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

Review and Measurements of Sony UDA-1 DAC & Amp

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This is a review and detailed measurements of the Sony UDA-1 DAC, headphone and power (speaker) amplifier. It is on kind loan from a member. It seems the UDA-1 was released back in 2014 with a retail price of US $799. Depending on the color, I see used ones around $350.

First impressions are positive on UDA-1 with a very hefty box and controls that feel nice:

Sony UDA-1 DAC and Amplifier Audio Reviews.jpg

There is no display but what is there is functional. Here is the back panel:

Sony UDA-1 DAC and Amplifier Back Panel Audio Reviews.jpg

Disappointed to see a fan in there for a box with such modest capabilities (rated at just 23 watts/channel). I had headphones on during testing so don't know how loud it gets.

Nice to see line in/out which makes my testing a lot easier as I can test the DAC and headphone/power amplifiers separately.

Note: I used to work for Sony in early 1990s so I have a soft spot for the company. Keep that in mind as you read this review.

DAC Audio...

Review and Measurements of Rane PS1 Phono Amp

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This is a review and detailed measurements of the Rane PS1 Phono stage/preamplifier. It is on kind loan from a member. It has been discontinued and seems to have come out circa 2002 (?). I can't find a price for it.

If you are not familiar with Rane, it is a company focused on pro audio and has written some of the best tutorials on audio. Needless to say, my expectations are quite high here with respect to the engineering of the PS1.

The PS-1 is an industrial looking thing:

Rane PS1 Phono Preamplifier Audio Review.jpg

The back panel makes you even less proud to put it on display:

Rane PS1 Phono Preamplifier Back Panel Audio Review.jpg

An external AC transformer with split tap powers the unit using a phone/RJ-11 style cable.

There are both unbalanced (RCA) and balanced (screw terminals) for output. I had to make a bare wire XLR cable to mate with the balanced output.

The shell of the balanced screw terminals was quite lose so I opened it to see what is going on...

Review and Measurements of Emotiva XPS-1 Phono Amp

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This is a review and measurements of the Emotiva XPS-1 Phono stage/pre-amplifier. It is on kind loan from a member. The XPS-1 costs US $199 from Emotiva or Amazon.

The XPS-1 looks and feels fantastic despite its bargain price:
Emotiva XPS-1 Phono Pre-Amplifier Audio Reviews.jpg

It reminds me of a very high quality piece of instrumentation than home audio gear. Shame that the form factor will probably relegate it to somewhere behind your regular audio gear.

The XPS-1 is powered by a 12 volt/0.5 amp universal switching power supply that is barely bigger than a mobile phone charger.

As you see, the XPS-1 supports both moving coil (MC) and moving magnet (MM) cartridges. There are a set of dip switches which seem to set the input impedance of the XPS-1. To wit, setting it to the lowest value of 47 ohm, severely reduced the output from my analyzer which has an output impedance of 20 ohm.

All in all, the XPS-1 nails the industrial design of a budget phono amplifier.

Phono Stage...

Review and Measurements of BSS BLU-BIB & BLU-BOB1 DAC/ADC

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This is a review and detailed measurements of Harman/BSS BLU-BIB 8 channel analog to digital converter (ADC) and BLU-BOB1 8 channel digital to analog converter (DAC). They are on kind loan from a member. The BLU-BIB retails for I think US $930 and so does the BLU-BOB1 but I see the latter on Amazon for US $790 and free shipping.

This is how the pair look:
Harman BSS Soundweb BLU-BIB and BLU-BOB1 Audio Review.jpg

I suspect most of you are not familiar with these two products. BSS is a company that Harman acquired a few years back. Their speciality is audio signal processing/DSPs that are easily programmed using their interactive software. The BOB1 and BIB are expansion output/input modules should you run out of ports on their DSB units. All products communicate using physical Ethernet link but not logical. That is, you can't talk to them from a computer but they communicate with each other over this link and can handle up to 255 channels of digital audio with sample rate up to 96 kHz...

Measurements of RME ADI-2 DAC and Headphone Amp

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I reviewed and measured the RME ADI-2 DAC a year ago. That was just prior to getting my new Audio Precision APx555 so the measurements don't directly compare to what I publish now. So a local member kindly loaned me his ADI-2 DAC to get fresh measurements.

If you are not familiar with RME ADI-2 DAC, it is a DAC-only version of the RME ADI-2 Pro. The former costs US $1,099 and the latter, US $1,999. It is an all-in-one DAC, headphone amplifier plus remote control. It has better connectivity with all the jacks in the back rather than dongle in RME ADI-2 Pro. The menu system is world's easier to navigate than the RME ADI-2 Pro. It has built-in parametric EQ and pretty spectrum display.

