Aphex 207D

Dual-channel Mic Preamp

Published in SOS April 2008
Bookmark and Share

Reviews : Preamp

Can a two-channel preamp at this price really give you the best aspects of tube and solid-state circuitry?

Paul White

Aphex_207D_01.eps.s

Unlike many tube-based mic preamps, the Aphex Model 207D is a hybrid design that uses a solid-state front end followed by a tube gain stage — the idea being to offer the best of both worlds. The solid-state circuitry provides low noise with a good transient response, while the tube provides the 'flavouring'. Of course, every American technical innovation has to be given a trademarked name, and for the 207D the power under the hood is 'Tubessence'!

Overview

This 1U, rackmount, dual-channel preamp uses Aphex's established 'reflected plate' tube technology to give the performance of a tube running on a high voltage while actually running on a low-voltage circuit. Essentially they've taken an under-run tube and put solid-state feedback circuitry around it to counter the increase in plate resistance that otherwise occurs when a tube is run at a very low voltage. This approach saves on cost, extends tube life and also enables the unit to be powered from a switch-mode power supply that can adapt to local line voltages automatically — something that has the happy side-effect of keeping manufacturing costs down. It is also safer, because normal tube HT voltages are high enough to be lethal!

A delayed switch-on circuit mutes the audio path until the tube has warmed up, and to indicate the status the power LED at first glows orange, then turns green when the unit is ready for operation. The 48V phantom power source (which is independent for the two channels) also ramps up when activated, to avoid stressing the microphone circuitry.

In addition to its two channels of hybrid solid-state/tube circuitry, the 207D also features a switchable limiter and an inbuilt 24-bit digital converter with word clock connection that can operate at up to 96kHz, with both AES/EBU and S/PDIF digital outputs. The limiter is useful in situations where you can't accurately predict the maximum peak input level, and there's no setting up required: once it is switched in, the limiter automatically operates to prevent clipping. The circuit is Aphex's own optical design and comes from the much more costly Aphex 1100 two-channel and 1788 eight-channel preamps. It detects the level at the preamp output, but works on the mic input line to limit the signal prior to preamplification. Because of this approach, it can increase the effective headroom by up to 20dB — though, of course, for the highest audio quality it is best to have a limiter only step in on occasional peaks. I'm not 100 percent sure if this limiter works fast enough to avoid all clipping, but it is certainly fast enough that you don't notice any.

Aphex207D_03_rear.eps.s
Photos: Mark Ewing
The 207D features both AES/EBU and S/PIDF digital outputs, on XLR and phono connectors respectively.
The 207D features both AES/EBU and S/PIDF digital outputs, on XLR and phono connectors respectively.
The 207D features both AES/EBU and S/PIDF digital outputs, on XLR and phono connectors respectively.

The 207D is set out quite differently from the earlier 107. Every channel features a phase-invert switch, a 20dB pad switch, and a low-cut filter, as well as an LED display to indicate available headroom.

Each mic input offers 20 to 65dB of gain, and the high-impedance instrument input also allows up to 65dB of gain to be added. For line-level signals you use the mic inputs with the pad switched in and double-check that the phantom power is switched off! The output operating level can be set (using slide-switches) to -10dBv or +4dBu to suit semi-pro or pro systems, and the output level can be trimmed using the trim pots on the front panel. Power comes into the unit via a standard IEC mains cable.

All the audio connections accept balanced connectors — the outputs are available on both XLR and jacks, the mic inputs are XLRs, and the line and instrument inputs (the latter are, for ease of access, located on the front panel) are jacks. Both mic channels also have an unbalanced insert point on a TRS jack, which allows other processing to be patched post-preamp but pre-converters.

The digital section, which comes as standard on this model (the original 207 is no longer available), comprises both AES/EBU (XLR) and S/PDIF (phono) outputs, as well as a word clock input on the usual BNC connector. When the 207D is hooked up digitally, the sample rate can be stepped through using the button between the centrally-mounted bar-graph meters, and the LED indicators display the available choices of 44.1kHz, 48kHz, 88.2kHz, 96kHz or external sync.

Testing Times

Aphex make a number of claims for their circuitry, including greater dynamic range and frequency response than traditional tube circuits, as well as very low noise — so I was keen to put this to the test. As I found with the earlier Aphex 107, when I reviewed it many years ago, the 207D warms things up in a very subtle way. It creates a sense of air around the sound, which makes me think that some subtle high-end enhancement also takes place. The result is a slightly more detailed, crisper sound than you'd expect from a strictly neutral preamp — something that can help the signal survive subsequent processing without becoming dull — but other than that the signal path is very clean and transparent-sounding, and this preamp seemed happy with all of the mics I plugged into it.

