True Dynamics models two different super rare vintage (late 1940s and 50s) single channel compressor/limiters: the Presto 41A Limiting Amplifier as used with the company's disc cutting lathe and the Industrial Transmitter and Amplifiers (ITA) LA-1B Limiting Amplifier as used in mono AM radio transmitters in the 1950s. The two actual hardware units used for creating both plug-ins are part of Devin Powers' collection of hard-to-find, rare audio gear.

Both the Presto 41A and ITA LA-1B are available in the same GUI and you can instantly switch between them and keep the same knob positions although you may want to reset them more specifically to how you're using them on particular sources. I think that is a modern feature when offering more than one processor in a single plug-in.

Great To Have Both At The Ready!

On an acoustic guitar track, the LA-1B seem to have a little faster attack time compared to the P41-A but, for big squashes, the Presto was more forgiving and colorful. Using the high pass side-chain filter up at 900-Hz did relieve some pumping but I did end up choosing the more transparent-sounding LA-1B for this rhythm acoustic guitar track.

For a five-string bass guitar with active pickup electronics, I used the P41-A for a rounder tone. Five-string bass guitars with active electronics tend to sound electronic to me--especially the open B string. I used 1.5-seconds of Recovery Time (aka Release) and saw gain reductions right up to the red line on the Gain Reduction meter--about 8dB whenever Nathan East played an octave-up standout. The high pass side-chain filter was at 365-Hz and the compression did not "clamp" the life out of the bass.

On a very dynamic grand piano recording I preferred the LA-1B and used both the HPF and LPF side-chain filters. Here I wish there was a bypass button for these filters for a quick A/B. You have to drag their faders to 'off' to not hear their effect.

These are first order filters--6dB per octave. I set them to 1,200-Hz for the HPF and 3-kHz for the LPF. Only the frequencies between those two extremes are affected. On this hot piano track, I set the Gain Reduction control up to 22.7dB and Recovery was at 0.67-seconds. With the filters set this way for a narrow band of compression, I got a very articulated piano sound in which subtle 'filigree' and light flourishes were more present yet when the piano player played out big and loud, there was minimal compression of the left hand low octaves and no dulling of the high frequencies. More compressor plug-ins should have both HPF and LPF side-chain filters.

Finally for stereo bus compression of a music mix, I started with the P41-A and the HPF set to 432Hz. I got significant average level increases here with some dulling of peak moments as expected so I would have to readjust to compromise the maximum level possible. I switched over to the LA-1B without touching any controls and it was more transparent and clear in that it kept the bright attacks of the piano and acoustic guitars. This song had no drums.

So Kazrog's True Dynamics gives you two "schools of thought" on compression/limiting: a easy-going, musical and smooth touch with the Presto P41-A and a more strict, precise, clean, and (seemingly) accurate process using the LA-1B. And I love them both!

True Dynamics sells for $79.99 and is available as VST 2, 3, AU, and AAX Native.