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

Review and Measurements of Pro-Ject Pre Box S2 Digital

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This is a detailed measurement and review of Pro-Ject Pre Box S2 Digital. The unit is on loan to me from a kind member but it is one that I have been eyeing for good few months given the designer, John W, who is active on other forums. It was sold in Europe for a while until becoming available in the U.S. Retail price seems to be $399 and unfortunately not available on Amazon as of this writing.

Pro-ject Pre Box S2 Digital DAC 20180217_140621.jpg

As you see above, it is a very diminutive box compared to the Topping DX7/DX7s below it. It does have decent weight for its size and sticky feet so it is kind of supporting the heavy cables I have dangling behind it.

I always like to see a display on non-budget DACs as I like confirmation of what is being played, sample rate, format, etc. as often those can be transformed in software without the user knowing. The display here is small and grainy but good contrast. So for desktop use it is fine but in a rack, you need better eyes than me to see it from...

Measurements of Korg MR-2000S Professional Digital Recorder

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This is a detailed measurement of a Korg MR-2000S digital audio recorder. It is an older product which I think came out in 2009. But as you will see, its performance is anything but stale. This unit has tons of functionality but I am only testing the DAC portion of it. Later I may be able to measure its ADC features which includes recording to DSD formats.


All of my testing here is done at 24-bit/48 Khz. I did not utilize the USB port. Please read my tutorial on my setup and how these tests are conducted:

Let's start simple with frequency response:

Korg S2000S Frequency Response Measurement.png

There is a bit of peaking near cut off frequency no doubt due to digital filter. It is only +0.2 db though so inconsequential. There is also a blip around 100 Hz but that may be due to scalar in Audio Precision.

Next let's...

Measurements and Review of Schiit Yggdrasil DAC

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This is a review and measurement of two versions of Yggdrasil: one with upgraded "Gen 5" USB board and the other with both Gen 5 USB and "Gen 2 Analog board." The latter is a bit of a misnomer because the board actually has the DACs on it which accept digital input. This is a "statement" DAC from Schiit and retail price of $2399 plus shipping. In the world of high-end that is a "bargain" and explains the popularity of this DAC.



Both of these units were made available to me at our local audiophile society meeting. I had to do my testing while other activity was going on so a bit stressful with some potential for error. After seeing some oddities I asked if I could remeasure both of them and both owners were kind enough to let me do that in a more relaxed setting. Each trip cost me 150 miles of driving for a total of 300 miles. Yes, you better feel sorry for me or else! :D

I know all of you are...

Measurement and Review of Berkeley Alpha DAC

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This is a detailed measurement and review of the Berkeley Alpha DAC. The DAC retails for $4995 through dealers. It is an older design and this review is based on a prototype unit prior to manufacturing. There is now a version 2 with better clocking, etc.

Berkeley Alpha DAC.jpg
NOTE: My company (Madrona Digital) is a dealer for Berkeley products. And I led the acquisition of their previous company, Pacific Microsonics (makers of HDCD format) into Microsoft. So I consider the founders professional colleagues. Feel free to read as much bias as you see fit in this review.

The Berkeley DAC as you see above has very good connectivity sans the important USB input. They believe the digital noise from that interface must be kept outside of a DAC and make a USB to serial digital box. Outside of that omission, the box comes with remote control and adjustable volume (controlled in software). Everything internally is asynchronously resampled, putting the...

Review and Measurements of Chord Hugo 2 DAC and Headphone Amplifier

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This is a detailed measurement and review of the Chord Hugo 2 DAC. It retails for $2,700 in US. The unit I had in for measurements was from an ex-Microsoft colleague and recent forum member. I only had an hour or so with it and it is now returned.


This is an odd looking box to be sure. As you see above the oddity continues in its ports with S/PDIF input being a stereo 3.5 mm jack (it has dual S/PDIF inputs as a result). I had my friend operate the unit as I did not even want to try to decode the button lights. The unit has batteries and that is how I tested it, likely giving it an edge in mains related noise/distortion.

The claim to fame of Chord DACs is a super high-tap FIR filter for reconstruction. This one claims over 49,000 taps. This means each (upsampled) audio sample goes through this many computations before a value spits out. FPGAs are custom ICs that are very well suited for this type of application which is what...

Motu 8A Measurements And Review

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I use this Motu 8A as part of a 3 way active DSP speaker crossover. Its a cost effective (about $800 ) 8 in 8 out ADC/DAC interface aimed at studio work. It has USB 3, Thunderbolt, Ethernet AVB and optical connectivity. Audio connections are balanced/single ended TRS jacks. A headphone jack and volume control are situated on the front panel. Power comes from an external SMPS wall wart.

Casework is robust high quality aluminium shell in two halves. A small but clear LCD display shows channel level and other information.

More info here:


Hardware Teardown of Schiit Sys Passive Pre-amp and Switcher

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I recently performed a measurement and review of Schiit Sys Passive Pre-amp and Switcher . This is a quick hardware teardown of this unit.

