The Amtec Model 099 is a tube limiter based on the legendary Fairchild 660. The most important qualities of the original unit
such as the sonic character and the compression characteristics are preserved, but the functionality is significantly extended by
incorporating many new additions.
No attempts have been made to "improve" technical specifications like bandwidth or distortion, as doing so would inevitably
change the signature sound. Part of the charm of the Fairchild is its effect on the frequency response as well as variations
of the frequency response with gain reduction. The spectral balance and the harmonic structure change constantly with
The Model 099 (the same as its famous predecessor) works on a basic concept of varying bias of a single push-pull remote-
cutoff tube stage to achieve gain changes. The tube stage along with input and output tranformers and attenuators form
the simplest and shortest signal path possible in a compressor based on the concept. This simplicity has a paramount effect
on the sound.
The sound of this family of compressors is strongly dependent on the signal level that is fed into the audio path. The original
Fairchild unit was designed to be the most transparent limiter of its era with minimal side effects like distortion or compression
artifacts when used conservatively.
At low gain settings and with mild compression the 099 has subtle sonic imprint and a smooth sound. Its surprisingly
transparent tone changes considerably when the unit is driven harder. With every click of the input gain up the tone gets more
distinctive with more attitude, weight, warmth and richness.
For easier application of the high gain settings we incorporated an additional output attenuator which allows to reduce
the output level by 5db or 10db. The unit can be then driven harder contributing to the natural sounding distortion produced
by the tubes and transformers, giving more obvious and aggresive, but easily recognizable and pleasant sound.
The output attenuator switch serves a double function - it also acts as a termination switch. Contrary to other dynamic
processors based on the principle of varying bias, the original Fairchild is unique in that the push-pull remote-cutoff tube stage
is coupled directly to the output transformer and to operate properly the output transformer has to be adequately loaded.
Any load (ie. impedance seen by the output terminals) that is higher than the standard 600 ohms will make the tube stage
work in non-optimum conditions, changing the frequency response, distortion characteristics and the gain reduction law.
The compression indications would be even more inaccurate than they are even on the properly loaded Fairchild.
To eliminate the problem in the Model 099 we included the termination switch in the output attenuator. Just use the part
of the outside scale that indicates the input impedance of the next device. In case of old or faithful old-style units use the left
side marked 600 ohms. If the following device has modern-style high-impedance "bridging" input use the right side.
In the NORMAL mode the amount of compression is set by adjusting Input Gain and Threshold controls. The Input Gain
controls the signal level send to the signal path and this control uses a high-quality rotary switch adjusting the gain in 1dB steps
with a total range of 20dB. The threshold control is continuously variable and adjust the level send to the side-chain circuit.
The original time constants presets are preserved, but the 099 also offers settings that differ significantly and are more suited
to contemporary music production styles, what greatly improve 099's usability. Longer attack times allow for more punchy
and less squished tone to be produced under heavy compression.
The Time Constants control offers 6 classic presets with fast attack times and release times varying from fast to slow with two
of them featuring program dependent release times, a new Fast setting that has even faster attack and release times than
the fastest classic preset 1, and four completely new presets with longer attack and fast to medium release times.
These new settings enormously enhance the pallete of uses of the Model 099 to any application.
The ratio control, called DC Thereshold and hidden in the original and called Slope in the Model 099, lets to adjust the steepness
of the compression action, from very gentle to approaching limiting. The slopes have soft-knee where the compression has
a mild onset and then gradually gets more effective.
Contemporary music production styles also require a way to change the sensitivity of compression to ignore low frequencies,
so that the music is not pumping to high-level low frequency signals like the ones presented by a bass drum or bass guitar.
This feature is absent in the Fairchild, but is present in the Model 099 and offers a choice of 4 frequency points of side-chain
low-cut as well as a de-essing setting, which boosts high frequency tones to trigger compression.
The last modern function is a sidechain source selector. Most compressors, including almost every so called vintage ones, take
the signal to the side-chain circuit (that controls the compression) from the point where the compression has been already
applied, like the output of the unit. This topology is used in the classic Fairchild, hence in the Model 099 we named that option
Other configuration is when the signal for the side-chain is taken from the input. It sounds more modern and aggresive and
behaves differently particularly on transients. This configuration is known as "feed-forward" and is activated by selecting
The third option on the switch is also "feed-forward", but the signal to trigger the compression is taken from an external
balanced input on the rear panel. It lets to activate gain reduction on the signal brought to the Model 099 by another signal,
for example in case of compressing a mix while controlling it with a signal taken from an aux path on the console with different
instrument proportions. This third position is marked EXT.
Contrary to other variable-mu designs, the 099 is based on commonly available tubes by the use of a propertiary trick in which
different standard tubes are paralled and combined to achieve remote-cutoff characterists and curves of the 6386 tube.
This is a completely novel approach that never has been used before. It also allows for easy calibration of the static operating
point of each tube and the dynamic calibration of the composite tube stage.
The tubes used in the 099 are readily available and in case of mulfunction a replacement can be found on a Friday night, what
cannot be said about the original 6386 tube.
The tubes are mounted on the rear panel and are protected by a removeable perforated cover.
The complete retubing and calibration can be done without removing the 099 from the rack.
Input impedance: 2K ohms (transformer balanced)
Output impedance: below 150 ohms (transformer balanced)
External sidechain input impedance: 30K ohms (transformer balanced)
Recommended load impedance: from 600 ohms to infinity
-1dB points: better than 25Hz to 25kHz
-3dB points: better than 10Hz to 45kHz
Max output level (1% THD): +22dBu
Compression ratio: soft-knee, from 2:1 to 10:1 in 6 steps (NORMAL mode
Tubes: (2) ECC81 / 12AT7, (1) ECC82 / 12AU7
Power requirements: 230V/50Hz or 115V/60Hz (factory option)
Power consumption: 40VA
"I became aware of the 099 from an online thread. I had heard of Amtec from their pultec style eqs, which I knew were well
regarded. The 099’s design philosophy and aesthetic immediately caught my eye and the short youtube demo was enough to
convince me to buy one.
I'm so glad I did. After 15 years of running a commercial studio this is the single best compressor I own.
The 099 delivers in ways other units can only dream of. Great styling, ease of use and reliability are all important concepts in a
purchase like this, but at the end of the day it is the sound that is the key factor. The 099 delivers all you could want and more.
The compression curves and ratios are perfectly chosen, and the additional s/c filter is a real lifesaver for preserving bass heavy
material. The difference between the feed forwards / backwards settings is night and day, from modern percussive punch to
vintage tube thump with the flick of a switch.
No in built parallel compression I hear you say? YOU WOULDN’T WANT IT!!! The sound is totally addictive and you’d always
want 100% blend. The one single issue I can identify is that nothing sounds bad! You can spend hours fiddling and get lost in the
various combinations of input, threshold, side-chain etc. A good quick start would be as follows:
Position 1 is awesome for smashing drums, rooms etc, giving the most glorious 3-D depth and control. Position D is perfect for
busses / sub groups, giving them life and energy whilst holding them in place.
Each time I use this compressor I find a new thing to love. One of the coolest features is the switchable output impedance
selector. This is designed to help the unit interface better with older gear but can also double up as very cool tone control. If
your electric guitars are too bright try flicking over to the Hi-Z setting. The highs are gently rolled off and any upper mid
peakiness is tamed.
I’ve had the 099 for a month now and my 1176’s , distressors and beloved Fairchild 670 are all gathering dust. I'll definetly be
ordering a second unit to handle stereo duties.
Great job amtec!"
- George Apsion, the owner of KORE Studios, London