Articles, Reviews and Measurements of Audio Products

Monoprice 605030 Class D Amp Teardown

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This is a teardown of the Monoprice 150 watt Class D Amplifier which I just reviewed. The owner gave me kind permission to open it up.

Here is the overview shot of the entire unit:

Monoprice 605030 pro amplifier class D teardown.jpg


The heart of the unit is an integrated switching power supply and stereo class D amplification.

I was surprised to see an angled bottom mounted fan in a rack mounted device! Usually there is equipment stacked on top of each other, not leaving any air in there to suck in. Granted, this fan is tilted a bit but still. Even if intake air is available, it is just blown randomly against the top of the case. It will surely provide more cooling than without but most certainly not optimized. Good news is that it is a larger fan so you can get quiet versions or even temperature controlled ones. It is nicely socketed as marked so replacement should be...

Edifier R1280T Powered Speaker Review

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This is a review and detailed measurements of the Edifier R1280T Powered Bookshelf (computer) Speakers. I purchased a few weeks ago at a cost of US $99 for a pair including Prime shipping. Yes, a pair of powered speakers for just $99. Incredible value if the performance is there.

I must say I expected a larger speaker than what I saw in person:
Edifier R1280T Powered PC Desktop Computer Speaker Review.jpg


The retro look makes one think the speaker is multiple times the size it is. That said, I definitely appreciate the form factor as it is the largest I like to have for computer desktop use. I find the grill very attractive but to be a purist, I measured the R1280 without it and listened to it the same.

Back side shows what you expect in this price range and type of speaker:

Edifier R1280T Powered PC Desktop Computer Speaker Back Panel RCA Input Review.jpg


The pair of binding posts carry the speaker level signal to the other channel. This of course mandates a passive crossover. Company advertises 20 watts of amplification.

Surprisingly you get a remote and...

Monoprice 150 watt 605030 Amplifier Review

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This is a review and detailed measurements of the Monoprice 150 watt "605030" rack mountable "pro" stereo amplifier. It was kindly purchased new and drop shipped to me for testing. The 605030 costs just US $119 from Amazon including Prime shipping which is remarkably low.

From a distance the unit looks like any other pro, R1U amplifier:

Monoprice 605030 150 watt pro amplifier rack mount stereo review balanced.jpg


It looks rather cheap an unattractive to me but hard to imagine any pro amp getting some kind of design award for their looks.

Two gain controls are provided in the front which I appreciated. For testing I aspire for gain of 29 dB and I almost got there at max level as shown. That is how I tested the unit. There overload indicators which was nice

What I did not like one bit was the rather loud fan which runs continuously. Monoprice, please take another $5 from me and make the fan temperature dependent please!

Seeing balanced input in any amplifier at $115 price range is incredible but that is what we have...

Niles SI-2150 Class D Amplifier Teardown

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I just reviewed the Niles SI-2150 amplifier. This is a quick teardown of the same.

Here is the main entire amplifier in one shot:

Niles SI-2150 Amplifier Custom Install Stereo Audio Teardown.jpg


General construction seems fine.

The heart of the system are the two UC250LP-M OEM amplifier modules from Hypex. An input stage allows variable gain (board in blue) and speaker protection relays.

As best as I can tell, that complicated switching power supply is by Niles as it matches the color scheme of the buffer board. Looking at the capacitors, we see that they are the chinese brand, Jianghai:

Niles SI-2150 Amplifier Custom Install Stereo Audio Power Supply Switching Teardown.jpg


I can't get good information on them. They certainly are not a tier capacitor company but seems like a very big company producing capacitors. May be hard to replace them with other parts given the compact size required for the thin amplifier enclosure.

The Hypex modules use...

Magnepan LRS Speaker Review

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This is a review and detailed measurements of the Magnepan LRS (Little Ribbon Speaker). It was kindly sent to me by a member and costs US $650.

