Parasound P/LD 2000
A John Curl-designed, dual-mono line preamp with fully balanced circuitry, packed into a chassis big enough to make you check the shipping weight twice.
Overview
Size is the first thing you notice. The P/LD-2000 measures 19 inches wide, 3½ inches tall, and 15¾ inches deep - 4¼ inches with the feet. That's full rack width, and it looks more like a small power amp than a line stage. Next to a slimline preamp the difference is almost comical. It weighs 19 pounds, which is a lot for a preamplifier. The weight tells you something about what's inside.
The P/LD-2000 was the top model in Parasound's preamplifier line, and the company gave the design to John Curl. Collectors who follow high-end circuit topology know the name. It's a dual-mono design, so the two channels share only a power cord and a power transformer. Everything after that is separate. That kind of architecture usually shows up in far more expensive gear, and it's why the interior is packed so tight. Audio (May 1996, p.50) noted the paradox: the preamp is large for its type, yet its interior is crammed with circuitry. A single board taking up roughly 60 percent of the interior handles the power supply, signal-switching control, and the motor drive for the volume control. The actual signal circuitry lives on two stacked boards that also carry the switching relays and phono connectors.
The input and output complement suits anyone running a mixed balanced/unbalanced system. There are six unbalanced high-level inputs. One is a "Direct" input that can be set for balanced or unbalanced connection with a pair of toggle switches between the jacks. The Direct input, especially in unbalanced mode, takes a shorter and less complicated signal path - Audio (May 1996, p.50) called it the preferred input for the most serious listening. On the output side there's one balanced and two unbalanced outputs. One unbalanced output has fixed polarity, while the other unbalanced output and the balanced connector are switchable. Small diagrams silkscreened near the XLR jacks show pin numbers and signal polarities.
The signal path explains a lot of the measured behavior. Each of the five regular unbalanced inputs passes through its own switching relay. The collected output of those relays feeds one input of the Direct switching relay, whose other input comes from the balanced/unbalanced toggle. From there on, everything is fully balanced, including the volume and balance controls, which is the preferred but not the usual way to handle balanced signals. When an unbalanced source is selected, the negative signal phase is grounded through a 100-ohm resistor. The line amplifier's input stage is a complementary cascode differential circuit using J-FETs and bipolar transistors. It's direct-coupled into a complementary common-emitter second stage, which drives MOS-FET output devices acting as source followers. A three-op-amp-per-channel servo keeps differential DC offset low between phases and to ground. Audio (May 1996, p.50) found the overall parts quality suitably high, with quantities of film bypass capacitors in evidence. It judged construction quality adequate and appropriate but not particularly elegant.
So this is not a jewelry-grade component. The engineering is real, and the fit and finish is workmanlike. Anyone expecting the interior to look like a watch movement at this price will be disappointed.
The supplied remote duplicates every front-panel function except balance. It adds an output-polarity switch that isn't on the front panel at all, plus controls for other Parasound components. Remote volume is handled by a servomotor driving a four-gang Alps potentiometer. An LED on the volume knob shows its position, and it blinks during the power-on delay and whenever muting is engaged. The front panel also carries a headphone jack, a remote-control sensor, and pushbuttons for power, muting, and source selection, with the Direct input set apart from the other five. Audio (May 1996, p.50) found the preamp performed without a hitch except for the remote, which worked poorly in the reviewer's lab but fine in the listening room. It also wished balance had been included on the remote.
## Measurements and Sound
The numbers Audio (May 1996, p.54) measured describe a very quiet, very fast line stage. With unbalanced input and output, gain averaged 20.2 dB across the two channels, for a sensitivity of 48.7 millivolts. Balanced in and out added 0.6 dB of gain. Channel matching was excellent, within 0.1 dB under most conditions. Output noise from 400 Hz to 20 kHz measured 5 to 10 microvolts with the volume full up or down. It rose to 15 to 35 microvolts at the worst-case volume setting. That worked out to an IHF signal-to-noise ratio of 89 dB for balanced in/out or unbalanced in/out, 93 dB for balanced in and unbalanced out, and 86 dB for the reverse. Distortion with balanced input sat down in the noise, 0.001% or less, at output levels up to 1 volt.
Frequency response varied with volume setting, and the fully-up numbers are startling. Rise time was around 200 nanoseconds, corresponding to a bandwidth of some 1.75 MHz under instrument loading. Even at the worst-case volume position, 6 dB down, bandwidth was still about 90 kHz. Low-frequency response was quite extended, with no tilt on 10-Hz square waves. Crosstalk with the volume fully up was −100 dB or better to 20 kHz. At a more typical 20 dB down it degraded, but still beat −80 dB at 20 kHz even in the worst case, unbalanced in and out.
Input impedance at 1 kHz ran slightly higher in the right channel than the left - 57.3 versus 58 kilohms on the balanced Direct inputs, 28 and 29.9 kilohms unbalanced Direct, and 22.5 and 22.9 kilohms at the AUX inputs. Output impedance swung considerably with configuration, from about 150 ohms (balanced in, unbalanced out) to 600 ohms (unbalanced in, balanced out). DC offset stayed under 1 millivolt in the right channel throughout. AC line draw was about 200 milliamperes.
In listening, Audio (May 1996, p.54) described the sound as very alive and detailed, with an excellent sense of recordings' acoustic space. It also noted that some edgy CDs sounded a bit more edgy through it. Vinyl fared particularly well. The overall verdict was a fine combination of performance and versatility, a very good-sounding preamplifier that should appeal especially to those combining balanced and unbalanced connections.
## Living With One
The P/LD-2000's main selling point is its balanced/unbalanced flexibility. Plenty of preamps offer XLR jacks. Far fewer route a genuinely balanced signal path through the volume and balance controls the way this one does, and fewer still let you pick your Direct input's flavor with a toggle. If a system has a balanced source and a stack of unbalanced ones, the P/LD-2000 handles the transition without adapters or compromise.
On a used example, check the parts that age badly on any motorized-pot preamp: the remote, the servomotor and Alps pot assembly, and the relay bank. The remote's flaky behavior in the review lab is a known data point, so test every function before committing. Beyond that, the circuit is straightforward and the parts quality is sound.
The original price was $1,495, so the P/LD-2000 was never cheap. It remains a niche piece on the secondary market, sought by people who know the Curl name and want balanced capability without paying the premium that name usually commands elsewhere.
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