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

Audibility thresholds of amp and DAC measurements

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Introduction
A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC measurements.
Feel free to comment if you have any issues with the content of this post, be it technical, grammatical, or maybe just something that's poorly communicated.

Orange marks strict limits while green marks lenient limits.
UPDATE #1: There seems to be some confusion about the the implications of the thresholds in relation to audibility.
Strict thresholds guarantee that anything measuring better will be transparent.
Lenient thresholds are only lenient relatively to the strict thresholds, but are still very strict themselves from an audible point...

Review and Measurements of Schiit WYRD USB Filter

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This is a review and detailed measurements of Schiit WYRD "USB decrapifier." It is on kind loan from a member and retails for USD $99 plus shipping from Schiit direct.

This is a box that has USB input and output and external transformer input. It generates new USB power using the latter, and reclocks USB using a USB hub chip with the claim of it being more accurate. Externally it looks like the rest of the budget products from Schiit except that it has yet another finish than others:

Schiit WYRD USB Filter Review.psd.jpg

These solutions make "perfect" intuitive sense: USB is a computer port so by definition must have dirty power and signal. So why not clean them and generate better sound? Schiit doesn't provide any measurements to show efficacy of the product so that job falls on our shoulders.

For this testing I thought I should measure the performance of Schiit Modi 3 DAC per picture above. To cover our bases, I also tested with another DAC under review (March...

Review and Measurements of SMSL Sanskrit 10th DAC

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This is a review and detailed measurements of the SMSL Sanskrit 10th budget DAC. It retails for USD $100 on Amazon including shipping. I purchased mine (I think) from Massdrop at discount.

From pictures posted by SMSL, the unit looks like large plastic Lego pieces. Fortunately in person it looks quite a bit better:

SMSL Sanskrit 10th SK10 DAC Review.jpg

Remarkably at this price, the unit comes with a remote control. It also has three inputs: USB, S/PDIF and Toslink optical.

There is also a cute gimmick of the display rotating depending on whether you put it horizontal or vertical.

There are separate USB power inputs depending on whether you want to just use USB or S/PDIF. All my testing was done with the USB input jack.

If the performance is there, this would be quite a nice DAC to have. Let's see what the measurements show.

Measurements
I powered the unit and hooked it up via USB and was greeted with this disappointing dashboard...

Review and Measurements of Gustard A20H DAC & AMP

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This is a review and detailed measurements of Gustard A20H DAC and headphone amplifier. It is on kind loan from a forum member. It retails for USD $850 on Amazon with free shipping (from China?). I am accelerating this review because it is on sale on massdrop for USD $700. Still not cheap but more reasonable.

For your extra money you get a much larger and beefier enclosure with a large LCD display:
Gustard 20H Dac and Headphone Amplifier Review.psd.jpg

I usually clean the units and touch them up in photoshop but in this case I choose to leave it alone so that you can see how well it shows smudges and scratches. Overall the enclosure is bland but OK.

Claim to fame of this unit is stepped attenuator implemented using a bunch of relays. The volume knob therefor is a rotary encoder telling the unit where to set the volume. And therein lies the main usability issue I found: if you rotate the knob quickly, it will change very slowly! This is of course the opposite of what you want. If...

Review and Measurements of Aurender A10 Streamer

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This is review and detailed measurements of the Aurender A10 streamer and player. It was kindly loaned to me for brief testing by Gig Harbor audio. The unit retails for USD $5,500. For that, you get a streamer and DAC with 4 TBytes of storage and SSD for caching.

If you are not familiar with Aurender, they are the most common streamer I see at audio shows. In that regard, its price is not a larger percentage of a high-end audio system but of course, significantly higher than the typical desktop products we talk about.

The unit I tested was quite hefty and had pretty high-end fit and finish. Please excuse the quality of the mobile phone picture in dim lighting:

aurender  A10 Music Server & Player.jpg


The unit I was testing kept complaining about the SSD needing repair due to improper shutdown but it allowed me to use it anyway. Was strange that it did not use some kind of journaling file system to allow quick recovery from a power failure.

For my testing, I was only interested in its...

Measurements of Parks Audio Puffin Phono Stage

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This is a measurement of Parks Audio DSP- based PUffin Phono amplifier. Yes, you read that right: it uses a DSP for implement RIAA curves and many, many other functions. It was kindly loaned to me in person to test our meet at friendly audio shop, Gig Harbor Audio. The unit retails for USD $399 including Prime shipping on Amazon.

