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Review: Sonic Research Sonus Blue Induced Magnet Cartridge


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DSC_0814.jpg (216570 bytes) Listening on the Thorens TD124

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DSC_0820.jpg (166072 bytes) Listening on the Thorens TD150


This is the second part of an investigation into vintage phono cartridges to be paired with the Infinity Black Widow tonearm.  The primary qualifier in this search being that the cartridge must have a very high compliance in order to match well with the very low mass of the arm.  The second qualifier being a reputation for excellent sound qualities.  There is nothing made today that will meet the first requirement. The second requirement is not quite so hard but you must use a different tonearm, which brings us back to the first requirement.  Anything I choose will be of a vintage 30 to 40 years past.  Fortunately it is still possible to find NOS cartridges up for sale.  This is the condition I look for.

The search

After having experienced the Black Widow tonearm with the ADC XLM-II, (and liking what I heard), I had further interest to see and hear if the legendary Sonus Blue or Sonus Gold-Blue cartridges might have even better sound than I'd heard with the ADC.  So I went on a search for good sample.  These cartridges are rather scarce to find in working condition.  My first place to look was ebay.  Some days it seems you can find anything on ebay. I did find a scraggly assortment of Sonus cartridges up for sale.  Different labels.  Most were used and with questionable histories.  Some were noted as being in need of a new stylus assembly. (That would be a deal killer for me.)


I searched elsewhere across the internet using Google as my search engine. (and also Yahoo,  DuckDuckGo)  There is much anecdotal conversation about the Sonus cartridges but not so much discussion about those in good condition for sale.  So back to ebay.  I searched again and found one seller that had a New Old Stock Sonus Blue in its case up for sale.  The price was kind of steep at $249.95.  Not eager to part with so much for a vintage MM I put it in my watch list at my ebay home page and continued searching around the web.  But no luck over a two week period.  Afterward I pulled the trigger, a Buy It Now price.  The seller was "Merlin!!".  His after sale service was excellent.  I bought it on a Saturday and took delivery the following Saturday via 1st class mail.




But why would I be looking at these vintage phono cartridges at all?  My meaning, already stated in the first article of the series, is to take a look backward in time to sample those components I missed having any experience with back in the days when I might have. (I was focused on other stuff for quite some time.)  

To add further motive I could say that having a hobby that plays Lp records, a medium most of todays' humans have dismissed as being hopelessly obsolete, is to look backward to the time when records were a dominant medium for playing back recorded music.  It only seems natural that the equipment of those times might be just as vital now as they were absolutely necessary then. 

For the Black Widow tonearm, the first cartridge I tried was a Peter Pritchard design, the ADC XLM-II.  The XLM-II is a high compliance "induced magnet" moving magnet cartridge.  I have reported it along with more of my motives for doing so here. The second cartridge choice, the subject of this review, and also by Pritchard, shares a design similarity with the ADC XLM series.  Induced magnet.  Very high compliance.  Similar omni-pivot suspension arrangement.  Internally it is very similar to the XLM.  Externally, it looks rather different.  

Called the Sonus Blue it came into existence after Pritchard had sold his ADC operation to the BSR corporation.  Afterward Pritchard, with further thinking on his induced magnet design, started a new operation where he could continue his work building phono cartridges.  The new firm was called Sonic Research Corp.  Using the same generator body for several different cartridges within the range he differentiated his new models by the color of the front label and the stylus type. There was a Sonus Red label (bi-radial tip), a Sonus Green label (spherical tip), a Sonus Blue label (Pathimax tip -- a Shibata variant) and lastly the Sonus Silver label (Pathimax or elliptical tip) but  the silver had a  less compliant and rugged-ized suspension for use on tonearms of normal effective mass.  There was also a Sonus Blue 'Calibrated' which were Sonus Blues that were hand selected at the factory for having closer-to-nominal measurements.  All of this was circa 1976.  Later on there was a Sonus Super Blue and a Sonus Gold-Blue.

