I recently acquired a Sonus Gold Blue cart. What I have found, though, is it seems to be soft on the high frequencies. I have read others who commented about this with the Sonus and was wondering if this is characteristic of the Gold Blue? I have also read the suspension didn’t age well – is this high freq. roll off what happens when things stiffen up with age?
If anybody has any experience with this, please post. Thanks!
We would like to submit to the forum the results of our years of use and maintenance of the Sonus series cartridges.
MAINTAING YOUR SONUS STR
INTRODUCTION
A review of most of these posts are pretty much right on track. Several other key points also need to be addressed, and in this White Paper, we will examine the main reasons for these losses of high frequencies.
ANOLOG WORLD
We live in a real world. It encompasses all three dimensions, X, Y, and Z. Vinyl records are the real world. Like in any mechanical apparatus, things wear out. We will take them step by step.
MISS ALIGNMENT
One of the most problematic areas in the Sonus is the reduced upper high frequency end with the bodies fitted with an STR, or Shibata type Line Contact diamond. Over time, they become miss aligned due to the aging and stiffing of the rubberized pivot.
Secondly, all STR’s all suffer from*a higher sensitivity to alignment tracking errors over the Arc. The specified frequency range is not the same across the entire platter, that is unless it is used in a tangental, or linear tracking arm.
Aging and degradation occurs in the Sonus slowly, and over time.
OBSERVE DEGRADATION
One of the keys to observing this slow degradation is the loss of the right channel tonal balance. When it becomes obvious that this level is out of balance, then it is time to take action.
LOOK & MAINTAIN
Take the head off the tonearm and look at the tube angle as it my be twisted from due center.
We have found that over time, the rubber ‘Cantilever’ stiffens, and begins to torque the armature tube out of place from true center. The armature assembly is the ‘tube’ which consists of the mount for the diamond / needle and the actual armature magnet mounted behind the pivot point.
With an STR, the alignment into the V groove is absolutely critical. In fact, all stylus types must be properly aligned no mater what type of ‘needle’ you use, including Ellipsoid [Elliptical], Bi Lateral, or even the lesser sensitive, Spherical.
RESTORING ELASTICITY
One trick we would like to share is how we resolved and stopped this aging of the rubberized material.
RESETING THE RUBBER MEMORY
All rubber has a memory. Over time, the original position gets lost.
To reset it, simply remove the the needle assembly from the body and place it (just the armature) into a small cap of Alcohol, for say up to two hours. Overnight is ok, depending on temperature and age of the rubber. This method will restore the rubberized material back to it’s original texture, or elasticity if you wish.
Alignment of the tube can now be done by positioning a small pressure to center the tube back into position. We use a small 1/4” paint brush, and hold it there as the alcohol dries. As the alcohol is drying, slight pressure is applied, and most importantly, you must increase its temperature slightly by breathing on it to loosen and thus expanding the molecules.
Repeat if necessary. Experience shows it might take up to two days to reset its original memory.
If the tube / armature is still not centering, then simply skew the cartridge to the right, looking down from the top, to the angle the tube has been skewed. This is the last resort. You will hear the highs come right back.
Be persistent, and redo all of the above if it still will not center to its original memory.
VERTICAL MISS ALIGNMENT
Along with the most obvious stuck skewing angle by a dried out rubber cantilever, it most certainly occurs in the vertical arena as well.
Picture yourself in a cut away looking into the grooves of the record with the stylus on top of it. You will see two V’s, one on top of each other. The upper V is the stylus. The bottom V is the record.
As in the left / right memory problem, this X axis miss alignment also occurs. This results in the STR not being in equal contact on both sides of the groove.
You will hear a muddled response on one channel.
To correct this, simply torque the needle with precision tweezers with a slight twist to straighten it out. Be careful.
THE ARC
Also make sure that you have the correct ‘Arc’ for your tonearm. The Arc, or circle diameter, is listed in your turntable manual.
We use the Baerwald - Leopold protractor, as modified above to correct for the torqued tube mounts.
SUMMARY
The aging process or deteriorating elasticity of the rubber will remember its last position in both the X and Y dimensions.
Results in loss of High Frequencies.
NOTES
One more note on why these ‘Cantilever’ designs were warm.
The basic principle of transferring the mechanical motion through the rear Cantilever MM, is analogous to that of a Ribbon, or Velocity microphone. Those mics rolled off very smoothly above say, 15kHz, and produced a rich low distortion natural sound.
In the case of Sonus and others, these roll offs occurred just above 20kHz when new, and without correcting or maintaing them, this roll off occurs slowly down to 10kHz over time.
Final note
Maintaing these precision instruments is challenging to be sure. I would rather you trust a jeweler at your side and guide them on how to do it.
At an absolute minimum, just soak the stylus in warm alcohol for about two hours. Repeat this every two months.
OUR END RESULT
We have maintained out original stock of Sonus instruments for over 30 years, all with the original diamonds.
Gene Weed
STUDIO 57A*
