Explorations in Audio

Karsten Hein

Are you ready to Explore?

In 'Explorations in Audio' I aim to share some practical insights on setting up and optimising an affordable HiFi system. Although one would think that, really, all has been said about HiFi, some surprisingly simple questions still remain, e.g.: 'Is digital superior to analogue?' 'Do cables matter?' 'Can digital cables pick up interference?' 'Should speakers be placed on spikes?' 'Has evolution in HiFi made older gear obsolete?' 'Where should I place my sub?' 'Which room correction works best?' - On the other hand: 'Are these really the right questions?' - We shall see.

What’s new in eiaudio?

While the entries in this blog are divided into the three distinct categories above, you will find a mixed listing of the most recent postings below. The most recent article is shown first. If this is not your first time visiting, the listing below is a good place to quickly check if anything is new.

Your input is more than welcome, as long as you follow the basic audiophile rule of ‘ear over mind’. This means that you do not comment based on what you think you know, but only on the basis of your own listening experience. Please feel free to suggest gear for testing as well as leave comments on the descriptions provided here.

  • Dual CS 721

    Dual CS 721


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Turntables

    The CS 721 was Dual’s flagship turntable towards the end of the 1970s and is, by many, considered to rank among the best Dual turntables ever made. When there is disagreement between the experts, this is usually about the merits of the drive system. Proponents of idler wheel turntables, the ‘Treibrad Classics’, would cite Dual models CS 1219 and CS 1229 as their favourites, whereas belt-drive fans would give preference to the CS 5000 or CS 7000 Golden. The CS 721 was a direct drive design (DD) and, in all fairness to the other two camps, had the most audiophile specifications in terms of rumble, wow, and flutter of them all. However, we do not listen to specifications but to music, of course. And I must confess that I do love the straightforward sound of our smaller CS 505-3 as well. 

    In its most affordable form, the CS 721 was not the most beautiful deck on the market. Its plinth was a base of cheap plastic that was skirted with a frame of laminated wood. Dual had to rely on its good name in audiophile circles in order to be able to sell its products next to the sleek and slim looking Asian designs from Technics, Pioneer, Sony, etc. In fact, the new lack of genuine wood on the products of the German manufacturer from the Black Forest was already a tribute to the increasingly price-driven market. However, the pressure to surpass its competition by means of sophistication assured the CS 721 some highly sophisticated features that are rarely found on turntables of any age.

    One obvious highlight of the CS 721 was its tonally rich made-for-Dual Shure V15-III cartridge with its Super-Track-Plus stylus. The Shure V15-III was an excellent tracker with a low stylus force of merely 0.75g to 1.25g. The cartridge exhibited the usual Shure bass qualities while performing smoothly across an extensive frequency range from 10 Hz to 25,000 Hz. Sadly, the original Shure stylus was too worn out on our model, so that I had to look for a suitable replacement. My first impulse was to take the plunge on a Jico SAS stylus with boron cantilever; however, an indefinite delivery impasse from Jico forced me to settle for a Tonar Shibata stylus instead. Shibata needles were originally developed for use with quadrophonic recordings, reached deeply into the record groove, and, similar to Jico’s SAS styli, were capable of great nuance. However, listening to the two styli in direct comparison, it was hard not to favour the worn-out Super-Track-Plus for its amount of delicacy.

    I also decided that I was going to improve the plinth of the turntable to isolate any physical vibrations from the floating chassis, as the thin plastic vat did not seem sufficient for the job. You will find a full article on the project in the 'Explorations' section of this blog. The result was a solid wood plinth that held the original structure suspended whilst silencing any vibrations to the plastic through the use of rubber foam. I used tri-ball absorbers to further isolate the plinth from potential vibrations caused by steps, slamming doors, or the other Hi-Fi units in the rack. The result was a tonally rich, precise, and undisturbed sound, just as one would expect from one of Dual’s top players.

