Articles, Reviews and Measurements of Audio Products (As an Amazon Associate I earn from qualifying purchases)

Radio Frequency (RF) Analysis of Speaker Cables/Reflections

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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...

Review and Measurements of eXemplar Exception Phono Amp

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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:

eXemplar Audio eXception Phono Amplifier Audio Review.jpg

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

eXemplar Audio eXception Phono Amplifier Back Panel Audio Review.jpg

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...

Review and Measurements of Yulong DA10 DAC & Amp

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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:

Yulong DA10 Balanced DAC and Headphone Amplifier Audio Review.jpg

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...

Review and Measurements of Rega Ear Headphone Amp

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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:
Rega Ear Headphone Amplifier Audio Review.jpg

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:

Rega Ear Headphone Amplifier Back Panel Audio Review.jpg

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

Now, from design point of...

Study: Is I²S interface better for DACs than S/PDIF or USB?

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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:

Gustard U12 USB to I²S Converter Compared to Singxer SU-1 Review.jpg

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...

Review and Measurements of Singxer SU-1 USB to S/PDIF

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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:

Singxer SU-1 USB to SPDIF Converter Audio Review.jpg

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...

Review and Measurements of Little Labs Monotor Headphone Amp

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This is a review and detailed measurements of Little Labs Monotor Headphone Amplifier. It is on kind loan from a member. The Monotor costs USD $540 from Amazon including Prime shipping. Target market and company focus seems to be professional audio users.

That pro pedigree shows up in the design language of the Monotor:

Little Labs Monotor Headphone Amplifier Review.jpg

I would consider it a bit quirky and oddly cute at the same time.

Speaking of odd, there is a selector switch to choose various modes of listening from mono to only Left, Right, Left-Right, etc. which should come in handy in audio post production.

There are no less than four headphone connectors, two of each size. I tested the two 1/4 inch ones and they are identical in performance.

Volume control is small and has very few notches so was rather hard to adjust for measurements. For listening that may or may not be an issue for you. The control is analog by the way.

The backside naturally has balanced inputs...
Review and Measurements of Okto DAC8 8Ch DAC & Amp
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This is a review and detailed measurements of the Okto Research DAC8 8-channel DAC and headphone amplifier. I was sent a prototype unit for measurements. From my understanding, the company has been producing the internal DAC module for a while for the DIY market. But now are building complete systems. So what makes this an early production unit is not the DAC module but the integrated version with input and other features. The version I have has the Okto DAC8 module plus an off-the-shelf UBS Input. My understanding is that the final units in production in April will also have their own USB input implementation plus 4xAES/EBU. It will cost 989 EUR in this configuration (about $1,120 as of this writing). This version will be known as DAC8 Pro. I will just be calling it DAC8 from here on.

There will be two other versions, one with DSP and the other in stereo configuration where four channels are folded into one to get better performance. See:

Review and Measurements of Empirical Audio Synchro-Mesh

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This is a review and detailed measurements of the Empirical Audio S/PDIF and Toslink "reclocker." It is on kind loan from the manufacturer and costs USD $699 direct. Also on load is a linear power supply which from what I can figure out is another USD $799. So the combination tested for this review is USD $1,500.

Let me provide some background on why such devices exist and problem they try to solve.

S/PDIF interface was designed decades back by Sony and Philips. It is a way to get digital audio stream out of a device for external connection to a DAC. A poor design decision was made at the time to make the source the master and embed the sample timing within the data stream. Put simply, if you hook a DAC to a S/PDIF (or Toslink) interface, it needs to a) extract the clock to know at what rate it should play and b) stay in sync with the source. You may think that once the DAC has detect the sample rate is say, 48 kHz, it can play at that rate but it cannot. The spec allows...

Review and Measurements of PS Audio Sprout100

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This is a review and detailed measurements of the PS Audio Sprout100 integrated DAC, headphone and power amplifier. It is on kind loan from a member. The Sprout100 is an upgrade over the original Sprout and costs USD $599.

I remember the first time I saw the Sprout at an audio show. I thought it was utterly cute! It is small and handsome little package with a ton of functionality:

PS Audio Sprout DAC headphone amplifier and power amplifier review.jpg

As you see, in addition to functions I mentioned, it even has Bluetooth included. And moving magnet turntable input. It is a dream product for a frustrated marketing guy in a high-end audio company like PS Audio, wanting mass market product that appeals to the "younger audience."

The volume control is a rotary encoder with a built-in switch that powers the unit on and off. If you hold the button down, the LED color changes from purple to white, indicating bass boost is on. The rotary encoder is poorly programmed to have linear and slow response, making it very...

