Cartridge Alignment – An Introduction

Introduction

Having spent what seemed like an eternity trying to wring out the last ounce of performance from my Hana SL, I thought that my experiences could provide a few of my readers with a good insight into the basics of cartridge alignment.

Comparing disc styli systems of yesteryear with the modern-day  phono cartridge assemblies sets them light years apart. The technology of a steel or wooden needle attached to a diaphragm hardly compares to modern day electro-magnetic cartridge technology, the exotic materials used and innovations applied to todays sophisticated and computer generated diamond stylus profiles.

The modern cutting lathe has not changed a great deal from its original inception by Scully-Neuman and Manley but there have been leaps and bounds made in the design of the phono cartridge ‘generator’, its cantilever and stylus. Grooves in vinyl are between 0.004 and 0.008 mm with deviations between 0.0225 mm and 0.000075 mm (225nm to 75nm). These dimensions are minute, the shorter of which is less than that of visible light (380-700nm)! YET  they all have to be accurately cut into the vinyls surface.

Tracing these tiny deviations accurately and without damaging them, while at the same time being able to trace deviations more than a thousand (+60dB) greater is a challenging feet for any electromechanical device….enter the modern phono cartridge.

Clearly the relationship between the stylus and groove is VERY important. Only precise alignment, with no room for error, will trace and reveal all the sound information stored in those deviations. With such tiny deviations the stylus must also present a very tiny touch point and hence surface area. Even with todays low vertical tracking forces of 2gm or less these minute contact surface areas between the stylus and vinyl can create pressures of up to 500lbs per square inch.

Now you know why correct stylus alignment is a must for any audiophile system……well any vinyl replay system if you do not want to damage the vinyl.

With the help of a few simple tools, a little equipped and some basic knowledge, you can fine tune your analog rig for optimum performance. Let’s review the areas of adjustment.

Phono Cartridge Alignment Introduction

This post isn’t intended as a detailed set-up guide. Rather an introduction to the terms and issues associated with cartridge alignment. Hopefully providing my readers with the insight as to what has to be adjusted, why, how and with what.

The following cartridge and arm parameters need to be adjusted in order for your cartridge to optimally trace the groove information, minimize vinyl wear and provide the most exact electrical replica of the stylus movement with the lowest possible distortion:

• Vertical tracking force (VTF)
• Overhang
• Anti-skating or bias force
• Vertical tracking angle (VTA) – related to stylus rake angle (SRA).
• Azimuth
• Zenith

Before starting any alignment make sure that the turntable and platter are level, both side to side and front to back.

Vertical Tracking Force (VTF)

Setting the vertical tracking force is the very first step in setting up a cartridge and will be repeated several times during the setup process in order to fine tune the VTF. The recommended range is specified by the manufacturer and is typically between 1.5g – 2.2g. Excessive VTF will overload the suspension and can distort the cantilever both resulting in incorrectly setting the Vertical Tracking Angle. Too little force will cause the stylus not to sit fully in the groove and follow the deviations of each groove wall, ultimately damaging the vinyl. Surprisingly too much force is generally preferable to too little which will generally result in poor performance, tracing distortion and increased vinyl wear.

This force not only keeps the stylus in constant contact with the vinyl but aligns the cantilever, stylus and generator for its correct operation. In particular setting the vertical tracking angle and stylus rake angle close to where they should be. Adjusting this force in conjunction with the all the other parameters is essential to get the optimum performance from each cartridge.

VTF adjustement is accomplished by using:

1. The arms calibrated VTF dial.
2. A simple manual balance beam scale.
3. An electronic digital stylus force gauge. (preferred)

For modest systems methods 1 or 2 are generally adequate for setup. At audiophile level I strongly recommend the digital gauge due to its accuracy, ease of use and the frequency to which it will be put to use. They are not expensive, the Riverstone digital gauge shown below costs $19.95. I do not recommend this particular model as there is some magnetic material beneath the scale. If you space the cartridge well away from the scale surface, as shown below, the magnetic material has no effect on the gauge readings.

