Roger Mayer 456 Microphone Pre-Amplifier

Four pre-amps with tape simulation

Roger Mayer 456 Microphone Pre-Amplifier

Review by Russell Cottier

1964 he started building effect pedals for Jimmy Page. Mayer also designed and built pedals used by Jimi Hendrix, Jeff Beck and session guitar legend Big Jim Sullivan. After a year working for Olympic in 1968 Roger Mayer moved to the US and started his own company building limiters, EQs and recording consoles.

Roger Mayer now offers a wide range of guitar pedals and studio hardware. The 456HD series presents a tape saturation emulator and comes in a variety of formats. The 456 4 Channel Mic Pre has four channels of mic pre-amplification and 456HD tape saturation emulation as well as an option for Line Level input. There is also a two channel version of this unit available that can be retrofitted with an additional two channels later.

Looking at the 2U brushed steel rack it’s clear this is a short run boutique-type unit. The choice to implement labelling via plastic coated labels rather than a conventional screen print is unusual but perhaps suits the lozenge recesses in the front panel that house the controls for each channel. Illuminated VU meters top the control panels and it’s worth noting at this point that these kick off a fair bit of heat, the casing has no ventilation so can get a little hot to the touch.

The ultra linear high-speed Class A discrete pre-amplifiers are based on Roger Mayer’s circuit originally designed in 1968. The 22-way stepped potentiometers for Gain and Output allow accurate recall, and the knobs feel good to use. There are buttons for Phase, Line input and engaging the 456 circuitry, with an LED indicator adjacent to the switch. The ferrite transformers in this unit are all hand would in the UK and each channel has a separate Mic, Line and Output transformer all with linear phase, and frequency response up to 80kHz apparently. The rear of the unit sports gold plated Neutrik XLR connectors for I/O and the unit is supplied with a multi-region switched-mode power supply that connects via a two pin collared screw fitting.

In operation there are a few settings of which we need to be aware. Firstly, the unit should be calibrated, and trim pots are accessible via small drilled holes in the front panel stickers. This is essentially to trim the output level so as the unit cannot send a level that will cause digital clipping in your ADC, and to optimise the input level for the applied tape-style dynamic compression. The justification being that certain ADCs and DACs are calibrated to differing dbFS values for 0dBVU. It’s worth noting that the VU meter can be set to different position in the signal chain. However this is set via an internal jumper. For a unit targeted at professional users it would perhaps have been prudent to add a toggle switch to allow metering pre and post the 456HD processing.

Analogue tape simulation

In use without the 456HD processing the pre-amplifiers are nice and clean and give a low noise clear output. Frequency response seems nice and linear as one would expect and the unit provides a good front end for recording. Dynamic, condenser and ribbon mics behaved well with the unit and it sounded good with a variety of source material. As we push up into the distortion area of the pre-amplifier, the higher frequency harmonics start to creep in as one would expect, and it is possible to create some controlled transients in the tracking process without any audible artefacts, on sources such as snare drums and acoustic guitar.

Moving on to the 456HD processing, it’s noticeable this mode added some noise floor increase to the output, up to 3dB. However this was not too noticeable in use, and certainly added a little tape vibe. The aim of the processing is to create the colouration of Ampex 456 playing on a Studer A80, without the inconvenience of tape and without any latency. The unit can be used to apply this effect live during tracking or as a hardware insert. Notably the 456HD process treats the positive and negative phases of the signal with different circuitry and a definite asymmetry could be seen in printed audio. Compared to a host of tape modelling plugins and an actual A80 the unit did not give that exact ‘tape sound’ I was expecting, however it did do something rather nice to the input signals, in that they could be easily calibrated to not clip digitally, and the dynamics are gently massaged on the way in.

As tracks start to add up with this unit you get some dynamic coherency, but it’s very much a workflow choice as to whether you want to do this on the way into the DAW or at the mix stage.

At £6,000 for the 4-channel version this is no impulse buy but it might just solve a problem that exists in your workflow.