Audio Science Review: Articles, Reviews and Measurements of Audio Products

Review and measurement of Emotiva UMC200 pre/pro

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Emotiva umc200 front.png

040913_emotiva umc200_back.jpg

We'll start with the 12 khz Jtest in a 32k FFT. And what a graph it is. Yes, the horrid looking result is over coax connection. The peak jitter spikes are at – 65 dbFS. There are lots of them not much lower than that, and a wide area is raised by random jitter noise too. The spacing on the spikes is 600 hz. Thinking it might be some 60 hz harmonic I looked at the 0-300hz range and this unit is very good there. Highest is -124 dbFS and a bit lower. No hum here. If you notch out the 12 khz tone what is left is -63 dbFS over that 24 khz band. YIKES!!!!!
Dual Emotiva Jtest graph.png

The better looking result is over HDMI. It isn't a great result. The base has considerable widening and several tones close in, but much better than the coax. The close in spikes are spaced exactly at 101 hz. The highest level is the closest in at -80 dbFS. They fall below the noise floor about 1 khz each side of the main tone.

Well is...

Review and Measurements of Sabaj Da3 Dac compared to Dragonfly Black

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This is a detailed review and measurements of Sabaj Da3 DAC and portable headphone amplifier. For comparison, I selected the Dragonfly USB stick DAC and headphone amplifier. I purchased both units myself. As of this writing, the Da3 retails for USD $120 from Amazon including prime shipping. The Dragonfly black is a bit cheaper at USD $100 with Prime shipping.

From functionality and usability point of view the Sabaj Da3 leaves the dragonfly in the dust. Its OLED display while small, shows sample rate, output connection type and volume level. Volume level is achieved with up/down controls on the unit. The Dragonfly has only an LED which changes colors. Decoding what it means requires the enigma code book of the world war one. The Da3 also has "balanced" and unbalanced headphone outputs. For this review I only tested the latter.

Physically the Sabaj Da3 is larger as you can see from a picture of both connected to my laptop:

Sabaj DA3 DAC Dragonfly Black Review and Measurement.psd.jpg

The Da3 is clearly...

Hardware Teardown of Hifiman EF2A DAC and Headphone Preamplifer

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Pre request in my review of Hifiman EF2A and kind permission from its owner, this is the teardown review of the unit.

Let's start with the main board's top view:

Hifiman EF2A DAC headphone amplifier teardown main board.jpg

The heart of the unit is the now quite obsolete TI/Bur-Brown PCM2702 DAC chip. It came out circa year 2000 and only supports 16 bit audio at 32, 44.1 and 48 kHz.

The unit has analog input which I think goes through the OPA264 op-amps.


Surprising to see is the Philips TDA1308 headphone amplifier.


It is being used apparently to then drive the tubes. In other words, half-way through the signal flow we already have our headphone output but then we choose to mess with it with later stages. :) The headphone amp likely has nice gain and hence the reason it over-drove and clipped the input stage...

Review and Measurements of u-turn Pluto and ART DJPRE II Phono Preamps

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This is a review, comparison and detailed measurements of Review and Measurements of u-turn Pluto and ART DJPRE II Phono Preamplifiers. Both fall in the category of budget products with the Pluto retailing for USD $99 and the DJPRE II for just $49 (both include Prime shipping). Of the two, the DJPRE II has more bells and whistles:

U-turn Pluto and ART DJ Pree II phono preamp review and measurements.jpg

As you see, the DJPRE II has "low cut" filter switch together with input capacitance selector (100 or 200 pf). It also has a clipping indicator and variable gain switch.

The u-turn pluto on the other hand, is fixed function. No switches, indicators, or anything else other than the power LED.

Between the two, I like the look of the Pluto better. The DJPRE II screams hobby project box. And that bright blue LED is deadly. Needs some black tape to cover it for sure. It is a sturdy box though so it is just a visual preference.

