If you’re a vinyl enthusiast, you may have heard the term “quartz lock” thrown around in discussions about turntables.
But what exactly is it and why is it important?
In simple terms, quartz lock is a feature found on direct-drive turntables that helps maintain a stable speed for platter rotation. It uses a quartz phase-locked loop circuit to compare motor rotation speed to a reference frequency generated by a quartz crystal oscillator, and makes fine adjustments if necessary.
But how does this affect your listening experience? And when should you use it?
In this article, we’ll dive deeper into the world of quartz lock and explore its benefits and limitations.
What Is Quartz Lock On A Turntable
As mentioned earlier, quartz lock is a feature found on direct-drive turntables that helps maintain a stable speed for platter rotation. This is important because any variation in speed can affect the pitch and sound quality of the music being played.
When you press the quartz lock button on your turntable, it activates the feature and the LED next to the pitch slider turns green to indicate that it’s active. With quartz lock enabled, the turntable’s pitch control feature is disabled and won’t have an impact on motor speed.
This means that if you’re not a club DJ and just want to listen to your records at their intended speed, then you should use quartz lock. It ensures that your records are played at a consistent speed and that there are no fluctuations in pitch or sound quality.
Understanding The Basics Of Direct-Drive Turntables
Direct-drive turntables have the motor located beneath the platter, rotating it directly. This means that the motor is in direct contact with the platter and provides a higher torque compared to belt-drive turntables. As a result, direct-drive turntables are often preferred for demanding and professional uses.
One of the key features of direct-drive turntables is the quartz locking system. This system uses a quartz phase-locked loop circuit to maintain a stable speed for platter rotation. It does this by comparing the motor rotation speed to a reference frequency generated by a quartz crystal oscillator and making fine adjustments if necessary.
When you activate the quartz lock feature on your direct-drive turntable, it ensures that the turntable’s speed remains consistent and unaffected by any external factors. This means that any variations in pitch or sound quality due to speed fluctuations are eliminated.
In addition to quartz lock, direct-drive turntables also offer a wider range of pitch control options. This is because the pitch control feature is not affected when quartz lock is enabled. As a result, if you’re a club DJ and want to play with pitch, you can switch off quartz lock and adjust the pitch slider to your desired speed.
The Science Behind Quartz Lock
Quartz lock works by using a quartz crystal oscillator and a speed feedback system from the capstan. The pulse feedback frequency from the capstan is compared to the oscillator frequency, and if it is too high, the motor speed is lowered, and if it is too low, the motor speed is raised. This happens very quickly, ensuring that the platter rotation speed is maintained at a stable rate.
In addition to this, direct-drive turntables like the Audio-Technica AT-LP120 also use a quartz phase-locked loop circuit that compares motor rotation speed to a reference frequency generated by a quartz crystal oscillator. Fine adjustments are made to the platter drive should the values drift, ensuring that the speed remains consistent.
This closed-loop system includes a method of returning to the motor drive circuit information about the actual motion of the platter in real-time, which is used to make corrections to the platter drive that improve speed stability. This feedback system ensures that there are no fluctuations in pitch or sound quality, making it an essential feature for any serious vinyl enthusiast.
It’s worth noting that while quartz lock was invented to fix issues with speed drift in early direct-drive turntables, modern turntable servos are much more stable, making quartz lock less of an issue and more of a handy “press for correct pitch” feature. However, it’s still recommended for anyone who wants to ensure that their records are played at a consistent speed with no fluctuations in pitch or sound quality.
Benefits Of Using Quartz Lock
There are several benefits to using quartz lock on your turntable. Firstly, the use of quartz as a clock source provides unmatched stability in terms of speed regulation. Unlike traditional R-C clockbases, which can wander over time, temperature, and age, quartz remains stable and consistent. This means that the frequency generated by the quartz is known and the required diameters are exact, resulting in precise speed regulation.
Secondly, the use of a phase-locked loop (PLL) in conjunction with quartz lock ensures that the speed stability is unmatched. The phase comparator compares the clockbase with a feedback signal from a frequency generated (FG) coil placed under the capstan flywheel. The comparator’s output contains a phase difference or error, which is fed to a low pass filter to make a DC control voltage to the motor coil driver stage. This results in an increase or decrease in current pumped into the coils until the phase difference is effectively zero. This means that the speed accuracy is always within acceptable limits.
Thirdly, using quartz lock ensures ultimate speed stability over longer periods of time. Most non-quartz turntables will change speed over the course of a cassette tape and have differences from side A to side B playback. They are also not immune to variable resistance from the cassette itself. However, when you reference the speed against a quartz crystal, the speed stays pretty much constant unless external factors push playback outside the torque capability of the motor. This means that your records will stay pitch perfect for the entire Side A and Side B of a record, and pretty much never need speed calibration.
Limitations Of Quartz Lock
While quartz lock is a useful feature for maintaining speed stability, it does have its limitations. One limitation is that it only works within a certain range of speeds. If the motor speed varies too much from the reference frequency generated by the quartz crystal oscillator, the quartz lock circuit may not be able to make fine adjustments and maintain stable speed.
Another limitation is that quartz lock can only control the platter rotation speed, not any other mechanical or electrical components of the turntable. This means that if there are any other factors affecting the speed stability, such as a worn belt or faulty motor bearings, quartz lock may not be able to compensate for them.
Additionally, some users may prefer to adjust the pitch of their records for creative or personal reasons. With quartz lock enabled, the pitch control feature is disabled and users cannot make any adjustments to the motor speed.
Lastly, quartz lock is not a foolproof solution for all turntable issues. If there are any mechanical or electrical problems with the turntable, such as tonearm drag or motor issues, quartz lock may not be able to solve them.
When To Use Quartz Lock: Tips And Tricks
If you’re a DJ and want to use the pitch control feature to manipulate the speed of your records, you should turn off quartz lock. This will allow you to adjust the pitch slider and extend the range of the turntable’s pitch control. You can switch quartz lock off and push the pitch slider up or down until you hit the desired speed. The green LED will turn red, indicating that quartz lock is disabled.
It’s important to note that if you’re playing 78s, which are made from shellac and run at a different speed than vinyl records, you’ll need a different type of stylus. Additionally, some “78s” ran at slightly different speeds, so there wasn’t an exact standard in the beginning.
When using quartz lock, you can always confirm motor speed accuracy by checking the strobe dots on the platter’s edge to see if they line up. This will ensure that your records are being played back at exactly 33.3 or 45 RPM.
Alternatives To Quartz Lock: Belt-Drive Turntables
While quartz lock is a popular feature on direct-drive turntables, there are alternative options available. Belt-drive turntables, for example, have been around for decades and were considered the best option back in the day.
A belt-drive turntable features a heavy platter that, once up to speed, keeps a constant speed and is not slowed down by the movement of the stylus. However, they are reliant on more moving parts, which inherently makes them more prone to speed changes. If the belt is worn or the flywheel is damaged or isn’t machined properly, the speed will certainly be affected.
It is possible to improve the speed consistency of a belt-drive system by adding a speed regulator to the power supply. For example, Pro-Ject offers the Speed Box S2 which applies quartz-generated speed regulation to improve performance on many of their turntable range. Additionally, a heavier platter can also help keep the speed from varying.
While belt-drive turntables may not have the same level of precision as direct-drive turntables with quartz lock, they still offer a reliable and durable option for those looking to listen to their records at a consistent speed. Ultimately, it comes down to personal preference and what features are most important to you as a listener or DJ.
