Alex 54

Wammer
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About Alex 54

  • Rank
    Techie with ears

Personal Info

  • Location
    UK

Wigwam Info

  • Turn Table
    Townshend Elite Rock
  • Tone Arm & Cartridge
    Excalibur/Decca
  • SUT / Phono Stage
    Rega Fono MM MkII
  • Digital Source 1
    Linn KDSM Mk3
  • Digital Source 2
    Oppo UDP-205MR
  • DAC
    Linn KDSM Mk3
  • Pre-Amp
    Linn KDSM Mk3
  • Power Amp/s
    Nord One Up NC500 II
  • My Speakers
    Glastonbury Tor Mk1
  • Headphones
    Oppo PM-1
  • Trade Status
    I am not in the Hi-Fi trade

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  1. Alex 54

    AC Panel Meter

    It's a moving coil meter, you need to be absolutely sure what the coil sensitivity is before connecting it to anything. Just because the scale reads up to 300V AC doesn't necessarily mean that is what is needed to drive it.
  2. Audioquest Dragonfly Cobalt DAC and Headphone Amplifier By Alex Colburn Introduction: Four weeks into the COVID-19 lockdown I’m working from home and spending a lot of time sat in front of a computer screen in the study. Distractions are only too frequent; noises and voices filter through from inside and outside disturbing concentration and leading to long periods of gazing out of the window. Why is there so much activity, there’s supposed to be a lockdown in progress? I decided to try and lock out (no pun intended) the disturbances and donned a pair of headphones plugging them into the audio out socket on the computer. It seemed to be working, distractions eliminated and I get to listen to a great selection of music. Though I had plugged in the odd set of ear buds or cheap headphones in the past, this was the first time I had seriously considered trying some headphones of decent quality. Listening to music I am very familiar with on my Oppo PM-1 headphones it became painfully obvious the quality of the audio output on the computer was sadly lacking in many respects so I began to wonder what options were out there to improve the situation. A little bit of Internet research revealed a multitude of potential solutions ranging in price from a few tens of pounds (the usual multitude of Chinese offerings) to thousands. To narrow down the choice, I decided it had to be small and simple to implement, have USB connectivity, did not need external power or batteries and flexible enough to be used with other devices like mobile phones. I didn’t want to spend a lot either as hopefully the lockdown will not last forever. Reviews of the various options pointed me in the direction of Audioquest’s Dragonfly series of USB powered integrated DAC and headphone amplifiers. I eventually settled on their Cobalt model and in due course placed an online order with one of their numerous stockists. Interestingly, while speaking to the dealer on the phone, I learned that business was very good in the HiFi trade and generally bucking the retail trends during the pandemic. Description: Audioquest who are probably better known as a cable manufacturer, expanded their product range to include DAC’s a few years ago. The Dragonfly series of DAC/headphone amplifiers bear a marked resemblance to a USB pen drive, a long narrow body with gold plated USB A plug at one end and 3.5mm stereo jack at the other. Three versions are available with the colour of the casing uniquely identifying each model, Black, Red and Cobalt. Black is the entry-level model with price and performance increasing through the red to the top of the range Cobalt. The Cobalt model is a vivid blue colour and since cobalt is a hard shiny metal it clearly refers to the cobalt oxide that makes up the cobalt blue pigment well known to artists. The body construction appears to be a robust powder coated die cast aluminium with a colour coordinated plastic push-on cap to protect the USB connector when not in use. A translucent dragonfly logo emblazoned on the body is illuminated by multi-coloured LED’s inside the body to indicate its various operating modes. The Dragonfly was delivered in classy glossy packaging with instruction manual, free trial offers for the Roon control point software and Qobuz subscription, a protective leather storage pouch and Audioquest Carbon-level Dragontail USB A to USB C cable for connection to android mobile phones. Users of Apple iPhone/iPad devices with their proprietary “Lightning” connector will require an additional USB A to Lightning adapter cable. Audioquest recommend the Apple USB to Lightning camera adapter, which they say is more robust, sounds better and has the bonus of allowing simultaneous charging. Operating systems supported include: Apple OS X 10.6.8 (Snow Leopard) or later, Windows 7-10, Apple iOS 5 or later and Android mobile devices. Standard control point software such as Roon can be used to operate the Cobalt but Audioquest have worked with Qobuz and Tidal to integrate Dragonfly DACs with their apps over a broad range of platforms. Technical discussion: The casing of the Cobalt model has a deeper semi-cylindrical appearance than the other models in the range presumably because of the extra electronics packed inside. Based on the USB 1.0 standard, the interface runs on Gordon Rankin’s “StreamLength” asynchronous transfer firmware and does not require the installation of software drivers. Inside the DAC is the flagship ESS Sabre ES9038Q2M in mobile version, which generates an ultra low jitter clock signal to control the conversion process and a Microchip PIC32MX274 microcontroller. The “Monoclock” single clock architecture allows the Dragonfly to provide greater resolution and clarity compared to other DAC architectures with multiple clocks. Audioquest claim that the minimum-phase slow roll-off filter in the ES9038Q2M “results in naturally expressive sound that