For most arms it is essential that the stylus force is measured at the same level as the resting point of the stylus when on the vinyl. Being higher or lower than this will provide an inaccurate reading.

Overhang

As the stylus tracks across the record, it is important that the stylus remain tangential (at right angles) to the groove walls. Setting the overhang aligns the cartridge to follow an ideal arc across the record. Radial tracking arms as opposed to parallel tracking arms only have two points on the arc where the stylus is tangential to the vinyl cut. There are many theories with regard to selecting these two points. Arm manufactures provide templates that they believe will provide the best performance for their arm. These templates will normally conform to one of the three popular geometries:

1. Berwald – The distortion at the beginning, the middle (where it’s high) and the end of the record must be equal.
2. Stevenson – The alignment must minimize the distortion across the record.
3. Loefgren – The distortion is more important at the end of the record so its minimized by assuming a null point at the end of the record.

Each of these geometries provide different points on the arc where the stylus is tangential (null points) to the vinyl walls, providing the minimum tracing distortion.

1. Berwald – Null points are 66.0 and 120.9 mm.
2. Stevenson – Null points are 70.3 and 116.6 mm
3. Loefgren – Null points are 60.325 and 117.42 mm

To set overhang, you’ll need an alignment gauge. There are a whole range of overhang gauges available from free web sources, numerous vendors (see below), or you can make your own if you know enough about your arms design (not recommended for the beginner). I strongly recommend using either the template that came with your arm or one of the more expensive overhang adjustment gauges that measures the distance from the center of the turntable spindle to the center of your arm mounting; the pivot to spindle distance. These gauges also help you initially set zenith.

Overhang And Null Points

A Typical Alignment Gauge

The goal is to adjust the overhang distance so that when the stylus sits at each location the body is parallel with the lines on the template. This is achieved by either:

• Moving the cartridge in the headshell if it has slotted mounting holes or
• Moving the headshell on the arm if the cartridge has a fixed position in the headshell.

The position of the cartridge in the headshell may need to be adjusted later to adjust its zenith. In some cases this may result in the cartridge body being at a very slight angle to those same lines. However, after any adjustments the stylus must still hit both locations shown in the template.

See here for more information. Membership of the VinylEngine forum is required in order to download files.

Anti Skate Bias

Radial tonearm geometry creates a centripetal force that pulls the cartridge toward the center of the record. Anti skate bias counteracts this force, seeking to equalize pressure of the stylus on both sides of the groove. Setting the anti-skate force is still a hot topic for debate.

Most tonearms have calibrated, adjustable anti skating adjustment. The normal practice would be to set the anti skating to match the tracking force; (i.e. 2g of tracking force and 2g of anti skating bias). High compliance cartridges are more affected by anti skating force than low compliance cartridges and it is not uncommon for some cartridge manufacturers to suggest anti skating for low compliance cartridges at about one-half to two-thirds the level required for high compliance cartridges.

There are several ways of setting the bias force:

1. Some highly respected vendors such as Music Man suggest using a groveless record and adjusting the bias level for a slow inward drift of the cartridge, others disagree stressing that skating is a dynamic force and using a blank or grooveless disc will result in incorrect compensation.
2. Another method suggests lowering the stylus into the groove while watching from the front to see if the cantilever has a tendency to move inward or outward, then adjusting anti skate until there is no perceived deflection.
3. Using a test record that has a high level lateral L+R sine wave at typically 100Hz or 300Hz. The tone is either listened to and/or observed on a dual beam oscilloscope and the force is adjusted until there is either no distortion seen or heard on either channel or it is equal on  both. (my preferred approach)

The general consensus is that anti skating bias levels are generally set too high as they are often set on high level sine wave test signals (see 3 above). These signals are much higher than the average level cut into many discs resulting in bias levels that are set too high. Ultimately excessive bias force will cause additional wear to the outside groove wall.