Of course, you don't have to use the 207D as a mic preamp: as a simple DI box, it also turns in a classy performance, and here the limiter becomes a very useful ally against more enthusiastic level excursions, especially if you were using the 207D for live recording applications.

Verdict

All in all, this is a very classy-sounding and versatile preamp, that gives you the unmistakably glittery and flattering Aphex sound. It also represents great value at its current price, and there are very few comparable units available for the same budget — see the SSL VHD Pre review on page 146 of this issue for a list of some possible alternatives, though bear in mind that some of these do not offer a digital output as standard. 

In this article:
Aphex 207D £360
pros
Clean, pristine sound.
Switchable limiter.
Digital output.
cons
None really — though the bright, airy sound won't be to everyone's taste.
summary
A great-sounding and very affordable dual-channel microphone preamp and DI that has analogue and digital outputs.
information
£360 including VAT.
SCV London +44 (0)20 8418 1470.


SOS Readers Ads
GRAB A BARGAIN

£508,836

of Second-User Gear for sale now — don't miss out!

Neve 1073LB & 1073LB EQ

500-series Microphone Preamplifier & Equaliser

Thumbnail for article: Neve 1073LB & 1073LB EQ

Neve’s venerable 1073 preamp and equaliser are both now available in API’s popular ‘Lunchbox’ format. Were they worth waiting for?

Cloud Microphones Cloudlifters

In-line Microphone Preamplifiers

Thumbnail for article: Cloud Microphones Cloudlifters

Do these in-line mic preamplifiers mean you can use a passive ribbon mic with any preamp?

Slate Pro Audio Fox | Media

Dual-channel Microphone Preamplifier

Thumbnail for article: Slate Pro Audio Fox | Media

Test plots to accompany the article.

Cloud Microphones Cloudlifter

Audio Examples

Audio files to accompany the article.

Slate Pro Audio Fox

Dual-channel Microphone Preamplifier

Thumbnail for article: Slate Pro Audio Fox

With two channels and four ‘flavours’ on offer, Slate’s mic preamp promises plenty of flexibility. Does it also deliver on quality?

Neve 4081

Four-channel Microphone Preamplifier

Thumbnail for article: Neve 4081

Neve believe that there’s scope to bring classic designs up to date — and that’s exactly what they’ve done here, taking their revered 1081 mic preamplifier as the starting point.

Radial Tonebone PZ Pre

Acoustic Instrument Preamp

Thumbnail for article: Radial Tonebone PZ Pre

James Dunkley is on the case of the Radial Tonebone PZ Preamp.

Drawmer HQ

Preamplifier & D‑A Converter

Thumbnail for article: Drawmer HQ

Can a preamp and D‑A converter successfully straddle the pro-audio and hi‑fi markets? Drawmer believe it can...

Studio Projects VTB1

Microphone Preamplifier

Thumbnail for article: Studio Projects VTB1

This hybrid mic preamp can go from solid‑state clean to valve warmth — and for a surprisingly low price, too. Is there a catch?

Dave Hill Designs Europa 1

Microphone Preamp

Thumbnail for article: Dave Hill Designs Europa 1

This novel preamp design features a variable impedance and slew rate — which opens up a whole new world of possibilities from your mic locker...

MC AudioLab TP1tp

Valve Microphone Preamp

Thumbnail for article: MC AudioLab TP1tp

Can Sicilian manufacturers MC AudioLab bring a touch of Mediterranean magic to your recordings with their new boutique preamp?

Manley MicMAID

Mic & Preamp Switcher

Thumbnail for article: Manley MicMAID

The patchbay remains the cornerstone of most commercial studios, but using one to patch mics into different preamps can be risky — which is where the MicMAID comes in...

T-Rex SpinDoctor

Valve Preamplifier

Thumbnail for article: T-Rex SpinDoctor

Is a high-quality valve preamp in a programmable pedal just what the SpinDoctor ordered?

BAE 1073 MPF

Dual Solid-state Preamp

Thumbnail for article: BAE 1073 MPF

There are now several Neve 1073-inspired preamps available — but theyre not always 100 percent faithful to the original design. How close does this new contender from BAE come?

Focusrite Octopre MkII & MkII Dynamic

Eight-channel Microphone Preamps

Thumbnail for article: Focusrite Octopre MkII &  MkII  Dynamic

With upgraded mic amps and A-D conversion in their MkII versions, do Focusrites latest eight-channel preamps still lead the way at this price point?

