Dahlquist LP_1 Electronic Crossover

DQ-LP1 ACTIVE/ PASSIVE CROSSOVER

 I am downsizing and simplifying my system and no longer need the LP1.

I have used this crossover for many years, it has been flawless in operation.

The Dahlquist D0-LP1 is a unique line-level crossover which combines an electronic low-pass filter with a completely passive high filter. The LP1 is intended primarily for integrating a subwoofer into an otherwise full range loudspeaker system.  lt may also be used in the bi-amplification of a single loudspeaker system where the crossover point is from 40 to 400Hz. As with other electronic crossovers, the LP1 is connected between the preamplifier and the two power amplifiers; one amplifier feeds the main speaker, the other drives the subwoofer(s).

Please note: The LP1 requires the use of a second power amplifier.

 The active low-pass section, which feeds the subwoofer amplifier, is continuously variable from 40 to 400Hz and provides a cut-off rate of 18dB per octave. This steep slope is achieved through a non-ringing, staggered arrangement of 6-12-18 dB/octave slopes, preserving bass transients. Distortion is exceptionally low, measuring 0.005% THD. 0f particular importance in a device of this type is the performance of the high pass section which feeds the main power amplifier. Any distortion introduced in this stage will noticeably degrade the important middle and upper frequencies.

 In order to avoid such degradation, the high pass section of the LP1 is purely passive.

 Distortion is unmeasurable by normal techniques. lf it were possible to measure the THD of the LP1 ’s high-pass section, we would expect a figure like 0.000001%.  Since the high-pass section is passive, it may be necessary, depending on the desired crossover frequency and the main amplifier’s input impedance, to insert a capacitor or resistor into the terminals provided on the LP1 ’s printed circuit board. We have designed this to be simple enough for the average consumer to do himself-instructions and a kit of resistors and capacitors are provided with each unit-but, of course, the service technician may be called on in some cases.

The high-pass section can be set for any frequency from 40 to 400Hz; its slope is 6dB/octave.

This combination of active and passive circuitry insures the sharp cut-off and "tuneability" required to best integrate a subwoofer into a loudspeaker system, while not degrading main speaker performance. The owner’s manual provides complete instructions for the hook-up and tuning of the LP1, including an easy to use chart showing the appropriate combination of resistors and or capacitors to achieve a variety of crossover points.

Cosmetics are very good considering the age

Original packaging, user’s  manual, brochure, and parts package for modifying passive high filter corner frequency  

Unit has been upgraded:

New upgraded RCA input/output jacks

Additional power supply capacitance

Original stock 4558 IC’s replaced with sockets and OPA2107’s for improved performance allows for additional chip rolling.

Unit is well packed, double boxed ready for shipping, I will include shipping if full price is paid, lower 48 only!