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

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.

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

Inside ifi iOne Nano Portable DAC and Headphone Amplifier

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I reviewed the ifi nano iOne a while back. Before sending it back and with owner's permission, here are the guts of the unit.

I don't have much time to do a reverse engineering on it. So I will provide the top and bottom images of the PCB and let you all do that if interested :).

Here is the bottom side of the unit: (click on the image for full size)

ifi ione nano DAC teardown top PCB.jpg

I have marked the main engine: the DSD1793 DAC.

Clearly visible at the bottom is the all-in-one module from CSR for Bluetooth.

I can't see the markings for U500 on the right. And the numbers for the tiny output buffers seem proprietary to iFi.

Assembly looks very clean with no manual re-work.

Here is the top side:
ifi ione nano DAC teardown bottom PCB.jpg

The main item is the XMOS USB interface on a daughter card. Nice to see glue on the connectors to keep it from coming lose.

I also...

Review and Measurements of New JDS Labs Atom Headphone Amp

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This is a review and detailed measurements of JDS Labs Atom Headphone Amplifier. It was kindly sent on loan by JDS Labs in advance of its formal announcement and availability this week. It retails for USD $99. As such, I will be comparing its performance to other $99 amplifiers such as Schiit Magni 3 and Monoprice Liquid Spark.

The Atom is a nice departure from the JDS O2 in having proper RCA connectors in the back and 1/4 headphone jack in front (and 3.5mm in the back):

JDS Labs Atom Headphone Amplifier Review.jpg

The enclosure is plastic and lightweight but is stable enough to not move around with the weight of cables.

As you see in the comparison above, it is about 10% wider and deeper than O2. The volume control feels slightly less good than the O2 with the latter having more of a "hydraulic" feel.

There is not much else to say about it so let's get into the measurements and see how she does.

I started my measurements with a dashboard view of unity gain with 2...

Review and Measurements of Monoprice Liquid Spark Headphone Amp

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This is a review, detailed measurements and comparison of Monoprice Liquid Spark, Schiit Magni 3 and JDS Labs O2 headphone amplifiers. The Liquid Spark and Magni 3 retail for $99 but only the Monoprice comes with free expedited shipping. The JDS Labs O2 retails for USD $139 on US Amazon with free Prime shipping. JDS sells it direct for $129 plus shipping. So roughly speaking, all three are in similar price range.

The three headphone amplifiers look very different from each other:

Monoprice Liquid Spark Headphone Amplifier review.jpg

As you see, the liquid spark is quite chunky compared the other two. It also generates a bit of heat although nothing remotely of concern.

Connectivity is funky on the JDS O2 with 3.5 mm headphone jack for input. The other two have proper RCA inputs in the back and 1/4 inch in the front.

The Liquid spark comes with a large laptop style external switching supply. The other two have heavy linear wall-wart supplies with the Schiit Magni 3 being quite a...

Ethan Winer Builds a Wire Null Tester

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Ethan has built a null tester for testing audio interconnects to reveal differences between them. He has a new video on it which is kind of long on intro but then gets to the meat of the argument toward the last third:

Review and Measurements of Monoprice Portable Amp and DAC with THX

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This is a review and detailed measurements of Monoprice Portable Headphone amplifier and DAC with "THX AAA" technology. I purchased this earlier in the week for USD $279.99. With tax it came to little over $300.

For those of you who don't know, THX has come up with amplification module with feed forward error correction which serves to lower distortion in amplifiers. My review of Massdrop THX Headphone Amplifier showed it to have exceptional performance, far and above anything I have measured before. So excitement has been built up for the same technology (but not identical part) used in Monoprice version. Here, we are treated to a portable headphone amplifier and DAC all in one.

The Monoprice Monolith THX has a very serious, business-line appearance:

Monoprice Monolith THX Portable DAC and Headphone Amp Reviews.jpg

It is similar to a modern smartphone but much thicker and...

Review and Measurements of Audio-gd NFB28.28 DAC and Headphone Amp

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This is a review and detailed measurements of Audio-gd NFB-28.28 DAC, headphone amplifier and pre-amplifier. It is on a kind loan from a member and retails for USD $750 plus shipping from China. The unit is quite heavy so I suspect shipping will cost a few dollars.

This is a deep enclosure but half the width of the larger Audio-gd products:

Audio-gd NFB28.28 DAC and Headphone Amplifier Review.jpg

Navigating the unit is maddening. 7-segment LED digits are used to indicate input number, setting, etc. I searched for the manual but could not find any. Instead there is some random text on Audio-gd website that starts to deal with something about a problem they fixed. How a simple device is made so complicated is beyond me. The unit could stand serious cleaning up of the documentation and revamping of the user interface.