Monoprice Liquid Platinum Headphone Amp Review

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This is a review and detailed measurements of the Monoprice Liquid Platinum Headphone Amplifier by Alex Cavalli. It is on kind loan from a member. It costs USD $770 and is currently out of stock on Monoprice website. Alex Cavalli used to design, sell and manufacture his own tube amplifiers. In this case, I have read that he has done the electrical design and PCB and has veto power on any part substitution by the contract manufacturer. In other words, even though manufacturing is in China, no used, or off-brand substitution of parts is allowed according to him.

I find the look of Monoprice amplifiers to be bland and uninteresting. The Liquid Platinum is a bit better with the tubes sticking out and vents on top:

Monolith Monoprice Liquid Platinum Headphone Amplifier by Alex Cavalli Audio Review.jpg

This is a hybrid design meaning the output stage is solid state. This means that it is able to deliver very low output impedance, avoiding the issue that many tube amps have with high impedance and resulting change in...

Woo Audio WA7 & WA7tp DAC and Headphone Amp Review

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This is a review and detailed measurements of the Woo Audio tube WA7 DAC and headphone amplifier together with its companion WA7tp tube power supply. It is on kind loan from a member. The cost of the pair is USD $1,599 so not cheap. As of this writing, shipping is free but I assume you would otherwise have to pay for it.

Note: this is the generation 1 of the WA7. The generation 2 is supposed to have a better DAC (?).

I remember running into Woo Audio amp a few years ago and drooled over its industrial design. The WA7 series is not quite up there with the rest of the units but still benefits from its massive plastic transparent top to give it elegance and drool appeal:

Woo Audio WA7 Headphone Amp and WA7tp Power Supply Audio Review.jpg

Strangely, the power supply has a rotary control which does nothing. You push it in and it power cycles on and off. A multi-pin short cable attaches the two. Reading the reviews, there are complaints that no AC power cord comes with WA7tp. What the heck?


Do you need linear power supply for DACs?

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Probably the most asked about question about DACs on audio forums is whether an external, usually linear, power supply improves performance. It just makes sense that it would do that. Doesn't it? Well, let's see if we can figure this out.

I have been kindly loaned a Wyrd4Sound PS-1 power supply for testing. It has replaceable modules that let you configure it for different voltages. The base PS-1 price is USD $499 and includes one regulated output. Additional modules cost $100. The unit I have has three modules in it. Two are 9 volt and one is 15 volt. Sadly, I see no regulatory and safety certification on the PS-1.

I was also kindly loaned an Sbooster BOTW ECO years ago so I thought I test it too. It costs $399 and comes in many variations. Sbooster provides OEM products to many companies and does proper engineering as far as safety standards.

For switching power supply I compared the one that comes with Topping DX3 Pro. Topping also has a strong commitment to...

Review and Measurements of Sound BlasterX G6

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This is a review and detailed measurements of the Sound BlasterX G6. I purchased it last month for USD $150 from Amazon including shipping.

Typical of PC audio connectivity devices, the Sound BlasterX G6 is a combo device which includes an audio DAC, ADC, and headphone amplifier. This being targeted towards gamers, there are a lot of specific features in that regard which I did not test. My focus here is the pure audio performance.

The Sound BlasterX G6 looks better in pictures than in person due to lightweight, plastic case:

Creative Labs Sound BlasterX G6 Review.jpg

No, there are no batteries. The unit is USB powered and I used photoshop to erase the USB cable. I hope those of you picking on my photography are happy! :)

The volume control is a rotary encoder so turns forever in either direction. There are no notches but overall feel/stiffness is not bad. I did however find that there was a lag between turning the dial and my Roon player registering the change.


Review and Measurements of Gustard DAC-X26

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This is a review and detailed measurements of the Gustard DAC-X26 stereo audio dac. It is was kindly sent to me by Shenzhen Audio for testing. The DAC-X26 normally costs USD $1,299 but seems to be on sale at Shenzhen Audio for $1,169 as of this writing. Note that I have no relationship with either Shenzhen Audio or Gustard. And nothing was communicated other than wanting to send the unit in for testing.

The Gustard DAC-X26 is one heavy box. You can't tell it from the picture but it I promise you, it is:

Gustard DAC-X26 Audio DAC Review.jpg

I like the super clear display showing everything you need to know at a glance. There is a remote which I did not use for this testing.

The back panel has the inputs you expect including I²S input:

Gustard DAC-X26 Audio DAC Back Panel Review.jpg

There are two independent linear power supplies with their own transformers...

