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NuForce MCP-18 Multichannel Analog Preamplifier

Back in the mid-Nineties, I was still in the throes of home-theater madness and wrote: “Very soon, stereo will be only an output setting on your multichannel system.” Obviously, I was wrong. But many audiophiles do require a system that can serve for both home-theater multichannel playback and two-channel music. The majority of dual-system buyers opt for a digitally enabled multichannel receiver or preamp/processor, but some would prefer a more analog way to reproduce their analog sources than a digital preamp. NuForce has a solution: the MCP-18 multichannel analog preamp. It was designed to handle both multi-and two-channel analog sources in the most sonically unobtrusive manner possible. It is basically a source-selector and gain-adjustment device whose signal path has been optimized to obtain maximum transparency and minimum coloration. Priced at $995, the MCP-18 offers audiophiles a budget high-sound-quality alternative to multichannel digital pre/pros, while still retaining a system’s multichannel capabilities.

Technology and Ergonomics
The MCP-18 looks very much like NuForce’s companion model, the AVP-18 A/V processor. Both have a rhomboid-shaped front panel whose sides and top slant inward. For front-panel controls, the MCP-18 has two good-sized knobs on either side of a centrally located LED display panel. The MCP-18 has two sets of single-ended RCA 7.1 inputs, one pair of two-channel balanced XLR inputs, and two pairs of two-channel single-ended RCA stereo inputs. Outputs for the MCP-18 include one set of 7.1 single-ended RCA and one set of 7.1 balanced XLR connections. Both sets of outputs are simultaneously active.

Although the MCP-18 supports 7.1 channels, the main right and left front channels have a slightly different signal path than the rear, side, center, and subwoofer channels. According to NuForce’s Casey Ng, “What we wanted to do with the MCP-18 was to have it first and foremost serve as a superb two-channel preamp. We borrowed heavily from our P20 and HAP-100 designs. The front left and right channels use a digitally controlled, discrete-resistor-ladder circuit. This uniquely implemented resistor ladder is in the feedback loop of the high-performance op-amp circuit so as to have minimal impact on the signal chain.”

All of the MCP-18’s channels use silver contact relays for input selection to maintain signal integrity, but only the front two channels employ a resistor-ladder volume control. The other six channels use a combination monolithic switch/input selector and AGC (Automatic Gain Control) volume control. After the volume controls and linestage section, the signal goes through a single-ended-to-balanced conversion circuit (a phase-splitter) that generates the balanced signal.

When I asked Casey Ng about the MCP-18’s circuitry, he told me: “Basically, there is no ‘secret sauce’ in the MCP-18. The only secret is that our NuForce HAP-100 and MCP-18 are the world’s lowest-cost high-performance preamps that offer a stepped attenuator. Our own P20 is $5k and was originally intended to be the best-priced high-end preamp with a stepped attenuator. The MCP-18 has a very similar circuit and performance.”

The individual output level or trim of each channel of the MCP-18 can be adjusted independently via either its front panel or a credit-card-sized remote. The MCP-18 remote can also select inputs, adjust the overall volume, mute the signal, and turn the MCP-18 on and off. One control you won’t find on the remote is a left/right channel balance adjustment, but you can use the individual trim settings to achieve the same results.

The Setup
I used the MCP-18 as both a two-channel and multichannel preamp in my desktop and in my room-based systems. Depending on your front speakers’ capabilities, the MCP-18’s “purist” design and ergonomics may require some re-jiggering of your setup. Obviously, the MCP-18 was designed for use in a 5.1 or 7.1 multichannel system. If you have a player with multichannel analog outputs, such as the Oppo BDP-103, you merely hook up its outputs to one of the MCP-18’s two multichannel input sets, select it, and you get 5.1 or 7.1 (depending on your system’s capabilities).

 

With multichannel sources your source device will use its own built-in crossover system to send low-frequency information to the subwoofer and spare the front channels from low-bass duties. With two-channel sources, the MCP-18 gives you two channels of output. But what if you have a system that uses smaller front right and left speakers with limited low-frequency capabilities? With two-channel stereo sources, the MCP-18 sends the full frequency signal to your two front channels without any crossover to route bass into your subwoofers.

If you want to use your subwoofer with two-channel material you will have to do some extra work. You will need to set up a way to route your two-channel music through a crossover so that the bass will go to the subwoofer. Most subwoofers have low-pass/ high-pass crossovers built into them that you could use—merely run the line-level output from the MCP-18 into your subwoofer and then use its built-in crossover. But the disadvantage of this arrangement is that when you go to a multichannel source that already has crossed-over low frequencies to a .1 subwoofer circuit, the sound will have too much bass. To go from multichannel to two-channel and back requires changing the circuit path if you want to use your subwoofers for both two-channel and multichannel material.