Here is a quick shot of the unit while being tested with very dim light with my mobile phone:

Parks Audio Puffin Phono Stage DSP Review.jpg

The company is apparently well-known for its tube based phono stage. So imagine the shock and horror of its customer base when they heard that not only had he dispensed with tubes, but that the unit digitizes audio, processes it, and converts it back to analog. Sacrilegious! Quick search shows long threads of riots in street, folks feeling abandoned, going to psychiatrists and being asked about their childhood, etc.

Fortunately we are much more enlightened here...

Measurements of Nakamichi Dragon Cassette Deck

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This is a detail measurements of the iconic, Nakamichi Dragon Vintage cassette deck. It was kindly brought to me at a meet at our local audio store (Gig Harbor audio).

For those of you too young to know :), the Nakamichi Dragon has the reputation of being the best cassette deck available at the end of the cycle for the format. It came out in 1982 and retailed for USD $2,499. That would be $6,500 today's dollar so quite a lot of money. I was too poor to afford one at the time so it was a pleasure to get my hands on one finally for this test.

We were testing it in a dark room and this is just with the light of a phone so please forgive the poor lighting:

Nakamichi Dragon Cassette Tape Measurements.jpg

Unlike digital products and amplifiers, we are at the mercy of calibration tapes for testing such products. The owner had a few of them and that is what I used for testing.

I unfortunately did not capture the results of 1 kHz tone but here are some other frequencies.

315 Hz...

Review and Measurements of Audeze Deckard DAC and Amp

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This is a review and detailed measurements of Audeze Deckard DAC and headphone amplifier. It is on kind loan from a member and seems to be discontinued. Seems to be a product of year 2016 with retail price of USD $699. Owner has bought it used for much less.

The unit has rather unusual hefty metal enclosure with super sharp extruded aluminum edges that can easily pierce your fingers:

Audeze Deckard Headphone Amplifier and DAC Review.jpg

Other than that, the volume control feels very nice. There are RCA outputs and inputs in the back. The RCA out is variable and seems to just be connected to the output of the headphone amplifier. I only tested the unit as a DAC+Amp combo. With the front toggle switch, seems like you can use it as just a headphone amp/pre-amp if you wanted.

Looking for information on it, I ran into a CNET review saying this:

1544216992924.png


Is Steve Guttenberg right? Let's find out!

Measurements
I adjusted the output to typical 2 volt...

Review: Apple vs Google USB-C Headphone Adapters

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This is a review, detailed measurements and comparison of Apple's USB-C adapter to the current and last version of Google Pixel headphone adapters. The Apple adapter costs just $9 including one day shipping for free. The Google dongle costs $12.

Not that any of these are large by any stretch but Apple's is also the smallest of the three:

Apple iPhone USB-C Headphone Adapter Audio Review.jpg

Oddly there is no apple logo or markings on the device. The others don't have it either but I thought Apple would insist on that.

All three adapters work in Windows with the appropriate adapter and that is how I tested them, allowing my analyzer to fully control and quantify their performance.

Format wise, Apple's supports the key ones:
Apple iPhone USB-C Headphone Adapter Audio Formats Supported.png


So very similar to Google Pixel V2 and better than V1 which only supported 48 kHz.

Note that volume control in Windows is active at all times even if you use WASAPI exclusive mode!

Not much else to talk about than getting into...

Study: Headphone Amp Gains: Low or High?

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This is an analysis of whether you are better off using low or high gain mode in a headphone amplifier in their overlapped region. Traditional rule of electronic design says there is no free lunch: higher gain means higher noise. While this has become the "conventional wisdom" and one that I routinely state myself, forum member asked if there is any hard data to back this. So I decided to test the theory on two headphone amplifiers: the Schiit Magni 3 and JDS Labs Atom.
Schiit Magni 3 Headphone Amp versus JDS Labs Atom Gain Review.jpg

The test matrix here is infinite in scope. What volume does one choose for each gain to test? After pondering for a second or two :), I decided to go the defensible route of setting low gain to max and then matching the same in high gain. Both of these amplifiers have analog volume controls and in high gain, they can be touchy as far as getting accurate levels out of them but I managed to get close enough.

Let's see what the measurements say.

Measurements...