    Next to its precise and quiet motor, rigid tonearm, and legendary Shure cartridge, the CS 721 offered a host of adjustable settings that were class-leading at its time. Like all Duals of this period, it offered three transport screws to clamp down the chassis during transport. I always loved this feature on the Dual decks, as I had to spend lots of time transporting them in the car. Even the dust cover lift could be adjusted on the CS 721 just in case the spring should soften with age. The tonearm had a 2-fold dampened, adjustable counterweight and could additionally be altered in lateral length to perfectly accommodate most cartridge weights.

    The vertical tracking of the CS 721 tonearm could be calibrated via a lever. Most other turntables only offered socket screws for the purpose. In a similar way, one could adjust the lift angle and the precise touchdown position of the stylus on the record groove. The touchdown speed could be adjusted to suit the weight of the cartridge. It was interesting to note that the manual lift function was not affected by adjustments to the lift height, as this, too, was set via a separate control. When playing back records, the CS 721 could be set from single to infinity mode, by which it would repeat playing a record until it was manually interrupted. When taking a closer look at the headshell, I was surprised to find that the cartridge was clamped into position and additionally secured by two screws. I learned that there had been two headshells sold of which only one could be adjusted. So I ended up purchasing an additional TK-24 headshell to have more freedom in my settings.

    While the tonearm was adjusted by changing the lateral length of the arm and then via the knurled ring of the counterweight, a further adjustment ring was available to set the stylus down force. In combination, this was one of the most sophisticated settings I had ever seen. Anti-skating could be adjusted to suit conical and bi-radial styli. It was conceivable that the CS 721’s vast combination of settings would have been more confusing than helpful to some owners. On the other hand, listening to records had always been similar to fly fishing, with lots of time, skills, and effort needed to achieve a somewhat short-lived result. In other words, the Dual was anything but plug-and-play. All the more, it was gratifying to own and listen to, once the perfect setting was achieved, especially with its new walnut plinth.

    Related Articles:

    < Constructing the Plinth | Dust Cover Restoration >

    Dual Company History

    Christian and Joseph Steidinger started out as a manufacturer of clockwork and gramophone in the German Back Forest town of St. Georgen in 1907. The original company simply bore the family name, until they rebranded as Dual in 1927. The new company name was chosen in reference to their signature “dual-mode” power supplies in which they were true pioneers. Gramophones featuring these supplies, could either be powered by electricity or wound up for playback. Given their early success as a parts supplier, the Steidinger brothers began designing their own turntables.

    During the German economic recovery that followed World War II, Dual became the largest producer of turntables in Europe. The German economy still enjoyed a price advantage over the rest of Europe and became known for high-quality once again. The Steidinger brothers had to hire up to 3,000 factory staff in order to keep up with the growing demand in entertainment devices in the world. Although Dual stretched the brand into other consumer electronics items, their turntables have remained iconic to this day.

    The original Dual company went bankrupt in the early 1980s, following a decade of fierce competition from cheap and sophisticated imports from Japan. It was sold to the French electronics group Thomson SA. In 1988, the German company Schneider Rundfunkwerke AG bought Dual and then spun off the ‘Dual Phono GmbH’ to Alfred Fehrenbacher in 1993. Fehrenbacher produces Dual turntables 'Made in Germany', in the Black Forest town of St. Georgen, based on Dual’s original product lines until this very day.