is always emotionally engaging and never fatiguing” Audio file formats supported by the DAC include MP3, PCM up to 24bit 96kHz and MQA with the Dragonfly logo illuminating in different colours to reflect the mode the DAC is operating in. The relevant colour codes are, red: standby, green: 44.1kHz, blue: 48kHz, Yellow: 88.2kHz, light blue: 96kHz and purple: MQA. When I first used the Dragonfly, I found myself looking for tracks to check all the colour codes were working only to find that indeed they were! The ES9038Q2M incorporates a 64 bit bit-perfect digital volume control that is directly controlled by the host system’s volume, pause and skip controls. Recent research by Audioquest has resulted in the development of enhanced power supply filtering techniques to reduce the increasingly pervasive noise from WiFi, Bluetooth and mobile phone signals. Audioquest sell a Dragonfly accessory called the “Jitterbug”, a USB data and power noise filter which I suspect is the same noise filter technology used in the Cobalt but now available separately for the black and red models. Output from the DAC is passed to an ESS Sabre 9601 headphone amplifier, which has a 2.1Vrms output capacity that is capable of driving low impedance headphones. All of the Dragonfly series of DAC’s are firmware upgradeable for any future software enhancements. Audition: Due to special offers, I currently have subscriptions to both Qobuz Studio and Tidal HiFi so this was the ideal cross-platform method of auditioning the Dragonfly Cobalt. I used my Oppo PM-1 planar magnetic headphones in all listening tests. Both Qobuz and Tidal apps have the ability to completely bypass the computer audio system and control the Dragonfly directly leaving the audio stream blissfully clear of system alerts and interrupts. The computer audio system still works in parallel for system alerts so you may want to mute or turn the volume down for those. Initial impressions were good; the contrast with the computer audio I had become accustomed to was quite dramatic, what I was hearing sounded like HiFi rather than something more akin to lift music. Audioquest recommend leaving the Dragonfly permanently plugged in to a live USB socket so it’s warmed up ready to go straight from the off. I did notice over a period of about ten minutes or so the music began to be delivered with more authority so a short warm up seems essential. Even after many hours of use, the body remained just mildly warm to the touch, I couldn’t find any power consumption specs but it seems to be power efficient. The volume control has more than ample resolution and operated cleanly and smoothly without any apparent steps. Low-level fine detail was there, absolutely essential in creating a believable soundstage presentation. Instruments were definitively placed with good separation, stable positioning and no smearing. There was also the illusion of some level of image depth in as much as you can expect from a pair of headphones. Bass depth was available in spade loads with good attack and no timing issues, overhang or bloating. Oppo say the PM-1’s go down to 10Hz, not that you would be able to hear that low but Audioquest do not seem to quote a frequency response spec for the Cobalt. Mid range voice reproduction was clear and natural, Cara Dillon’s voice on “Live at the Grand Opera House” was as good as it sounds on the main system. High frequencies were crisp and clear, percussion on Evelyn Glennie’s “Ecstatic Drumbeat” was hard and fast with natural decays. One of my pet hates when listening with headphones is hearing noise during quiet passages but the Cobalt passed this test with flying colours. Though I often found myself using the volume control close to its maximum level, we all tend to listen at higher levels when using headphones, the Cobalt still delivered ample volume into the 35 Ohm Oppo headphones. The illuminated logo was useful in confirming the data rate of the music I was streaming, both Qobuz and Tidal apps have settings to limit the stream bandwidth presumably so as to limit consumption of mobile data allowances. Audio performance on mobile devices was to all intents and purposes indistinguishable to that on a laptop or desktop. There was a noticeable increase in battery usage on an iPhone but it should still give many hours of listening from one charge. The main negative aspect to operation using a mobile phone was having a clunky adapter and the Dragonfly hanging off the bottom of it, if I was out on the move the combo would be tiresomely inconvenient. Conclusions: For many, and I include myself here, the biggest attraction of the Dragonfly is its size, simplicity of use and broad compatibility. The fact that it has all these properties and also turns in a great performance is a bonus. Having now spent several hours a day over many days listening to the Dragonfly Cobalt which is much more than I would normally spend listening to the main system I feel confident in saying it would give many expensive stand-alone DAC/headphone amplifier combos a good run for their money. Considering the price-performance ratio of the Dragonfly Cobalt it is good value for money and I’m certainly glad I invested in one. Technical specifications: Input: USB 1.0 Output: 3.5mm jack socket, 2.1Vrms, 16 Ohms minimum headphone impedance Files formats supported: MP3, PCM up to 24bit 96kHz and MQA Microcontroller: PIC32MX274 DAC: ESS Sabre ES9038Q2M Headphone amplifier: ESS Sabre 9601 Volume control: 64 bit bit-perfect digital Dimensions: 12mm H, 19mm W, 57mm L Price: £215 Associated review equipment: Oppo PM-1 planar magnetic headphones Apple iMac computer Apple Macbook Pro computer Apple iPhone 8 Apple USB to Lightning camera adapter
  3. The components causing the PCB burn look like zener diodes to me, probably some kind of shunt regulator for the HV rails.
