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.

  • Tube Town PI18

    Tube Town PI18


    Author: Karsten Hein

    Category: Explorations

    Tag(s): Guitar Amplifier

    Some weeks ago, Martin asked me if I could help him sell his guitar amp in Frankfurt. Having only limited experience with equipment for musicians myself, I asked him if he really thought I was the right person to contact about this. 

    He explained to me that he was selling an 18 watts all-tube amplifier similar to the old Marshall legends. At its heart was a generous Tube-Town board by the name of PI18. This allowed the finished amplifier to resemble the well-known Friedman "Pink Taco”. 

    Martin had not built the amplifier himself but rather asked Peter of Linnemann Amplifiers in Ilmenau to do the job for him. Upon Martin’s request, Peter set the amp’s board to “tight” to resemble the British sound. The 18 tube watts in combination with the 12-inch Celestion full-range driver were sufficient for an ultra-dynamic sound experience. This amp could play loud if needed. On the other hand it could be played sofly, just from changing the settings on the amp.

    At over 60cm in width and 50cm in height, this was a sizeable guitar amplifier, and its 17kg of weight did serve to highlight the quality of materials and craftsmanship throughout. Nothing seemed amiss or even accidental on this amplifier. The synthetic leather finish had been applied seamlessly around its softened corners. The colour scheme was perfect.

    And although I was not too happy carrying Martin’s amplifier upstairs and have not yet heard it perform myself, I can easily understand that this one deserves to find a new owner who will once again appreciate its genuine capabilities that are so much more than modern digital equipment sometimes has us believe.


    • Type: all-tube guitar amplifier
    • Amplifier output power: 18 watts
    • Features: FX loop (bypass)
    • Tubes: 3x 12AX7 (pre), 2x EL84 (pwr)
    • Tone adjustment: tri-band equalizer + gain
    • Tone structure: tight (British sound)
    • Sound impression: ultra-dynamic
    • Resistance: 4 / 8 / 16 Ohms, adjustable
    • Full range driver (12"): Celestion G12 M
    • Speaker power: 65 Watt
    • Frequency response: 75-5,000 Hz
    • Operating voltage: 240 volts / 120 volts
    • Replica: Friedman "Pink Taco"
    • Dimensions: (W) 610mm, (H) 530mm, (D) 230mm
    • Weight (incl. power cable): 17 kg
    • Manufacturer: Peter Linnemann Amplifiers, Ilmenau
    • Country of manufacture: Germany
    • New price: approx. 1,400.00 EUR
    • Year of manufacture: 2021

    Jörg Hegemann
  • Duevel Bella Luna

    Duevel Bella Luna


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Loudspeakers

    [Test in progress. Full review coming up.]


    • Type: floor-standing 2-way loudspeaker
    • Design: omnidirectional, vented cabinet
    • Frequency response (±3dB): 40 Hz - 23,000 Hz
    • Power handling (RMS): 150 watts
    • High-frequency driver: 4,4cm titanium dome tweeter, horn-loaded
    • Midrange-to-bass driver: 22cm dynamic, kevlar diaphragm
    • Woofer specifics: die-cast chassis, M-roll surround
    • Diameter of horn diffusors: 280mm
    • Gap between diffusors: 47mm
    • Crossover frequency: N.N.
    • Crossover design: phase-linear
    • Power sensitivity (SPL): 91 dB
    • Nominal impedance: 6 Ohms
    • Dimensions: (H) 1050mm x (W) 325mm x (D) 325mm
    • Weight: 30 kg
    • Country of manufacture: Germany
    • Year(s): 1999 - 2023

    crossXculture Business Language Training
  • Canton GLX 100

    Canton GLX 100


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Loudspeakers

    In 2013, not long before our daughter was born, my wife Sabina and I went out to search for a pair of loudspeakers for us to restart our journey in the appreciation of music. When it came to audiophile pleasures, we were both out of practice and felt unsure of what to aim for. Visiting some local HiFi showrooms around Frankfurt, we finally decided that we did not understand enough about loudspeakers to make a permanent decision. However, we did feel some attraction towards Canton speakers that outperformed the competition in terms of clarity. We finally settled on a pair of used Canton Vento 890 DC that we bought from a vendor in Günsburg, Bavaria, unaware that the company was actually located very close to our home in Frankfurt am Main.

