Pulsar Modular's P821 MDN Tape is a remarkable sounding approximation of the Stephens 821B tape machine. Let me be clear; this is not another they-got-the-rights-to-sell-a-tape-machine-so-they-did-a-pretty-GUI-on-top-of-a-cookbook-EQ-with-variable-delay-some-hiss-plus-distortion-plug-in. This release is worthy of its heritage.
A man of remarkable technical aptitude, John Stephens [Tape Op #54] spent part of his career working at NASA's Jet Propulsion Laboratory [JPL]. Many requirements in the space and military fields necessitated the invention of brand-new technologies. He would later use his experiences questioning groupthink and even the assumptions of physics as he developed his products. The result was that Stephens' tape machines were as unique as they were rare. From the tape path, transport alignment, power supply, tape tension, and input/output, just about everything going on in a Stephens machine broke accepted conventions. Consequently, a high-level understanding of these differences matters to get the most out of this plug-in. I became interested in Stephens' designs when I bought a 3M Series 79 16-track. Instead of navigating a gauntlet of guides, rollers, and tension sensors found on a Studer, Ampex, or MCI, 3M used only two rollers. Another studio owner said it looked like a Stephens. I knew he was talking about a machine responsible for Pink Floyd's The Wall, Steely Dan's Aja, and many other classic albums. Artists such as The Grateful Dead, The Cars, and Fleetwood Mac recorded on these and often purchased their own. But I didn't know much about the why. While both 3M and Stephens valued a low torque, simplified tape path, they soon diverged on just about everything. After modifying Series 79 machines for a few years, Stephens realized the only way to improve major systems was to start from scratch. The resulting breakthroughs directly impacted the sonics of his machines and, in turn, the Pulsar Modular's plug-in.
So, what were some of the main differences, and why did it matter to the sound? Removing the gauntlet of guides and rollers reduced tension so much that heads lasted significantly longer. Stephens also ensured that tape passed over the heads totally square and ruler flat, taking head wrap concerns out of the equation. Once aligned at the factory, the head assemblies stay in place, removing the need to adjust azimuth and zenith in the field. His first crystal-based timing circuit was superior to standard designs (later, he would shift to a gear solution that made the finest Swiss watchmakers smile). These choices led to another astonishing benefit: Almost no wow and flutter (0.03% average, worst case 0.05%). Stephens removed all transformers and/or tubes, opting for a clean I/O. His power supply, with positive ground, increased signal to noise. Meanwhile, the simplified circuits (many not listed here), lower torque demands, and minimal I/O significantly reduced overall power consumption. That translated to less heat and less operating noise. The Stephens ran so quietly that some studios kept them in the control room rather than a distant machine closet.
Many of those advantages matter if you happen to own a machine, but how does it affect a plug-in? It makes the tape choice more significant. Counting cassette variants and freeware, I own over 22 “tape” plug-ins. With many of them, settings like bias and even tape formula have negligible or minor impacts on the sound. Some simply apply a different EQ curve to the signal and call it a day. However, changing tape stocks is very noticeable with the Pulsar Modular P821 MDN Tape. Other than with my Ampex ATR using the Merrill Audio Pure Tape Head Preamp, this plug-in is one of the only times I've really appreciated tape itself, or at least to this degree. The P821 MDN Tape has two formulas, 456 (gold reel) and 900 (blue), and can run at 15 or 30 IPS. And remember what I said about bias? Don't ignore it here, where under and overbiasing opens up a way to manipulate transient and high and low frequency response. Maybe Pulsar Modular will include additional tape stocks in the future, but don't worry; these two cover vast sonic territory, especially if you're willing to tweak a little.