Stylus Rake Angle (SRA)

SRA or Stylus Rake Angle, is a critical parameter that's associated with VTA, and due to the necessities of cartridge design, is firmly bound to the VTA. This is the angle of the stylus itself relative to a line perpendicular to the record. It is critical that the SRA match that of the cutting head as exactly as possible. Unless this happens, not all of the information available in the groove can be read. In a way it's analogous to a tape head alignment. Since there's no effective way to directly or indeirectly measure the actual SRA, as we can't know for sure what the cutting head's SRA was, it is necessary to determine the best setting by ear. To get the absolute best sound from a record, it is necessary with line contact style and eliptical cartridges to adjust the SRA for each record to match the SRA of the cutting head. If this is done, most arms will require tracking force adjustments also (see the next section on VTF). Since most arms do not allow for easy and repeatable micro-adjustments of VTA/SRA, and most audiophiles want to enjoy music instead of adjusting equipment, a compromise position is usually chosen. Choosing this compromise usually involves setting SRA/VTA using an average thickness record and not worrying about it. Other methods might include using several different thickneses of records and finding the best compromise, or using platter mats of different thickness, or even using your favorite record label as the reference disc. All methods require some kind of tradeoffs. The General effects of improperly set VTA/SRA will be in the frequency extremes. If the setting is too high (where the arm slopes down toward the cartridge), the bass region generally gets muddy and thick, and the cartridge may sound more bright and strident than it should. Setting it too low (where the arm slopes down from the cartridge) may result in overly taught bass, and a reduction in upper frequency information. When you get the VTA/SRA right, the sound seems to lock in and become very focused, and the music will just sound right. This has been reported by many listeners to happen over a very small range of adjustments. In other words, you may make adjustments over a relatively large range with little change in sound character, and then you'll hit a small range where minute changes are readily audible. My personal theory is that this happens when the SRA is almost precisely aligned to that of the cutting head, although there are other theories out there as to the lock in effect.

Figure 4