    Canton was our entry ticket to audiophile listening, even before we fully grasped what this might mean. The 890 DC were revealing speakers that could show the merits and flaws of a system in an instant. They led to us gradually improving our front-end from the music source, via the preamp and amplifier, to the cables connecting the devices, until we noticed a flaw in the Ventos themselves: No matter how hard we tried, we could not get those speakers to sound tonally balanced. The treble, and perhaps also the upper midrange, simply sounded too bright to be natural and did not match the otherwise commendable sophistication of the speakers. Listening to the Ventos could easily become tiring because of this effect and we ended up selling them.

    Exactly ten years had passed since our original purchase, and I found myself listening to a pair of Canton speakers once again. Instead of being large floor-standers, however, the GLX 100 were small and inconspicuous bookshelf speakers. They were finished in modest anthracite rather than our Vento’s shiny silver, and the soft fabric dome tweeters made me hopeful that the resulting sound would be less harsh than I had previously experienced with or 890 DCs. And I was sure to give the GLX 100 bookshelf speakers the royal treatment by putting them on our MDF loudspeaker stands and taking good care when positioning them in the room to get the tonal balance right. The GLX 100 had been a gift to my daughter from her great aunt, and I was glad to have the opportunity of auditioning them here first.

    As usual, the Cantons opened with a wide soundstage and even gave the impression of proper stage depth when placed a little deeper into the room. Their depiction of female vocals was penetratingly transparent, thus creating an instantly engaging experience that kept the ears at high alert. I also noticed a raspiness in the upper midrange that I had trouble identifying. It could be that there was some competition between the midrange and the tweeter that was causing it. Just to be sure, I removed the front metal grille which, to my ears, made matters worse. These speakers had obviously been designed for the grille to be in place. To achieve greater tonal balance, I moved the GLX 100 closer to the front wall. This gave them improved bass foundation, however, it did not lessen the energy of the treble which proved to be too much for my ears.

    I reluctantly turned on the tone controls on our preamplifier and dialled back the treble by 2-3 dB. This was my last resort when speakers were obviously off balance. The silvery and over-accentuated treble subsided and revealed a pretty decent speaker underneath. Without this measure, the GLX 100 were obvious candidates for ear fatigue, if they were driven with a semi-revealing front end. Engineered for the point of sale, the Cantons would have dazzled shoppers in the 1980s and have enjoyed the ride home more often than they deserved. There was no question that Canton knew how to build great speakers for those who had the money and interest in learning about them, but I could easily see that they also knew how to sell speakers to those still new in this territory.


    • Type: 3-way bookshelf speaker
    • Principle: closed, with dynamic drivers
    • Frequency range: 28 - 30,000 Hz
    • Crossover frequencies: 800 / 5000 Hz
    • Low frequency slope: 12 dB per octave 
    • Midrange slope: 6 dB per octave
    • Tweeter: 20 mm, fabric dome tweeter
    • Midrange driver: 28 mm, fabric dome tweeter
    • Woofer: 220 mm, paper cone
    • Nominal impedance: 8 Ohm
    • Power handling (RMS): 65 Watt
    • Resonant frequency: 69 Hz
    • Terminal: spring-secured for 2mm cable
    • Number of terminals: single wire
    • Dimensions: (W) 245mm x (H) 370mm x (D) 215 mm
    • Country of manufacture: Germany
    • Weight: 5.5 kg
    • Year(s): 1983

    80s night
  • Dual CV 1260

    Dual CV 1260


    Author: Karsten Hein

    Category: Gear & Review

    Tag(s): Integrated Amplifiers

    This rather pretty looking Dual CV 1260 integrated amplifier was handed down to my daughter from her recently deceased great aunt. It came along with a Dual CS 630Q direct drive turntable, a Dual CT 1260 tuner that was connected via 5-DIN plug, and a Denon DCD 660 CD player. There was even a Dual C 816 tape deck that I had some trouble finding worthwhile cassettes for in these days. Two Canton GLX 100 bookshelf speakers served to wrap up the Mid-Fi ensemble. Before surrendering these new arrivals at our house to our 9-year-old daughter, I had to test them and make sure the were safe to use, of course. Any publication of these test results is purely incidental, of course.

