Spin Doctor

The AFI FLAT.DUO Record Flattener And Vinyl Relaxer
Even if it's not severe enough to make your needle skip, a warped record creates all kinds of havoc for your cartridge and system. As the cartridge rises and falls like a roller coaster, the inertia of the arm causes the tracking force to rise and fall dramatically. This gives the cartridge's suspension a workout, crushing the stylus and cantilever upwards as it goes up the warp, stretching it out as it goes down the other side. In addition, this flexing of the cartridge's suspension creates big changes in the stylus rake angle, and there's a phenomenon called peak warp wow, in which warp-induced variations in the VTA result in unstable pitch. Cantilever deflections can also send ultralow-frequency signals to the rest of the system, sapping your amplifier's power and causing your woofers to pump in and out. So even if your cartridge is still able to negotiate the warps, the defects in the sound are easily heard. Bottom line: Warp-free records are best.

Dr. Ullrich Kathe is a passionate German audiophile who recognized the problems I just described and how they affect vinyl-playback performance. After many discussions on the topic with his dealer, HiFi-Studio Wittmann in Stuttgart, they joined forces to create a solution: the AFI FLAT. DUO made by Audio Fidelity Improvement (footnote 3). During two years of development and a long procession of prototypes, they discovered an interesting thing: While the flatness of the record is critical, the flattening process has an additional sonic benefit, which Kathe describes as tempering the vinyl.

At first, I thought the name FLAT.DUO referred to the machine's dual processes, but that's wrong. The FLAT.DUO adds the ability to process two records at once, stacked one above the other with an intermediate disc separating them.

When a new record is being pressed, the hot vinyl is cooled rapidly so that it can be removed from the press to make way for the next copy. Kathe feels that this rapid cooling locks in the molecular structure of the vinyl in a way he describes as "stressed"; slower cooling would result in a more relaxed vinyl structure that is harder and more consistent across the record side.

The flattening process heats the record to a point where it becomes semi-elastic, followed by a slower cooling process that allows the vinyl to harden in a less stressed fashion. A similar tempering process is routinely used to improve the hardness and durability of steel and other metals, so why not vinyl?

Once he hit upon the benefits of tempering, Kathe worked to separate the flattening and tempering processes, developing ideal heating and cooling parameters for each. The FLAT.DUO lets you choose whether you want to flatten or temper a record, with a program designed to handle each process. There is a third program for flattening shellac 78s; I'm pretty sure this is the first record flattener to offer this option.

In person, the FLAT.DUO has a somewhat funky appearance, with textured soft-touch surfaces that remind me of a fancy foam cooler. It's clearly well made, but it lacks the sleek shiny black surfaces and aluminum hardware of AFI's earlier models.

While Kathe developed ideal, default programs for both processes, AFI says that the settings may be different for especially thick or thin records. A menu system lets you adjust details including the target temperature, how long to hold the record at that temperature, and how fast the record cools. I mostly used the default program, with good results over a variety of pressing types.

Searching through my thousands of records for badly warped ones proved a bit frustrating, as it turns out most of my records are pretty flat. But my copy of Promises by Floating Points with Pharoah Sanders (Luaka Bop 6 80899 0097-1-3) was pretty wavy. One cycle through the FLAT.DUO made it mirror flat. I achieved similar results with several other records, then I went looking for something more challenging before attempting the ultimate challenge, my half-speed-mastered Elvis Costello.

Eventually I came across a 1970s pressing of Chicago Transit Authority with a very severe edge warp. It wasn't just unplayable; it was too severely warped to work in any of the fancy cleaning machines I have on hand. I was able to squeeze it into my Spin Clean, so I carefully washed and dried it before putting it in the FLAT. DUO. After two standard cycles, there appeared to be little or no improvement, so I raised the temperature a bit and doubled the heating interval. After two more cycles, the warp just wasn't going away. So for now I've concluded that while the FLAT.DUO does a great job with most warped records, it can't perform miracles. I'm going to keep trying with higher and higher temperatures and see what happens—what have I got to lose? I will hold off trying to flatten the Elvis Costello half-speed until I learn more about the FLAT.DUO's limits.

To help me test the relaxation function, AFI importer Musical Surroundings included two sealed, identical Clearaudio pressings of Anne-Sophie Mutter's recording of the Beethoven violin concerto with Herbert von Karajan and the Berlin Philharmonic (Deutsche Grammophon 2351 250). Out of the shrink wrap, these 180gm records were both flat as pancakes, so I was able to relax one then compare it directly to the untreated version. Before I did any of that, I listened carefully to both to ensure that they sounded the same. Then I fired up the FLAT. DUO in relax mode. This setting heats the record to a lower target temperature but holds it there for longer before cooling it very gradually, giving the vinyl ample time to come back to room temperature evenly. The process takes about four hours, but as with the flattening mode, once started, the machine requires no user input and shuts itself off when finished. As instructed, I cleaned each record carefully before relaxing or flattening.

Saying you're going to relax my record is the type of thing that would normally get my BS detector flashing, but at the end of the day, you just have to listen. After relaxing, it was clear that something had happened to the treated disc. The focus and coherence was a tad improved, and the lower strings had a bit more body and weight. It was similar to the improvement you get when your cartridge's stylus rake angle is perfectly dialed in: subtle but unmistakable. Switching back to the untreated record to confirm made the changes easier to pinpoint.

I must admit that I'm a bit baffled as to why this was happening. I proceeded to relax a few more records, but with the process lasting over four hours, it's hard to do a direct comparison unless you start with two identical records.

At $2500, the AFI FLAT.DUO is a pricey way to fix a problem that should never exist in the first place. But when you add in the sonic benefits of the relax function, its cost is easier to justify. Get together with your audiophile friends and share the expense. In the meantime, I'm going to continue trying to get that Chicago record ruler flat.

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Footnote 3: Audio Fidelity Improvement, HiFi-Studio Wittmann Brucknerstraße 17 70195 Stuttgart (Botnang) Germany Tel: +49 711 69 67 74. Email: kontakt@wittmann-hifi.de. Web: wittmann-hifi.de. US importer: Musical Surroundings, 5662 Shattuck Ave., Oakland, CA 94609. Tel: (510) 547-5006. Web: musicalsurroundings.com.