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Kenetek T4B Opto-Attenuator Modules

"Big thanks for getting these out. I don't know why anyone would buy elsewhere. Your T4B's put the magic back in my LA3A's while UA and others are getting out of line. Thanks for making a great product that keeps the vintage equipment enjoyable. Make Jim Lawrence proud!"


"It sounds great, at first listen, it seems to hold the shapes of the transients better than my Drip t4, even under heavy gain reduction. Good work you've done here."

    -Ben Witte
    "bdubya" on ppro

"I have now used your T4b's for a month or so and I think they work exactly as they should. Compression is smooth and easily controllable. Perfect. Absolutely."

    -Roni Martin

"I used my new LA-2A clone today at church (Vocal Buss Only) and blew away my sound guy. Your T4B’s were crankin’ out some silk brother!"

    -Carl Dennis



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The Kenetek T4B is a direct, drop-in replacement for the Teletronix and Urei T4A, T4B and T4C opto-attenuator modules.  The electroluminescent panel (EL panel) is custom built to our specifications and provides a smoother, more musical attenuation curve than T4B units from other vendors. T4B units built with these panels are much more musical and will restore the classic behavior of your LA-2A, LA-3A or BL-40. Your unit will be smoother and more versatile, and you will find it becomes a pleasure to use again.

Kenetek has been building, servicing and restoring Teletronix and Urei LA-2A Tube Limiters for 20 years. By necessity, we had to exhaustively research the components, materials, suppliers, construction and history of the T4B unit. We discovered that the modern EL panels built by the "Original Equipment Manufacturer" (which was at least four times removed from Grimes, the original manufacturer of the EL panel used in the original LA-2A and LA-3A units) has updated their materials and manufacturing techniques to provide a brighter, more efficient and reliable EL panel. You see, the primary use for their panels is for instrument lighting in aircraft. While the "improvements" they made may benefit pilots, they were actually detrimental to the performance of the opto-attenuator units used in LA-2A, LA-3A and BL-40 units. Modern panels have a much lower threshold voltage and put out more light at lower voltages than the original panels. The result is that opto-attenuator units using these panels exhibit a sharp knee at the threshold of compression, and the unit goes into heavy compression much sooner than the classic units. It is difficult to dial in the exact amount of compression desired, and the musicality and versatility of the compressor is diminished.

The Kenetek T4B is hand built from specially selected components and is guaranteed to be the most accurate T4B you can buy. The photocells, EL panels and finished units are graded and matched using our custom-built, computer-driven T4B tester, which gives us unmatched precision and accuracy when testing T4 units.

This screenshot compares two Kenetek T4B units, one built with the new Kenetek EL panel and the other built with an EL panel from the "OEM" supplier. This graph plots the resistance of the photocells dependent upon the voltage applied to the EL panel.  Notice the difference in the shape of the two curves. The Kenetek EL panel responds much more gradually to the applied voltage, giving a softer, smoother knee.  The OEM panel's response is much sharper, acting more like a brickwall limiter than a compressor.  The difference is not subtle, and the Kenetek EL panel yields a much more musical compression curve. 


This screenshot shows the results of the Pulse Test. A 1 kHz, 65 VRMS pulse is applied to the T4B and the resistance of the photocells is then measured for a total of 10 seconds. As you can see, the responses of the cells match almost exactly.



This screenshot shows the results of the Dynamic Range Test. The resistance of the photocells are is measured while a 1 kHz signal is applied and varied from 0 to 100 volts peak. Once again, the cells are almost an exact match.



Kenetek T4B Electro-Optical Attenuators are warranted against premature failure due to material and manufacturing defects for a period of three years from date of purchase. Simply return the unit to Kenetek and we will, at our option, repair or replace the unit at no cost.  You are responsible only for shipping expense to our facility. This warranty does not cover damage or abuse. The warranty seal on the unit must be intact and undisturbed.

Do yourself and your classic opto limiter a favor. Try a new Kenetek T4B opto-attenuator in it.