Anti-Skating Bias Issues

Most anti-skating adjustments are no more than the turn of knob or the movement a weight. Too high causes undue stress on the cantilever and can result in it being moved from its optimal zenith position and create excessive wear on the outside groove wall. Too low will not keep the stylus in contact with the outer groove wall and cause distortion. Some arms employ weight, string and pulley systems to create the bias force. The setup of these must be viewed with some care especially when associated with unipivot arms. Incorrect alignment of the forces created by the bias weight can cause the arm to twist and upset the cartridges zenith. The string that connects to the arms pivot must be kept dead parallel to the arm when the cartridge is resting on the record or it can result in changes to the cartridge zenith.

VTA and SRA

Vertical Tracking Angle (VTA) and Stylus Rake Angle (SRA) are two terms used to describe the angle of the stylus relative to the vinyls surface. They are not the same thing as can be seen from the drawing, but the terms are often and incorrectly used interchangeably by many audiophiles. The angle is usually set by adjusting the height of the arm at its pivot or by inserting shims between the cartridge and headshell.

Correct SRA is achieved when the angle of the playback stylus matches that of the record cutter head used to make the original master lacquer; typically 92 degrees. This sets the VTA to approximately twenty degrees, plus or minus five degrees, varying between cartridge manufacturers. The VTA/SRA needs to be adjusted to achieve minimum distortion and optimum playback results. Other variables such as record thickness, stylus shape and variations in cartridge construction, also make this adjustment necessary. In general most cartridge manufactures adjust their suspensions and cartridge geometries such that when the arm is parallel to the vinyl surface and the correct VTF is set, the VTA/SRA will be close to optimum.

There are several of ways to set the SRA:

1. Using a digital USB microscope and measurement software allows very accurate adjustment to the often referred to “ideal” setting of 92 degrees (Michael Fremer has an excellent tutorial here).
2. Using a test record with 4KHz and 60Hz tones and a spectrum or distortion analyzer. Adjust the pivot height for minimum intermodulation distortion.
3. By ear. Some listeners feel the ‘best’ setting for VTA/SRA can only be determined through listening tests. Starting with the arm parallel to the record surface and raising and lowering the tonearm in small increments until the best setting is achieved (many listeners find that they end up with the rear of the arm very slightly lower – I DID). In searching for the ideal angle, there are several things to listen for.
   1. Look for the point at which the soundstage comes into best focus, providing maximum width and depth simultaneously.
   2. Surface noise is generally at a minimum .
   3. You will find (to a varying degree depending on the cartridge) a shift in tonality. Usually a positive VTA results in an emphasized top-end, while lowering the setting toward negative will soften the high-end and increase the bass.

Due to arm design and stylus shape and size, some cartridges will be far more sensitive to SRA than others. Generally, the lower the center of gravity of the arm and the more exotic the stylus profile, the more sensitive to the adjustment of SRA. All cartridges however, will benefit from proper SRA alignment.

It is important to note that SRA is directly related to the VTF. As tracking force is increased cantilever deflection increases, changing the angular relationship of stylus to groove. So fine tune VTF before setting the SRA.

Azimuth

Azimuth in my opinion is far more critical than any other setup parameter, except maybe VTF. It has a profound effect on stereo imaging, depth of field and overall stereo stability.

So what is azimuth? It is the left to right tilt of the stylus when viewed straight on from the front of the cartridge. Depending upon the stylus and cantilever mounting accuracy and assuming the stylus has been symmetrically ground and polished, the correct alignment is when the stylus is exactly perpendicular to the vinyl surface; not necessarily the cartridge body. As styli have become increasingly small, setting the stylus azimuth by eye has become increasingly difficult. However a mirror, light and small magnifying glass can work wonders and provide and excellent starting point. After setting the anti-skating force to zero, adjust the cartridge rotation until the stylus is exactly perpendicular to its reflection.

The azimuth critically affects channel separation and channel level so its correct setup is essential. There are several ways to set the azimuth to its optimum value, and setting for identical channel levels is NOT the correct approach. Common approaches include:

1. The Fosgate Fozometer.
2. An AC millivolt meter or good quality multimeter (my preferred approach with a dual channel meter).
3. An dual channel oscilloscope.
4. Out of phase channel cancellation.
5. By ear using a mono voice track.

