Aphex 207 Tube Mic Preamp

When I reviewed the Aphex 1100 microphone preamplifier two years ago, I fell in love with its magnificent sound. I jumped at the opportunity to check out its baby brother, the Aphex Model 207 Two-Channel Tube Mic Preamplifier.
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When I reviewed the Aphex 1100 microphone preamplifier two years ago, I fell in love with its magnificent sound. I jumped at the opportunity to check out its baby brother, the Aphex Model 207 Two-Channel Tube Mic Preamplifier. This new box combines the main circuit of the Aphex 107, including the patented Reflected Plate Amplifier tube circuit with the patented Aphex MicLim circuit that is one of the highlights of the Aphex 1100.
Product PointsApplications: Studio

Key Features: MicLim limiter, Reflected Plate Amplifier circuitry, 48V phantom power, low-cut filter, 20 dB pad, polarity reverse

Price: $649

Contact: Aphex Systems at 818-767-2929, Web Site.

The front end of the Aphex 207 ($649) is a discrete solid state transformerless amplifier crafted for particularly low noise and high common-mode rejection. Since it runs without feedback, it is an ideal input stage as it never reflects any feedback current back to the microphone. The output stage of the 207 incorporates Aphex's patented Reflected Plate Amplifier (RPA) circuit. While using a single 12AT7/ECC81 tube, the circuit provides a clear and detailed tube sound while avoiding the typical limitations of conventional tube circuitry like short life, noise, heat and low bandwidth.

Weighing 6 pounds, the Aphex 207 is a 1RU, 8.25-inch deep box. The pre has a dynamic range beyond 90 dB, -129 dBu EIN and 65 dB of gain. The attractive silver-gray front panel includes a power switch with a power LED that glows yellow during the standby start delay to allow for tube warm-up time, and then green when the unit is ready to operate.

Both channels have identical features. On the front panel, a 1/4-inch jack provides instrument input with an impedance of 1 megohm. This matches all coil type pickups and powered pickups. Fully passive piezo pickups work but they typically do not deliver a full range sound. When a plug is inserted, the mic input is inoperative.

Each channel has five front panel mounted switches that activate the various features of the Aphex 207. When a switch has been selected, it glows to show its status. The phantom power switch activates 48V phantom power. The pad switch inserts a 20 dB pad at the microphone and instrument inputs. The low-cut switch activates a 70 Hz low-cut filter. The MicLim switch activates the MicLim circuit. A limiting LED lights to show when limiting is taking place. The unique MicLim circuit follows the sound envelope like any limiter but actually works at the microphone level before any amplification takes place. A typical limiter cannot protect a mic preamp from clipping because it placed in the signal chain after the pre. The MicLim eliminates the possibility of preamp overload.

The gain knob adjusts the microphone preamplifier and instrument gain. The output trim pot (adjustable with a small flat-head screwdriver) works in conjunction with the 207's output level switch to precisely match any external equipment. Each channel's 10-segment meter indicates the available headroom in decibels below clipping.

The rear panel is equipped with a pair of Operating Level switches that selects the channel's operating level at either -10 dBV or +4 dBu. Each channel has a female XLR connector for microphone input, a 1/4-inch TRS jacks for insertion, and both male XLR and 1/4-inch TRS jacks for audio output. The output impedance of the XLR jack is low enough to drive loads of 600 ohms and higher. The insert point allows EQ, compression, etc., to be inserted into the signal path before the tube output stage. An IEC connector and line cord are provided for power.

In Use

I achieved excellent results using the 207 in a variety of studio applications. Before I started, I followed the advice of Aphex and ran a 1 kHz tone through the 207 and increased the gain control until the output headroom meter read zero. I ran the output of the 207 into the input of my iZ RADAR multitrack hard disk recorder and used a small screwdriver to set the output trim on the 207 to match the maximum input level on my RADAR. From that point on, I was able to record particularly hot signals into the RADAR without being concerned with nasty digital clipping. In normal use, the limiter is virtually inaudible so unless you are pushing the point of excessive limiting it will not color the sound. The MicLim feature can always be turned off as well. Though, in every instance, I preferred the end result with the limiter on.

I used the 207 on kick and snare (using an AKG D112 and a Shure SM57 microphone respectively) and the pre delivered a full, rich sound with plenty of attack. Using the 207 with a stereo Royer SF-12 for drum overheads yielded great results. I found that by pushing the gain into extreme limiting, I was able to make a drummer in a fairly small room swear that he was John Bonham reincarnated (I confess, I was convinced as well). The pre also performed flawlessly on a wide variety of percussion instruments from hand drums to tambourines and shakers.

On electric guitars I tried the 207 with the new Royer R-122 (my current desert island microphone), a Sennheiser 421 and a Shure SM57 and in every instance it worked like a charm. The pre also did a fine job coupled with a Neumann KM 86i and a Royer SF-1A to capture an acoustic guitar performance. I recorded bass and keyboards through the instrument input and had good results in both instances. Pushing the bass to the point of excessive limiting worked well in a couple of situations.

Perhaps the strongest point of the 207 is in recording vocals. I had killer results recording both male and female vocals (with a wide variety of microphones). I found the low-cut filter to be very musical (translate: usable). When activated it takes away the rumble without thinning out the vocal.

Through the use of the MicLim feature, the 207 is able to controllably capture overly dynamic performances without squashing out the passion of a fantastic performance. Then the RPA tube stage adds subtle yet musical tube warmth to the final signal. I am constantly amazed at how appealing the sound of 2nd order harmonics is to the human ear.


I have yet to hear anything in the price range of the Aphex 207 (nor do I expect to) that offers the high-quality sound of the 207 coupled with its long list of features. The only real downside that I encountered was the instrument input's lack of compatibility with unpowered piezo pickups. Adding a direct box in the chain and going through the mic input instead of the instrument input solves this problem without a hitch.


Apple 400MHz PowerMac G4 Digidesign Pro Tools v5.1 Mix+; RADAR 24 hard disk recorder with Nyquest 96 kHz card; MasterLink hard disk/CD recorder; Lucid Gen-X-96 Clock; Mogami cabling; Hafler amplification; Alesis PMC TB1, Yamaha NS-10M monitors; GML 8200 parametric EQ, Tube Tech CL-1B compressor, Empirical Labs Distressor compressor, Pendulum Audio 6386 Variable MU compressor/limiter; AKG C28B, AKG D112, Neumann KM 86i, Royer R-122, SF-1A, SF-12, Sennheiser 421, Shure SM57, Sony C-800G microphones.