    I must confess that there was something exciting and liberating about reviewing gear at this price level. After all, unless developers were asked to add intentional flaws to their designs, there was no reason why lower-priced gear could not sound as good or even outperform higher priced contenders. Proper acoustics had very little to do with the price of the components and was more reliant on the ingenuity of its designers. The speaker manufacturers Elac and KEF had demonstrated numerous times that audiophile listening pleasures were possible even at modest price points, and examples of purposefully poor designs were not difficult to be found in the industry. Rotel, for instance, had given their RC-9608X preamplifier a plastic floor board that sacrificed the pharadeic cage that the full metal enclosure would otherwise have offered. Manufacturers need to make sure that their devices perform according to the relative position that is reserved for them. 

    Therefore, I did not know what to expect of Dual’s 1984 amplifier. For one thing, it had a larger brother, the CV 1460 Class-A amplifier of the same year that offered 95 watts per channel into an 8 Ohm load. And then, both devices were no longer built by Dual in Germany, but rather by the Japanese manufacturer Denon. As I unwrapped the 1260 from its protective bubble foil, I noticed how positively sturdy and heavy the unit felt. At just over seven kilos, the moderate-sized amplifier did not feel puny at all. Turning the Dual on for the first time, I was positively surprised by the elegant look of the softly illuminated output level meters. I made a mental note to capture these in my photos of the unit. I did not want to test the CV 1260 in combination with the Canton speakers, and so I hooked up our Epicure 3.0, half expecting the little amp to fail miserably.

    I began my listening explorations with Carla Bruni’s 2014 live album A L’Olympia that I played on our trusted Denon DCD 1420 CD player. Our Epicure 3.0 speakers were connected via 2m runs of Belden 9497 as single wire. As both the speakers and the Denon amplifier had spring-loaded binding posts for small diameter speaker bare wire, I had to clip off my usual banana plug terminations. The idea that speaker cables need to be terminated to be of higher quality is relatively modern, of course. In reality, fewer material transitions and less mass in the signal path should have a positive effect on sound. The tinned Belden snapped into place, and, as these cables had already seen many hours of use, the resulting sound was pleasant and balanced from the very first minute. It was the instantly familiar sound signature of excellent receivers, such as the Harman Kardon 730, that surprised me most about the Dual. 

    In combination with the Epicure 3.0, the midrange sounded warm and alluring. The soundstage was clean and well-ordered, and there was a surprising amount of space around each music event, especially when considering the relatively moderate power of approximately 2x 90 watts into 4 Ohms. Rated at 44 watts power consumption at idle and labelled as Class-A amplifier, it was safe to assume that average household listening volumes were served by pure Class-A transistor power. This certainly showed in the music performance. While the Dual presented a realistic amount of detail, the top-end never felt detached or edgy. There was wonderful cohesion and flow in the music, although the dynamics did not quite reach the level of a Luxman L-10

    Bass performance was in balance with the rest of the music. It was not as tight-fisted as on the Luxman L-10 and also not as boomy as on the Pioneer SX 850. Complex bass sounds were better layered than on the Harman 730. The more I listened, the more I fell in love with the abilities of this integrate amplifier, and as the sun set, I started to enjoy the illuminated front with the level meters waving consistently at under 1 watt. The piano keys on Carla Bruni’s album sounded deliberate and simmered naturally, and I was once again reminded how good the Epicure speakers really were, even when powered by an inconspicuous mid-Fi Dual amplifier from the early 1980s such as this one. What a delightful discovery this was. My daughter would be spoiled from the onset by beginning her journey into music with this Dual.