    • Turntable type: Fully automatic
    • Motor: direct drive, electronically controlled
    • Motor type: Dual EDS 1000-2
    • Speeds: 33.33 and 45rpm
    • Platter weight: 1.5 kg, aluminum die cast
    • Platter weight with rotor: 3.0 kg
    • Platter size: 305mm, dynamically balanced
    • Pitch control: +/- 10%
    • Wow and flutter: < 0.03%
    • Rumble: > 70dB
    • Tonearm: extended tubular, 2x damping
    • Tonearm effective length: 222mm, height adjustable
    • Cartridge: Shure V15 III (1973 - 1987)
    • Stylus pressure: 0.75 to 1.25g (1.0g)
    • Stylus type: Microline, elliptical diamond
    • Channel separation: 28dB @1kHz
    • Frequency range: 10 - 25,000 Hz
    • Cartridge inductance: 500 mH
    • DC resistance: 1,350 Ohms
    • Resistance: 47 kOhms
    • Output: 3,5 mV @1kHz
    • Cartridge weight: 6.0 g
    • Turntable Weight: 7.8 kg
    • Dimensions: (W) 424 mm x (H) 150 x (D) 368 mm
    • Country of manufacture: Germany
    • Year(s): 1976 - 1979

    Jörg Hegemann
  • Constructing a Plinth (Dual CS 721)

    Constructing a Plinth (Dual CS 721)


    Author: Karsten Hein

    Category: Explorations

    Tag(s): Turntables

    Dual turntables were arguably among the best Hi-Fi devices ever made. One reason for this may have been Dual's early start in the technology, their background in precision instruments, their rootedness in steadfast Black Forest traditions, and perhaps also their geographical proximity to the fabled EMT broadcast equipment manufacturer in the Black Forest town of Lahr, about one hour’s drive from Dual’s home in St. Georgen. Dual would have been among the choices available to Elektromesstechnik engineers looking for new opportunities, and vice versa, in doing so they were cross-pollinating and adding to the expertise of both companies.

    Dual’s CS 721 turntable was sold during the late 1970s and offered state-of-the-art music reproduction in combination with its standard, and by now legendary, Shure V15-III phono cartridge. The turntable offered a myriad of settings for the Hi-Fi enthusiast which made it very attractive, but basic models were somewhat reduced in terms of chassis costs, as Dual was already faced with increased price competition from Asia. For our model of the CS 721 this meant that a solid wood plinth had already given way to laminated surfaces and plastic. This was especially true for the plinth, which was arguably the weakest point of this player.

    Since all the Dual’s other components were of exceptional quality, versatility, and musicality, I looked around for available plinth upgrades. However, the models I found were either not very pretty or very expensive. I was looking for a solution that would enhance the acoustics and be an understatement at the same time. And, ideally, I would be able to use all original parts in case someone wanted to build it back later. So, I decided to construct a plinth around the plastic base and to silence any vibrations with evenly spread rubber foam cushions. I would then choose feet for decoupling that combined ultra-strong support with excellent acoustic insulation. In combinaton, these enhancements should raise the Dual to the next level. At least this was my hope.

    I bought solid strips of high-quality American walnut to form a frame that I cut to fit using a miter saw. My friend Thomas was available to support me in this, because getting the trim perfect proved to be a lengthy and difficult process given the semi-professional equipment we had available to us. We glued the pieces to a base board and cut a three cm notch into the back board to hold the cables. I then applied a foam rubber band along the outer edges and across the base board to support and quiet the original plinth construction. We used beeswax to finish the surfaces, as opposed to oil, and placed the Dual CS 721 inside. — Voila!

    I must say that I am happy with the new design and love the sound. How do you feel about the look? Click on the header picture of this article to leave your comment below.


    • Type: Dual CS 721 plinth, and similar
    • Base material: beech multi-plywood
    • Side material: American walnut, waxed
    • Dimensions: (W) 424mm; (D) 368mm; (H) 60mm
    • Acoustic liner: 5x3mm foam rubber
    • Feet: Audiocrast Tri-Ball Absorbers

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  • JBL Xtreme 2

    JBL Xtreme 2


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Loudspeakers

    It seems that from the 1950s right up to the 1990s, adventures in Hi-Fi were about exploring the limits of what was technically possible in terms of faithful sound reproduction. Size, look, and cost seemed to be of lesser concern to Hi-Fi manufacturers and the proud owners of the gear at the higher end of the market. Monstrous receivers, such as the Kenwood KR-9400 of 1974 to 1976, and loudspeakers the size of wardrobes, such as the Electro Voice Patrician 800 of the mid-70s to early 80s, all stood testimony to this fact. The primary music source of this period was the vinyl record, of which Hi-Fi enthusiasts tended to own impressive collections.

