Saturday, June 19, 2021

Markaudio-SOTA Tozzi One Speaker Kit

Introduction

The Tozzi One speaker kit is likely the easiest speaker kit on the market. I assembled it in an hour, half of which was spent looking for my tools, and cleaning up. This is the perfect kit for beginners as there is no soldering involved - all you need is a screwdriver. 

Description

Based on their in-house CHN 50 full-range driver, the Tozzi One is built around an ABS and fiber-reinforced cabinet. 






The driver is mounted in a shallow wave-guide, while the cabinet is rear-ported. Sensitivity is rated at 85 dB, and impedance at 6 ohms. The anechoic frequency response is specified at 80 Hz - 22 kHz (+/- 6 db). The cabinet measures 200 x 126 x 200 mm, and weighs 1.42 kg. The cabinet is angled up slightly, so you should be fine listening to it in the nearfield while placed on your desk. 





The waveguide has a textured finish, while the sides of the cabinet are finished in a faux leather wrap. 

Assembly is straightforward enough. The instructions were in Japanese, but the diagram is clear enough to figure out. 



A thin gasket is placed between the front baffle and the speaker driver. The driver is held in place with five hex nuts. The supplied wiring is terminated in push-on terminals and o-rings, so you just need to connect them to the speaker driver and supplied five-way binding posts. The rear panel foam needs to be affixed using the supplied double-sided tape. Install the gasket into the rear panel groove, and attach it to the speaker cabinet with screws. That's it! Building and programming a custom keyboard is far more challenging than this. 

The beauty of full-range driver designs is that there is no crossover to mess around with. From a technical viewpoint, you get the best possible coherence from using a single driver and higher efficiency and purity from skipping the passive crossover. There is no free lunch though. Asking a driver to cover the whole frequency range results in uneven response. Most designs have to rely on complex cabinet designs with some form of a back-loaded horn to get usable bass output. 


Sound Quality

Straight out of the box, you get a clear and engaging sound but with some rough edges. A few hours of run-in sorts that out nicely.

As expected from a full-range driver speaker, you get a lovely transparent and coherent sound. The Tozzi One sounds bigger than it looks although the very limited low-frequency output and extension makes it more optimal for background listening in a large room, or listening in the near-field.  

To be continued ... 



Wednesday, May 26, 2021

Elekit TU-8600R Integrated Amplifier

Introduction

Problem Statement - You want a quality integrated tube amplifier, but no means to afford one. No problem, just build your own ! Assuming you have decent soldering skills, and are not instruction-intolerant (sadly, that rules out my teenage daughter), the Elekit TU-8600R lets you enjoy quality on the cheap. You will need about four full days to build one, but the effort is well worth it.

Description

The Elekit TU-8600R is a 300B single-ended integrated tube amplifier kit from the nice folks at Elekit of Japan. The TU-8600R is neither a basic kit nor design, and has parts quality and design features found in high-end models.

The power transformer is a high-quality R-core type, with low magnetic flux leakage. The solid state rectification uses Schottky fast recovery diodes. The power supply circuit includes ripple filters and plenty of regulation stages. An active automatic bias adjustment system means no fiddling with bias pots, and optimal sound quality at all times.

Parts quality is generous with plenty of Japanese branded resistors and capacitors. The PCB thoughtfully provides sufficient space for you to install large boutique coupling capacitors too. After all, isn't that the whole point of DIY, the freedom to express yourself ?

The TU-8600R's circuit is based on a single 12AX7 input tube, which then feeds dual 12AU7 tubes. The latter's two triode sections are wired in parallel to drive the 300B power tube. The output transformer has speaker taps for both low and high impedance speaker loads (selectable by a switch on the rear). A headphone socket allows you to enjoy your Elekit with your favourite pair of cans. Jumpers on the PCB allow you to adjust the headphone output level, and the colour of the power LED.

Although the TU-8600R is an integrated amplifier, there is only one set of RCA inputs. This could be a deal-breaker for some, although you could purchase or build an input switching box to get around this. 

