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Sytek MPX-4Aii: The four-channel mic preamp that gets 'Respek'By Art Douglas, updated October 28, 2002
Recently, a local church asked me if I would be able to record a few Classical music concerts for them. I was happy to accept the challenge. However, I realized that I would have to upgrade my signal chain, especially my microphone preamps. I normally used a small outboard mixer for recording Rock music but knew it would be too noisy to track Classical music.
I did not know much about mic preamps, so I spent some time talking to recording engineers. They suggested the following characteristics: Low noise, neutral, and transparent. I quickly compiled a list of four recommendations. Two of the preamps sold for $500, and I auditioned them locally through two different music retailers. Although both of these units were better than my mixer preamps, I could easily hear sonic flaws in them and I did not find them to be neutral.
![]() At a friend's studio, I heard an Earthworks Lab 102. I found the sound impressive and it met all my criteria. However, it exceeded my planned budget. Finally, someone suggested the Sytek MPX-4Aii preamp, which I had never heard of before. I researched these and found that Steve Albini recommended them. The MPX-4Aii is a four-channel, single rack space unit with a solid state transformerless class A discrete input. The manufacturer offers different configurations including optional Burr-Brown ICs on two of the channels, for “silky-smooth” sound, according to the sales literature. The listed specs are +75 dB gain, noise -96dBm, 0.0015% THD at 65dB gain, and a bandwidth of 10 Hz to 85 kHz +/-0.25 dB. The front panel controls appear minimalist but straight forward, all black buttons, knobs, and lettering, on a brushed aluminum face plate. Each of the four channels has a gain knob, marked from 1 to 9, a peak led, and three buttons for mute, phase, and +48v phantom power. The only other control is an led illuminated rocker switch for power, on the far right side. I contacted Mike Stoica, the designer of the preamp and owner of Sytek. He told me that the Chicago, Houston and Seattle symphony orchestras owned the MPX-4Aii as well as Steve Albini and Aerosmith. And, they were paying customers. So, I placed my order for an MPX-4Aii with the optional Burr-Brown ICs on channels three and four. Unpacking the shipping box, I found the MPX-4Aii felt hefty and solid. The back panel contains only a male and female XLR connector for each channel, and an IEC power cord connector with an integrated fuse holder. On the front, the gain knobs feature stepped potentiometers, which also felt smooth, but sturdy. I counted 40 individual clicks. I patched the unit into my DAW, and was immediately pleased. By just talking into a dynamic mic and adjusting the gain control, I could hear that the unit was dead quiet, and there was headroom to spare. I found the signal clarity to be exceptional. Switching over to a Burr-Brown channel, I discovered a richness that it added to my voice. I excitedly called my friend at his studio to tell him what I had just heard. He asked if I could bring the preamp over, so he could hear it for himself, and compare it against his Earthworks Lab 102. I went right over, and we set up some mics, to recorded a series of tests with both preamps, using the acoustic guitar, a bass amp, a flute, a saxophone, our singing voices, and a crash cymbal. The results seemed to be a toss-up. The Earthworks seemed fuller on the lower midrange and bass. The Sytek possessed a more pleasing smoothness on the high frequency content. Our preferences bounced back and forth depending on the source material we used. Both units sounded very good.
After owning the Sytek for a few months, I consider it a joy to own. I think of the sound of the standard channels as quiet, transparent, clear, and ultra fast. The top end is exceptionally smooth, with no solid-state brittleness at all. I never seem to run out of headroom. The Burr-Brown channels share all of the same sonic advantages, but add a darker thicker flavor. Initially, I did not find many musical uses for the Burr-Brown channels besides vocals. However, I found that large condenser mics pair nicely with the Burr-Brown channels on a variety of sources. I've talked to other Sytek owners online. And, yes, we have some minor complaints. I would like to have a low cut filter on my preamp, since not all of my microphones have this. Some people would like to see an input attenuator pad, and it has also been noted that even when the gain is set all the way down, the unit is still passing signal at +12 dB of gain. This does not bother me, since there is also a mute button. A calibrated gain knob would also be nice, instead of being marked 1 through 9. However, no one complains about the sound quality. My friend who hosted the preamp test in his studio bought two units for himself. One other sticking point: My unit did not come with an audition. I see no possibility of someone buying this preamp and not wanting it. However, a reasonable return policy would be nice. Mike Stoica seemed more than happy to respond to any of my email questions. You can order the Sytek preamps directly through him. Sometimes, he sells dealer returns on Ebay, which is where I bought my MPX-4Aii. The Bottom Line: Approximately $200 per channel, exceptional sound, lots of headroom. Recommended. Editor's note: For a time, the Burr-Brown option was replaced with the National Semiconductor LF357. Mojo Pie never could obtain a unit with the LF357 for evaluation. Note that the Burr-Brown option is available again as of July 2003. The new Burr-Brown option (not the same chip) may not impart the silky sound or richness discussed in this review. Link relating to this review: Sytek Audio Systems
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