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Classic tube tone and loads of gain, in a single-slot 500 Series module

Review by Paul Vnuk Jr.

Retro Instruments was launched in 2006 when Phil Moore built a spot-on, updated recreation of the famous Gates Sta-Level tube limiter (circa 1956). In addition to reviving period designs, Retro has also crafted its own Powerstrip Recording Channel, the 2A3 Dual Program EQ, the aptly named DOUBLEWIDE dual-slot 500 Series tube compressor (reviewed October 2015), and the updated DOUBLEWIDE II.

The second 500 Series offering in the Retro Instruments line is the new 500PRE, comprising a tube-style microphone preamp based on the input topology of the Retro Sta-Level. Unlike its DOUBLEWIDE cousin, the 500PRE tightly packs three tubes and two transformers into a single slot.

Top to Bottom

The 500PRE is painted Retro grey. It sports a pair of smooth yet nicely resistant input and output pots, and a trio of chunky two-position toggle switches for 48v phantom power, phase inversion, and a choice of low or high input gain.


Inside the sealed enclosure are three new-production TAD 12AT7 tubes, and a pair of CineMag transformers on the input and output stages.

Specs and Functions

There are two functions or attributes of the 500PRE to bring to your attention: the low and high gain switch gives you the choice of either a two-stage low gain topology with 48dB of gain, or a three-stage high gain mode with 76dB of output gain. Secondly, the 500PRE is designed so that when sound is pushed liberally into the unit, the tubes exhibit tube limiting characteristics somewhat more so than your standard or typical tube overdrive.

Total Harmonic Distortion: <.05% at +4 dBu output from 20-20000 Hz

Frequency Response: +/- .25 dB from 20-20000 Hz

EIN: -128 dB (150 ohm terminated)

Typical Output Level: +4 dBu

Output Clipping Level: tube limiting threshold +18 dBu, +24 dBu clipping headroom

Input Level Range: -72 dBu to +12 dBu

Input impedance: >1000 ohms from 20-20000 Hz

Output Impedance: 600 ohms transformer balanced

Power Consumption: +/-16 Volts 155 ma. 48 Volts 3 ma

In Use

Thanks to its impressive 76dB of gain, the 500PRE will handle any microphone you throw at it. It’s an excellent choice with low output ribbons, dynamic mics, and lower output vintage-style tube mics.

Saturation vs. Compression

The gain staging and circuit design of the 500PRE exhibits tube limiting qualities. The 500PRE gets bolder and more weighted the more you drive into the unit. This bumps and even blooms the sound forward and holds it firmly in place rather than merely adding harmonic overdrive as many tube preamps do.

Of course, you can push it into overdrive if you wish and dial down the output to prevent clipping the next device’s input. The real magic of the 500PRE however is how it can go from clean and pure to blunt, saturated and thick.

This is the type of classic preamp well suited to darn near everything. I found it to be a natural on vocals and percussive sources like kick and snare. I do wish that it had a 1/4” instrument input, but when combined with a good direct box, the 500PRE is amazing on direct bass as well as on bass cabinet with a Shure SM7B. The unit is also great for reamping digital sources to add tube weight and color, so better consider a pair!


The Retro Instruments 500PRE is sonically everything I love about the sound of the Sta-Level, in preamp form—vintage in tone and style, but tonally broad enough for the modern studio.


Price: $895

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