    With the advent of more compact music formats, such as the CD (Sony 1982; Philips 1983), the DAT (Sony 1987), and ultimately the MP3 player (Saehan 1997), the audio market was intrigued to learn what else could be made smaller and more convenient. After years of bigger and better devices, the focus of the new millennium was about the question of how much size, weight, and cost could be sacrificed, before the magic of what once was music was lost. Mainstream Hi-Fi engineering therefore began building smaller and lighter gear. Loudspeakers became tall and slim to hide in the living spaces rather than dominate them. Consumers were attracted to smaller speakers that would offer much of the sound of their taller cousins. 

    Speaker cables first disappeared into the walls, before they were ultimately replaced by WiFi or Bluetooth and disappeared altogether. The KEF LS-50 and 'LS-50 wireless' of 2012 to 2022 are cases in point. The LS-50 are compact bookshelf loudspeakers that can best show their sonic virtues when positioned on proper Hi-Fi stands, taking into consideration the dimensions of the room, etc. The wireless version, which is slightly more expensive, offers the added advantage to the Hi-Fi newbie that nothing can go wrong in terms of grounding, interconnects, and loudspeaker cables. It is no surprise that, at the time of writing this article, the versatile and unobtrusive KEF LS-50 have been in production for over 10 years. And yet, the LS-50 is still a conservative home speaker design. Other manufacturers that have taken versatility to the next level.

    The JBL 'Xtreme 2' were the second generation of JBL’s Xtreme Bluetooth speakers, and the pair that is on display here, was owned and given to me for testing by my long-time friend Thomas Kubalsky, who had previously helped me with a number of Hi-Fi issues. He had originally bought them that he could listen to music on his lengthy bicycle tours. To Thomas, the advantages were that the JBL’s canister-shaped body could easily be attached to his load-carrying bicycle, that they were water-proof, and that they had quick-charging batteries that would provide a playback time of up to 15 hours. Bluetooth connectivity had been a positive asset to him as well, but not an absolute must, given the close distance between cellphone and speakers when attached to his bike. By the time these photos were taken, his JBLs had already accompanied Thomas and his bicycle on numerous trips for at least 10,000 kilometres through excessive heat, dust, and rain.

    On the day I decided to take the JBL Xtreme 2 home with me, they had already played a few hours of music at our children’s summer fest at the kindergarten. Thomas had shown me how to pair two Xtreme 2 speakers with my smartphone to create a small array. Although the JBLs had two sets of loudspeakers built in to each unit to allow for stereo playback, the intelligent Bluetooth profiles allowed for left and right channel allocation, when two Xtreme 2s were present. In fact, the profiles allowed for the inclusion of up to 100 loudspeakers in a single array. This amount of speakers should have been enough to power any cocktail or beach party. What really attracted me, though, was the opportunity to learn about the sound quality of such a versatile system with Bluetooth connectivity. How would this hold up in a listening comparison with some real Hi-Fi speakers?

    Similar to other small cabinet designs, the JBL Xtreme 2 used passive radiators to suggest a larger cabinet volume and to improve the bass extension of the two smallish dynamic drivers. This was not a new principle but had been used on many famous speakers, such as the KEF Calinda, built from 1975 to 1976, and the Epicure EPI 500, built from 1973 to 1981. And while the Calinda had one passive radiator at its front, the EPI 500 used one radiator on each side of the cabinet, just like the JBL Xtreme models. And since I still had the EPI 500 set up in our second listening room and was perfectly happy with their sound, what better place to set up the small JBLs. To allow for quick A-B comparison, I placed the Xtremes on top of each EPI speaker with their drivers being flush with those of the EPIs.