Don't use this cartridge, or any of its like, unless you carry it with a very low effective mass tonearm. There are but a few tonearms low enough in mass to make proper use of this extreme high compliance cartridge.  The Infinity Black Widow is one such tonearm at 3 grams effective mass.  Another is the Mayware Formula IV (4grams effective mass) or the Sonus Formula IV, Transcriptors Vestigal.  Another would be an SME III with exchangeable arm wands (rather than the replaceable headshells of the earlier SME 3009 genre).  Generally speaking, the requirement here is for tonearms of less than 6-7 grams effective mass.  Mounting the Sonus Blue to heavier tonearms tends to result in just average sound quality and early failure of the suspension element within the cartridge.  That is why you should not use a medium mass or heavier tonearm with this cartridge.  It is bad juju if you do.


The Setup DSC_0814.jpg (216570 bytes) Listening on the Thorens TD124   DSC_0820.jpg (166072 bytes) Listening on the Thorens TD150

At present there are two turntables within the listening room ready to accept the Black Widow with Sonus Blue. A restored Thorens TD124 and a restored Thorens TD150.  Each being different from the other in drive type.  A third turntable, a Technics SP10 mkII is also standing nearby but I have yet to cut an armboard that will be needed to mount the Infinity tonearm to it.  For now, the two Thorens will suffice to analyze the essential qualities of this arm and cartridge pairing.  The TD124, having an idler driven platter, will offer greater energy at the platter rim.  The TD150, a polar opposite to the other, gets a mere 2 watts of energy out of its synchronous AC motor to drive the platter assembly by means of a very elastic belt.  With the TD150, there is much less energy at the platter rim to keep it in rotation.  

Having listened to the above two turntables with the Black Widow and ADC XLM-II it will be possible to make direct listening comparisons between the ADC and The Sonus Blue.  A to B.  Inquiring minds want to know. 

The owner's manual suggests a vertical tracking force of 1 to 1-1/2 grams.  I set the tracking force at 1.2 grams.  
Overhang geometry is aligned per Baerwald with nulls at 66mm and 120.9mm.  I used a TAD Arc protractor to adjust this important parameter.  
Azimuth adjust is per mirror method.  As mounted, the mirror indicates a perfectly aligned reflection.  A decent starting point, but not absolute.  Azimuth is adjustable out at the headshell of the BW tonearm. 
Vertical tracking Angle is listed as 20 nominal.  The manual also indicates that the top mounting surface of the cartridge should be closely parallel to the record surface while at play. These are visual approximations used as an initial set point.  Fine tuning of the VTA/SRA can be made by listening to familiar records I keep at hand and use for the purpose of adjusting VTA/SRA.  The Black Widow tonearm is adjustable for VTA/SRA by means of a set screw at its base which is loosened enough to allow vertical adjustment of the tonearm base pillar position, then locked again.
The BW tonearm in this review is equipped with a fluid damping trough with paddle.  For the low compliant Sonus Blue, I keep the trough empty.  No motion dampening needed, I think.
Anti-skate on the BW is a magnetic design.  I've set the slider to 1/2 grams of opposing force.
Using the HFN001 test record, side 2 - track 2, I've measured tonearm/cartridge resonance at 9hz.  This is within the optimal zone (8-12hz) and is at a frequency I sometimes tune other arms/cartridges to.
The owner's manual suggests 400 pF max capacitance and 47K ohms of resistance.  The original phono cables have been replaced with a modern din plug (female-Cardas) and wire (23ga ofc Canaire), from din plug to rca plugs has a measured capacitance of 70 pF left and right channels . The original internal wires (copper) within the tonearm are a 23 gage at the cartridge tags which splices into 33ga wire about the pivot and down to the din output. These are retained.

DSC_0808.jpg (219528 bytes) Stylus type: Pathimax. Pritchard describes this grind as a Shibata with more conical intersects between the ground faces. Stylus mounting is not nude. It appears bushed. In the photo, note the splatters of blue color on the tubular aluminum cantilever. Further identification that this is a "blue".


Listening  listening room environment (click on thumbnail to view image full size)

It is noted above that the cartridge came to me as NOS. (new old stock)  Sometimes, when a NOS product is purchased, the thing arrives dead.  Other times one questions the reason for the existence of this NOS item.  Why was it not sold back in its day?  Was there an unreported defect?  There is definitely some risk associated.  If dead, I'm out my $249.95 (plus $5.00 postage).  At best it will be just like a new cartridge and simply require the normal mounting and alignment procedure (noted above) and then a normal break-in period where the suspension loosens up a little while playing records.  Not all cartridges require the same number of hours to be fully broken in. 