Review: Battle of Schiit Audio DACs

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This is a review, detailed measurement and comparison of Schiit's Modi 2 (uber), Modi 2 Multibit and Modi 3. I have reviewed the Modi 2 uber and Modi 3 before so this is mostly focused on how the Modi Multibit compares to them. I have purchased all of them personally at different times. The Modi 2 Uber is now replaced by Modi 3 with the latter costing USD $99 plus shipping. The Schiit Multibit fetches quite a premium compared to that to the tune of USD $249 plus shipping. Is the extra cost worth it? This is what this review is about.

Starting from the top, Schiit seems to be playing with its design in each one of these units:

Schiit Modi Multibit Review Compared to Modi 3.jpg


Switch type, color and finish seem to vary some...

Review and Measurements of Audirect Beam and AQ Dragonfly

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This is a review, measurement, and detailed comparison of two "thumb drive" sized combo DAC and headphone amplifiers: the Audirect Beam and Audioquest Dragonfly Black. I had reviewed the latter last year but it was with my old measurement gear so I thought I perform a fresh set of data on it given the popularity of Dragonfly. I purchased the Audirect Beam from Amazon a few months ago for USD $104 (about $114 with tax). I purchased the AQ Dragonfly for USD $99 from Amazon just the same. The Audirect Beam is on sale for $80 on massdrop and hence the reason I thought I review it now just in case you want to take advantage of its sale.

The Audirect Beam is the smallest DAC+amp I have seen, sans the phone USB-C dongles:

Audirect Beam Portable DAC Review.jpg

It has a spring-loaded, nice feeling momentary rocker switch for turning the volume up or down. Sadly in practice it would not change level correctly, requiring multiple toggles.

The volume control changed the...

SMSL SU-8 Version 2 Balanced DAC

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This is an update to my previous review of SMSL SU-8. At a retail price of USD $212 on Amazon and balanced outputs, the SU-8 could provide a very compelling proposition. Unfortunately the performance of the balanced output in my first review sample was disappointing, showing significant switching noise. SMSL was kind enough to send me a second unit recently and I put it to test.

There is no functionality difference so see the previous review for details of that. Briefly here, you get a nice looking unit with a tiny display and remote control:
SMSL SU-8 DAC Version 2 Review.jpg

[the 44.1 kHz on the display is not showing all the way due to my camera shutter not being in sync with its refresh rate.]

Let's get into measurements and see how she performs.

Measurements
Let's start with our unbalanced dashboard:
SMSL SU-8 DAC Version 2 Unbalanced Measurement.png


This...

Preview: Monolith by Monoprice Desktop THX Headphone Amp & DAC

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This is an early look of the Monolith by Monoprice Desktop Headphone Amplifier and DAC with THX amplification technology. The unit was kindly purchased by a forum member and drop shipped to me. And that is where the trouble began but more on that later. The Monoprice THX amp and DAC retails for USD $480.

The Monoprice THX amp and DAC has the same design language of other "monolith" units which translates to a serious look. There is brushed metal on front and very shiny and glossy enclosure which instantly shows fingerprints:

Monoprice Monolith Desktop Headphone Amplifier and DAC Review.jpg


Let's backtrack a bit. I have ordered three products from monoprice. The first one never came and I only found out about it a few months later. I then ordered two other products from them both of which were sent to a remote neighbor. Their street and house number are one digit off from us. Hard to imagine how someone could be this bad at reading addresses yet be in delivery business.

Worried that this unit would also...

Review and Measurements of Allo DigiOne RPI S/PDIF

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This is a review and detailed measurements of the Allo DigiOne Raspberry Pi digital audio (S/PDIF) interface. It retails for USD $99 and is on kind loan from Allo. Unlike its higher-end brother (DigiOne Signature), this is a single board implementation at half the price.
Allo Digione Raspberry Pi SPDIF Output Jitter Review.jpg

When combined with a Raspberry Pi, and a suitable "audio operating system" (e.g. Volumio used in this review), you have a $135 networked S/PDIF interface. Hook the output of this board to your favorite DAC and you automatically add networking to it, allowing you to place the computer server elsewhere and stream content to your audio system.

Testing digital audio outputs is quite different than our typical analog measurements. Here, we are interested in how pure the digital output is as to produce good performance out of any DAC regardless of how good its S/PDIF interface is. I took a shot at this when...