Using the appropriate test tracks played back on just the left or right hand channels, the ideal result from this calibration is that the channel levels and separation (crosstalk) are set to be almost the same for both channels. This is achieved by rotating the cartridge headshell a fraction of a degree at a time and measuring the signal in the corresponding non-driven channel, then repeating with the other channel. You are not trying to match levels and obtain the highest separation for each channel. If you do this some cartridges will become severely miss-aligned. If the stylus is more than a couple of degrees off vertical when you have finished, you have gone too far or you have a bad stylus and/or cantilever. For high separation cartridges >>30dB there can be significant differences between the left and right hand channel separation maxima (this is normal). So optimize the separation for the lower channels value. Small errors in channel level can be adjusted for using your pre-amp or main amplifier.

The easiest device to use is the Fosgate Fozgometer and is considered by many to be an excellent tool for this purpose. However, as it is trying to maximize both separations its use can in some instances result in excessive azimuth rotation. So use with caution. It is an expensive device and limited to just one function. In my opinion a dual channel AC millivoltmeter or scope is much more useful and accurate but does require a little more expertise.

My personnel favorite is the two channel AC millivolt meter as you can see both channel levels simultaneously and they are already calibrated in dB’s so determining the actual separation is easy.

A dual beam oscilloscope may also be used but the level readings and separation takes a little more time and effort to calculate.

If test equipment isn’t available to you then you can:

1. Play a monophonic track (lateral cut L+R), reverse the phase of one of the cartridges outputs and sum them together. Good azimuth adjustment will be when the summed mono output is at its lowest volume.
2. Play a monophonic record (lateral cut L+R) with just a voice or vocal recording, no instruments. Good alignment can be achieved when you get a clear and stable center image precisely centered between your two speakers.

In an attempt to achieve a very rigid arm design some manufacturers, SME, Rega etc. do not provide a headshell that can be rotated. In these cases the cartridge can only be rotated by shimming one or other sides between the cartridge body and headshell. While this is a REALLY tedious and time consuming process it is ultimately worthwhile. I do not recommend shimming the arm base in order to twist the arm as it will change its bearing geometry. With a fixed headshell I highly recommend checking the separation first to see just how far off equal it is in order to determine whether azimuth adjustments are really necessary.

Zenith

Having set the stylus azimuth in the vertical plane we now need to dial in the stylus zenith in the horizontal plane. Looking at the cartridge from above it is the rotation of the cartridge in the headshell; as if around a clock face. Many head-shells provide very limited or no zenith adjustment. So what does it affect? Mainly the channels phase ensuring that the peaks and troughs of a L+R sine wave occur simultaneously and in phase on both channels. It may be adjusted in two ways:

1. Using the overhang alignment gauge.
2. Using a test record and oscilloscope. (my preferred approach)

The easiest way to set the zenith is by eye using an alignment gauge with a grid. Simply set the stylus on one of the alignment points, sight down the cantilever and align it with the grid line immediately below the cantilever.  I find this remarkably accurate. This assumes that the stylus has been accurately mounted on the cantilever.

Alternatively, and for greater accuracy, use a dual beam scope and 1KHz lateral L+R sine wave. Simultaneously monitoring the left and right channels adjust the rotation until the peaks and troughs of the waveforms line up (in phase). You may also use the scope in XY mode and adjust for a ‘perfect’ 45 degree line running bottom left to top right. This will rarely be a perfect line and will often show as a very flat ellipse.

Comments

All the above adjustments are interdependent. So once you have set them, you WILL need to go back and recheck them all. This iterative process can be quite time consuming and laborious. I can testify to that. BUT, it will all be worthwhile when you listen to the final results.

