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By Nick Irving

Recording Studios around the world adopted Allison Research's Kepex and Gain Brain modules as an integral part of their drum sound in the early 1970's.

In the mid-1970's the inventor of these classic audio processors, Paul Buff, moved his company from California to Nashville, and a second major era in drum signal processing was born: The Valley era.

We hope you enjoy the second installment of our History of Allison Research and Valley People.


Allison Research moved from California to Nashville in the early 1970's. After a short period, they joined up with another studio equipment manufacturer, Valley Audio. Together they became Valley People.

Valley People were the hottest company on the studio block in their day, defining the sounds of hit records world wide for over a decade, and counting members of The Beatles and The Beach Boys among their clients.

In the late 1970's Paul Buff developed the Valley VCA (voltage controlled amplifier), the TA-101. The hugely popular Gain Brain and Kepex modules were re-designed around the new Valley VCA, and became the Gain Brain II and the Kepex II. They became the new standard for studio drums in the 1980's and beyond.

Besides the updated Gain Brain and Kepex modules, new designs around the Valley VCA included the now infamous Dyna-mite, and later the Comander (Compressor / Expander) and the 610.

Founder Paul Buff left Valley People in the early 1980's, after which point the company was known as Valley International. They continued operating for a few years but fell into financial difficulty and were eventually aquired by Galaxy Audio in the late 1980's. The name changed again, this time back to Valley Audio. Galaxy retired the Valley brand in the early 1990's.

But the story didn't end there...

Allison Research California
Allison Research Nashville
Valley People logo
Valley International logo


Key to the new generation of Valley products was Paul Buff's trademark gain control element - the TA101, aka the Valley VCA.


A VCA is a Voltage Controlled Amplifier and is a significant development from the earlier Allison FET-based modules.


Valley became a major rival of DBX, whose own VCA design had revolutionised audio technology with the 160 compressor.


The Dyna-mite limiter/gate was aptly named, for the characteristic it imparts on drums can be described as nothing short of explosive.


Dyna-mites were initially housed in a beige plastic box (pictured), however they were later produced in the standard 19" rack format.


Dyna-mites are a favourite of drum producers and mix engineers the world over, on individual drums, overheads, the drum buss or as a parallel buss compressor.



The original KEPEX (Keyable Program Expander), introduced in 1970, was the first product from Allison Research. It was an instant hit with recording engineers and producers, and was therefore an obvious candidate for re-design around Paul Buff's new TA101 VCA.

The Kepex II hit the market and took over where the mark I left off. Kepexes are prized for their ability to tighten-up close-miked drums, in particular.


The original Gain Brain from Allison Research, introduced in 1971, was  a FET (field effect transistor) compressor/limiter. The circuit was completely re-designed around the new Valley TA101 VCA, the result became the Gain Brain II.

As with the previous generation of Allison Research modules, the combination of the Valley Kepex II and Gain Brain II became the first choice for producers and engineers in the 1980's and beyond. In fact, they're still in regular use in many of the world's top recording studios today.



Key to Valley's new products of the 1980s was Chief Technical Officer Michael 'Doc' Morgan.

Doc Morgan was responsible for a number of important Valley products including the Comander (Compressor / Expander), Leveler and DSP 800 series modules, the Gatex 4 channel expander/gate, and with Gary Carrelli, the 610 Stereo Compressor / Limiter / Gate.


Having been dormant since the early 1990's, the Valley brand was purchased by PMI Audio in 2007. The resurrected Valley People (including original Valley CTO Doc Morgan) are now working on bringing out the classic Valley modules in the modern-day standard 500 series format. The Valley TA101 transistor array is now back in production in Nashville, TN.

As of 2015, only the Dyna-mite 500 series module has been released (pictured), though there are plans for the Gain Brain II, Kepex II and Comander modules to be reissued in the not-too-distant future.



We reported last month on the work involved in restoring our Allison Research Gain Brain modules. The Valley modules are a newer design and have fewer potential issues. The main considerations are:

Electrolytic capacitors - these age and should be changed. Any Valley module around now is at least 25 years old and should have its electrolytic capacitors replaced. Old capacitors can leak, damaging equipment, or their values can drift with age, so the units don't perform as they should. A complete re-cap will ensure your module's use for many years into the future. And no, replacing the electrolytic capacitors will not change the 'Valley sound'!


Valley modules have newer LEDs to their Allison elder siblings, which used some of the first LEDs ever made. It's highly unlikely any LEDs in Valley modules will need to be replaced.


While the Allison Research modules were entirely discreet electronics, the Valley modules have a number of integrated circuits (IC's), which are usually mounted in sockets on the boards. Sometimes these IC's may need to be re-seated to ensure proper connection. You can clean sockets with DeOxit D5 spray.


We recommend all electronic work be carried out by a competent professional. If you're in Sydney we recommend Colin Abrahams, Sydney's top tech.

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