Tear down of Neurochrome HP-1 High Perf Headphone Amp

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This is a tear down of the Neurochrome HP-1 High performance Headphone amplifier. My review of HP-1 showed exemplary distortion and high power handling. With kind permission from its designer, here is a look at what is inside.

Here is a lower resolution shot of the PC board:

Neurochrome HP-1 Teardown PCB low res.jpg


For 4X higher resolution, click on this attachment:

Neurochrome HP-1 Teardown PCB med res.jpg

You may have seen my tear down of massdrop THX AAA 789 amplifier which had plenty of empty space. Not so here. As you see, nearly every inch of space is used.

Unlike the massdrop THX 789, the power supplies for the HP-1 are internal. We have two switching supplies from the reputable Mean Well Taiwanese company. I am assuming one...

Review and Measurements of Apogee Groove DAC and Amp

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This is a review and measurements of the Apogee Groove portable DAC and headphone amplifier. It is on kind loan from a forum member. As small portable DAC+Amps go, its retail price of $295 is quite high. I see factory refurbished ones at $149 though on Apogee website.

Apogee is best known for their professional audio products so their entry into personal audio is quite a departure for them.

As USB audio "thumb drive" form factors go, the Apogee is quite a bit more substantial:

Apogee Groove Portable DAC and Headphone Amplifier review.jpg


Volume wise, it is probably double the size of typical thumb drives. The larger size allows rubberized up/down volume buttons with excellent feel. There is no "plastic" feel to the unit either, making you think you can sit on it and nothing bad would happen to it.

The three LEDs roughly show the volume level. During music playback, they change to color to green and are fully analog. Each has individual intensity which once maxed out, lights up the one above it...

Tear down of Massdrop THX AAA 789 Headphone Amp

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With kind permission of the owner, I took apart the Massdrop THX AAA 789 headphone amplifier. If you have not seen it yet, check my my review of Massdrop THX 789.

The internal structure of this unit follows other models from Massdrop. I was impressed with the effort to keep all the components on one side using mostly SMT (surface mount) parts. The bottom of the PCB is only through-hole pins which I am assuming was wave soldered.

Here is lower resolution shot of the PCB with my annotations:

Massdrop THX AAA 789 teardown main PCB reduced2.jpg


Click on this attachment to get 4X higher resolution image.

Massdrop THX AAA 789 teardown main PCB reduced.jpg

I have 4X larger image yet again. Send me a message if you want that.

The biggest shock here is that there is no "THX module" of any sort! No custom or hybrid parts that I can see. Instead, we have a bunch of exclusively Texas Instruments parts...

Review and Measurements of Neurochrome HP-1 High-Performance Amp

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This is a review, detailed measurements and comparison of Neurochrome HP-1 high performance headphone amplifier to Massdrop THX AAA 789. It is on kind loan from company designer and owner, Tom Christiansen. I learned about Tom in chasing a review he had done of a passive volume control. I was very impressed with his depth of knowledge and thorough analysis using an Audio Precision analyzer. Tom is an analog designer, having worked for famous and large leaders in the industry (National Semiconductor and Texas Instrument). He is quite active in DIY audio forum, sharing his knowledge of engineering and audio. Needless to say, I was excited to get my hands on his products to test starting with his HP-1 headphone amplifier given its superlative measured specifications.

The HP-1 comes in all forms from bare PCB to fully populated board and finished package. I received the latter:

Neurochrome HP-1 Headphone Amplifier Review.jpg

The retail price for this version is $1,249. Bare...

Review and Measurements of Nobsound NS-DAC3 Pro DAC & Amp

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This is a review and measurements of Nobsound NS-DAC3 Pro DAC and headphone amplifier. It is on kind loan from a member. I see it on Amazon for USD $140 with free shipping from China.

This is the type of DAC you see in tons of Chinese websites with tempting features for the price. As you can imagine, there is nothing glamorous about such products. The packaging is as cheap as you can get. There is even a small CD with the drivers for your nostalgic feelings about computing days long gone. A couple of photocopied pages complete the picture as far as the manual is concerned.

The metal enclosure is not bad though and brings some uniqueness in this super crowded market:

Nobsound NS-DAC3 Pro DAC and Headphone Amplifier Review.jpg


As you can see, increasingly we see Bluetooth added to these small DACs. Also nice is dual headphone jacks.

In the back we have the usual S/PDIF, Toslink and USB inputs.

Anyway, let's see how she measures.

Measurements
Here is the dashboard view using the headphone jack...
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