  4. Leema Acoustics Tucana II Anniversary Edition By Alex Colburn Introduction: Leema Acoustics is a UK based manufacturer of high-performance audio equipment founded in 1998 by two ex-BBC sound engineers, Lee Taylor and Mallory Nicholls. Leema originally concentrated on loudspeaker design and manufacture culminating in their first product, the Xen micro monitor which was originally only available to the professional market. Following the success of the Xen speaker, Leema decided to expand into the audio electronics market and launched the Tucana integrated amplifier in 2006 to much critical acclaim. Since then, their electronic product range has expanded to include amplifiers, DACs, streamers, music servers, phono stages and analogue and digital cables. The intervening years have seen the Tucana upgraded initially to the Tucana II and more recently to the Tucana II Anniversary Edition reviewed here. New features include, upgraded printed circuit boards with 2oz gold plated copper tracks (1oz is the usual standard) to reduce inter component track resistances, critical capacitors upgraded to Nichicon’s audio grade MUSE series, Noratel “extra quiet” low-noise toroidal transformers, precision matched output transistors and silver soldered Leema Reference 2 speaker cable between PCB’s and speaker terminals. Description: The Tucana is delivered in a necessarily robust cardboard carton packed in high density recycled foam packaging. Weighing in at a hefty 18kg, this is surprisingly heavy for such a compact integrated design. The case is predominately constructed from substantial machined aluminium plate and custom moulded aluminium finned heatsinks. Available in a silver or black anodized finish (heatsinks in both versions are black), the Tucana has the look and feel of a quality built product. All aspects of control can be achieved using the front panel but the amplifier comes with a weighty anodised aluminium IR universal remote control that will control all the current range of Leema audio products. Leema also build “LIPS” (their proprietary communication system) into their audio products so users can easily integrate other Leema products into their system. The user manual includes a comprehensive collection of certified test reports detailing results from tests carried out during each stage of the build process for an individual amplifier. The rear panel sports nine pairs of gold plated RCA connections, six un-balanced inputs, a tape loop (fixed level output), preamp outputs and one balanced input (XLR). Potential users should note the right and left balanced inputs are located on the left and right sides of the amplifier respectively, the reverse of the usual orientation. Fully shrouded gold plated loudspeaker terminals that will accept 4mm plugs, spade connectors or bare wires are mounted at each end of the rear panel. Two proprietary “LIPS” connectors are provided adjacent to the centrally located IEC mains input. There is no phono input which some would expect in an integrated amplifier but this is simply a reflection of the recent trend towards stand-alone phono stages and indeed Leema cater for this market themselves. The illuminated front panel power button toggles the amplifier between standby and on, there is no off condition. Leema recommend the Tucana is left in standby mode as it consumes minimal power and is essential for “LIPS” operation. Additionally, the Tucana will remember previous input and volume settings while in standby mode and restore the settings when powered up. The large volume control is of the rotary encoder type and rotates freely without click or end stops. A ring of 32 LEDs surrounding the volume control indicate the current gain setting; intermediate steps are indicated by adjacent LEDs being illuminated giving a volume setting resolution of 64 steps. Two LEDs below the volume control flash to indicate overload and thermal limit conditions which reset automatically when the condition resolves. An arc of 7 illuminated push buttons switch between inputs with an additional row of 4 buttons for GAIN, BALANCE, MUTE and TAPE selection. Pressing GAIN allows the volume of the currently selected input to be pre-set to +/-10dB of the master volume setting allowing the user to match sensitivities between inputs. Two 3.5mm jack sockets provide a high quality headphone output and a duplication of the MULTI2 input to allow the connection of MP3 devices. Leema have put some considerable effort into designing the microprocessor controlled volume/mute control, I could not fault its efficiency in preventing me from potentially doing something stupid while switching sources. Technical discussion: The design topology within the Tucana is that of “dual mono” from power supplies all the way through to power amplifiers, the mirror-image internal view shows that this also extends to the PCB’s and physical layout of individual components. Each channel has separate toroidal transformers, rectifiers and reservoir capacitors with a third transformer used to power the control electronics and effectively isolate digital from audio power. Input switching is achieved using gold flashed silver contact relays controlled but a microprocessor, the signal then passing to high quality OP275 operational amplifiers. The buffered input signal is then passed to microprocessor controlled Burr Brown precision attenuators that function as the volume control. The attenuated signal is then fed to the power amplifier inputs. The power amplifiers use a classical differential input stage feeding a constant current loaded class A voltage gain stage to drive a class B push-pull emitter follower output stage. To reduce output impedance and increase output current delivery, the output stage consists of three