In the August/September issue we provided an introduction to do-it-yourself (DIY) audio and touched upon several DIY ideas - one of them being system tweaks. In this issue we well take a closer look at some simple and common system tweaks that can be applied to your analog setup. When it comes to turntables there are several accessories and tweaks that can be applied, some of which can be inexpensive to implement and yet can provide startling improvements. Tweaks are not just for high-end systems and often it is entry and mid-level rigs that can benefit the most. Most turntable tweaks are focused around mechanical isolation, damping and vibration. A turntable wall bracket is a good example. The idea is that the turntable is placed on a wall mounted support to improve isolation from the floor and unwanted vibrations such as those produced by speakers which are coupled to the floor. Both Rega and Pro-Ject produce turntable wall-mounts and a DIY version can be as simple as brackets and shelving. Turntable isolation platforms are another example. A simple DIY mass-loaded turntable isolation platform can consist of a heavy wooden cutting board resting on split racquet balls or isolation feet like the Vibrapod Isolation Devices that you can find at an online store like partsconnexion.com. But perhaps the most common (and simple) turntable tweak is a record clamp and there are several to choose from. Like Hi-Fi audio components, record clamps can range widely in quality and price - the $30 Pro-Ject Record Clamp and the $1500 Harmonix TU-812 MKII Record Clamp are just two examples. This article will provide and overview of record clamps and instructions on how you can build a simple record clamp using a hockey puck so you can try one out for yourself at little to no cost.
A record clamp is a device used to improve the contact between the record and the turntable mat. This is typically accomplished through the use of a weight placed on the record. There are three basic types of record clamps. Threaded clamps screw onto threaded spindles and the applied force can be adjusted by tightening the clamp. Collet style clamps also allow you at adjust the applied force by pushing down on the clamp and turning a knob to grab onto the spindle. The most common type of record clamp is a round weight which slides over an unthreaded spindle. In addition to providing a better record to platter interface and reducing unwanted vibrations and resonances, record clamps can help flatten some minor warps or bowing of the record which helps maintain proper tracking. It is fairly evident that the main variable for record clamps is weight and this likely has you asking what is the optimum weight of a record clamp? The optimum weight will depend on several factors but primarily the sub-chassis of the turntable. For turntables that are spring-loaded, too much weight may interfere with the proper functioning of the springs and alter the resonance of the design. A larger weight can be used for heavier turntables, but before you reach for a heavy record clamp keep in mind that the additional weight will be transferred to the bearing which could result in increased wear on the bearing. Now I realize that does not answer the question about the optimum weight and that brings us to the first requirement for this DIY record clamp - patience. A hockey puck was chosen for a number of reasons, they are commonly available, inexpensive, easy to work with and light enough that it can likely be used with light sub-chassis turntables and not overload the bearing. Often the cost of tweaks is not measured in terms of money but rather in time invested due to many trials so patience is a must. Consider the hockey puck record clamp a starting point, one that will let you easily try out the idea for yourself at little to no cost. Should you find that the clamp provides an improvement that you would like to pursue further, let the journey begin.
A standard ice hockey puck is a hard disk made of vulcanized rubber. Hockey pucks are about 25 mm (1 inch) thick, about 76 mm (3 inches) in diameter and usually weigh between 155-170 grams (5.5 and 6 ounces). The hockey puck record clamp is ultra-simple to construct requiring just one small hole to clear the platter spindle and making the hole is the easy part. But first you must locate the centre of the hockey puck and you want to do this accurately so take your time. There are several methods that can be used to locate the center of a circle which you can research for yourself (google: “find center of a circle”). The following steps will locate the center of a circle using a right-angled object like a right-angle triangle from a geometry kit.
Step 1 Place the right-angle corner of any object at any point on the circle. Any point will do.
Step 2 Make a mark where the two sides of the right-angle cross the circle.
Step 3 Draw a line between these two marks.
Step 4 Place the right-angle corner of the object at any other point on the circle. Any point will do, but for greatest accuracy, make it about a quarter the way round the circle from the first point.
Step 5 Make a mark where the two sides of the right-angle cross the circle.
Step 6 Connect these two points with a straight line. This is the second diameter.
Step 7 Done! The point where the two diameters intersect is the center of the circle.
Once the center has been located take some time to measure and make sure that you are in the exact center of the puck. You can drill a hole using a 9/32-inch drill bit and a drill (hand or power). Drilling half-way through the puck is more than sufficient and if you prefer you can measure the length of the spindle and drill to the exact depth (for a depth guide I used masking tape on the drill bit). With this hole size, the puck should fit snugly against most unthreaded spindles but you should check the size on your turntable. If the fit it too tight, you can enlarge the hole slightly using the drill bit and your hands. Of course the above instructions can be applied to virtually any round disc or cylinder that you would like to convert into a record clamp. A note of caution, if you are using an MC cartridge, do not use ferrous metals (steel) for a record clamp.
Now for the fun part - testing out the record clamp. My turntable is a stock Rega P1 (reviewed in our February/March 2009 issue). The musical selections consisted of albums that I was very familiar with and I purposely selected some normal and heavier weight vinyl. The first album I tried with the hockey puck record clamp was an original 1979 pressing of Supertramp - Breakfast in America [A&M SP-3708]. Immediately I noticed an overall improvement with the bass response which was tighter and better defined - bass response is often the weak point of entry-level rigs. There was also an improvement to the soundstage which now seemed wider and also to the imaging which without the clamp sometimes seems out of focus. Next I moved onto to a 1993 reissue of Kraftwerk - The Man-Machine [Capitol / EMI SN-16302]. The vinyl weight of this album is not noted but I figure it is about 150-160 grams. Kraftwerk albums are typically great recordings that are clean, dynamic and with a deep bass range. There is plenty of bass on this album and like the previous album the record clamp provided an overall improvement to the bass response which was now tighter and more dynamic. I also tried the clamp with Feist - Let It Die [Polydor, 2004, 180g]. While there were improvements to the bass response, image and soundstage, the improvements were generally subtle relative to the previous albums. The greatest improvement was realized with the Supertramp album which was also the oldest, most played and lightest of the three. Overall I was rather pleased with the results of the hockey puck record clamp especially considering that all it cost was a little time. I am definitely interested in trying a collet style clamp with my P1. Your mileage will vary with a record clamp, but if you have some time to invest, give the hockey puck a try.
For more Audio DIY projects check out Giovanni’s website http://diyaudioprojects.com