    • Type: integrated solid-state amplifier
    • Principle: Class-A amplification
    • Output power (RMS): 2x 60 watts
    • Frequency range: 10 - 45,000 Hz
    • Signal-to-noise ratio (line): 88 dB
    • Signal-to-noise ratio (phono MM): 68 dB
    • Channel separation: input 70 dB / output 55 dB
    • Signal damping: >70
    • Number of audio inputs: 5
    • Phono (cinch): 2.5 mV / 47 kOhm (MM)
    • Tuner (cinch): 200 mV / 47 kOhm
    • Tape1 (DIN): 200 mV / 47 kOhm
    • Tape2 (cinch): 200 mV / 47 kOhm
    • Monitor (cinch): 200 mV / 22 kOhm
    • Number of audio outputs: 3
    • Rec-Out Tape 1 (DIN) / Tape 2 (Cinch, Ri 470 Ohm)
    • Headphone socket (jack-type): 6.3 mm
    • Tone control: bass and treble (+/- 6 dB), loudness
    • Bypass of the tone controls: not available
    • Filter: subsonic
    • Loudspeaker terminals: two (8-16 Ohm)
    • Power consumption: 680 watts (max.), 44 watts idling
    • Features: two combined VU meters, illuminated
    • Dimensions: (W) 440mm x (H) 97mm x (D) 265mm
    • Weight: 7.1 kg
    • Country of manufacture: Japan (Denon)
    • Year(s): 1983 - 1985

    Digitising Records
  • 30. High-End Network Noise Filter

    30. High-End Network Noise Filter


    Author: Karsten Hein

    Category: High Fidelity

    Sintron Distribution GmbH sells a whole range of affordable gear under the name of Dynavox to target entry-level audiophiles. Among the many worthwhile components, there is the VR-70E II tube amplifier that, with some minor amount of tweaking, performed very well in our listening setup. The Dynavox brand name can also be found on audio accessories such as cables, plugs, and power distributors both with and without filter technology. The Dynavox X7000, which lent its components to the construction of the High-End network filter that is the subject of discussion here, had most likely been a capable power conditioner to begin with. However, the aim of this construction project was to take filtration technology to the next level.

    My first exposure to the High-End network filter project was on one of my routine visits to my trusted audio technician. As I walked into his shack, I could see him applying a string of ferrite beads to a freshly laid power cable inside the Dynavox X7000’s housing. I was surprised by the amount of free space inside the large X7000 cabinet, and Winfried explained that the original filter design had only taken up about a hand’s breadth of room inside the 43cm wide enclosure. And yet, the unit was large enough to hold far more sophisticated filters and even allowed for the use of isolating transformers. Winfried further explained that Dynavox’s use of high-quality materials on the cabinet, sockets, and switches made it the ideal basis for his new construction.

    This must have been in early 2020, and it was not until two years later that I asked Winfried what had become of his High-End network filter design. He seemed pleased about my asking and offered to lend it to me for a few days so that I could find out for myself. He explained that he had galvanically separated the audio circuit from the household grid through isolating transformers allowing for 300 watts of throughput power. When seen from the rear of the unit, looking from left to right, there were two power sockets filtered for analog music sources, two power sockets intended for digital music sources, and two sockets without filters. On the power input side, a number of ferrite beads served to prevent high frequency noise from passing through the interior circuits.

    Winfried’s new power filter stages were designed to target the anharmonic frequencies of 50 Hz. These were at 150 Hz, 250 Hz, 350 Hz, 450 Hz, etc. The filters became more effective the higher the anharmonic frequency was. Distortion measurements conducted by an independent laboratory found the filter strength to be 60 dB at 1,000 Hz and 90 dB at 10,000 Hz. These were very good results for any power conditioner. In addition to this, Winfried’s High-End network filter provided DC protection through a combination of bridge rectifier and capacitor and also maintained the original voltage control display that could be switched off for maximum noise protection. The touch and feel of the finished unit was great. It felt as if it had been carved out of a solid piece of metal, an effect that was supported by its weight.

    Back in our upstairs listening room, I connected the filter to the same wall outlet that had already proven itself as being relatively free of distortion on our existing system. As we lived in an apartment building that was a home to four families and located in a mixed residential and industrial area, all observations on the electrical noise floor were relative and subject to change, depending on the day of the week, the time of day, and the number of other household devices that were active on the grid. In addition to this, our house was located within a five kilometre radius from the airport and about 800m beeline from the local tram and train lines. On clear days, we also had unobstructed view of the radio tower on Feldberg and the airport’s revolving radar with visual signal light—not to mention the many cellphone antennas that were perched on nearby buildings. 