There are lots and lots of inputs and outputs. I let you read the documentation for yourself. For my testing I used the USB input and either balanced XLR output for DAC...

Review and Measurements of Chord Mojo DAC and Amp

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This is a review and detailed measurements of Chord Mojo portable DAC and headphone amplifier. It is on a kind loan from a member. Retail price is USD $599 but I see Amazon showing it for $532 including prime shipping.

The Mojo is a small but chunky and heavy as portable headphone amplifiers go:

Chord Mojo DAC and Headphone Amplifier Review.jpg

The case feels like it is filled with lead and you could run a car on top of it and have it escape unscathed.

Let me get out of the way that I am not a fan of its whimsical look. But much worse is forcing a human to decode hues and color intensity of lights to detect what mode the unit is in. Why oh why? For $600, I expect something more informative than what is offered here. I will for example happily take a rotary volume control over those two blue buttons for volume level.

The Chord products are popularized by its designer, Rob Watts who is quite active online, and in audio shows/conferences. Having technical designers mingle with social media...

Review and Measurements of Denon AVR-4306

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This is a review and detailed measurements of the amplifier section of the Denon AVR-4306. At the time of this writing, we are still searching for a high-performance amplifier at reasonable prices. None of the new gear purchased has achieved the right bar so I dug into my inventory of old audio products and found this Audio/Video receiver. I think I bought it 12 to 15 years ago. I see mentions of it as far back as 2005. So in audio terms, it is a grandpa. :)

I see the AVR-4306 on Amazon from a number of sellers starting at $389. On ebay, I found $189 including free shipping.

As expected, these AVRs are huge as compared to desktop or even some pro products I have tested. The number of jacks seemingly is a marketing thing with more the merrier.

Yamaha AVR-4306 AVR Home Theater Review and Measurement.jpg

For my testing, I only focused on using the unit as a 2-channel amplifier and put it in "CD direct" mode. I also tested it in "pure" mode but made no difference.

Let's get into measurements and see if...

Review and Measurements of Behringer A500 Amplifier

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This is a review and detailed measurements of the Behringer A500 "Reference" Power amplifier. I purchased this unit on suggestions from members from Amazon for just $199 including Prime shipping.

Being targeted at the pro market, this is rack-mount unit with heft heatsinks on each side:

Behringer A500 Amplifier Review and Measurements.jpg

Full compliment of inputs are provided from RCA to balanced XLR and TRS. No input selector is provided though and the manual warns against simultaneous connection to more than one input.

The plastic volume knobs feel cheap but otherwise, it seems to be a sturdy build.

The manual says it has a class AB output stage. I am assuming some kind of power rail voltage switching is used to keep power consumption generally low but I have not confirmed this.

For my testing, I used a 4 ohm dummy load and balanced XLR inputs. Let's get into measurements and see how she did.

EDIT: the first revision of this review had tested the A500 with the input...

Review and Measurements of NuForce STA-200 Power Amp

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This is a review and detailed measurements of Optoma/NuForce STA-200 Power Amplifier. It is on kind loan from a member. I see it listed for USD $499 including Prime shipping. Looking elsewhere, it appears to have a list price of $1299.

This is one attractive enclosure that does not usually come in a $500 package:

Optoma NuFroce STA-200 Power Amplifier Review and Measurement.jpg

The finish is slightly textured and looks pretty nice.

Feature wise, there is nothing there but a set of RCA inputs and speakers. The RCA inputs are paired with speaker terminals on each end of the unit so you better have RCA cables that separate that much.

Somewhat out of character is a traditional extruded aluminum heatsink poking out the back. I guess this avoids having to put the heatsink inside and having to vent the enclosure. The heatsink is pretty small though and it was cooking even when testing the unit at just 5 watts/channel. I worry about its ability to run OK at full power for any extended amount of...

Review and Measurements of Topping TP60 and FX Audio FX502SPro Amps

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This is a review, measurement and comparison of two speaker amplifiers: Topping TP60 and FX Audio FX502SPro. I purchased both personally. The TP60 retails for USD $199 with free prime shipping but goes on sale frequently on Massdrop where I purchased it for just $135. I bought the FX502SPro for $68 from ebay but I see it listed at $89 right now.

From build quality to size and weight, the Topping TP60 blows away the FX Audio FX502SPro as you see in this picture on my bench:
Topping TP60 and FX Audio FX502SPro Audio Amplifier Review.jpg

The TP60 is probably four times larger. Part of that is due to the fact that it has dual linear power supplies built into it. The FX502SPro on the other hand, comes with a large laptop sized external switching supply that is nearly its own size!