    In setting up the EPI 500 speakers, I had taken special care to achieve the perfect balance of dampening and support. By placing the Xtreme 2s directly on top of the Epicures, therefore, I was sure to benefit from that same advantage. During my listening tests, I made sure to raise or lower my ears to the level of the tweeters when switching between speakers. At the time of the test, the EPI 500s were still powered by our Kenwood KR-9400 receiver, a combo that offered an agile and forward sound with lots of natural bass slam. At the same time, the Epicures’ natural timbre was maintained, which made this combination quite enchanting, especially when it came to the playback of real-life music events. It would be interesting to learn, just how much of the original music event would be transported through the smallish JBL Bluetooth speakers. I was fully prepared to believe that this was just another convenience gadget with few other merits than being small and portable.

    When comparing equipment, I tended to listen to the same albums played over and over again. Tonality, agility, transients, and natural bass were just some the characteristics I was interested in. The Epicure speakers could sound anything from muddy to sharp, depending on how they were positioned, supported for stability, and decoupled from the floor. If these aspects were in harmony, they were capable of superb tonal balance, and natural bass. Although with the Epicure bass was not extremely structured, I enjoyed that it was neither laid on too thick nor too lightly when paired with a good amplifier, such as our Becker ST-200, Dynavox VR 70, or even the Kenwood KR-9400 receiver. I put on Diana Krall's album 'Turn Up The Quiet' and listened to this via the EPI 500s first.

    When I switched over to the JBL Xtreme 2s, I again had to wake the Bluetooth connection from its sleep and noticed that the unit I had paired as slave woke up only five seconds later. There was also a small amount of lagging and crackling involved, before the connection was perfectly established. At the same time, I was impressed with the palpable image that the JBLs created smack-centre between the speakers. This effect was instantly familiar to me from well-conceived wired connections. The next aspect that caught my attention was the great similarity in tonality between the EPI 500s and the Xtreme 2s. Both speakers presented Diana's voice in a highly believable fashion and with very similar timbre. The Epicure speakers did manage to separate the vocals from the upper bass a little better and therefore sounded slightly less muddy in this area. This difference, however, was much less than I would have expected.

    The JBLs remained particularly faithful to the source material during slower and more organised passages of music. The louder and faster the music became, the more the speakers began to reveal their natural limitation. This is not to say that they sounded at all bad or poorly designed, it was just that some of the attack and order of the Epicures was not present when listening to the same track via the JBL speakers. To be honest, I would not have thought that portable Bluetooth speakers would even merit such a comparison, but with the JBLs, it did not seem all too far-fetched. This impression was also reflected back to me by my colleague Landon, who walked into the office smiling, saying: "Karsten, I would not have thought to see the likes of them in this office" while pointing at the Xtreme 2s. Upon giving him a demonstration, however, Landon seemed perplexed and, like me, had to confess that he would have assumed the difference between the speakers to be much greater. "So, they are really not bad, huh?" Landon said as he walked over to his desk.

    When pairing the two Xtreme 2s for the first time, they were automatically set to 'Party Mode', which meant that each speaker was playing the full stereo image. This had the advantage that they could be positioned far apart, without sacrificing music information at the point of listening. To set them up in 'Stereo Mode', I had to first download the 'JBL Connect' or 'JBL Portable' app from the App Store. Switching the devices into Stereo Mode only took a few seconds, however, I did experience an issue by which I had some trouble in trusting the music information to be intact. This impression may have stemmed from sudden changes in channel volume that I consciously noticed on a few occasions. The stereo image also seemed overly emphasised at times with a strong but rather unpredictable three dimensional effect and a slightly hollow sound. [This was possibly due to a timing issue between the two channels called Hass effect. Thank you, Jens.] In consequence, there was a slight strain on my ears, which I had not experienced with the speakers set in 'Party Mode'.

