RECORDING September 2022 - 54

REVIEW
API Select T25 Tube Compressor
A new tube-take on a classic compression style
REVIEW BY PAUL VNUK JR.
he new T25 Tube Compressor is the second tube-based product in the
55-year Automated Processes Incorporated (API) history. Part of the
API Select Series of audio processors, the T25 Tube Compressor is
a feedback-based Field Effect Transistor (FET) design with a Class-A tubebased
output stage that offers warmth, weight and extra grit when pushed.
T
A Select Crowd
Announced last year, the API Select Series allows the long-standing company to
explore new paths and technologies, including re-releasing a few past models that
initially flew under the JDK Audio banner more than a decade ago. This includes
the solid-state API SR22 Dual Channel Compressor and SR24 2-Channel Parametric
Equalizer released originally as the JDK R22 and R24 (both reviewed April 2011).
The tube side of the select series begins with the T12 Tube Mic Preamp that we
reviewed in January of this year, and the T25 compressor. The Select Series also
contains a pair of TranZformer guitar/bass-focused stomp boxes.
Big, Blue and Glowing
The 2U high 19 " rack mount T25 features a robust all-metal chassis finished in a deep
metallic blue inline with the other Select Series models. The T25 Tube Compressor is similar
to the T12 Tube Mic Preamp, featuring a pair of matching channels, each flanked
by a large circular backlit analog VU meter on the right and bright orange glowing
tubes behind stylish metal vents on the left. Like The T12, the T25 is also top vented to
prevent getting too hot. While the look and style of the Select Series breaks with years
of API tradition, the knobs and controls are very much in the signature API style.
The T25 is a 2-channel compressor that can be used in dual-mono or linked with
equally reactive thresholds for stereo use. Each channel has:
* 11-step attack time switch (20µS to .8mS)
* 11-step release time switch (50mS to 1.2S)
* 4-step ratio switch (2:1, 4:1, 8:1 and 20:1)
* 31-detent input/threshold potentiometer
* 31-detent makeup gain potentiometer
In addition to the output VU meter, there is a 10-segment LED gain reduction meter
and a peak/clip LED. Below the VU meter is a further collection of 4 backlit API style
54 RECORDING September 2022
push buttons for D-S (engages a 6 kHz
fixed high-frequency side-chain de-essing
circuit), THRUST (a unique side-chain
control that will dig into further in a moment),
In (takes the compressor in and
out of the signal path) and Byp (hard
bypasses the entire unit). Finally, in the
center of the device is the Link button.
Around Back
On the back of the T25 are both balanced
XLR I/O and parallel balanced
1
/4
" TRS I/O. Note that there are no external
side-chain options on the unit. A
robust internal toroidal transformer and
power supply handle power.
Tubes and Transformers
Internally the T25 uses the same
12AT7WC and 12BH7 dual-triode vacuum
tubes as the T12, along with a custom
API output transformer on each channel.
Nicely you can remove the compressor
from each channel's signal path and
drive signals into the tubes and transformer
for added harmonics and even
full-throated overdrive. This can also be
done with the compressor engaged.
THRUST
The unique THRUST side-chain circuit
was initially found on ATI Paragon live
mixing desks. When ATI purchased API
in the late 1990s, the THRUST circuit
started its migration into many API series
compressors. Today it can be found
on the famed API 2500+, the 527, 529
and more.

RECORDING September 2022

Table of Contents for the Digital Edition of RECORDING September 2022