I purchased this unit used about 5 years ago for 400.00 USD in order to add stereo subs to my system and control the crossover point. I then replaced all of the capacitors as well as all the RCA connectors at the back, the red power LED & one of the dashpot level control switches on the front. I used it for about two years -- but then replaced my preamp with one that had two main outputs and bought a pair of active subs that were built with a cross-over board matched specifically for my main speakers ( ML CLX and 2 Descent I subs) - so I no longer need this unit to integrate the subs into my two channel system.
The unit works perfectly - and is in fairly good cosmetic condition for it's age ( 40 + years old) -- I will include numerous pdf copies outlining the rebuilding process and the usage instructions. You can do some research on line and you will find that this was a well respected piece of gear in its day -- and still is. A simple capacitor change is required based on the impedance of your pre-amp ( a 5 minute job -- explained well in the provided paperwork. I can e-mail the manual to anyone interested in more detail -- just let me know.
The Dahlquist DQ-LP1 is a unique line-level crossover which combines an electronic Low-Pass filter with a passive High-Pass filter.
The LP1 is intended primarily for integrating a subwoofer (or two) into an otherwise full range loudspeaker system. It may also be used to bi-amplify a single loudspeaker system where the crossover point is tunable from 40 to 400 Hz.
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).
The active Low-Pass section, which feeds the subwoofer amplifier, is continuously variable from 40 to 400 Hz 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.
Of 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 6db/octave High-Pass section of the LP1 is purely passive and can be set for any desired crossover frequency by inserting a capacitor and/or resistor into the terminals provided on the LP1's printed circuit board.
The front panel frequency control does not effect the High-Pass frequency. Push-button switch S1 allows complete passive defeat of the High-Pass section and muting of the low frequency section to instantly restore the system to single amplifier operation.
This combination of active and passive circuitry insures the sharp cut-off and tuneability required to best integrate a subwoofer with a loudspeaker. The Owner's manual provides instructions for the hook-up and tuning of the LP1, including an easy to use chart showing the appropriate combination of resistors &/or capacitors to achieve a variety of crossover points. Now you can.
Based on the price I paid for this -- and the time and money I spent refurbishing it -- $400.00 Canadian is a firm & fair price. I've been reluctant to sell it because of the work I put into it -- but I doubt I will ever need it again -- so it's just gathering dust
Shipping costs and PayPal fees at buyers expense. Located in Etobicoke ------ sorry -- but the unit is not hooked up in order to demo it -- but I guarantee it is in good working condition.
Copies of info gleaned from the web -- as well as schematics & a parts list used when rebuilding the unit --- Sorry no original packaging or literature