Both units have external transformers. Pluto has its own branded unit that has 9 volt AC...

Amir Buys a New Audio Precision Analyzer (APx555)!!!

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Yes, you read it right: I now own a second and the latest state-of-the-art analyzer from Audio Precision, the APx555. She is sitting here next to her elder unit to the left I have been using until now:

Audio Precision APx555 Audio Science Review Measurements.jpg

Avid readers know that I have been getting a lot of mileage out of my much older AP2522 unit. Despite being nearly 20 years old, it has had excellent performance. Great analog design and power of signal processing had kept it relevant for such use even now.

Alas, a few reasons prompted me to buy the new unit. First and foremost is the fact that the software for the new model allows me to directly talk to computer audio products through ASIO interface. You may have seen my difficulty in using my older analyzer there when a DAC doesn't have USB input. With APx555, I am able to now drive those products over USB just as well as it can using S/PDIF, Toslink, and analog output out of the analyzer. This makes measurements now the same whether I use USB...
Review and Measurements of HIFIMAN EF2A DAC and Headphone Amp
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This is a review of the HIFIMAN EF2A tube DAC and headphone amplifier. It is on a kind loan from a forum member. The retail price is $169 USD but I see it on Amazon for $139 plus shipping. I seem to recall it going on massdrop also. This is a small unit as you can see here, dwarfed not by one but two Audio Precision analyzers;

Typical of these "hybrid" headphone amplifiers, the tube is used as the input stage and the output drive is transistors. The see through lid shows a row of power transistors which hints at higher than normal output power.
Review and Measurements of HIFIMAN EF2A DAC and Headphone Amp.
Review and Measurements of Cypher Labs Theorem 720 and Fiio Q1 DAC and Headphone Amp
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This is a detailed review, measurements and comparison two portable DAC and headphone amplifiers: the Cypher Labs Theorem 720 and Fiio Q1 DAC. The Theorem 720 is on kind loan from a member. It is a circa 2013 product and quick look on third-party sellers on Amazon shows a retail price of $1,000. I own the Fiio Q1 and it retails for just $69 (plus $8 for shipping on Amazon). Obviously this is not an even match from price point of view but the Q1 was the only portable DAC+headphone amp I had that includes a battery like the Theorem.

Physically, the Fiio Q1 is quite a bit more slick and pocketable than the Theorem 720:

Cypher Labs Theorem 720 DAC and Fiio Q1 Review.jpg

The Theorem 720 on the other hand looks like a hobby box. Definitely not for the pocket but portable nonetheless.....
Review, Measurement and Comparison of Schiit Modi 2 Uber and Topping D30
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This is a detailed review and measurements of the popular Schiit Modi 2 Uber DAC and comparison to Topping D30. I own both units. The Modi 2 Uber edition is one of the three versions of this DAC and retails for $149 plus shipping. The Topping D30 is available on Amazon Prime for $119 and includes shipping so good bit cheaper.

The two are similar in features in that both have three inputs: USB, S/PDIF coax and Toslink optical inputs. Both have external power bricks. The Topping has its power switch on the front which I prefer to the back switch of Modi 2 Uber. I also like the English labels on Topping as opposed to alien symbols used in Schiit Modi 2 Uber....

Hardware Teardown of Schiit Fulla (V2) DAC and Headphone Amplifier

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I recently performed a review of Schiit Fulla DAC and Headphone amplifier. This is a follow teardown of the unit.

Let's start with top down view of the unit:

Starting on the right side we see the typical USB controller (Cmedia CM6631A) driving an AKM AK4490EQ DAC. An external flash IC holds the firmware for the device....

Review and Measurements of KORG MR-2000S ADC & Comp. to RME ADI-2 Pro

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This is a review and detailed measurements of KORG MR-2000S ADC and comparison to the ADC portion of RME ADI-2 ADC. I have previously measured the DAC portion of KORG MR-2000S and RME ADI-2 DAC.
The KORG has been on loan to me from a kind owner. It will be shipped back tomorrow so I won't be testing anything on it after the review. I own the RME ADI-2 Pro and will do more testing on it in the future.