    Hence, I switched the speakers back into 'Party Mode' (or mono, in that case) and instantly felt much happier with their performance. In conclusion, I was able to report that the Xtreme 2 were acoustically well-engineered loudspeakers with excellent tonality, whose merits remained sadly concealed by a rather unstable Bluetooth connection. In 'Party Mode', with each speaker playing the full stereo signal, some aspects of vocal and instrument playback were similar to the better speakers of this world. In 'Stereo Mode', however, Bluetooth made the speakers lose all sense of proportion, flinging individual notes at random into the room. The occasional drop in volume, or even the disappearance of one channel altogether, put a strain on the listener and took away from the relaxing and reassuring aspect of the music. In short: A better connection would have turned these into far better speakers, because, physically, they really had a lot going for themselves.


    • Type: portable stereo loudspeaker
    • Connectivity: bluetooth version: 4.2
    • Features: speaker array integration
    • Profiles: A2DP V1.3, AVRCP V1.6, HFP V1.6, HSP V1.2
    • Tweeters: 2.0 cm x2
    • Woofers: 6.99 cm x2
    • Passive radiators: 800mm x2 
    • Rated power: 2 x 20W RMS; bi-amped
    • Frequency response: 55 Hz – 20.000 Hz
    • Signal-to-noise ratio: > 80 dB
    • Power supply: 19V, 3A
    • Battery type: Lithium-ion Polymer 36Wh
    • Battery charging time: 3.5 hours
    • Music playback: up to 15 hours
    • Inputs: 3.5mm headphone jack
    • USB output: 5V, 2A (maximum)
    • Transmitter power: 0-12.5 dB/m 
    • Transmitter range: 2.402 – 2.480 GHz
    • Dimensions: (H) 136 x (W) 288 x (D) 132mm
    • Country of manufacture: China
    • Weight: approximately 2.4 kg
    • Year(s): 2018 - 2022

    80s night
  • Audiocrast Tri-Ball Absorbers

    Audiocrast Tri-Ball Absorbers


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Accessories

    Following my positive experience with the Chinese-made Aucharm acoustic absorbers on our Thorens TD320 turntable earlier this year, I felt encouraged to explore an alternative tri-ball absorber design for our Dual CS-721 turntable. Three months had passed since my original purchase, during which I had further experimented with the Aucharm absorbers. And, although I was generally happy with how they worked, I had also detected a slight wobble that appeared to stem from the three liner holes of the top-liner being asymetrical to the holes in the base. It was difficult to say if this was an error on the side of the producer or simply a part of the design philosophy. Instead of standing stable on the three metal balls, the top section would wobble, until a Hi-Fi unit was placed on top.

    The Aucharm absorbers had two interesting features that made them ideal for the TD320. The diameter of the upper support was smaller than that of the base underneath and perfectly complemented the Thorens' round chassis indentations. And they were height-adjustable to level an uneven surface. These features did make them intersting to keep, despite the slight wobble, but they also made me curious as to what else the market had to offer. The Audiocrast absorbers perfectly filled that niche for me, as they looked to be more sturdy. In addition, I found it interesting that the Audiocrast absorbers came in different colours to better match their equipment. The choices were solid silver, black, and gold. The colour presented here is obviously silver, even if we ultimatley decided to go with black for our Dual CS-721 turntable, because it looked more accomplished in combination with the original black top half of the plinth.

    The Audiocrast absorbers were not height adjustable. This was important to keep in mind, if one was to be fussy about the turntable being absolutely level. They also featured a centre prong with a rubber seal around it. The rubber seal held the top half of each absorber in place over the base. A welcome feature, if the unit on top was to be pushed across a shelf or the floor, however, this design would also compromise the insulation characteristics of the absorber, simply because there was an additional acoustic bridge in addition to the ball coupling. Furthermore, the Audiocrast absorbers had 1mm plastic cushions on the top and bottom surfaces that might affect the overall purity of sound. My expectations therefore were not all too great, and I ordered a spring-based absorber system in addition to the tri-ball absorber to have more choice when comparing the affect on sound.