The TP60 has dual inputs whereas the FX502SPro only has one. Rear speaker terminals on the FX502SPro are toy sized whereas the TP60's are much more substantial.

FX Audio rates the FX502SPro at 70 watts per channel...

Review and Measurements of Massdrop THX AAA 789 Amp

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This is a review and detailed measurements of the just Massdrop THX AAA 789 headphone amplifier. It was drop shipped by request of a kind member for testing. It retails for USD $349.99. The unit had a log gestation period with customers having to wait months to receive the first allotment. The second drop had a ship date of February so if you have not gotten in line, you will be waiting a long time for one. Is the wait worth it? Let's find out.

On the industrial design, Massdrop is using their current design language for their larger desktop audio products which in my opinion is a good thing. While the unit does not have a luxury feel to it, it looks serious and not cheap:

Massdrop THX AAA 789 Headphone Amplifier Review and Measurement.jpg

Very conveniently, there are three headphone jacks in front: 4-pin XLR for balanced headphones, and both 3.5 mm and 1/4 inch for single ended. As usual, please note that the word "balanced" here simply means more potential power, and has nothing to do with...

Review and Measurements of Topping DX3Pro DAC and Headphone Amp

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This is a review and detailed measurements of the brand new, Topping DX3Pro DAC and headphone amplifier. The company kindly sent me a pre-production unit. I usually buy my Topping products unless they are not available in the market as was the case here. The retail price will be $219.99. I expect production to start soon given the high finish of the unit I have.

It is hard to fall in love with budget desktop audio products but there are exceptions and this is one of them. The Topping DX3Pro is darn cute!

Topping DX3Pro DAC and Headphone Amplifier Review and Measurement.jpg

The yellow LED as with the Topping D10 adds a much needed touch of color and uniqueness to the unit. The volume knob adds more to that sauce, making for a small box and you enjoy glancing at on your desk.

Surprising for a small unit, as seen in the picture, you get a remote control and all the functionality in its larger brother, the Topping DX7s. You can select the volume control to apply to line out, headphone out or both...

Review and Measurements of Cavalli Liquid Carbon X

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This is a review and detailed measurements of Massdrop's Alex Cavalli Liquid Carbon X headphone amplifier. It is on kind loan from a member. I think the retail price was $299 but since the drop is over, I am not 100% sure. Someone should comment if that was not the case.

The Liquid Carbon X is an attractive headphone amplifier. It manages a luxury feel despite its low cost. Here you see it below the new Topping DX3 Pro dac and headphone amplifier (review to come).

Massdrop Cavalli Liquid Carbon Headphone Amplifier Review and Measurement.jpg

The Liquid Carbon X is covered in semi "rubberized" paint which while feels nice, tend to show any dirt or dust. So keep a rag next to it if you want it to look good.

As you see in the front, it has both balanced and unbalanced connections. Same is the case in the back where there we have both balanced XLR and unbalanced RCA connectors.

Overall, it is a thumbs up on design, look and feel.

For power, it comes with what looks like a laptop switching power supply, producing whopping...

Review and Measurements of Asus STX II PCI Sound Card

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This is a review and detailed measurements of Asus STX II PCI Express sound card. It is on kind loan from a member and retails for USD $219 on Amazon including Prime shipping. Full list price is $299.

This is a medium sized PC card which oddly requires external power. You can see it here together with the recently reviewed USB DAC, the Khadas Tone Board:

Asus STX II Sound Card Audio Review and Measurements.jpg

So inch for inch, it better measure a lot better. OK, some of that real estate is dedicated to headphone output and analog input which the Khadas board lacks. Still, with all the space, extra shielding, etc. it better do well. Asus specification shows near state of the art performance specs:


If it lives up to these specs, it would rate at tier just below state-of-the-art desktop DACs. Will it get there? Let's measure it and find...

Orchard Audio ApplePi DAC and Volume+Clocker Reivew

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I recently reviewed the Orchard Audio ApplePi DAC. In this review I will be testing the optional "Volume+Clocker" which adds hardware volume control and more precision clock. It retails for USD $99.99 plus shipping and is on loan from the company.

Here you see my test sandwich of Raspberry Pi, Volume+Clocker and ApplePi DAC:

Orchard Audio ApplePi DAC plus Volume-Clocker Balanced Review.jpg

You can see the volume control poking out on the side. Unless I missed it, there was no knob for the volume+clocker. This should be supplied as it costs very little and makes for a more professional and complete package.

For completeness, I will be testing the balanced output of the ApplePi DAC. As you can see in the above picture, the ApplePi DAC ships with mini-XLR balanced connectors. Company sent me a couple of XLR adapters which I used for this purpose. They were massive...
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