The KORG MR-2000S is a stand-alone (and connected) professional audio recorder whereas the RME ADI-2 Pro is just ADC/DAC. So not in the same class of...

Hardware Teardown of xDuoo TA-01 DAC and Headphone Amplifier

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This is a follow up to my review of xDuoo TA-01 DAC and headphone amplifier. The TA-01 is powered by an external switchmode power supply:

xDuoo TA-01 DAC Power Supply.jpg

Nearly a dozen screws hold the unit together. Once open, you are greeted with this:

Cleverly, it uses some kind of off-the-shelf DAC module vertically mounted...

Review and Measurements of XDuoo TA-01 and Schiit Fulla V2 DAC and Headphone Amp

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This is a review and measurements of the XDuoo TA-01 tube DAC and headphone amplifier and comparison against Schiit Fulla (V2) solid-state DAC and headphone amplifier. Both are on loan to me from kind members although I had also purchased a Schiit Fulla V2. I may compare the two Schiit units later in light of some of the review outcome.

The XDuoo TA-01 retails for USD $160 on Amazon including Prime shipping. The Schiit Fulla is $99 from Schiit direct (not sold elsewhere) and you have to add shipping to it. So prices are not identical but close.

The XDuoo as you see in the above picture, resembles an aircraft instrument or something. It definitely has nice design cues. The volume is hefty and feels nice with that big knob. Toggle switch and power indicators are nicely in the front. It comes with an external switching power supply. It...

Measurements of Focusrite Forte recording interface

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I measured the Focusrite Forte recording interface. In this case focusing on the DAC. This was a nice two channel recording interface which has been discontinued. The ADC and DAC chips and much of the circuitry is what is used in the current Focusrite Clarett line of interfaces. It has two microphone inputs with up to 75 db of gain which is higher than usual. Also line level and instrument inputs (for guitars). Headphone, and monitor outputs. It is a 24bit/192 khz ADC/DAC. The Forte has a Display Port dongle for some connections and a touchscreen for many of the controls. It connects via USB using ASIO in windows and Focusrite software in Mac. It sold for most of its life around the $450 to 400 mark.

The measurement FFTs are all 32K FFTs as is the custom on ASR. The spectrograms used a 2k FFT. As is Amir's custom I'll start with a 12 khz -1 db tone. Very...

Review and Measurements of Topping D10 as USB to S/PDIF Converter

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In my, I was asked how well the D10 does as a USB to S/PDIF (and Toslink) converter since it has those outputs. I thought I make this review and measurement its own topic.

The Topping D10 is nice and tiny and no bigger than many USB to S/PDIF converters. What's more, it has a nice display which many lack, showing the sample rate:

At $75 including shipping (albeit on Massdrop), it is also price competitive with other such converters.

Let's get into measurements and see how it does.....

Review and Measurements of RME ADI-2 Pro (comparison to ADI-2 DAC)

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This is comparison review and measurements of RME ADI-2 Pro against the RME ADI-2 DAC. The former has both analog to digital conversion in addition to digital to analog. I purchased that combo unit because I hope to make use of its ADC for measurements in the future. According to RME, ADI-2 DAC has some additional refinements in design which they say are not measurable. Well, I hope to measure them. :)

I purchased the RME ADI-2 Pro by contacting RME in Germany/US and received kind accommodation pricing. With the retail price of USD $1,999, even with my discount, it is still pretty serious amount of dollars. The RME ADI-2 DAC which I reviewed earlier, comes at a much more reasonable price of $999.

Physically the units are almost identical as far as size and general design...