As I noted in that review, there is not much in this box:

We have two inputs on right top side, controlled with the front panel push on/push off switch. The output then goes through the potentiometer ("pot") next to it on the way to the rear left set of RCA jacks.


Review and Measurements of Schiit Sys Passive Pre-amp/Switcher

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This is a measurement and review of the Schiit Sys switcher and passive pre-amp. It retails for just $49 plus shipping which is reasonable. The unit is on loan from a member so not new.

Schiit Sys 20180208_145701.jpg
I will do a teardown later but for now, there are just two inputs, one output, and a volume control in there. No other passive or active components.

Let's start with frequency response at different volume control settings:

Schiit Sys passive volume frequency response measurement.png

Frequency response is essentially rule flat to 30 Khz which is nice.

Channel matching starts with a small deviation and grows to 0.5 db at 12:00 o'clock volume setting. Lowering the volume to 3:00 o'clock increases this error to 1.3 dB. So probably not a good idea to use it below 12:00 position.

Phase measurement between channels is boring and inconsequential:

Schiit Sys Phase Shift Measurement.png

Let's look at channel separation:

Schiit Sys Channel Separation Measurement.png

Bottom two lines are...

Soekris DAM1021 R2R DAC Measurements

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I have finally managed to borrow a Soekris R2R sign magnitude dac to measure. Essentially I bought this dac for a speaker project. I was/am agnostic about the DAC technology, however there is no denying R2R measures more poorly than typical delta sigma. I was particularly interested in its FPGA filtering capabilities for crossover duties. Ultimately it wasnt the solution I wanted so the dac now resides with a friend who has put it in a box with very pleasant subjective results.

Note that I had a few issues with 50Hz and harmonics pick up. I will investigate later, so crap below 1kHz please ignore. I have measured this DAC under other circumstances previously and I know its not an issue with it.

This board is the 0.05% resistor version which will exhibit higher harmonic distortion (maybe 9dB or so) than the more expensive 0.01%/0.02% resistor version

The unit is driven I2S over HDMI cable from a Gustard U12...

Measurement and Review of Schiit BiFrost Multibit DAC

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This is a review and measurements of Schiit BiFrost Multibit DAC. It retails for $599 plus shipping and is on loan to me from a kind member of the forum. For this review I will be comparing it to the Topping DX7 which retails for $200 less ($399).

Note that this is the special "multi-bit" version of the BiFrost DAC which uses a R2R ladder DAC from analog devices (AD5547). This is an extra cost option.

The Schiit BiFrost Multi-bit comes in a plain looking silver box. It is more substantial than the smaller DACs they offer like the Modi 2 but it still does not give one feeling of high-end or high-quality.


Connectivity is very sparse with USB, Coax and Toslink inputs and only unbalanced RCA output. No AES/EBU digital input or balanced outputs. In contrast the Topping DX7 has all of these other inputs/outputs in addition to headphone output.


A cheezy toggle switch in the back turns the...

Teardown of the Emotiva DC-1 DAC

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This is a teardown of the Emotiva DC-1 DAC and headphone amplifier as a follow up to my review of that unit (see

Here is an overall shot of the unit:

Emotiva DC-1 DAC and Headphone Amp PCB inside 20180202_132513.jpg

Overall layout is good. AC mains comes in from the right, goes up to the transformer. Below that we have the digital cluster and flow is to the left ending in analog and headphone outputs.

Immediately though, there is a major source of concern. Check out the IEC plug:

Emotiva DC-1 Missing Ground Lug 20180202_132521.jpg

We have a 3-prong, grounded IEC socket but the ground lug doesn't go anywhere! It must be connected to the case as this is metal and an electrical short can energize it. Only a double insulated piece of equipment can be run on two wires. Which this is not.

This is a major safety flaw! I can't recommend purchasing this equipment on this basis!

And look at how the mains hot...

Measurement and Review of Emotiva DC-1 DAC

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This is a detailed measurements and review of Emotiva DC-1 DAC. It is kindly loaned to me by member Sal1950. It retails for $499 including shipping from Emotiva direct. The features and size is very close to my recently reviewed Topping DX7 DAC.

As you see in above picture it has extensive set of inputs and outputs. We get USB, Coax and Toslink S/PDIF, and balanced AES/EBU digital input. But we also get an analog input! On the output side we have both balanced and unbalanced. It includes a built-in power supply with a toroidal transformer which I appreciate at this price point.....

Topping DX7 DAC & Headphone Amplifier Review and Measurements

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This is a detailed review and measurements of the Topping DX7 DAC and integrated headphone amplifier. Frequent readers of this forum know that I am a fan of Topping D30 DAC. It measures excellently and is a bargain at $130 shipped. While the D30 has distinctly budget feel to it, such is not the case with Topping DX7. From cardboard packaging and custom foam to the heavy aluminum case the DX7 brings a much higher quality feel. It nearly rivals my Exasound E32 at 15 times the price. I purchased mine through Amazon for $299 shipped. Strangely it shows not available anymore:


Front panel as is an OLED display which has great contrast and gives nice confidence of what is being played as far as sample rates and formats (DSD and...

