Preamplifiers — VTL TL 2.5i

The VTL TL-2.5i is the valve line preamplifier of the Performance Series from the California company founded in 1981 and led by Luke Manley. Hand-built in California, it brings much of the circuitry and power supply design of the larger TL-5.5 Series II into a simpler, more affordable chassis. Buyers can order it with an internal MM and MC phono stage or install that board afterwards.

Key specs that matter

The line stage runs on two 12AU7 and two 12AT7 valves. Gain is switchable between 8 dB and 14 dB, maximum output is 30 V RMS and THD is 0.02% from 20 Hz to 20 kHz. Signal-to-noise is 90 dB and channel separation 75 dB at 1 kHz. Connectivity covers six line inputs, or five with the phono stage installed, two pairs of RCA outputs, a tape loop, a record output and a processor loop for home theatre. Power consumption is 100 W, rising to 150 W with the phono stage. The chassis is 483 mm wide, 381 mm deep and 102 mm high, and weighs roughly 11 kg.

Engineering and use context

VTL gives its line stages a high-current, low-impedance valve output. Every gain stage has its own stiff power supply, the supplies are fully shielded, and the power transformer is designed for a very low radiated field. Negative feedback is lower than in earlier VTL preamplifiers. Volume and balance use 27 mm laser-trimmed controls, the remote handles volume and mute, and a mono function works on both line and phono inputs. The optional phono stage uses two 12AX7 valves for MM with 37 dB of gain, while an active MC mode adds a 12AU7 for 52 or 58 dB. A step-up transformer route gives 60 dB, and MC loading is adjustable from 100 ohms to 47 kohm. The circuit board is glass fibre with heavy copper traces, the chassis is 16-gauge steel with aluminium top and sides, and the RCA jacks are gold plated. The finish is silver or black, and the IEC power cord is detachable. The external TP-2.5i phono stage puts the same circuit into a chassis of its own for owners who want a separate unit.

Pairing

The high output voltage and low-impedance output stage suit VTL's ST-85 and ST-150 stereo power amplifiers as well as most valve and solid-state power amplifiers with single-ended inputs. The second pair of RCA outputs allows bi-amping or the addition of a subwoofer. The low gain setting helps with high-output digital sources, and the processor loop brings a surround system in at unity gain.

Alternatives

VTL's TL-5.5 Series II is the larger line preamplifier of the range, with balanced operation.