Articles, Reviews and Measurements of Audio Products

This is a review and detailed measurements of the SMSL DO200 MKII stereo USB DAC. It was sent to me by member @lunagreenjp 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:


RCA output is nearly as good:


Performance is noise limited as is the case with all DACs in this tier:


What noise there is, is very low:

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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...

Hello everyone. Found three accounts today that were hijacked and spam posted under their alias. Maybe it is coincident but just to be on the safe side, please change your ASR password as soon as you can.

Thank you.

This is a review and detailed measurements of the Hypex NCx500 NCOREx reference design amplifier. It was sent by the company and kindly assembled by our local expert, @Rick Sykora.

As you see the sample is a "monoblock" configuration (one channel) driven by Hypex SMPS1200 switching power supply. The only other board is the Ncore standard interface board. The gain as set is almost 12 dB. EDIT: see follow up below review for with buffer (27 dB gain) performance.

Here is a close up:


Note that this board includes a pre-amp (buffer). I am testing per above in unbuffered mode.

During use the amplifier as a whole was extremely stable and never changed its temperature, nor did it go into protection mode. A sole XLR connection is the input to the unit. All fits in...

This is a review and detailed measurements of an upgrade for the venerable Behringer Ultra-Drive Pro DCX2496 by Behringer MODs. An upgraded unit was sent to me for testing. The upgrade itself costs £138 in UK and £115 outside UK.

The board fully upgrades the existing DAC board:

I like the clear notations on every subsystem. And the fact that the company has included measurements to show efficacy of the upgrade -- rarity!

Note that unlike the stock unit that goes up to some 10 volts (clipped) the upgrade's max output is about 4.5 volts. I am told by the designer, Simon Ashton that this is to make it more compatible with hi-fi equipment.

Behringer MODs DCX 2496...