In an article posted by the Boston Audio Society from 1976, there are notes from a speaking engagement given by Peter Pritchard to that audio club. *(see footnotes)  Among the many points of he offered he did mention that the elastomer he used in the suspensions of both his ADC and Sonus cartridges were of a material impervious to atmospheric decay.  Given this heartening information it might be worth hoping that the NOS cartridge might be as good as the day it was made.  Lets hope.

To start, I had it on the TD124.  The first five hours it sounded like my memory of the ADC XLM-II.... only a bit more constrained, less alive, less extended.  But this impression changed as the hours added up.  After 5 hours of steady play it began to sound much more alive and more extended.  Quite worth the listen at this point but not ready yet for any serious listening.

At 30 hours  the sound seems fully developed.  Highs seeming to be well extended and airy.  The low frequency range gained authority as well as additional detail.  Midrange seems of a piece with the upper and lower ranges.  A good sense of aliveness, rich in texture and timbres with those records that offer such.  Attack transients seem very, very quick.  Dynamic capability is very great and capable of reproducing sudden and explosive dynamic transients.

At 40 hours the sound seems much the same as at 30 but with, perhaps, some subtle loosening up still. At this point the entire range of reproduction seems fully developed and ready for some close listening.  

In case anyone wonders the RCA plugs (Bullett - oxygen free copper ) plug into the RCA input of the Hagerman Trumpet phono stage.  At its input the Hagerman provides a 47K ohm resistor.  I've been using the Hagerman Trumpet for a couple of years now and am familiar with its sound when processing the signals from a variety of cartridges.

At this point I remounted the tonearm/cartridge onto the TD150.  I should note that while the TD150 does not offer the same amount of visceral thrust, there are some sonic qualities of the TD150 I value.  It has a sense of ease and effortlessness.  It gets the flow in a very natural manner while at the same time offering quick transients, sudden dynamics.  

On either turntable, there is nothing at all relaxed or laid back about this cartridge and tonearm combo.  

Mercury SR90300. Byron Janis, Prokofiev piano concerto No. 3, Rachmaninoff, piano concerto No. 1, , Kondrashin, Moscow Philharmonic.  (matrix code: RFR-8 both sides) performance / recording circa Spring 1962 on site in Moscow. Robert Fine, Wilma Cozart, Harold Lawrence & Robert Ebernez on 35mm magnetic film with their mobile recording studio in the van.

The Prokofiev. The initial energy pulse of the flutes and piccolos, the transients, have a very sharp attack.  Fast.  Loud.  Suddenly very loud -- and just as suddenly - gone. Very short sustain. Fleeting.  Attack is the functional word here.  Upon first exposure, it shocks the senses.  Having heard this record on occasion with different front end setups, I can say that the speed of the transients rendered by the Sonus Blue/Black Widow setup is on par if not perhaps even faster in comparison with the better equipment I've heard it so far.  Janis' piano strikes are also of the sharp attack - short sustain type.... and these too are reported in a clean articulation giving the sense of speedy delivery.  

This record is well known for its exceptional dynamic content.  It is among the most dynamic I've heard.  That is why I choose to audition the Sonus Blue with it.  Overall there is no let down.  This time It is still a very, very dynamic experience to listen through the Prokofiev Concerto No.3.  

The weightiness of the piano is another issue altogether.  As with the other moving magnet cartridges I've experienced this one, the Sonus Blue, does not provide as much  ballsy body to it as do the moving coil cartridges I've experienced.  It is that sense of robust gutsy presence; -----  In my experience moving coil cartridges tend to have it, moving magnet cartridges......not as much.

Yet, there is weight.  Between the piano and orchestra there is bass, bass with much low frequency detail. At one point one can easily identify between the two instruments in the low octave piano strikes as the double bass plays the same notes in unison.  It is to experience a pleasant addition of texture and timbre.  Such stuff is entertaining and provides some satisfaction for this listener. 

Beethoven String Quartets: Philips 6500 -180.  Quartets No. 10 and no. 11.  Quartetto Italiano.