Review and Measurements and miniDSP 2x4 HD DSP and DAC

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This is a brief review and measurements of miniDSP 2x4 HD Processor and USB DAC. I purchased this online and seems like the price as of this writing is USD $207 as of this writing. This is a USB DAC with Toslink optical input and analog/digital in, four channel digital signal processor (DSP).

The DSP features can be used to implement everything from active speaker crossovers to full room correction/equalization. While the former functionality is easy enough to implement, the latter is up to you to program. This is a "raw" platform with no intelligence of its own. If you want room equalization, you have to figure out how to program its individual parametric filters or FIR parameters.

The unit comes in a shiny aluminum case that feels decent and has just enough weight to not get dragged too badly by the myriad of connections you would have to hang from it...

Review and Measurements of Schiit Fulla (V1) Dac and Headphone Amplifier

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This is a review and measurement of the Schiit Fulla DAC and headphone amplifier. It is the version 1 and is on kind loan from a member. If you are interested in V2/current version, I have purchased that, and the review will be forthcoming.

The Version 1 is a diminutive unit, a bit larger than the typical "thumb drive" sized USB DACs. It is made from folded metal like the larger Schiit products.
Schiit Fulla V1 DAC Picture.jpg

There are some sharp corners especially around the volume control knob that I wished were rolled off. Speaking of the volume control, it has rather low level of travel but it works and is convenient to have.

Format wise, this is an older DAC so limited to 96 kHz sampling rate as reported by Roon:

Schiit Fulla V1 DAC Roon Format Support.PNG

Yes, the USB identifier indeed says "I'm Fulla Schiit." Would be quite funny if the performance is great. Let's see if that is so in our measurements. If you are not familiar with my tests, I suggest reading my...

AES Paper Digest: Do Audio Op-amps Sound Different?

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This is a digest of the Audio Engineering Society (AES) conference paper titled, “Distortions in Audio Op-Amps and Their Effect on Listener Perception of Character and Quality.” ( As the name indicates, it is a controlled listening test to see if there is audible difference between Op-amps (integrated small amplifiers) when operated below their clipping point.

In recent years, it has become quite fashionable to talk about what Op-amp are used in audio products or swap one for the other in the same vein. While subjective outcomes abound on efficacy of such differences, question becomes if there is any formal, controlled listening tests that can give us reliable indication of audible differences in Op-amps.

The paper in question aims to answer this question. It has good pedigree when it comes to its authors which includes the famous mastering engineer, George Massenburg, and other researchers from various...

Review and Measurements of Intona USB Isolator for Audio DACs

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This is a review and measurement of Intona USB Isolator. In the last few years there has been a proliferation of USB filters, cleaners, regenerators, feeding on fear of audiophiles of noisy computer ports. Intona doesn't actually play in that market directly. They built this device for industrial control applications where strict isolation from the machine being controlled is required. Audiophiles however, have been interested in the unit just as they are in other devices in this category.

This unit is on a kind loan from a forum member. It retails for USD $229 plus $29 shipping to US. It comes in a nondescript, plastic box. No pretense of being a audio jewelry here. For this review I compared the Intona to Uptone Regen and TotalDAC D1. You can see the full collection here:

Interestingly the Intona...

Review and Measurements of RME ADI-2 DAC

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This is a review and detailed measurements of RME's new ADI-2 DAC. This is a spin off from their highly regarded ADC/DAC combo, the ADI-2 Pro. I have purchased the Pro for my testing but a member was kind enough to loan me the DAC only version reviewed here. I will measure and post any differences between the two at a later time.

The ADI-2 DAC retails for USD $999. The black version I received looks quite attractive with nice white LED highlights around controls and a high-resolution and highly responsive LCD display.

From a pure DAC functionality, it is better executed than my ADC/DAC. It has a remote control and unlike mine, has proper inputs for S/PDIF as opposed to a dongle.

The unit has huge number of settings and display material that is navigated through four switches and three rotary encoder, all of which are "clickable." Unfortunately this...
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