Усилители мощности стерео — Lehmann Audio Stamp

The Stamp is a small stereo power amp built by Lehmannaudio of Cologne, a company better known for headphone amplifiers and phono stages. It shares the narrow footprint of the Linear headphone amplifier, and the maker presents the two as a pre/power combination. Lehmannaudio aims it at owners of small loudspeakers and at second systems, and the later Stamp SE was developed from it. Around 2007 it sold for about EUR 625 to 675.

Key specs that matter

Maximum output is 20 W per channel into 4 ohms. Frequency response is 12 Hz to 20 kHz within 1 dB into 4 ohms, and voltage gain is 20 dB. The chassis measures 110 x 280 x 44 mm and the net weight is 1.9 kg. Buyers can choose chrome, silver aluminium or black aluminium. With 20 dB of gain the amplifier multiplies its input voltage by ten, so a preamp or a player with adjustable output level has to sit ahead of it.

Engineering and use context

Amplification is based on a Tripath TA2020 chipset, a switching design that Tripath marketed as Class T, with proprietary control of the pulse-width modulation. It is fed by an oversized linear power supply. Its toroidal mains transformer, rated at 60 VA, is shielded magnetically and statically, and Vishay reservoir capacitors add up to 15,000 uF. Parts from Nippon Chemi-Con, BC Components and Epcos are used, the double-sided circuit boards carry a 105 um copper layer, and internal audio wiring is solid-core throughout. DIP switches on the underside convert the unit into a monoblock for bi-amping, so a pair of Stamps can power woofers and tweeters on separate channels when the speakers have split terminals. An optional mounting kit fixes the case horizontally or vertically under a desk, on a shelf or on a wall, which keeps it out of sight in a tidy workspace. Mains power enters through an IEC socket on the rear.

Pairing

Lehmannaudio advises loudspeakers with a sensitivity of 87 dB per watt or more. Signal enters through two RCA phono sockets, and loudspeaker cables attach through two pairs of 4 mm sockets rather than binding posts, so thin banana plugs are needed. With a Linear acting as the volume control, the pair forms a compact pre/power setup for a desk or a small system.

Alternatives

The Lehmannaudio Stamp SE keeps the same output rating in a larger, thicker-walled case with Mundorf, ahp and Mogami parts.