Meet the Legend: Teletronix LA -2A
aka Tube Opto Compressor
The go-to weapon for most engineers when it comes to vocals or bass...
history
Travel back in time...
…to find out how the LA2A was created, and about some of its most famous users from the golden era of analog recording to the present day… read more>>
specs
what it actually is...
…that everybody is raving about and what makes this wonderful sounding compressor so special it became the legend it is today… read more>>
how it works
What it does...
…to the signal that’s being passed through the LA2A. Learn what happens inside and how it achieves its characteristic behavior… read more>>
guides
How 2 built 1...
…of these iconic pieces of gear yourself! I’ll show you the first and most important steps to build an authentic tube opto comp from scratch…read more>>
tube opto compressor
history...
James F. Lawrence founds the Teletronix Engineering Company in Pasadena California
Introduction of the Teletronix LA-1 of which only about a 100 units were made
Introduction of the Teletronix LA-2
improvements on the original design lead to the release of the LA-2A (grey faceplate) The first time a turret board was used instead of plain point-to-point wiring . Better wiring layout led to lower noise floor
Lawrence sold Teletronix to Babcock Electronics in California
Studio Electronics (owned by Bill Putnam) which was later renamed to United Recording Industries (UREI) took over Babcock Electronics’ broadcast division including the Teletronix brand
UREI continued to manufacture the LA2A but with a silver faceplate instead of the grey one
The LA2A was discontinued due to slow sales after the development and introduction of solid state technology drove out space consuming tube gear (resulting in products like the LA-3A & LA-4)
Bill Putnam Jr. refounded Universal Audio reissuing the LA-2A – this time with a grey faceplate again.
The rise of analogvibes begins…
...specs
Limit/Compress Switch: switches the unit between both modes, but the difference is rather homeopathic – only with extreme Peak Reduction settings you’ll notice a difference
VU meter: either reflects the amount of gain reduction applied or the actual output level of the unit
Gain control the amount of gain applied to the signal AFTER the actual compression circuit – kind of the make up gain. In fully CCW position the signal is completely attenuated – in fully CW position it will most like not only blow your speakers but even your entire room – the LA2A is a gain monster!
Meter switch: controls the VU meter to either show gain reduction, output +4 dbu (todays studio standard) or +10 dbu
Peak reduction controls the amount of gain reduction applied – even though the front panel layout suggests it comes behind the gain pot, this actually is the first pot the signal hits after entering the circuit
R3 Stereo Adjust control to adjust the gain reduction control voltage when connecting two units for stereo use
UTC A-24 output transformer
The T4B opto cell – this is where the magic happens! Learn more about how this component works and what it does inside of the LA2A in my „The 3 knobs“ e-paper
12AX7 & 6AQ5A tubes of the gain reduction control circuit
R37 frequency response control of the gain reduction control circuit learn more about it in my „The 3 knobs“ e-paper
12AX7 & 12BH7 tubes of the amp circuit
UTC-HA100x (or UTC A-10) input transformer
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how it works...
Part I - Overview Teletronix LA2A
This is a first introduction and overview of the iconic tube opto compressor explaining the controls as well as the major components on the back.
Part II - Main components & gain reduction of the LA2A
In this video we’ll dive a little deeper into how this wonderful piece of gear actually works – focussing on the gain reduction control circuit, the part of the LA2A that actually takes care of the compression.
Part III - What the heck is a T4 cell?
At the heart of the LA2A compression circuit is the T4B cell. It’s considerably responsible for the smooth compression character. In this video I’ll show you how the T4B cell works and what it actually does.
Part IV - The amp curcuit
The second major part of the LA2A is the amp circuit – or the tube make-up amp. In this video I’ll explain the basic structure of the amp circuit – more details can be found in my „The 3 knobs“ e-paper.
Get to the hearth of it. Part I -IV collected in this free paper:
All clear? Now, let's watch it in action!
Featured: The Teletronix LA-2A in action.
In this great little video Doctor Mix shows the LA2A in action. In case you never used a real LA2A before, this will give you good first impression.
» analogvibes have created the most authentic and beautiful recreations of vintage classic studio gear available. «
» Words can’t describe howproud and excited I am to have these built with my own two hands. «
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guides...
This "Build Your Legend Series" will enable you to build your own legendary tube opto compressor from scratch.
It includes a 25 pages wiring layout, a complete and linked bill of materials, to make sure you get every part you need as easy as possible.
And, last but not least, the ultimate step-by-step building guide, with no step missed!
All for free, you’ll get the full versions delivered with your chassis set. For now, have a look at the previews:
Note: If the mouser cart is missing a (few) part(s) check out this video how to find substitute parts and feel free to inform us.
...time to wire it up a notch
Part V - The Tube Opto Compressor blue print
Now you are good to go, but also please watch this video - it's only a matter of life and death!
How to electricute yourself (NOT)
In this short video I give you some quick advice about to be save and sound whilst building your legends. Also have a look at the how-2-build-it epaper. There you’ll find the six essentiell rules which should make building your own tube gear a safe ride.
Still got a question? You can ask us everything you want...
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There are a lot of very nice and extremely qualified fellows (way more then Martin ;-), who would gladly help you out.