For the measurements, I took an abbreviated set but I think it paints the picture quite well.

DAC Measurements
Dashboard view is with USB input...

Audio: How We Hear

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Our resident technical and psychoacoustic expert and research/industry luminary, @j_j, recently gave a talk at our local chapter of Audio Engineering Society. He calls it Hearing 099. I tried to make it more descriptive and hence what is in the title. It is not very accurate but hopefully it is enough to get your attention. :)

I should tell you in advance that JJ's talk is a mix of very simple and useful information -- some summarized in just one sentence -- and others which will be complex and probably hard to understand for most of you. The simple messages are spread throughout the presentation so please set aside an hour and listen to it. And don't skip the last 5 minutes, whatever you do.


The talk will be the start of your understanding of our hearing system and likely something you will come back to often. It will also be a jumping point to learn more using other online resources. It is the best presentation I...

Review and Measurements of QSC DCA2422 Amp

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This is a review and detailed measurements of the QSC DCS2422 "Digital Cinema" Power Amplifier. It is on kind loan from a member. It must be sold through specialty channel as I can't find it available much. From the bit of searching I did, it seems to go for US $550.

This digital cinema characterization applies to the connectivity of the box. Otherwise this is a normal power amplifier in rack mount configuration:
QSC DCA2422 Digital Cinema Amplifier Audio Review.jpg

There is a nice dial with wide range of gains you can dial in. I liked the clipping indicator.

There is a speed controlled fan which is good. What is not good in home hifi situation is that even in its slowest mode there is a whine to the fan that is audible from 6 feet away. If you are going to use this amp, it would need to be in an equipment closet.

The back panel shows the locking SpeakON speaker connectors and only a pair of XLR inputs:

QSC DCA2422 Digital Cinema Amplifier Back Panel Audio Review.jpg

Given the programmable gain...

Review and Measurements of Monoprice Hybrid Tube Amp

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This is a review and detailed measurements of the Monoprice Hybrid Tube Power and Headphone Amplifier. It is on kind loan from a member who sent it to Monoprice to be fixed twice. It costs US $199 from Monoprice direct. I can't find it on Amazon but there is a "Rockville" amp that looks identical and it goes for even less at US $149.

When I first reached for this amplifier, I thought it was a high-end, $1000 headphone tube amp or something. Imagine by shock that it turned out to only cost $199 or even lower per above. They have nailed all the signature bling of a much more expensive amplifier:

Monoprice Stereo Hybrid Tube Amplifier Audio Review.jpg

In person it looks even better than it does in above picture (available light late at night). We have a rather heavy unit, with fine feeling volume control, VU meter and those signature rings around the tubes. Heck, it even came with plastic covering the plastic/wood looking sides! I don't understand the economics of these things at...

Review and Measurements of Pioneer VSX-LX303 AVR

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This is a review and detailed measurements of the Pioneer Elite VSX-LX303 Audio/Video Receiver (AVR). It was an impulse buy when it went on sale on Amazon a couple of weeks ago for US $369 including Prime shipping. It is currently US $399. I needed a replacement for my current Pioneer Elite AVR that is connected to our living room TV which is limited to 1080p.

From the outside, not much is changed compared to my Pioneer Elite:

Pioneer VSX-LX303 AVR Audio Review.jpg

The only improvement is the input selector dial on the left. On mine, it is very stiff. Here is loose and a bit easier to manage. The knobs are large but tactile feedback is poor. I guess they assume you are going to use the remote anyway. Still, I miss the large knobs on audio gear of the 1970s and 1980s.

When I purchased the VSX-LX303, I assumed it had an efficient class D amp like my current Elite. Alas, it does not. This is an issue for me as my current AVR is in a closed cabinet with not a whole...

Review and Measurements of Monoprice THX Desktop DAC & Amp

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This is a review and detailed measurements of the Monoprice THX AAA Desktop DAC and balanced headphone amplifier. It is on kind loan from a member. It costs US $480 from Monoprice direct including free shipping. The only other desktop headphone amplifier with THX AAA amplifier is from massdrop and it doesn't have a DAC, nor is it easy to find. So if the Monoprice performs, it will be a major win seeing how it also includes a DAC for only $80 more than Massdrop.

I previously tried to measure this unit when it first came but unfortunately it failed on my bench.

