 line driver if you want. We used a JLM Audio Regurgitator kit for out rack of eight 34128’s. They are available as one complete PCB that shares ground and +/-15 volt connection through all eight channels.
- Geoff Tanner at Aurora Audio is an invaluable source of information on all things Neve
- The Hook Studios sells reproduction Neve knobs and caps suitable for the 542 series.
- The Group DIY forums have the collective brain power to solve any pro audio tech issue.
- JLM Audio offer superb, simple kits that make all those tricky little bits a piece of cake.