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TCL-2
TCL-2 PHILOSOPHY & DESIGN
The TCL-2 Twincom is an entirely balanced topology from input to output, meaning that pin
2 and pin 3 have their own, discrete, mirror-matched amplifiers. Even when the TCL-2 is used
with unbalanced signals, the internal circuitry remains balanced. These mirror-matched amplifi-
ers are comprised of both vacuum tubes and discrete J-FETs, each topology selectable via a front
panel Twin Topology switch.
Dynamics control is achieved via a passive precision-matched resistor network in which a
matched LDR array (light dependent resistor) is used as a shunt element between the positive
and negative legs of the network. Thus, the audio present at the output of the unit has not
passed through an LDR or VCA. Avoiding LDRs and VCAs in the audio path results in im-
proved (more accurate, minimally colored) sonic performance.
Because of TCL-2’s unique design qualities, it is best suited for applications offering a balanced
high-level (+4) source and a balanced bridging load (3,000 ohms, or greater). Operating the
unit in a -10 dBu nominal environment may not provide adequate drive for optimal use. When
wired to an unbalanced destination, the output XLR connector pin 3 should remain floating
(unconnected). See the suggested unbalanced interface cable wiring configurations shown later
in this manual.
All TCL-2 design decisions have been made towards the goal of absolute sonic neutrality and
timbre purity:
1.) No audio transformers. The vast majority of professional vacuum tube audio equipment
uses audio transformers. Yet, as someone once said, “there is no transformer that sounds like
no transformer.” For this reason. Millennia avoids audio path transformers and relies on other,
“less colorful,” coupling techniques.
2.) Lower, tighter gain and threshold structure. Because less inherent amplifier gain generally
translates into heightened sonic reality, the TCL-2 is designed with a modest 20 dB of overall
gain; lOdB available as make-up gain. The threshold range (-20 to +30 dB) is similarly struc-
tured for optimal sonic performance. Due to this optimized gain structure, compression or
limiting of very-low-level signals (less than -20 dBu at the input) is not possible, whereas com-
pression or limiting of very-high-level signals (+30 dBu at the input) is possible.
3.) No bypass relays or audio path switching. Input signals are always in-circuit, thus avoiding
the need for switched / relay signal bypass (read: audio path switch points degrade over time).
When the TCL-2 is “bypassed,” only the actual dynamics side-chain control is removed from
circuit. The audio signal remains in-circuit (via tube or solid state amplifier).
4.) Single amplifier design. In keeping with Millennia’s minimalist philosophy, the TCL-2 is
designed around a single audio path amplifier. This amplifier acts as input buffer, dynamics
follower, and output driver. The amplifier is mirror imaged so that single but mirror-matched
amplifiers follow both pin 2 and pin 3, respectively.