    To filter out the cacophony of electric noises on our power grid was the proclaimed job of Winfried’s network filter. Where, if not here, could a device of this kind prove its merits? — I connected our Rotel RC-960BX preamplifier to the power output that was designed for analog devices and our Denon DCD-1420 CD player to the power output for digital devices. Both of the sources were considered solid entry-level components. I then connected my custom-built Echle LF-3519 solid state amplifier directly to the wall outlet and warmed up the system. The first thing I heard was a mild buzzing sound emanating from the filter’s large transformers, followed by the by now familiar noise floor from the high-gain amplifier. I was a little disappointed that the amplifier’s noise floor did not drop significantly with the filter attached. Sadly, this did not change even when I connected the amplifier directly to the unfiltered output of Winfried’s power conditioner.

    I chose a-ha’s 2017 MTV Unplugged album “Summer Solstice” as listening sample, as it was a solid live recording with natural instruments, spoken and sung male and female vocals, and a small venue audience that could sound believable in our listening room. Songs like ‘This is our home’ provided a bass drum impression that allowed for a good sense of proportion, attack, and decay. Listening with the filter in place, I noticed that stereo imaging was much improved. ‘This is our home’ begins with a spoken introduction in which the first speaker is sitting further to the left. Without the filter, the two musicians appeared to be speaking from the same position. There also seemed to be more space around the instruments with the sound stage panning further and more seamlessly from left to right. The position of the audience seemed more realistic with fewer holes in the sound stage.

    Power plug polarity had a major effect on the overall sound signature. This came as a surprise to me, as I would have expected the network filter to have a harmonising effect between the units. Without the filter in place, it was immediately clear to me which plug polarity was my preference. However, this was not so easy for me to decide with the filter in place. In one plug combination the sound became lighter and more airy and in another darker and tonally richer. I would normally have preferred the second, as it offered a stronger mid bass and a weightier and fuller sound, if it had not been for an increased amount of grain in the midrange that made vocals slightly less believable. No matter how much I tried different plug combinations, I was always left between those two choices: darker and more voluptuous with slight grain on the vocals or light and airy without the grain. But which one was correct?

    Listening to music without the filter again, I noticed that tonality remained slightly shifted upward towards light, airy, and slightly sharp in the treble. Bass notes were lacking a little energy and could not free themselves so much. My preference would have been to keep the filter in place, and to set plug polarity to produce the darker tonality but without the slight sense of grain. This, however, was a result that I failed to reach on our system. I decided to report my findings back to Winfried, hoping that he could further help me in understanding the unit and the effect I had found.  — Audiophiles are a tough species to satisfy, I suppose. 

    < 4. Power Filtering | Dynavox Tube Amp (Part II) >


    • Type: 240 volts power isolator and filter
    • Isolation principle: galvanic separation
    • Features: soft-start (to offset transformer magnetisation)
    • Filter principles: low-frequency harmonics and HF noise
    • Filter frequencies: 150 Hz / 250 Hz / 350 Hz / 450 Hz (anharmonic)
    • Filter strength: 60 dB (@1,000 Hz); 90 dB (@10,000 Hz)
    • DC-filtration principle: bridge rectifier and capacitor
    • Throughput power (max.): 300 VA
    • Power sockets (switched): 2x analog, 2x digital, 2x direct
    • Switchable display (on/off): mains voltage input, LCD (amber)
    • Cabinet basis: Dynavox X7000 Power Conditioner
    • Dimensions: (W) 430mm x (H) 100mm x (D) 305mm
    • Country of manufacture: Germany (custom-made)
    • Weight: 18.5 kg
    • Year(s): 2020 - 2023

  • Let's explore together

    Let's explore together

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    If you happen to live in the greater Frankfurt / Rhine-Main area and own vintage Hi-Fi Stereo classics waiting to be explored and written about, I would be honoured to hear from you!

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    Audiophile greetings,