Articles, Reviews and Measurements of Audio Products

This is a review and detailed measurements of the Hypex Nilai500DIY class D amplifier module with PS500DIY power supply. Parts were provided by the company and member @Rick Sykora was kind enough to assemble it:


As indicated, the single channel amplifier is on the left and the power supply on the right. The amplifier has built-in preamp providing three levels of gain (12, 22 and 28 dB). A jumper selects the appropriate level. At 12 dB, you need about 12 volts to reach full power which requires a pro audio interface or a pre-amp with that level of output. The sole input in this configuration is balanced.

In use the amplifier was exceptionally solid even when pushed hard. It kept going and stayed very cool. It is rated to 2 ohm (see measurements below).

Edit: in the original review I had the top open so I could change the gain settings. Alas...

This is a review, listening tests and detailed measurements of the wired V-MODA M-200 closed back headphone. It is on kind loan from a member and costs US $300.

It it just me or does this thing look homely? It is a small headphone as well so fit is not the most comfortable. It is light though.

The company uses lofty words to describe the M-200: "a reference over-ear studio headphone for precision listening, mixing and mastering." Let's see if it delivers on that.

V-MODA M200 Measurements
While I could get excellent matching between the channels at my reference 425 Hz, I could not even get close in bass. Searching online I see another review complaining about poor matching there so this is a defect that is built-in. So let's go with that and see the full frequency response:


What mix of good and bad news. Nice compliance in mid-range but terrible above and below. Other reviewers match the...

This is a review, listening tests and detailed measurements of the Zidoo EverSolo Z8 stereo balanced DAC and headphone amplifier. It was sent to me by the company and costs US $699.

As you can tell this is not "yet another desktop DAC." A beautiful and responsive 3 inch LCD display can provide different levels of information including three types of VU meters! The menus are so rich that on first use you are prompted to choose your language. SO many things are configurable down to level of brightness of the ring around the volume control! (I set it to highest for this picture.) More useful settings include being able to set the steps from for the volume control starting from 0.5 dB going to 2 dB. Company clearly has extensive software development experience (as evidenced by their media/video players) which they have brought to bear here.

The back panel holds...

This is a review and detailed measurements of the HEDD Audio Type 20 MK2 DSP studio monitor (active speaker). It was sent to me by the company and costs US $2,399 (each):

As you see, this is a ported 3-way design using an AMT tweeter. You also get the option to close the port using an extremely tight fitting insert and flipping the CoP control in the back to that configuration:



Being a DSP speaker, you also get nice features like AES digital input and pass through. You also have a choice of activating the FIR filter using the "Lineariser" control.

Speaker is incredibly heavy and stout for its size, imparting a feeling of quality.

I guess at the reference point (from memory, a point between the three drivers). I tested the speaker twice: once in open...

This is a review and detailed measurements of the SMSL DO200 MKII stereo USB DAC. It was sent to me by aoshida-audio who is a distributor for SMSL and costs US $469.

Not much to complain about here as it fits the latest design of SMSL line. I like the clarity of the LCD and large volume indicator. Back panel is a you expect:



Standard SMSL remote control is provided.

SMSL DO200 MKII Measurements
Let's start with our usual dashboard with XLR output:


Superbly low noise and distortion lands the unit in our 20 best DACs tested as far as sum of distortion and noise:
[ATTACH...

This is a review and detailed measurements of the ifi iPurifier 3 "USB Audio and Data Signal Filter." It is on kind loan from a member and costs US $149.

The iPurifier 3 comes in a gorgeous and nice to feel ceramic (?) enclosure. The enclosure give is enough weight to feel substantial but not too much as to strain the connector. It is an in-line device and comes with three useful adapters which should cover all your USB connection needs.

In case you are wondering what this is for, here are the company specs:


Think of it as a USB repeater of sorts. For the purpose of this review, I take for granted that it does all of the above. Question becomes if our audio DACs need such an upstream device to "clean" their USB connection.

ifi iPurifier3 Measurements
My favorite device for testing USB signal quality is a Schiit Modi 2 which in the past has show very high sensitivity to...

This is a review and detailed measurements of the RØDE AI-Micro portable audio interface (dual microphone input and headphone out). It is on kind loan from a member and costs US $79.

As you probably can tell, this thing is tiny! Digital interface is USB-C and dual mics plus headphone are 3.5mm jacks. Unit is plug and play on Windows. It has variable input gain which I figured was being controlled by the volume setting in Windows control panel.

RØDE AI-Micro DAC Measurements
Treating the headphone out as line out we get:


As a DAC, it is pretty poor but for the application of using it with a headphone, it is probably OK. What was strange was clock instability. It is possible this is due to AP software but I am fairly certain there is something wrong with the clock implementation. It would jump between 1000 Hz and 0.9999 every few seconds causing large amount of interference in the FFT.

Noise may...

This is a review and detailed measurements of the ZeroSurge 2R15W AC filter & surge protector. It is on kind loan from a member and costs US $239.

I like the descriptive model name: it has two (2) outlets and is rated for 15 amps. A hefty AC cord gives one confidence that it can carry that much current.

If you are not familiar with the company and this product, their products (and that of another competitor) use "series" non-destructive surge protection devices. Traditional surge protectors rely on components that are in parallel with the line and sacrifice themselves should a sufficiently powerful surge arrives. Some can fail this way with catastrophic results (think smoke and fire). They are cheap and have the advantage of having no impact (if well designed) on power delivery of the unit. Series protection devices like the one in this review, shunt the power instead and are able...

This is a review and detailed measurements of the Rotel RB-1070 stereo power amplifier. It was released in early 2000. Can't find the cost then but I see it used for around $400 to $500.

I have always found Rotels to be most attractively designed power amplifiers. One look at that front panel and you immediately think of muscle and beauty in design. Alas, the extruded aluminum in front which gives it that look, is cosmetic. There are two others internally which do the job of cooling this classic AB design. In use the heastsinks got pretty warm to touch to give it some air to breath.

Not much news in the back other than nice inclusion of trigger input/output:


Rotel RB-1070 Measurements
The unit warmed up nicely without its performance changing much:


So let's see what our dashboard of 1 kHz tone does into 4 ohm load:


The amp is...

This is a review and detailed measurements of the Sony Xperia 5 IV high-end smartphone audio performance. I purchased it recently for US $799 but I see normal price of $998.

I went through extensive search for a month to find a replacement for my aging Samsung S8+. I wanted a phone with analog out, OLED high-resolution display, wireless charging and 5G. Believe it or not, in US, this translates to only two phones, both from Sony. The Xperia 5 Mark IV and Xperia 1 Mark IV. I read all the reviews of these with people only complaining about overheating and complicated camera app. Turns out the overheating is only caused by recording 4K video for a while, something I never do.

Another critique was the cost of the 1 Mark IV. Thinking the 5 Mark IV is just lower res version, I purchased it, not realizing it actually has slightly smaller display. This, turns out to be a showstopper. You can't quite tell from above picture but these phones from...