The industrial design is good:
Monoprice THX Desktop DAC and Balanced Headphone Amplifier USB Audio Review.jpg

The display looks a bit grainy to my eyes but it does the job. What doesn't is the volume control. It is digital which is fine. Not so fine is that it runs way behind the volume knob if you turn it quickly...

Vintage Audio: Measurements of Arcam Black Box 3 mk1

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As requested by @andreasmaaan here I made some measurements of an old DAC: the Arcam Black Box 3 MK1 which I bought new in 1991 (without MK1, see below). It retailed for around € 780 then (converted). Here are the front and the back:

arcam bb3 front.jpg

arcam bb3 back.jpg
It supports 44.1 and 48 kHz samplerate with 16 bits - that was the standard back then ...

Somewhere later around 1997 I fell victim to op-amp rolling and replaced the original op-amps (LM627CN) by OPA134PA. Two can be seen on this photo of the internals on the right PCB (audio mother board).The LF411 is used as DC servo. Two others are hidden on the backside of the left PCB (digital audio board). The result is my version MK1:

arcam bb3 intern.jpg


The measurements are done with REW, using an RME ADI-2 PRO fs, an old Edirol...

Review and Measurements of Teac AX-501 Amplifier

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This is a review and detailed measurements of the Teac AX-501 integrated power (speaker) amplifier. It is on kind loan from a member. The AX-501 is part of the reference series from Teac so doesn't come cheap as desktop products go. I see the price at USD $999 on Amazon plus $35 shipping. There is a discount for silver a USD $899 but Amazon doesn't sell it for some reason.

When I reviewed the Teac HA-501 Headphone Amplifier, I heaped praise over its modern retro look. The AX-501 takes that to an entirely different level with addition of a couple of super cute, yellow background VU meters:

Teac AX-501 Integrated Amplifier Audio Review.jpg

What is that? I should have took the shot with the VU meters working and the light turned on? Well, the owner played a cruel joke on me by not supplying me with the remote and leaving the setting to off for the VU...

Review and Measurements of Teac HA-501 Headphone Amp

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This is a review and detailed measurements of the Teac HA-501 headphone amplifier. It is on kind loan from a member. The HA-501 in black costs $549 including Prime shipping from Amazon. Oddly, the silver color is much cheaper at $354! Black anodizing must have become very expensive. :) The black does look a lot nicer though so it would be tough to settle for silver.

The HA-501 is one of the most attractive desktop audio products. If you are a fan of the 1970s and 1980s hi-fi gear, the Teac is the best way that look could have been modernized yet hold its retro appeal:

Teac HA-501 Headphone Amplifier Audio Measurements.jpg

The controls feel fantastic and the head of the class for sure.

Controls are not unusual other than addition of "damping factor" which simply adds a resistor in the path of the headphone output (measurements later).

The other odd thing is the auto-muting. When you unplug the headphone, the red audio mute LED comes on and will not go off until you turn the...

Rolling Op-amps in Gustard H20 Headphone Amplifier

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I reviewed the Gustard H20 which is a high-end headphone amplifier yesterday. Its owner kindly sent me some high-end op-amps to "roll" in there to see what difference it makes.

The task was pretty easy. The top screws come out of the H20 and if you tilt the unit, the lid falls out exposing its pretty guts:

Gustard H20 Headphone Amplifier Teardown Review.jpg

Everything is surface-mounted so not replaceable other than the pair that are socketed. You can see that I swapped one of the channels to Sparko's Lab SS3602 from TI/National LME 49720:

Gustard H20 Headphone Amplifier Sparkos Lab SS3602 LME 49720 op amp rolling.jpg


There is massive price difference with the LME retailing for just $2.68 and the Sparko's for whopping $79.80. There better be good bit of improvement for it to be worth putting two of those in there for nearly USD $160.

Op-amp Rolling Audio Measurements
Since the Gustard H20...

Review and Measurements of Gustard H20 Headphone Amp

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This is a review and detailed measurements of Gustard H20 balanced input and output headphone amplifier. It is on kind loan from a member. The H20 costs USD $930 but I see it on sale from shenzhenaudio for USD $840. I think it was also sold on Massdrop for $800. Either way you look at it, it is not cheap.

The H20 comes in black and silver. The unit I have for testing is the silver:

Gustard H20 Balanced Headphone Amplifier Audio Review.jpg

The H20 is quite heavy and large. Controls feel good although I am not a fan of relay controlled volume. There is a racket that is sharp pitched as you adjust the volume.

The two 1/4 inch jacks are not the same. The first one has a resistor inline (see measurements). The second is straight through.