Empirical Labs EL9 Mike-E

Microphone Preamplifier & Compressor

Thumbnail for article: Empirical Labs EL9 Mike-E

Empirical Labs, purveyors of some of the most versatile compressors around, apply their dynamics expertise to a mic preamp.

Benchmark MPA1

Dual-channel Microphone Preamplifier

Thumbnail for article: Benchmark MPA1

Benchmark strive to make their products exactly that: something against which the competition should be judged. So how does their new preamp measure up?

AEA RPQ

Dual-channel Microphone Preamplifier

Thumbnail for article: AEA RPQ

AEA have tweaked the design of their TRP ribbon-mic preamp, already something of a favourite, to create a device thats much more versatile — and without compromising on quality.

A-Designs Pacifica

Two-channel Microphone Preamplifier

Thumbnail for article: A-Designs Pacifica

Striking a useful balance between the transparent and the characterful, this high-quality, US-made preamp design brings versatility to the studio and some colour to the rack...

PreSonus DigiMax D8

Eight-channel Mic Pre & A-D Converter

Thumbnail for article: PreSonus DigiMax D8

Presonus combine their respected analogue and digital technology in this affordable ADAT-equipped preamp.

SPL Rackpack

Modular Preamp & Processor System

Thumbnail for article: SPL Rackpack

Sound Performance Lab have developed an enviable reputation for their hardware products, and now you can buy more for less with their modular rack system.

Audient Mico

Dual Microphone Preamplifier

Thumbnail for article: Audient Mico

With two channels of mic preamp, a phase-alignment control, digital outputs and clean signal path, the Mico offers you an awful lot of Audient for the money.

Universal Audio Twin-finity 710

Hybrid Microphone Preamplifier

Thumbnail for article: Universal Audio Twin-finity 710

Which is best, tube or solid state? When it comes to investing in a preamp, thats a question you may no longer need to ask...

Golden Age Project Pre 73

Microphone Preamplifier

Thumbnail for article: Golden Age Project Pre 73

This highly affordable device is based on the circuitry used in Neves legendary 1073. So can you really get a classic vintage preamp sound on a budget?

Arsenal Audio R20 & R24

Microphone Preamplifier & EQ

Thumbnail for article: Arsenal Audio R20 & R24

This new brand by revered high-end equipment manufacturers API is much more affordable than their established lines. So there must be a catch, right?

Grace Design M201

Microphone Preamplifier

Thumbnail for article: Grace Design M201

Regular readers will know that our Technical Editor isn't prone to excessive use of hyperbole — so when he calls a product "awesome", "stunning" and "sublime", it's probably time to sit up and take notice...

Thermionic Culture Rooster

Valve Microphone Preamp & EQ

Thumbnail for article: Thermionic Culture Rooster

Is this latest addition to the Thermionic Culture flock something for the company to crow about?

Focusrite ISA One

Mic Preamp

Thumbnail for article: Focusrite ISA One

The ISA preamp range has graced professional recording facilities the world over — but this classy single-channel model is within reach of the home and project studio.

Synchronia Sound Skulptor

DIY Mic Preamp System

Thumbnail for article: Synchronia Sound Skulptor

The DIY approach to audio equipment needn't mean bargain basement, and if you apply this principle to high-end vintage gear it might just save you a small fortune — without compromising on quality.

Sebatron VMP 2000eVU

Valve Mic Preamp

Thumbnail for article: Sebatron VMP 2000eVUAustralian company Sebatron aim to start building their brand in the UK with this 'character' preamp.

WIN Great Prizes in SOS Competitions!

 

Home | Search | News | Current Issue | Tablet Mag | Articles | Forum | Subscribe | Shop | Readers Ads

Advertise | Information | Privacy Policy | Support | Login Help

 

Email: Contact SOS

Telephone: +44 (0)1954 789888

Fax: +44 (0)1954 789895

Registered Office: Media House, Trafalgar Way, Bar Hill, Cambridge, CB23 8SQ, United Kingdom.

Sound On Sound Ltd is registered in England and Wales.

Company number: 3015516 VAT number: GB 638 5307 26

         

All contents copyright © SOS Publications Group and/or its licensors, 1985-2014. All rights reserved.
The contents of this article are subject to worldwide copyright protection and reproduction in whole or part, whether mechanical or electronic, is expressly forbidden without the prior written consent of the Publishers. Great care has been taken to ensure accuracy in the preparation of this article but neither Sound On Sound Limited nor the publishers can be held responsible for its contents. The views expressed are those of the contributors and not necessarily those of the publishers.

Web site designed & maintained by PB Associates | SOS | Relative Media