Spin Doctor #4: Platter Mats, Clamps, Weights & the Timerette

The next time you’re preparing to play a record, try doing a little experiment. Once you have the record mounted and spinning but before you lower the stylus into the groove, lower your gaze to just below record level and look for a gap between the platter and the record. It helps if there’s a light source or a brightly colored wall behind the platter. You may discover a gap—that very little of the record’s playing area is making true contact with the platter mat or (if there is no mat) the platter. Another way to test this is to take a record you don’t care much about, put it on the platter, then tap with your finger in the groove area listening for a click as your finger pushes the record down and it contacts the platter surface.

Warps obviously lead to such problems, but even records that appear flat make scant contact with the supporting surface. Turntable and aftermarket accessory designers have recognized this problem for decades.

Up until the mid-1970s, most platters had built-in mats that supported the record on ribs or rings, and while they didn’t make contact over a large area, at least they made contact points more predictable. This thinking has come back recently, with limited-contact mats like the Ringmat, Hexmat, and Music Hall Cork Mat, all of which support the record over small areas.

The product that took this thinking to its ultimate extent was the rare Meitner AT-2 platterless turntable from about 30 years ago (above), which clamped the record at the label and provided no support at all under the playing area. Designer Ed Meitner believes that air is the best interface because it doesn’t reflect time-smeared energy back into the record.

When the AT-2 was new, I worked at a retail store that had one on demonstration. The main thing I recall was its uncanny ability to take a seemingly flat record and make it look like a giant Pringle spinning around. The arm would have to work pretty hard to keep the cartridge seated in the groove of the undulating record, wobbling up and down in the air.

By the late ’70s, we started to see thicker and smoother rubber mats, from companies including Technics, Luxman, and Thorens. The first real attempts to create a more intimate bond between the record and the platter also arrived in the late 1970s, with the J. A. Michell record clamp, VPI’s HW-1 record weight, and the Oracle Delphi: the first turntable sold with a built-in clamping system. These products were designed to press the record against the platter, an approach that remains popular. A couple of years later, in 1980, Luxman introduced the PD-555, a turntable that pulled the record onto the platter using vacuum suction, an idea borrowed from professional cutting lathes used to cut record lacquers. Audio Technica offered an accessory mat called the AT666, which allowed you to add a vacuum hold-down mechanism to almost any turntable.

Clamps vs weights

People tend to lump clamps and weights together, but they function differently. Most clamps are designed as an integral part of the turntable platter, with a threaded spindle onto which you screw down the matching clamp. Most clamping systems employ a small lift washer, which surrounds the spindle under the record, holding the record slightly above the platter so that the clamp, which presses down beyond the washer’s circumference, forces the playing surface down into the platter.

This flexing action results in much more intimate contact than just placing the record on the platter, but it’s not without pitfalls. Many platter surfaces have a shallow recess in the area where the record label sits, which helps accommodate records’ extra thickness in the label area. But that thickness can vary a lot from record to record. With thinner records, over-tightening the clamp can press the label too far into the recess, causing the rest of the record to flex back up over the playing area. You can use the gap test I described at the start of this article to decide how much to tighten the clamp to maximize groove-platter contact.

While most clamps are part of a system, with a threaded platter spindle, a few can work on almost any turntable. Designed by Lou Souther, who created the first purely mechanical linear-tracking tonearm, the Clearaudio Clever Clamp (pictured above) is one of my favorites because it is so simple and weighs next to nothing. It’s a molded, clear-plastic dish that looks a bit like an ashtray stolen from a 1970s McDonald’s, but with a hole in the middle that grips the spindle tightly when you push it on. I find it great for occasional use with dish warps on turntables you wouldn’t normally use a clamp with. The Record Doctor clamp is similar except it uses a screw-down collet to grip the spindle. Finally, there’s the current version of the original Michell Record Clamp, the only universal clamp I’m aware of that includes a lift washer so that it can do that flexing trick to help flatten records.

In contrast to most clamps, record weights are quite universal, and hundreds of designs exist. Weights can improve things in two ways, first by pressing the record down onto the platter so it makes better contact and reduces some types of warps, and second by dampening resonances in the vinyl. Some weights, such as the Stillpoints Ultra HDI V2 and the HRS ADL and ADH, incorporate sophisticated damping technology said to minimize record vibrations.

Taking things to the edge

An additional category of record flattener is the periphery ring, a heavy steel ring that hangs off the outer edge of the record, holding down the record by its rim. VPI’s Periphery Ring Clamp and Clearaudio’s Outer Limit are good examples. Both should be used with a center weight. If used properly, the set will provide the most intimate record-to-mat interface achievable without a vacuum platter.

Periphery rings, though, make me nervous. I don’t like having a hard-metal surface so close to where I drop the needle at the start of the record side. I also find them a pain to deal with when it’s time to switch to a new record. I’ve seen a couple of people hang the ring around their necks while making a record change.

The myth of record slippage

When people ask what weights and clamps are for, some reply that they keep the record from slipping. Those people are wrong: That isn’t something that actually happens. Consider: Hip-hop scratch DJs often use a hard felt mat called a slipmat to perform their craft, but even with a slipmat, there’s only slippage when they put their hand on the record. When they remove their hand, the music resumes, playing almost instantly, at the correct speed.

To be sure, I put the slippage theory to the test. I put a record on my Brinkmann turntable with its lift washer and clamp removed. The record was sitting on the slick glass platter surface with no hold down. I marked the edge of both the platter and record with small pieces of tape so that any relative movement would be easy to see. Even after I played the side five times, there was zero shift in the relative positions of the platter and the record. None.

More considerations

Another thing I sometimes hear is that adding a weight or clamp causes premature wear of the platter bearing. Theoretically, that could happen, but it’s important to consider how much weight is being added relative to the weight of the platter itself. Most weights and (especially) clamps weigh just a few ounces, against a bearing designed to support several pounds of platter. Maybe it’s a good idea to avoid using a weight that adds 1lb of extra mass to the platter of a cheap turntable, but in most cases it shouldn’t be a problem.

An important exception is relatively lightweight, soft-suspended designs like the Linn; adding weight likely will affect the tuning of the suspension, requiring an adjustment to the springs to compensate so that the suspension doesn’t bottom out. Many Linnies would howl at the suggestion of adding a weight or clamp to the LP12—but recently Tangerine Audio, an “approved” Linn aftermarket supplier, introduced the Evenstar, which they describe as a “stabilizer.” That description doesn’t make much sense to me because a record is already quite stable just sitting there on the platter. A more accurate word would be “damper” or “coupler.”

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