NOTE: as you will see later, this is a special review with far more detail than I usually show in a speaker test. I thought it would be "fun" to see much more extensive treatment of these speakers. Result was three full days of measuring, processing, processing again and again, generating slides, generating those again, and again. I hope you appreciate the extra work that has gone into this review and no, I won't be doing this with future reviews. :)

Given the detail level, this is not for a casual reader of these reviews. As such, feel free to skip to subjective listening results and conclusions.

I was thankful for the thin and relative light weight of the LRS when I went to measure it and carry it to my listening room:

Magnepan LRS Ribbon Speaker Stereo Review.jpg


As you can sort of tell from above picture, there are two panels side-by-side...

Niles SI-2150 Class D Amplifier Review

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This is a review and detailed measurements of the Niles SI-2150 Class D amplifier. It is on kind loan from a member. He purchased it refurbished and I see it for sale at $367. Original cost seems to be US $850.

By using efficient Hypex UcD250LP class D amplifier modules, the SI-2150 manages to fit in a small, 1U rack chassis:

Niles SI-2150 Amplifier Custom Install Stereo Audio Review.jpg


Niles is targeting this amp as Custom Integration (CI) channel so has good control as far as trigger and such:

Niles SI-2150 Amplifier Custom Install Stereo Back Panel Inputs Audio Review.jpg


In use, the unit stayed cool and calm. When pushed into clipping it will go into protection. Sadly it stays in that mode until it is power cycled rather than recovering on its own.

Nice set of gain controls are provided which lets you get precise channel matching -- something that is rarely the case in many amplifiers. I set them to 29 dB for my testing.

Amplifier Audio Measurements
As usual we start with our 1 kHz tone dashboard into 4 ohm load:

Niles SI-2150 Amplifier Custom Install Stereo Audio Measurements.png
...

Yulong Aquila II DAC and Headphone Amp Review

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This is a review and detailed measurements of the Yulong Aquila II USB DAC and headphone amplifier. It was kindly purchased by a member and drop shipped to me for testing. It costs US $640.

The Auila II breaks the mold of rectangular boxes for desktop DACs with compound angles:

YULONG Aquila II USB DAC headphone amplifier stereo review.jpg


The volume control also navigates the menus by first pushing it in multiple times until you land on the on screen item to modify and then turning the dial. The display is IPS and has very fine resolution which I appreciated.

The back panel has the usual connectivity:

Best USB DAC Balanced with Headphone Amp Back Panel Inputs XLR RCA Review.jpg


The unit was plug and play with Windows over USB connection. Operationally it ran somewhat warm but no worse than other high performance DAC and amps.

Balanced DAC Audio Measurements
For the DAC portion I focused on performance of the XLR output only. Here is our dashboard:

YULONG Aquila II USB DAC headphone amplifier Audio Measurements.png


Two years ago I would jump with joy at such low distortion and noise...

Audiophonics EVO-SABRE Balanced RPI DAC Review

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This is a review and detailed measurements of the Audiophonics EVO-Sabre Balanced DAC. It was requested by a member and the company was kind enough to send me one. It costs 239,00€ including tax and 199,17 € without (US $235).

The EVO is an unusual DAC in that it both works stand-alone due to use of an on-board microcomputer and display, and also as a slave to Raspberry Pi single board computer:

AUDIOPHONICS EVO-SABRE RPI Streaming Balanced DAC Audio Review.jpg


I tested it in stand-alone mode but you can plug in the RPI on the right and it will feed it power and I think its USB port becomes a peripheral to RPI.

The unit requires 9 volt input and is not self-powered with USB. I used my bench power supply to provide that as no power supply comes with it.

I was impressed with the quality of the OLED display with sharp, clear graphics. A remote control is also provided which is nice.

DAC Audio Measurements
As usual we start with our dashboard driven by the USB input:

AUDIOPHONICS EVO-SABRE RPI Streaming Balanced DAC Audio Measurements.png


Not bad...

NAD M28 7 Channel Purifi Amplifier Teardown

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I recently reviewed the NAD M28 multichannel amplifier based on Purifi modules. As promised, this is a tear down of the unit with kind permission of the owner.