precision matched pairs of paralleled output transistors. Each stage has been optimised in line with the design philosophy of guru Doug Self with additional enhancements from the Leema designers. Class B power amplifier designs should be reasonably efficient but the thermal design characteristics of the Tucana seem excellent, in normal use the case ran at 35˚C and despite several hours playing at high volume I was unable to get this up to more than 45˚C. The manual states thermal trip occurs at 70˚C but I cannot imagine any normal domestic situation where this kind of temperature will be achieved. Audition: To avoid any possibility of source/amplifier interference, I used the fully isolated transformer output on my Linn Klimax DSM Mk 3 to drive the balanced inputs on the Tucana. Leema do not state a recommended “burn-in” period but the Tucana took several hours to reach optimal performance. With the volume set to maximum gain, an ear to a speaker confirmed the amplifier’s low noise specification. Technical specs and pedigree were telling me the Tucana should be able to look after itself so I decided to throw it straight in the deep end and start by playing Jean Guillou’s rendition of Mussorgsky’s Pictures at an Exhibition on The Great Organ Tonhalle, Zurich. The Tonhalle instrument is one of Europe’s great organs with 32’ pipes housed in superb acoustics and is a challenge to portray on any HiFi system. Soundstage presentation was good producing an image with good breadth and depth, medium and higher pipe ranks could be located quite accurately. Reproduction of the Tonhalle acoustics was accurate and entirely believable. Despite the considerable power demands in the lower registers, bass delivery was tight maintaining timbre and with a seemingly effortless character. Turning to orchestral music, The Atlanta Symphony Orchestra’s rendition of Gustav Holts Planet Suite conducted by Yoel Levi is my favourite performance of this piece. Mars was delivered with the power and authority you would expect, the strident brass was well integrated with timpani and string sections. Peaceful Venus was very good for demonstrating the woodwind section and Mercury the string section. The exuberance of Jupiter comes over well with good dynamics and instruments well separated in a detailed image. Saturn comes over with its full measure of dreariness, there’s not much more to say! Uranus is presented with great dynamics particularly from the tympani and Neptune simply speaks for itself. Overall the Tucana does a good job presenting orchestral music; certainly it would fit in nicely to a classical fan’s system. Having just purchased Steve Wilson’s re-mastered edition of Porcupine Tree’s In Absentia in 24bit/96kHz, I thought this would be an excellent recording to evaluate performance on rock music. Wilson’s heavy guitar riffs on Blackest Eyes are a delight along with some dynamic drumming, snare drum was fast and rim shots hard and precise and cymbals shimmered nicely. Complex passages maintained instrument separation so individual threads were easily followed. Acoustic guitar sounded solid with great detail, individual notes starting and stopping with good timing precision. Cara Dillon Live at the Grand Opera House (24bit/48kHz) is an excellent atmospheric live recording of voice and acoustic guitar. Cara’s voice was crisp and natural sounding with no hint of the sibilance so often found on lesser systems. Piano notes had good attack with the timbre you would expect from a grand piano. Sound output from the bodhran extends from the upper bass to the mid range of frequencies and consequently challenging to reproduce but the Tucana achieved this with ease. The headphone socket was auditioned using my Oppo PM-1 planar magnetic headphones with the supplied 3.5mm jack cable. Sound quality was generally good though not really powerful enough to drive the PM-1’s to decent volumes. This is a somewhat unfair criticism as the impedance of the PM-1’s is right at the lower recommended limit of 32Ω. I suspect the design is optimised for use with more efficient headphones intended for MP3 player use. Conclusions: The Tucana II Anniversary Edition integrated amplifier is available through an extensive network of UK dealers. Leema Acoustics offer a two year parts and labour warranty on all their products with an option to purchase a further three years. With a retail price tag of £4995 including VAT the Tucana must be considered a significant investment for the majority of HiFi enthusiasts but in view of its overall performance and excellent build quality it represents a good investment that is unlikely to disappoint whether they be a rock or classical fan. Highly recommended! Technical specifications: Output power: 150W RMS into 8Ω, 290W RMS into 4Ω or 520W RMS into 2Ω. Total harmonic distortion: 0.004% @ 10W RMS 1kHz. Frequency response: 5Hz to 100kHz +0dB to -3dB @ 1W Signal to noise ratio: <-100dB @ 285W into 4Ω. Output impedance: 0.05Ω. Damping factor: 160. Output current: +/-50A. DC offset: +/-50mV max. Input sensitivity CD input: 565mV RMS. Input sensitivity other inputs: 311mV RMS. Weight: 18kg. Power supply: 230V 800W Max. Dimensions: 440mm wide x 320mm deep x 110mm high. Associated review equipment: Source: Linn Klimax DSM Mk 3. Speakers: Modified Townshend Glastonbury Tor Mk1/Townshend Maximum Supertweeters. Headphones: Oppo PM-1 Interconnects: Nordost Tyr 2 balanced XLR. Speaker cables: Nordost Heimdall bi-wired Z-plugs. Power cords: Nordost Heimdall II
  5. The logo is Plessey and 7.1uF is still within spec so I wouldn't worry about it.
  6. The output impedance of the preamp you quote is way too high, are you sure this is correct? Also the input sensitivity should be in mV rather than mA.
  7. Ditto! Great caps been very pleased with them.
  8. Alex 54

