Articles, Reviews and Measurements of Audio Products

This is a review and detailed measurements of the Essence HDACC II-4K HDMI and USB DAC. It is on kind loan from a member. It costs USD $699 from company's website although it is on sale currently for $599.

For years, I have been looking and asking DAC manufacturers to include HDMI input in their DACs. As many of you know, HDMI is the standard delivery format for digital video. Without HDMI input, you cannot listen to the advanced, multi-channel audio formats on such platforms as Blu-ray Disc and its UHD version. When there is a HDMI input on some DAC, it is for PCM only and no compressed format is offered. Essence solves fills this much needed gap with their DACs with HDMI input. Both Dolby True-HD and DTS Master Audio HD are decoded internally allowing you to feed the native bitstream to it.

It includes all this functionality plus balanced output and analog input plus headphone out in a very small and attractive enclosure:

As the...

This article is to expand upon earlier discussions about reflections and their potential for harm in a digital transmission system as applied to the audio world. I will be qualitative as much as possible, but numbers are bound to creep in. This is also not meant to be a rigorous analysis, more a hand-waving explanation to help folk see what is happening in their system.

First consider a digital driver (source) and load (receiver) connected by a transmission line (cable). The driver and cable are matched with impedance Zo, and the load has mismatched impedance Zx as shown in the figure below. At the top, a single pulse is launched from the source toward the load. The pulse, now a forward signal, travels down the line to the receiver. Even at nearly the speed of light it takes a little time to get there.


As the...

Room interactions are often discussed as one of the primary reasons similar (or even dissimilar) systems sound different. If you read the “Reflections and DACs” article you saw how reflections and standing waves can interact along a transmission line. As it happens, sound waves in a room also interact, affecting the amplitude of sound you hear at different frequencies. Sound waves from more than one source (for example, two speakers) will meet and interact. Sometimes they add, sometimes they subtract (cancel), but there will be interactions in any room. “Ah, but what about absorption?” you might ask. Ah, but remember I said “more than one source”. If I put two speakers in a perfect anechoic chamber, absorbing all sound when it interacts with any surface (walls, floor, ceiling), there are still those two sources to consider. If I sit between them...

Mod note: our technical expert @DonH56 wrote this series article a while back. As I get time, I am porting them here.

Alternating current carriers in a conductor tend to travel near the surface. This happens due to opposing eddy currents from the magnetic field generated whenever alternating current (a.c.) flow is present. These are not generated by direct (d.c.) flow since current flow is all in the same direction and thus opposing eddy currents are not created. The effect is frequency-dependent, resulting in carriers traveling closer to the surface at higher frequencies. Because less cross-sectional conductor area is used as frequency increases, the effective resistance rises as frequency increases. Note that at d.c. (0 Hz) the entire cross-sectional area of the conductor is utilized.

Skin depth (sd) is the depth at which current density has fallen to about 1/3 (actually, 1/e, or about 0.37x) the density at the surface. The definition arises from EM equations...

This is an article our technical member @DonH56 kindly wrote on another forum and place. I am copying it here given the recent interest in its content:

Apples vs. oranges, anybody? In this thread we’ll take a look at speaker cables from an RF perspective, not something usually discussed. Although closer to my professional life than the usual audio analysis, I would not have thought of this except for the prodding by (“interaction with” if you prefer) a fellow engineer. I would have said transmission line effects at audio frequencies are negligible. Was I wrong? Well, the jury is still out, but it makes for an interesting thread, so here we go!

Recall that wires have impedance terms (resistance, inductance, capacitance, conductance – RLCG) distributed along their length. They reduce the cable’s bandwidth, reduce the effective damping factor at the speaker terminals, and add distortion (though the cable’s nonlinearity at audio is insignificant – I am not covering...

This is a review and detailed measurements and listening tests of eXemplar eXception Phono stage (amplifier). It is on kind loan from a member. The cost as listed on eXemplar website is USD $6,950.

For a piece of equipment listed at such a high price, the eXception comes in pretty ordinary boxes, one holding the tube amplifier, and the other the power supply:


If the front is ordinary, the back panel is utilitarian at best:


The boxes look like chassis you buy from ebay and in your garage drill and put jacks and such in. At $7,000, I expect far better.

The two inputs are Moving Coil and Moving Magnet even though neither is identified such. I did not play with the loading but a couple of RCA plugs with a trim pot is supplied for I assume varying the input impedance? I looked online but could not find a manual for it. So I left this alone.

There is no power supply in the this...

This is a review and detailed measurements of Yulong DA10 balanced DAC and headphone amplifier. It was kindly sent to me by Shenzhen Audio for testing. It costs USD $1,200 but is currently on sale for $1,150. Needless to say, my expectations are high at this price range.

The industrial design is unremarkable, sans a large, rather high resolution display:


The display seems to be designed for audio nerds in the way it highlights the sampling rate of music being played in large, center part of the display , leaving the volume indicator to tiny font on bottom right. From usability point of view, I like to see the volume level in the middle and sample rate at the bottom.

What is nice is seeing everything at once from filter settings to different modes. A click of the volume control lets you cycle through them and by...

This is a review and detailed measurements of the Rega Ear Headphone Amplifier. It is on kind loan from a member. The Ear costs USD $395 from Amazon including Prime shipping. From the bit of research I did, seems like the Rega Ear was released back in 2013/2014.

It doesn't take much to get me to dislike the look of any audio device. The Rega Ear does everything to push me there:

While the enclosure is metal the front panel is the cheap plexiglass that was maybe in fashion back in 1970s. The silver buttons add insult to injury as do the easy smudges you get on it. All of this is strange as I consider Rega at the lower tier of "high-end" audio electronics.

The back panel doesn't change the impression either, neither does the AC adapter which had its case already starting to fall apart:



At least put some bling in there with gold RCA connectors or something at this price.

Now, from design point of...

This is an analysis of I²S interface to see if it is superior to S/PDIF or USB interconnects for audio DACs. From what I recall, it was PS Audio that popularized I²S for external DAC connections. Phillips (now NXP) had invented I²S years early as an internal protocol to route audio. It was not and has not been blessed for external use over cables. This use has been ad-hoc with no real attempt at any kind of standardization. As a result, schemes for external use vary, some use HDMI connectors, others RJ-45 (ethernet) and so on. Even with the same connector, the wiring may not be the same. You can see the HDMI variation of it here in the devices I tested for this review:


Note that despite use of HDMI connector, there is absolutely no compatibility with HDMI as used in video and home theater. All that is in common is use of the connector or cable, not the language spoken over it.

The motivation for I²S instead of S/PDIF...

This is a review and detailed measurements of the Singxer SU-1 USB to S/PDIF, AES/EBU, and I²S Audio Bridge (converter). It is on kind loan from a member. I think the SU-1 was released back in 2016. I hear a lot about it so I am happy to have one to review now. Looking on Amazon, the SU-1 costs USD $400 including Amazon shipping. This is a lot of money to pay in this day and age when USB is built into just about every modern DAC. To use it then, it better far outperform native USB interface on DACs as many people believe.

Other than somewhat fancier feet, there is nothing to distinguish the SU-1 from countless other products from China. Here, you see it in the middle of the stack of gear I used to test it:


There is nothing to select so not much to say as far as usability. The unit was was plug-and-play in Windows without the need for any driver.

The backside shows nice set of output connectors with notable absence of Toslink...