Preamplifiers — TEAC HA-507

The HA-507 is a pure analog headphone amplifier from TEAC that also works as a line preamplifier, and it belongs to the compact Reference 500 Series. Its aluminium chassis is about the size of an A4 sheet, so it fits on a desk as easily as in a rack, and silver and black finishes are both listed.

Key specs that matter

Two XLR inputs (40 kohm, up to 6 Vrms) and two RCA inputs (20 kohm, up to 3 Vrms) feed one XLR output with 50 ohm output impedance and 7 Vrms maximum, plus one RCA output at 100 ohm and 3.5 Vrms. Balanced headphone sockets are a 4-pin XLR and a 4.4 mm Pentaconn, rated at 6,700 mW per channel into 32 ohm, 4,200 mW into 100 ohm, 1,800 mW into 300 ohm and 950 mW into 600 ohm. The 6.3 mm and 3.5 mm jacks give 2,300 mW into 32 ohm and 250 mW into 600 ohm, and loads from 16 to 600 ohm are accepted. Frequency response runs from 10 Hz to 150 kHz (+1/-4 dB), THD+N is 0.0006% and the A-weighted S/N ratio is 110 dB. The unit measures 290 x 84.5 x 243.9 mm, weighs 4.6 kg and draws 30 W.

Engineering and use context

Its topology is dual mono and balanced throughout, using four Class AB amplifier elements first designed for driving speakers. For unbalanced headphones the internal amplifiers switch to an active-ground mode, and gain has high, mid and low settings. Volume is set by TEAC-QVCS Advanced, a ladder resistor network split into four circuits (L+, L-, R+, R-) that moves in 0.25 dB steps and is motorised for the RC-1340 remote. Inputs are selected by FET switches without mechanical contacts, and the TEAC-HCLD 2 buffer drives the line outputs. Audio and control circuits have separate supplies, and the toroidal transformer for audio has left and right windings feeding 18,800 uF per channel through Schottky diodes and discrete low-feedback regulation. The 2.8 mm top plate rests in its slots without screws, the metal Stressless feet give three-point support, and cooling works without a fan.

Pairing

TEAC matches it with the UD-507 DAC, built around the TRDD 5 discrete converter, for a headphone system with separate digital and analog boxes, and with a Reference 500 power amplifier for speakers. A rear switch activates preamp pass-through, so an owner with a separate high-end preamp or an AV surround processor can use the HA-507 purely as a headphone power amplifier while gain and balance stay active. Trigger in and through terminals allow switch-on with other units.

Alternatives

The nearest other TEAC preamplifier is the UD-701N from the Reference 700 series, which combines network streaming and a DAC with its preamplifier stage.