Предусилители — Karan Acoustics Master Collection LINEa

The Master Collection LINEa is a two-box line preamplifier from Karan Acoustics of Serbia, and it was the first model presented in the Master Collection range. Milan Karan moved the power supply circuitry into a separate case, called the PSUa, to bring noise below the level reached by the one-box LINEb. The design reflects some 30 years of his amplifier work, and Karan guarantees it for five years.

Key specs that matter

The LINEa offers six line inputs - four on XLR and two on RCA - each at 30 kOhm, and two balanced XLR outputs with an output impedance of 90 ohm. Gain is switchable between 6 dB and 9 dB. Nominal output is 1.55 V RMS, and the maximum reaches 18.0 V RMS balanced into a 600 ohm load. The input accepts up to 5.4 V RMS at the 6 dB setting or 3.6 V RMS at 9 dB. Response is flat from 20 Hz to 20 kHz and extends from 1.5 Hz to 3 MHz at minus 3 dB. THD and IMD are both 0.003% at full output, and noise lies more than 120 dB down unweighted. Karan quotes a rise and settling time under 450 ns and a slew rate of 1,500 V per microsecond. Each box measures 504 x 126 x 390 mm, the control unit weighs 16.2 kg and the supply 17.1 kg. Power draw peaks at 60 W on 115 V or 230 V mains, with a tolerance of 10%.

Engineering and use context

The circuits are DC coupled and very fast, and Karan states that they introduce no phase shift or timing error across the audio band. Volume is handled by a fully balanced attenuator built four times over, switched by ultra fast relays and using custom non-magnetic resistors held to 0.1% tolerance. The printed circuit boards use a special insulating base material with copper traces 75 um thick. The preamplifier units stand on Critical Mass Systems CS2 1.0 isolation feet, the same family of support used across the Master Collection.

Pairing

The two balanced outputs make it simple to drive a pair of monoblocks or to bi-amplify with two stereo amplifiers. Karan's POWERb MONO, POWERb STEREO and POWERa models share the same chassis width. Sources with high output levels are best used with the lower gain setting, since it raises the input overload point, while the higher setting helps sources with lower output. The two chassis together need two full-width shelves, and the connection between them should be kept tidy and short.

Alternatives

The Master Collection LINEb is the one-box preamplifier in the same range, keeping its power supply inside the main chassis rather than in a separate unit.