    To my surprise, the Audiocrast absorbers surpassed the Aucharms in combination with our Dual turntable with American walnut plinth at an instance. Bass frequencies sounded cleaner and had slightly greater punch. Both the Audiocrast and the Aucharm absorbers surpassed the spring-loaded absorbers, as their impact on sound was still comparable. It seemed that the sping-loaded absorbers, while being superior isolators, did not offer enough stability to quiet the inherent vibrations of the turntable motor. Alternating between the three absorber designs, I found that the black Aucharm look worked far better with our Dual than the silver ones did. As the Audiocrast absorbers sounded superior in combination with our CS-721, however, I would need to order them in black as well. The spring absorbers, on the other hand, were so special that, at the time of writing this, I was not sure if there was a scenario in which their lack of support might ever come in handy.


    • Manufacturer: Audiocrast
    • Type: tri-ball acoustic absorber
    • Application: vibration dampening and insulation
    • Base material: aluminum alloy
    • Ball material: stainless steel (ceramic optional)
    • Available colours: silver, black, gold
    • Load capacity (set of four): 200 kg (max.)
    • Dimensions: (W) 39mm; (D) 39mm; (H) 23-24mm(*)
    • Centre screw (optional): 8mm
    • Weight: 264-272g per set; (66-68g, each(*)
    • Country of origin: China

    (*) Note: differences in weight and dimension are due to variations in ball diameter

    Digitising Records
  • Dynavox VR-70E II (Part 2)

    Dynavox VR-70E II (Part 2)


    Author: Karsten Hein

    Category: Explorations

    Tag(s): Power Amplifiers

    When I wrote my first review of the affordable Chinese import tube amplifier back in January 2022, I promised that I would write an update on my impression of the VR-70E II after it was returned to me following some modifications. My reason for having the amplifier revised had been the level of humming, its lack in audiophile frequency extension, as well as poor transients and imaging, which altogether resulted in a certain blandness of sound. My original tests had been conducted with our Dynaco PAS-4 tube preamplifier and the formidable 8 Ohms Tannoy XT-8f tower speakers.

    Upon my handing in the amp, the tube specialist had offered a speedy service within a couple of weeks, to which I had agreed. Then, however, he had somehow gotten caught up in other projects and seemed to have forgotten about me. When he then started to ignore my phone calls—after five months of patience on my side—I decided that enough time had been wasted and picked the VR-70E II up in close-to-original condition. I think we were both surprised and sad that I should have taken such resolute measures, but it seems that I had simply run out of patience with him. On my drive home, with the amp in the back of our car, I was wondering what could be done next: Sell it? Keep it for a later project?—I would need to listen to it one more time to make my final decision.

    Now, I am not sure if you sometimes have a sonic memory of the things that you have listened to. We commonly have this gift when it comes to scents or smells. As we often connect scents with emotions, we tend to remember them for a long time. This is especially true for the early experiences in our lives, and we might remember the smell of our kindergarten, or school, or perhaps of the house of your grandparents. Well, it seems that some people have a sonic memory.

    For instance, I vividly remember the sound signature of my first CD player. This was a 1988 JVC XL-Z444, and I recently even purchased this unit again, just to enjoy the sound one more time. This was not an audiophile CD player by any means and it does not need to be discussed in this blog, but its stoic crudeness and pitch-black backdrop certainly had its charm and served to set it apart from vinyl records, cassettes, and radio broadcasts at the time. I really celebrated listening to it again and having my juvenile memories confirmed. In a similar way, I still held a sonic memory of VR-70, and I was a little bit frightened of having this revived the second time around.