On balanced XLR output, you have a choice of stereo 4-pin or dual three pin. I tested with the former.

The back panel sports a good set of connectors:

Gustard H20 Balanced Headphone Amplifier Audio Review Back Panel.jpg

There are a set of RCA inputs to the left and two...

Review and Measurements of ENCORE mDAC DAC & Amp

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This is a review and detailed measurements of the ENCORE mDAC battery operated portable DAC and headphone amplifier. It is on kind loan from a member. As far as I can tell, the mDAC came out in 2014/2015. It cost USD $129 when released.

It is chunky metal box with sharp edges which bother me a bit:

ENCORE mDAC DAC and Headphone Amplifier Audio Review.jpg

The on/off button is quite hidden on the side. The volume controls are on top but controlling the down button is a challenge with headphone jack plugged in.

The mDAC runs a bit warm so good thing it has battery or it would suck up the phone one down.

PC connectivity is a bit strange in that the data USB jack does not charge it so I had to connect two cables to charge and use it.

I won't bore you with more and will post the Z reviews on the functionality.

Audio Measurements
Testing the mDAC as a DAC was not that functional as at full amplitude, it clips even into a very high impedance load (i.e. not stressed at all). So I had...

Review and Measurements of ENCORE mDSD DAC & Amp

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This is a review and detailed measurements of the ENCORE mDSD portable DAC and headphone amplifier. It is on kind loan from a member. The mDSD costs USD $126 on Amazon with free (non prime) shipping.

The encore is quite chunky and blocks adjacent USB ports as a result:

ENCORE mDSD DAC and Portable Headphone Amplifier Audio Review.jpg

It is a solid chunk of aluminum so no worries about throwing this in your case/backpack when travelling.

There are a set of volume up/down controls. They adjust the output level without being connected to the Windows/OS volume control which is nice.

There is not a whole lot to talk about here as far as operation other than it running a bit warm so power consumption is going to be on the high side.

DAC Audio Measurements
Our dashboard shows that typical of many of these portable DACs, the output level is insufficient (less than 2 volt) to be reliably used as a pure DAC:

ENCORE mDSD DAC and Portable Headphone Amplifier Audio Measurements.png


THD+N is just slightly over the spec (which is measured...

Follow Up: Lounge Audio LCR Mk III measurements

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In a recent review of this phono stage, there was some discussion of the approach taken for measurement and interpretation of phono stages. This post is a follow up with additional measurements which I (and other designers and users of phono equipment) find necessary for evaluation. This a "in addition to" rather than "instead of" for Amir's review, but I'd like to not only present measurements, I wish to also go into the whys and hows of things which are peculiar to the genre.

And I'll start things out by thanking Amir for sending the unit to me, as well as @dinglehoser who volunteered his unit to let me dissect its performance a bit.

As usual, my test setup is centered on an APx525 analyzer, but I also pressed into service a Hewlett-Packard 3466A volt-ohm meter and a Kikusui COS6100M 100 MHz scope.

Let's start with the basics. I...

Review and Measurements of Klipsch PowerGate DAC & Amp

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This is a review and detailed measurements of Klipsch PowerGate Multifunction streaming power amplifier, DAC, Bluetooth and phono preamplifier. It normally costs USD $499 but for some reason it is on Amazon for USD $150 including Prime shipping! This puts the PowerGate in direct competition to SMSL AD18 and Topping MX3.

The front panel of the PowerGate is plastic and not all that nice looking:

Klipsch PowerGate Streaming Amplifier Audio Review.jpg

The buttons and rotary control have good feel though. Strangely the LED bar showing the level only goes 2/3 of the way up on the left and not all the way around.

There is a headphone jack which I will be testing in the review.

The back panel shows a very feature rich set of options...

Class D Amplifiers 101

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This is a quick overview of how class D amplifiers operate. Note the “D” does not mean “digital”; it is simply the next letter in order as standards bodies enumerated amplifier types (A, B, C, D, E, F, G, H, I, etc.) It takes an analog, not digital, input and produces a pulse width modulated (PWM) output. I apologize in advance for the length.

The figure below is a simplified schematic diagram of a class D amplifier. It is a rather busy diagram, so we’ll step through each piece from input to output. First the input signal, Vin, is applied to the input buffer (shown as an operational amplifier, opamp). The negative input of the opamp receives the feedback signal (Vfb) from the output (Vout). The output of the buffer is the difference between these two signals, providing a modified signal to the rest of the amplifier. The feedback signal allows the amplifier to correct any errors at the output, improving linearity (e.g. lowering distortion) and stabilizing the circuit so part...
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