Numbers 10 & 11: played with emotion and flair. Tone is well balanced between the three instrument types providing warmth of the cello mid bass, soprano voice of the two violins and the alto of the viola. As the playing gets louder the resonating belly of the cello contributes woody body tones to mingle among the string tones.  Never do the violins sound strident or tipped up.  Even when the volume is turned up to "life-like" levels, tonality is comfortable to the ears.  These textured sounds seem well detailed.

Unlike the previously auditioned Merc SR90300, this record does not provide  lightening fast transients or explosive dynamic.  Rather, the initial energy pulse of these notes has a touch of cushion to the beginnings, then a sense of body and then trail-off one might sense as being natural to the style of of the musicians.   Another contrast between SR90300 and this string quartet  is that sense of body and weight; it seemed somewhat lacking on the former is now entirely acceptable on the latter.  

Cat Stevens; Tea For The Tillerman.  Analog Productions / QRP pressing 200g.

I chose this album for the Sonus Blue audition because of its generous quantities of acoustic instrumentals which are rich with timbre and texture.  These are acoustic instruments amplified through an attached microphone as on the double bass.  A typical song structure on this album is: intro -   verse / chorus / repeat.  The intros on these songs tend to be just a few bars of guitar leading into the verse -- a Stevens vocal lyric that tells a story. This part of it is sung with delicacy and accompanied softly via guitar or violin and/or double bass. When the song gets to the chorus  there is a dynamic swing going loud that has the dbl bass producing some genuine slam, drums may kick in as the entire ensemble plus vocals fairly well rocks and rolls. The double bass is notable throughout for the woody tones emanating from its belly and through its F-holes. There is prominent string slap.  This happens time and again, song to song,  throughout the entire album. I find it tasty.

The Sonus Blue/BW managed the dynamic swings quite well, producing satisfying amounts of slam and with speed and emotion. Vocals and instrumentals are richly detailed. The double bass is well reproduced for the timbre and texture I expected to hear.   Satisfying.

Led Zeppelin II, Classic Records 180g.

For a hard rock title I chose this album for its dynamic transitions from folk to full-on bluesy rock. There is lots and lots of atmospheric spaces to be explored within the sound fields created here.  

To begin this is an album that most readers are very familiar with and have known it much of their lives -- as I have.  However, as my system equipment list has evolved over the years I can't help but notice just how much more I can see deep into this album than back when I had bought it new in 1970.  The first track, side one, is Whole 'Lotta Love.  At the drum solo, there is an attempt a creating a psychedelic atmosphere on the part of the band. While John Bonhams' drum kit cymbals ring and shimmer, hang and float to the left and right , Page,  with help from a mixing console and recording engineer Eddie Kramer, creates wicked electronic sound effects, Plant moans and screams as from a distance.  There is a theramin added into the wailing mix of it.  My minds' eye imagines an alternate space.  Almost but not quite demonic in feel.  Not a happy space, but not very scary.   A place with depth and volume for a surreal interlude.  And, yes, I was clear of mind while auditioning this piece for the review.  What is important to note here is that with the Sonus Blue/BW this bit was a convincing illusion.  Lesser gear would not have allowed such a vivid recreation. 

Throughout the album the Sonus Blue/BW allowed for a stunning and highly atmospheric experience. Dynamic transitions were quick and with slam. There was a great sense of atmosphere and space throughout.  I will say the the drum hits and bass, while well articulated and fully extended and fleshed out in detail, did not have the same level of force as I've heard the piece coming through other tonearms and cartridges.  The Shelter 501-II, for instance can present a much more forceful delivery and a much greater sense of body and solidity than does the subject of this review.  However, If memory could not reference this comparison, I might not miss it.

Conclusions and summary:

At the onset I meant to make comparisons between the Sonus Blue and the ADC XLM-II previously auditioned.  The reason for this is the similarity in design and perhaps a desire to decide if the Sonus line of cartridges are really a continuation of Peter Pritchard's XLM line from the days when he owned ADC.  

My subjective impression taken from listening I've done so far is that the ADC XLM-II and the Sonus Blue when played from the same tonearm do in fact sound very similar in overall character.  They are from the same daddy.  ;-)  Yet, and after listening for nearly 50 hours on each cartridge I can say that while they have much in common, I think the Sonus Blue is allowing a little bit more atmosphere, a little more texture, slightly more detail than what I was getting with the ADC. ***

When auditioning the full orchestral and hard rock records I noted above the comparison between every moving magnet cartridge I've heard and every (low output) moving coil cartridge I've heard.  In that comparison the moving coil cartridges (low output types) have all produced a much greater sense of having greater body and solid musical presence.  Meatier, is a term that comes to mind.  In this comparison the Sonus Blue and the ADC XLM-II are alike in that they behave like other moving magnet designs producing a lesser sense of body.  But when there is not reference to a low output moving coil cartridge in comparison, nothing is missing.