Build Experience

Elekit gets first prize for having the best instructions I've ever received with an audio-oriented kit. The instructions rely on very clear diagrams and steps to guide you every step of the way. The PCB is marked clearly and even reminds you when components are required to be installed on to the reverse side of the board. Plenty of due care and consideration went into ensuring that the assembly is as painless as possible. 

The sheer parts count and complexity of the PCB makes this project highly unsuitable for a first-time build. The soldering of the transistors was the most delicate part of the build, as the solder pads are dangerously close. I would also highly recommend that a temperate controllable iron be used. 

In my case, I chose to upgrade the stock resistors to Takman Carbon film ones, and the coupling capacitors to Amtrans AMCY Golden Black. I also bypassed the volume pot and wired the input jacks directly to the main PCB. The input sensitivity will be high, but if you are able to adjust the output level on your source (e.g. a DAC with volume control), you should be fine. 

Starting off at the professional assembly area a.k.a. dining table.

The Takmans are too large to fit and the legs have to be bent in a curved fashion to fit the board.

Soldering of the resistors is complete.


Plenty of space for upgrading the coupling capacitors.

This is the top side of the board. The main circuit is on the underside.

Testing phase. I made a boo-boo here. 

Running-in phase. 

The only mishap suffered was when I wired the input wiring to the wrong solder pads. I happily soldered them to the input pads. They should have been wired to the output pads instead (Elekit refers to them as output pads in the sense that they receive the output from the potentiometer). 

The power and output transformer connect to the PCB via push-on Molex connectors. Since the stars were aligned, I decided to run in both the stock output transformers and the Lundahl ones which are optional. 

One criticism I have is with respect to the sheet metal covers. They have a fair amount of ring, and degrade the sound quality. This was very noticeable when I installed both after my run-in process was completed.

Sound Quality

Paired with Genalex 300B tubes and a variety of 12AX7 and 12AU7 tubes from my stockpile, I gave each set of output transformers about 10 hours of run-time before I did any critical listening. I used my Totaldac DAC (using digital volume control) and icOn4 Pro as preamplifier, and my Vivid Giya G4 speakers. 

The Elekit is highly detailed, fast and open. The tone is light and clear, so if you are seeking the vintage 300B tone (warm, full and midrange-centric) you should look elsewhere. Despite the low power on tap, vocals and smaller works were an absolute treat with the Vivid. While the midrange was not overly liquid, the presentation was clearly in the tube amp camp. 

Soundstaging and imaging was holographic with pinpoint placement and excellent depth and width. The bass control and dynamics were satisfactory, but this is not the reason why you choose a single-ended tube amp. I believe that given the right set of loudspeakers (i.e. high efficiency), the Elekit would have no problem bringing the house down.

Swapping in the Lundahl transformer is the point where the Elekit is transformed from competent to world-class. The gains in detail retrieval, control over both ends of the frequency spectrum and refinement make the Lundahl a solid investment proposition. Elekit supplies the stock transformer even if you opt for the Lundahl, so you could always upgrade in the future, only losing out on having additional shipping costs.

The Elekit is good enough to be your end-game amplifier unless you suffer from equipment polygamy (which Audiophile doesn't ?). I was heartened to find such high quality at an affordable price, knowing that many would be able to enjoy its fine musicality.  

Conclusion    

There is a sense of rightness to the Elekit, and there is the invaluable ability to dial it in precisely to your taste through judicious choice of parts. 

It comes in at an attractive price tag, so the only real downside is that you need to spend the time and effort to build it yourself. However, most Elekit dealers would offer a build service for a fee, or be able to refer you to someone who could. Best Buy and Highly Recommended.

Elekit TU-8600R Integrated Amplifier

Price - POA

Elekit kits are available from :-

Horizon Acoustics

1 Pemimpin Drive
#08-11, One Pemipin
Singapore 576151
http://www.horizonacoustics.com


Tuesday, April 13, 2021

Astell&Kern USB-C Dual DAC Cable

Introduction

Chances are that you use your notebook, tablet, or mobile phone to play music, especially through a streaming service like Tidal or Spotify. Sound quality is typically poor or mediocre. Integrated audio chips work in noisy electrical environments, and usually lack the necessary power to drive high-quality headphones. 

