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Tube Tech SMC 2A Hellfire Modulator Tube Processor

Many of you are quite familiar with Tube Tech, the Danish manufacturer of high-quality pro audio gear in the familiar blue package. The SMC 2A is Tube Tech's latest contribution to its already long list of microphone preamplifiers, equalizers and compressor/limiters, all of which incorporate tubes as the basis of their design.

Many of you are quite familiar with Tube Tech, the Danish manufacturer of high-quality pro audio gear in the familiar blue package. The SMC 2A is Tube Tech’s latest contribution to its already long list of microphone preamplifiers, equalizers and compressor/limiters, all of which incorporate tubes as the basis of their design. Its products have always been quite impressive, but with this latest offering, the company may have outdone itself.
Product PointsApplications: Recording; mixing; mastering

Key Features: Three-band stereo tube compressor; adjustable threshold, ratio, attack, release and gain make-up per band; adjustable crossover

Price: $4,395

Contact: Tube Tech/TC Electronic at 800-288-5838; 805-373-1828; Reader Service 196.


+ Sonic quality

+ Individual bands are fully adjustable

+ Good metering


– None

The Score: This unit is a winner on all fronts: tracking, mixing and mastering.

The Tube Tech Stereo Multiband Compressor (SMC) is exactly what its name implies – a stereo unit that provides three compressor bands per channel. This is achieved with three independent stereo optical compressors divided into low, mid and high bands governed by two crossover networks between the low/mid and mid/high bands.

These crossovers provide continuously variable frequency selection from 60 Hz to 1.2 kHz between the low/mid band and from 1.2 kHz to 6 kHz between the mid/high band. The design maintains an optimum summing of the three bands, so frequency response is flat (+/-0.25 dB) when the gain controls for each band are set the same.

Besides an output gain control for each band (continuously variable from off to +10 dB), there are also Threshold, Ratio, Attack and Release pots provided for each band. All pots (which are conductive plastic) on the box are continuously variable, giving maximum choice of values but guaranteeing that recalls will be more of a challenge.

Completing the SMC 2A’s front plate is the main output gain pot (off to +10 dB), power switch with Tube Tech’s signature amber power indicator, clickless bypass switch and a well-defined LED display to indicate compression. Each band has an 11-segment display that shows gain reduction from 0 to 20 dB.

The XLR inputs and outputs on the back of the unit are balanced by fully floating transformers and the eight tubes found within require proper ventilation. The frequency response is rated from 5 Hz to 60 kHz (+/-3 dB) and the noise is <70 dBu.

Reviewing the Tube Tech SMC 2A was indeed a love affair, but, as with all relationships, I encountered a few bumps in the road – particularly in the beginning. Upon receipt of the first unit, I noticed a discrepancy in the right/left gain structure. Without hesitation, the West Coast representative brought a replacement unit (which he personally calibrated) to the studio where my tests were underway.

To my surprise I experienced the same problem with the second unit. As I adjusted the unit with stereo program passing through, I found that it was alternately right or left heavy by up to 1.5 dB. Needless to say, if this were your stereo mix you would be quite concerned! When I again called Tube Tech with the problem, the folks there were quite amazed since the right/left balance was thought to be accurate within 0.5 dB.

To fully understand the problem, let’s go a little deeper into the design of the unit. After processing, the output of all three stereo bands goes to three separate gain-control pots from where the outputs are then summed together and continue to the main output gain pot.

I found out through later discussion with its designers that each stereo gain pot (three bands; one main) was rated to be accurate within 0.5 dB! This means that the cumulative effect could ultimately be much worse depending upon the settings of these various output pots. After a long overseas discussion with a disappointed Tube Tech executive, several options were discussed; two weeks later a new unit arrived at my door.

Simply adding a pan pot (positioned neatly above the master gain pot) solved the problem. This quick action demonstrates the kind of commitment this company has to the quality and performance of its products. (Note: unfortunately, a few of these units were shipped before the additional pot, but it’s an easy modification. Contact Tube Tech at the number above for details.)

In use

The Tube Tech SMC 2A is one of the best-sounding and useful products I have encountered in quite some time. To refer to it as outboard gear does not really do it justice. In my estimation, it is a true mastering tool.

For those unfamiliar with multiband compression, it can make taming the most unruly track a snap. I started with all my outputs at the 0 dB position and the threshold setting for each band in the off position. At this point the unit has virtually no effect and you can use the clickless bypass switch to verify this.

Band by band, I lowered the threshold until I achieved just a bit of gain reduction. I then adjusted the crossover points where you can see (with LED indicators) and hear at which point the unit “grabs” certain instruments. Finally, small adjustments in gain at the individual outputs can alter the sonic shape of your mix.

I can’t say enough about the sound of this unit, particularly in the high end. The amazing thing with this processor (when applied judiciously) is that it seems to do the opposite of what its name implies. Instead of sounding more compressed it sounds more open! A flat one-dimensional mix suddenly becomes more expansive.

I was lucky to have this unit during the mixing of Lionel Ritchie’s latest project and it proved a great asset. The depth and dimension it added to one ballad in particular was astounding. At the same time, I learned one had to be very careful with this unit. It can have a somewhat addictive effect that encourages overuse. It is the same experience I encountered when using the SMC 2A’s first cousin, the TC Electronic Finalizer. To combat the urge, I suggest maximum use of the bypass switch to reference the original program and rely on your ears.

The SMC 2A should not be overlooked for use on individual instruments. I tried the unit on various instruments, stereo and mono, with great results. One surprise was its effectiveness on all the vocals, especially lead. After limiting to taste, the Tube Tech allows you to crank up the output of the high band in surprising amounts to achieve fantastic results.


As the Danes would say in their own language, the SMC 2A is “utrolig” (incredible, astounding, unbelievable). At $4,395 (list price) the Tube Tech Stereo Multiband Compressor is poised to be placed exactly where it belongs in the marketplace: top recording facilities, mastering houses and in engineer and producer racks everywhere. Audition the SMC 2A as soon as possible and let the love affair begin.