When the focus is on how much detail this cartridge reproduces in comparison to the other moving coil types I have, I will say I've been pleasantly surprised at just how good both the ADC and the Sonus Blue are at musical detail retrieval.  They don't miss much and the moving coils I've had don't seem to have an advantage in this category.

I think where I like the Sonus Blue best is in a near-field (close-in) listening situation and listening to acoustic instrument pieces.  String quartets, jazz ensembles, folk music.  Little girls playing guitars (Joni). These are all rendered beautifully and to great listener satisfaction.  It is the larger more powerful recordings where I long for a rig that can make a more ballsy presentation.

I like what this tonearm and cartridge do for the TD150.  It sounds faster and livelier, more dynamic and expressive than with any previous tonearm and cartridge pairing I've had on it to date.  It may take up permanent residence on the little Thorens.  The TD124, I think , appreciates heavy tonearm carrying low compliance moving coil cartridges. In that way it can do some serious slam.


Other notes:

This cartridge, the Sonus Blue, has a compliance rating of 50x10-6cm/Dyne. For the non-techies among us that means a really,(really), softly sprung suspension.  In fact, there were very few tonearms with low enough effective mass to correctly match up with this cartridge.  But when the cartridge is matched to an appropriate tonearm it will report an arm/cartridge resonance within the happy range between 8 - 12 hz. 

The Infinity Black Widow tonearm used in this arm mates well with the Sonus Blue.  Together they measure an arm/cartridge resonance at 9 hz.  (HFN 001 test record - side 2, band 2)  Nicely in the "happy zone".  If all is well with this cartridge, I should not experience any early suspension failures.  Time will tell.

The Sonus Blue, as well as the ADC XLM  cartridges in general have had a reputation for early and abrupt failures of its highly compliant suspension. A typical failure would result in a collapsed cantilever.  There are various owner anecdotal accounts of this happening under conditions that most audiophiles would consider normal use for any other phono cartridge. It is not always clear that suspension failures resulted by mishandling , effective mass mis-match between arm and cartridge or thru other causes.  Pritchard himself said that it was not possible for the elastomer of the suspension lement to suffer atmospheric degradation.**  .  He did note that there was a problem with cantilever failures on previous ADC XLM models due to electrolytic reaction between the different metals of the cantilever and armature.  In an 1976 article ** he said the following: "ADC ;had stylus assemblies coming undone because the cantilever and armature were made of different metals, and there was an electrolytic reaction between them.  Sonus puts a plastic barrier between cantilever and armature."

Sonus Blue specifications from user manual:

Voltage Output 4.0 mV @ 5cm/sec
Compliance: 50cms/dyne x 10-6
Vertical Tracking Angle: 20 nominal
channel balance 1dB
Recommended load: 47k ohms
Total Cartridge weight: 5.5 grams
Tracking Force range: 1 to 1-1/2 grams
Stylus Tip Form: Pathimax----(similar to Shibata but  more conical at intersecting ground faces)



*NOS: new old stock.  Remaining from back in the day, previously not having been used ,or if sealed seal must be unbroken. In this instance the clamshell case that the cartridge was sold in was not sealed...... but appearance of the cartridge indicates a total lack of any previous use.  A bit of lint and dust from having been stored within its container, -otherwise fresh.

** Article. w3/bostonaudiosociety.org/pdf/bass/BASS-04-08-7605b.pdf

***There is a difference in stylus design.  The XLM-II is listed as having a "Diasa" elliptical tip.  The Sonus Blue is listed as having a "Pathimax" which the designer (Pritchard) says is a slightly modified Shibata grind. Neither of these stylus types are nude mounted. But there is a difference to be heard between two cartridges when the main difference is in the grind geometry at the diamond stylus.  Shibata tips are known to retrieve excellent detail and greater amounts of it than will an elliptical.