Astell&Kern have released a USB-C DAC / headphone amp that provides an instant boost to your sound quality and lets you use your 3.5mm wired equipment with devices that lack a headphone jack, like some of the new mobile phones.

Description



The USB-C Dual DAC Cable ("Dual DAC") is based on twin Cirrus Logic CS43198 MasterHIFI Digital-to-Analog Converters. The CS43198 is a Delta-Sigma oversampling DAC that supports up to 384 kHz sampling rate / 32-bit resolution for PCM and DSD 256. 

As expected from an Astell&Kern product, the Dual DAC is finished to a high standard. The compact metal Zinc alloy body (it is no bigger than a thumb-drive at 50 mm x 17 mm x 10.3mm !) houses an integrated circuit with bespoke designed capacitors and an optimised audio circuit to minimise power fluctuations and provide premium sound quality. 

Astell&Kern claims that the analog amplifier is powerful enough to drive a variety of high impedance headphones with a 2V rms output level (condition no load). Output impedance is suitably low at 2 ohms, which should ensure lower distortion into low impedance headphones. 

The fixed cable is a durable 4-core cable made out of a core of Technora aramid fiber, with a layer of thick silver-plated copper wrapped around it, followed by a further layer of copper wire in a spiral arrangement. The tastefully angled housing is carried over to the matching USB-C connector. A single LED indicates operation, while volume is controlled through the device it is paired with. 




Operation

The Dual DAC worked without any issue with a variety of devices I tried - a Samsung Galaxy S10+ mobile phone, a Windows 10 notebook, and a 2020 Macbook Pro notebook. The bulk of my listening was done on the Samsung, playing music either through the Tidal or USB Audio Player Pro app. Power-draw was modest and I did not notice any adverse impact on battery life. Sadly, the Dual DAC is incompatible with iOS devices due to current limitations through their ports. Both high-resolution PCM and DSD files played without any issue.



The USB-C connector is quite large and may not fit properly through your mobile phone case. My case cut-outs were not big enough and I had to remove my phone case to plug in the Dual DAC. I am in two minds about the fixed lead. I like the idea of a fixed cable, but it is quite short and in the case of my Windows 10 notebook, the USB ports are located on the side of the screen, which left the Dual DAC suspended in the air.

Sound Quality

The Dual DAC provided a significant uplift in sound quality and drive capability, with the improvements most noticeable on difficult to drive headphones. I tried it with a variety of IEMs, as well as two headphones - a Beyer DT880 (250 ohm version) and an E-MU Teak. Most of my listening was done on the E-MU for reasons explained below.

The most striking improvement was in the reproduction of low-frequencies. The Dual DAC added a tight punchiness that went deep. Vocals gained clarity and refinement, adding sweetness and uncovering details that were previously obscured. High-frequencies too gained extension and airiness, giving music and brighter and more illuminated tone. The soundstage opened up, with an increase in dimensionality and the sense of acoustic space in the recording.

Pairing the Dual DAC with IEMs brought improvements in sound quality, but the Dual DAC's strength was in bringing extra current and voltage drive for more difficult to drive headphones (within reason). While the DT880 showed improvements with the Dual DAC, it lacked the dynamic freedom and ease compared to my desktop headphone amps. The E-MU Teak is easier to drive in comparison and was very comfortable with the Dual DAC, even at high levels. Given the compact size of the Dual DAC, this is a reasonable compromise.

I was impressed with the high level of sound quality delivered by the Dual DAC and can highly recommend it to Android phone users who want the best sound quality on the go, or to business travelers that need a high-quality and portable audio rig.

Conclusion 

From a pricing standpoint, the Dual DAC is a premium product that carries a corresponding price tag. The competition offers similar products, some at a lower price point with features like balanced drive capability. I think the pricing is fair, and like any Astell&Kern product, you get lasting pride of ownership. 

The Dual DAC will be available in May 2021 at a retail price of S$ 189- Highly Recommended.

You can purchase the Dual DAC from AV One (https://av1group.com.sg), Connect IT, E1 Personal Audio, Headphones.SG, Jaben, Stereo Electronics, and Treoo.com.