Measurement and Review of JDS Labs USB OL DAC

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This is a measurement and comparison of JDS Labs USB OL DAC against the NWAVGUY's Objective DAC (also sold by JDS Labs). I also compared it to my reference budget DAC, the Topping D30. See my measurements of Objective Rev b DAC here:

And topping D30:

The JDS Labs OL DAC comes with USB-input variant at $99 which is what I purchased. And another with Toslink optical input pushing the price a whopping $40 more to $139. The Objective DAC sells for $129 which is the same price as Topping D30. But topping is a lot more feature rich with Toslink and S/PDIF inputs.

As you see in the above picture, the OL DAC improves on the Objective...

Hardware Teardown of Topping D30 DAC

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This is a hardware teardown and analysis of Topping D30 USB DAC. No doubt many of you have read my review of the D30 and know that it is my current favorite for a budget DAC ($129). There seems to be two revisions of this DAC out there so this will outline the unit I tested.

Four hex screws releases the back panel allowing the board to easily slide out without much adventure:

Topping D30 USB DAC Top Board Teardown.jpg

The board is clean with no modifications, soldering issues or any problems visible. No, you don't want to "eat of it" but for a value-oriented product, I see nothing wrong with it. Here is the revision of the board by the way:

Topping D30 USB DAC Revision.png

This larger than normal budget DAC board sizes affords very good separation between the digital and analog side. Connectors are nicely spaced out which should reduce crosstalk. On top of that, there is a nice...

Review and Measurements of iFi iPurifier S/PDIF Digital Audio Filter

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This is a detailed measurement and review of iFi iPurifier. This is a device that is advertised to clean up your coax S/PDIF signal from all ills including the common flu to audio distortions. It is a tiny little box the size of a thumb drive:

Not shown is the fact that it actually needs external power and iFi ships it with their switching wall-wart "iPower" power supply.

This is not a filter device but rather, one that receives digital data over S/PDIF, buffers it (puts it in memory) and then retransmits it. iFi has a nice block diagram of it on their site:


Who wouldn't want their waveform cleaned up in red and turn it into the one in cyan? It is like getting an enema. Not that I have had one but I imagine it being the same.

Because the iPurifier regenerates S/PDIF, it should have good ability to remove...

Review and Measurements of Gustard U12 USB to S/PDIF Converter

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This is a review of Gustard U12 which converts USB input to S/PDIF, Toslink, AES/EBU and I^2S. The U12 retails for $170 shipped from Amazon as of this writing. I will be comparing it to Audiophilleo 1 (about $500), Fiio E10K ($76) and Melodious-Audio MX-U8 ($269). Sadly my Berkeley Alpha USB is broken so I can't test against it even though it is at much higher price point.

Gustard U12.jpg
The Gustard U12 is for people who have existing DACs and would like to add USB connectivity to it. The device has very good functionality with both consumer S/PDIF and AES/EBU...

Measurement and Review of Hifime Sabre 9018 USB DAC

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Time for measurement and review of another budget DAC: the Hifime Sabre 9018 USB audio DAC. It retails for $80 shipped from Amazon. The closest device I have to it is the Fiiio E10K USB audio DAC which costs nearly the same at $76 on Amazon. Click to see the detailed review of Fiio E10K.

The Hifime comes in one of the lowest budget packages I have of any DAC. It is a tiny, plastic unit with permanently attached 3-4 inch USB cable and a 3.5mm headphone jack. It has a sole red LED light indicating it is on. Even the plastic package it came...

Electrical Grounding Talk

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No doubt you all are familiar with audiophiles attempting to make their systems better with dedicated grounding systems for their audio equipment. Incredible amount of myth and wrong intuition is involved in such motivations and endevour, sometimes leading to very unsafe electrical systems that are not compliant with electrical safety code.

I was online and got prompted by youtube to watch this video by Mike Holt. Not sure how many of you know him but his is the most famous electrician I know. He has had an online community for seemingly forever and they argue almost as much as we do about audio! Anyway, here he is giving a talk I think for other electricians on what grounding is, and is not. Because it is a trade talk, it may be a bit challenging at times to follow but it is still a very well done presentation. He goes over key principles that are gotten wrong by audiophiles and electricians alike. And walks through the scenarios where dangerous conditions are created.


Hardware teardown of FX-AUDIO DAC-X6 USB DAC

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This is a hardware review of FX-AUDIO DAC-X6 USB DAC. For measurement and listening tests go to this article:

As noted in that review, this is an ultra low cost $58 DAC and headphone amplifier. They provide the overall block diagram thusly:


And that matches what is inside:


I have indicated with arrows the flow of signals. Following the USB input, we go into Via VT1603 USB interface. The digital data is then handed to Crystal Semiconductor CS8416 which is also the S/PDIF interface. The provides the serial interface to the heart of this device, the Cirrus Logic CS4399 DAC which costs about $6 in volume. The analog output then gets buffered through Ti/Burr Brown OPA2134. From there, this path splits. One goes to the rear RCA jacks and the other, to TI6120...
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