Alignment Equipment Overview

While it is possible to reasonably align a cartridge by eye and ear on a modest stereo system using a few simple tools, that will not be sufficient for audiophile systems. Especially if they have Shibata or more exotic stylus profiles. Ideally you will need the following tools for a full and accurate alignment:

1. A test record. Recommendation – The Ultimate Analogue Test LP.
2. A very small level. – To set the turntable plinth level in both directions – very important.
3. A mirror. – To initially set stylus azimuth and zenith.
4. A small screwdriver. – For the headshell screws.
5. A magnifying glass or jewelers eye piece.
6. A digital sylus gauge. These are available from many audio vendors including: Amazon, Acoustics Sounds, Hi-Fi Heaven, Elusive Disc, Music Direct and many others. See here. Be sure that there are NO metallic materials in the area where the stylus and cartridge body rests. This will cause a high and inaccurate reading. Check your digital stylus gauge with a small magnet to ensure that it is not attracted to any part of the measurement area.
7. The arm manufacturers overhang alignment template OR
8. A universal overhang alignment tool from any of these vendors: VPI, Pro-Ject, Fieckert, Clearaudio, Mobile Fidelity and others. Some of these models comes with a built in mirror. See here.
9. An AC millivolt meter or good quality multimeter AND/OR A
10. A dual beam oscilloscope. – Your PC or laptop with appropriate software (some free) can be used for this function. See here for several vendors.
11. A USB microscope. – Many models are available from $20 on Amazon. Read the specifications and user reviews carefully. This is a ‘nice to have’ and allows you to easily see the stylus mounting and help measure the SRA with the cartridge in place.
12. LOTS AND LOTS OF PATIENCE.

Stylus Profiles

In the ongoing attempt to extract all the information from the groove deviations and cause the least amount of vinyl damage, numerous stylus profiles have been developed. These include:

• Conical – the original, and still used today.
• Elliptical – most common and cost effective.
• Line Contact -Shibata.
• Exotic

Remember that the more hi-tech the stylus profile the less tolerant it is to being miss-aligned. So don’t spend a lot of money on an exotic stylus if you are not going to take the time to correctly align it. That can result in a performance that is worse than selecting a poorly aligned cheaper stylus design and can result in greater damage to the groove wall.

Comparing the above two images it can be seen that even in the simple case of the basic elliptical stylus that it provides a far better ability to accurately trace the small deviations in the groove walls. These more exotic stylus shapes also provide a significantly improved stylus to vinyl contact surface area improving tracing and reducing wear.

Cartridge Loading, Pre-Amp Gain and Connectivity

The nominally quoted, very small output voltage from a phono cartridge, ranges between 0.2mV and 5mV. Phono cartridges are designed to be connected to a pre-amplifier that presents it with a particular impedance load. This impedance is made up of two parts: resistance and capacitance (any inductance can be ignored). These two parameters are selected by the manufacturer in order to optimize the cartridges frequency response and voltage output. So it is important that your pre-amp can be adjusted to provide the correct loading in order to get the best possible response from the phono cartridge. For most moving magnet phono cartridges and high output moving coil cartridges a load of 47Kohms and 50 picofarads is generally considered acceptable. Typical pre-amplifier gains required to correctly drive the main amplifier are between 45dB and 55dB. However, low output moving coil cartridges have very wide resistive loading ranges and higher amplification requirements, but are less impacted by incorrect capacitive loads:

• Resistive load 50 – 1000 ohms
• Capacitive load 50-1000 picofarads
• Gain 60db – 70+dB

All cartridges put out much higher voltages than their nominal value when tracing loud and dynamic passages of music. It is therefore important that the pre-amplifier has a high overload or headroom margin, typically +20dB or better. This will prevent signal overload and clipping, reducing any distortion by the pre-amplifier.

Phono cartridges may be connected to the pre-amplifier in one of two ways:

• Unbalanced – Phono/RCA connector  – the most common by far.
• Balanced – 3 or 5 pin XLR – high end audiophile systems.

Most phono pre-amplifiers do not support input balanced connections, only the more expensive models. The major and only real advantage of a balanced connection is that it is far less susceptible to the pickup of hum and RF noise. Especially if you use star quad cabling. Balanced connectivity does not inherently provide a ‘better’ sound.

You now have the information to take one giant step for audiophiles and your vinyl replay system.

See the following links for additional information:

• Phono Cartridge Basics 101
• Hana SL Review and Review Update
• The Ultimate Analogue Test LP Review
• Soundsmith Cartridge Alignment
• Musical Fidelity MX-VYNL Review and Review Update