Review and Measurements of LH Labs GO2Pro Infinity DAC & Amp

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This is a review and detailed measurements of the LH Labs GO2Pro Infinity portable DAC and headphone amplifier. It is on kind loan from a member. It costs USD $480 including a 20% discount as of this writing. So full retain price is a whopping $600!

I tested the regular GO2Pro version a while back but it was with my less standardized tests.

The GO2Pro Infinity is a chunky unit the size of a mobile phone but much thicker and heavier:

LH Labs GO2Pro Portable DAC and Headphone Amplifier Review.jpg

I like that the sides are chamfered which makes them fit the hand better and poke you less.

The color and graphics also give the unit a somewhat luxury look, separating it from the crowd of products in this category (battery operated headphone DAC+amp).

There are separate USB jacks for data and charging. I wish the data one could do both for desktop use.

The on/off switch is a stiff slider which I guess is good so it won't accidentally turn on by itself and drain the battery.

I was not a fan...

Review and Measurements of Holo Audio Cyan DSD DAC

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This is a review and detailed measurements of Kitsune Hifi's Holo Audio Cyan DAC with DSD option. It is on kind loan from a member. The Cyan comes either in PCM R2R with headphone amp or just DSD (you can also get both). The cost for the DSD version is USD $1099. I am assuming you have to pay shipping on top of that.

While the pedigree of off-the-shelf DIY case cannot be erased, the Cyan DAC adds enough touches to make it look nicer than the crowd:

HOLO Audio DSD Cyan Review.jpg

I am especially fond of the dot matrix white LEDs. Not a good choice in the bedroom likely but otherwise, it is bright and legible.

As noted, the headphone amp option is deleted from the DSD version but oddly the volume control and jacks are left there. I guess it saved them manufacturing cost to make another front panel without those holes. From what I recall, even the headphone circuits are in there but just disabled. The reason being that the DSD stream doesn't allow digital...

Review and Measurements of NAD 7050 Streaming Amp

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This is a review and detailed measurements of the NAD 7050 integrated DAC, amplifier and streaming playback. It is on kind loan from a member. It appears the product was announced in 2014 and since discontinued as I can't find it on sale anywhere. The cost was USD $999 from what I can gather.

The unit can be used both horizontally and vertically. A rotational sensor changes the display orientation conveniently. Here is its upright position which I consider better for sound since the electrons can naturally free fall into the speaker terminals:

NAD 7050 Networked Amplifier USB DAC Review.jpg

The outside has what appears to be some sort of rubber glued to it. It is soft to touch but picks up dirt very easily and is impossible to clean due to sticky nature of it.

The large knobs imply great feel which they don't have. They wobble as you rotate them. The larger knob is the volume control which had an odd delay in updating the display as you rotated it. Overall, a good effort...

Review and Measurements of Musiland MU1 Headphone Adapter

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This is a review and detailed measurements of the Musiland MU1 portable DAC and Headphone "dongle." It is on kind loan from an overseas member (the third of the package he sent me!). The MU1 costs $35 so quite a bit more than $10 price we are used to but in grand scheme of things, it is not much money if it brings more enjoyable than other throw-away dongles.

From the outside, the MU1 does have a premium feel compared to cheaper alternative:

Musiland MU1 Headphone Adapter Reviews.jpg

We have that aftermarket braided wire which in this case is functional and gives the impression that it won't fall apart quickly. There is a proper logo so you know what you own too. :)

Getting this dongle working required using USB-2 port again as I was the case with the HTC dongle I reviewed earlier today. Unlike the other dongles though, I did not have to jump...

Review and Measurements of HTC Headphone Adapter

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This is a review and detailed measurements of the HTC USB-C DAC and Headphone "dongle" aimed at mobile phone industry. It is on kind loan from an overseas member. I can only find overseas pricing for it but I think I found one site that listed it at USD $12. In that regard, it falls in the same price category of Google and Apple dongles.

As you can imagine, there is not much to this little adapter:

HTC USB-C Headphone Adapter Review.jpg

Hard to predict if the cable will fail sooner or later than its competitor.

Ghost in the Machine
When I received the HTC dongle, I had a heck of a time getting it to be recognized by Windows. I plugged it into the same USB-3 capable ports I use for testing every DAC. Here though, nothing would happen when I plugged it in. Reboot did not help either, nor would it show up in device manager in any way. I then tried it on my USB 2 front-panel and it worked! This is surprising as with other USB-C adapters, it is the other way...
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