    With five months having passed since my original test, the set-up environment of our smaller system had meanwhile changed. The Dynaco tube design had given way to our Restek V1 solid state preamplifier. The speakers, too, had been replaced. Instead of the Tannoys, a pair of Epicure EPI 500 had found its way into the lineup and had just been optimised in terms of coupling towards the hardwood floor. In the meantime, I had learnt from trying to match the Dynaco with our B&K ST-140 amplifier that this preamp could easily have a lowpass effect in some set-up combinations. In my first test, I had all too hastily attributed the experienced loss in top-end to the Dynavox amp. This had happened, because I had been as yet unaware of the PAS-4’s shortcomings in terms of compatibility.

    Hence, when I sat down to listen to the VR-70 E II this time around, the treble was more open and spacious with improved transients right from the start. I was also happy to find that the original tube-hissing that I had heard from the amp had disappeared. The reason for this was twofold: first, the Restek V1 was a dead-silent preamp to begin with, whereas the PAS-4 produced a mild tube hissing on its own; second, the technician had found a grounding problem with the VR-70 itself. He saw that the properties of its pharadeic cage had been compromised by the bottom plate being paint-coated. He had consequently removed the paint to include the floor plate with the chassis grounding scheme. This had a significant effect on the VR-70's noise floor, which was now hardly audible, even with the ear held near the tweeter.

    The original lowpass effect in combination with the Dynaco had also made me overly hasty in turning the amp in for service—after just 40 hours of listening. Since then, the technician had adjusted the amp’s bias to 350 mV and allowed it to run for a few more hours. This, too, had given the factory-new amplifier some time to homogenise its frequency response (break-in time) and helped to take some of the initial harshness off the critical vocal section. With the top-end having opened up and the bottom end having gained power due to reduced grounding noise, there was now more depth and dimension to the music in many ways. In direct contrast to the B&K ST-140 solid state amp, which had performed to our satisfaction in this position before, the VR-70 E II presented a considerably larger stage with very similar tonality. 

    Vocals seemed grainier on the Dynavox, an impression that did not lessen even when the tubes were at full operating temperature. At the same time, voices seemed slightly more distant on some recordings. I especially noted this effect on Tony Bennett & Diana Krall’s album “Love is here to stay”. This may have been intrinsic to the Chinese tubes that had surely not been chosen for their superior tonal characteristics but rather for their bang-for-buck regarding their use on an entry-level amp. At the Dynavox’s current quality of output, I was fine with the idea of having to upgrade the tubes in some not-too-distant future in order to fulfil the promise of audiophile bliss.

    From my original four complaints about the amp: bland top-end, tube hissing, poor imaging, and grainy voices, only the last point remained. And this—surprisingly—despite all original parts still being present. I felt a little silly for not having tried matching a different preamplifier in the first place, but then again, I probably would not have learnt about the chassis grounding issue on my own. The experience only shows why it is so important that this page is called “Explorations in Audio” and not 'Facts' or 'Truths' in Audio. Life means ever learning, and only the mindset of the Explorer can expect and appreciate the surprises that the journey brings. To prove the point, and also to treat myself to today’s Father’s Day present from my wife, I will stop writing and focus my attention on the 1970s album “New Skin For The Old Ceremony” by Leonard Coen on vinyl.

    Back to Part 1 | [to be continued with new tubes…]


    • Power output (RMS, 8 ohms):  2 x 40 watts
    • Input impedance:  20 kOhm
    • Pre-amplifier tubes:  2 x 6F2 (ECF82)
    • Power amplifier tubes:  4 x EL34 (ultra-linear)
    • Tube bias:  300 - 350 mV
    • Frequency response:  10 - 40,000 Hz
    • Total harmonic distortion:  0,1%
    • Signal to noise ratio:  >88 dB
    • Damping factor:  N.N.
    • Output terminals: 4/8 Ohm, gold plated, for spades or bananas
    • Dimensions:  (W) 35,0 cm x (D) 30,0 cm x (H) 18,5 cm
    • Weight:  14,5 Kg
    • Year:  2013 - 2022

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