    Failing Capacitor?

    Looks fine to me but the ultimate test would to measure it at a number of frequencies.
  9. Alex 54

    Failing Capacitor?

    I can't see it being leached through the epoxy end caps but the only way to find out is to wipe it off and see what is underneath. If you find pores then the cap will need to be replaced but I suspect the spots were on there before it went into the crossover.
  10. Alex 54

    Failing Capacitor?

    You could try wiping it off with a little solvent, if it comes off and the epoxy underneath is pristine you will know it's external contamination.
  11. Alex 54

    Failing Capacitor?

    I doubt it's a problem with the cap, probably came from somewhere else like the bitumised board the crossover is mounted on.
  12. Digital volume controls work by bit-stripping the digital signal data and this affects the resolution and dynamic range of the data. The architecture of the volume control in the DSM's operates at greater bit depth than in the DS's giving audibly better results. It's not that the DS volume control is not good, many will attest it is very good, just not as good as that in the DSM.
  13. Sounds more like a dealer problem to me. My dealer placed the order with Linn and was given a time slot for the upgrade so they could tell me when to get the DSM to them, which I did, and it was returned within a week.
  14. Sounds more like a dealer problem to me. My dealer placed the order with Linn and was given a time slot for the upgrade so they could tell me when to get the DSM to them, which I did, and it was returned within a week.