Many subwoofers have multiple selectable inputs. This allows you to have one input coming from the MCP-18’s sub output as well as a second input—a stereo pair coming from the MCP-18’s front left and right output, connected simultaneously to your subwoofer. The front left and right stereo feed will go through the subwoofer’s internal crossover and then to your power amplifier. When you want to listen to two-channel sources you’ll employ the subwoofer’s crossover. But when you listen to multichannel sources you’ll go directly from the sub output to your subwoofer. To accomplish this you will need to disconnect the stereo feeds from the subwoofer and connect them directly to your front-channel power amplifier. Depending on the physical location of your subwoofer and front-channel power amplifier, the switchover could be less than convenient.

I have two Parasound P7 ($1995) multichannel analog preamps, one in each of my two room-based systems. The Parasound P7 has very similar functionality to the NuForce MCP-18, but includes a built-in crossover for two-channel sources so that you can go seamlessly from two channels to multichannel, using your subwoofer with both kinds of sources. From an ergonomic perspective, it’s unfortunate that NuForce chose not to include a similar crossover scheme in the MCP-18.

When I set up the MCP-18 as a stereo preamplifier in my computer-audio system I used a different wiring arrangement. Since I didn’t have to worry about multichannel sources I connected the balanced XLR front left and right outputs directly to my front-channel amplifier and then connected the single-ended stereo outputs to my subwoofer. After adjusting the subwoofer’s output and crossover points, the setup was done and required no additional adjustments or cable switching.

Sound
Reviewing the sound of a preamp used to be easy. All you needed was another reference preamp that had a tape-loop circuit in it. We used to put the preamp under review in the tape loop and then switch it in and out of the circuit and compare the sound. The only preamp that I own that still has a tape loop circuit is an Accuphase C-200, and when I tried the tape-loop test I could not hear any difference when the MCP-18 was part of the circuit. Although the Accuphase was recently refurbished and operating within spec, either the MCP-18 was completely transparent or the Accuphase was not sufficiently high resolution for me to discern the differences when the MCP-18 was in the circuit. I needed to go to plan B.

Plan B was simple—connect more than one USB DAC via its analog outputs to the MCP-18 and compare the sound. Since my next review will be of several small-footprint USB DACs, this method killed two reviews with one “Stone,” so to speak. I connected several DACs to the MCP-18 and began listening.

 

Comparing DACs through the MCP-18 was enlightening in several ways. First I quickly learned to love the calibrated .5 dB step increments on the MCP-18. Using test tones I was able to accurately match the output levels on multiple DACs so that when I switched from one to the other I could make sure that differences in their different output levels were not affecting what I heard.

Although I could not do instant A/B switching from one USB DAC to another because the switchover required first changing the MIDI Out setting in my Mac computer, then changing the input selector on the MCP-18, and finally adjusting the output levels to match, I did get to a point where the switchover took under seven seconds. During these A/B tests it became obvious that the MCP-18 was sufficiently transparent for the subtle differences between DACs to be discernable.

During my DAC comparisons I discovered that it was very difficult for me to uncover the MCP-18’s intrinsic sound. When I changed DAC sources what I heard was the new DAC, not any colorations that I could attribute to the MCP-18. While I would never be so brash as to call any component completely transparent and neutral, in all my listening time with the MCP-18 I could not come up with any negative sonic characteristic that I could say was part of the MCP-18’s fundamental sound.

While I would not dispute that different preamps in different systems can sound better or worse than in others, in both of my room-based systems I was hard-pressed to find any noticeable differences between the sound of the MCP-18 and the Parasound P7 on multichannel sources. On two-channel sources I did hear some differences at first, but after readjusting my subwoofer settings so output levels were identical, the differences vanished. Both preamps produced equally large soundstages with the same amount of detail, dynamic range, and depth information.

Conclusion
If you are in the market for a multichannel analog preamp, you should consider the MCP-18, regardless of how much more money you were prepared to spend. It looks good, sounds virtually invisible, and even has a remote, all for under $1000. The MCP-18’s only drawback is that it has no built-in crossover for two-channel sources, but if you have full-range front left and right speakers this may not be an issue for you.

While I still subscribe to the opinion that no active preamp can be as transparent as no preamp at all, the MCP-18 is one of the most transparent preamps I’ve heard. It is also the least expensive preamp I’ve reviewed that has such a high degree of transparency. According to NuForce’s head honcho, Jason Lim, “Basically, the MCP-18 is a hidden gem in our products and on hindsight we grossly mispriced it.” NuForce’s “loss” could be your gain.

SPECS & PRICING

Inputs: Two RCA, one XLR, two 8-channel RCA
Outputs: RCA and XLR (XLR output is balanced)
Connectivity: RS232 Com Port: X 1;Trigger out: X 1
THD+N: 0.002% at 1kHz
S/N Ratio: 105dB
Frequency response: 10Hz–100kHz -0.06dB; 20Hz-20kHz-0.04dB
Dimensions: 17″ x 3.1″ x 13.4″
Power Consumption: 1W standby, 10W operating
Weight: 15 lbs.
Price: $995

NUFORCE INC.
47865 Fremont Blvd
Fremont CA, 94538
(219) 363-1328
NuForce.com

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