The amp was a delight to open with beautiful screws holding the attractive top down. Once removed, we are greeted to a nice and modular layout:

NAD M28 teardown purifi amplifier power supply.jpg


The right side is a unified power supply for all 7 channels. I searched quickly but could not find a matching Hypex power supply. The only markings on it are:

NAD M28 teardown purifi amplifier power supply marking.jpg


As you will see later, NAD marks their boards with their name so I suspect this was custom designed by someone and not NAD.

There was a question about the fuse size. The fuse is rated at 15 amps and 250 volts. Total volt-amps available then is 1800 assuming 120 volt mains in US. Assuming there is power factor correction, this translates...

Dynaudio LYD 5 Studio Monitor Review

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This is a review and detailed measurements of the Dynaudio LYD 5 powered studio/professional monitor (speaker). It is on kind loan from a member and costs US $499 each.

There is not much bothersome or unique about the look of the LYD 5:

Dynaudio LYD 5 Studio Powered Monitor Speaker Audio Review.jpg


The backside is perhaps more unique with slot port:

Dynaudio LYD 5 Studio Powered Monitor Speaker Rear Port Audio Review.jpg


As you see, there are a few settings. I used the following for testing and listening:

Dynaudio LYD 5 Studio Powered Monitor Speaker Test Settings.jpg


Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors...

NAD M28 Seven Channel Power Amplifier Review

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This is a review and detailed measurements of the NAD M28 Multichannel amplifier based on Purifi Eigentakt technology. It was kindly purchased by a member from a local dealer (Gig Harbor Audio) and sent to me for testing. The M28 costs US $4999 through its dealers.

As with the M27 amplifier I reviewed, the M28 comes in the same gorgeous industrial design:

NAD M28 Multichannel Purifi Class D Amplifier Audio Home Theater Review.jpg


At nearly 50 pounds, this is a heavy amplifier likely due to the weight of the enclosure as the class D amplifiers and it switching power supply are light.

The one thing I am not a fan of is the touch on/off button on top. It is not responsive. I wish the NAD logo was a hard switch.

The back panel shows how you do a first class job of termination...

Minidsp DDRC-88A Dirac Multichannel DSP Review

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This is a review and detailed measurements of the Minidsp DDRC-88A balanced 8 channel in, 8 channel out, Dirac and manual EQ DSP system. It is on kind loan from a member and costs US $999. The connectivity as you see is with phoenix connectors and if you order a set of cables to XLR for that, it would add another $60. A remote is included as I think a Dirac 3.0 license plus manual configuration software.

The front is business like and doesn't give you much control over the unit other than changing configs and volume:
Minidsp DDRC-88A Dirac Live multichannel room correction audio review DSP.jpg


Back panel shows the rich connectivity of both unbalanced (RCA) and aforementioned balanced:
Minidsp DDRC-88A Dirac Live multichannel room correction bakc panel XLR Inputs audio review DSP.jpg


Due to some mix up, I did not get the external adapter and had to use my lab power supply. It drew 750 milliamps at 12 volts.

To be clear, the DDRC-88A digitizes all the inputs, processes them using a DSP and then converts them back to analog. Stated sample rate is said to be 48 kHz at 24 bits.

The USB connection...

Parasound Zphono Phono Preamplifier Review

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This is a review and detailed measurements of the Parasound Zphono phono stage. It is on kind loan from a member and costs US $200. There are also versions with USB and ADC (for ripping Vinyl) and higher-end version with more control.

The look is unmistakably Parasound which is to say somewhat industrial and plain:

Parasound Zphono Phono Preamplifier stage MC M stereo review.jpg


The back panel shows the included, voltage selectable AC mains which I appreciate:

Parasound Zphono Phono Preamplifier stage MC M back panel input RCA ground AC Polarity stereo ...jpg


As you see the input gain can be changed from moving magnet (MM) to moving coil (MC).

Interesting to see an AC mains polarity switch. Not sure of the safety of that but I guess if you have a hum, it is worth having a switch like this to at least troubleshoot the problem.

Overall, the Zphono is a business-line phono amplifier with solid construction.

Phono Stage Audio Measurements
Let's start with our usual 1 kHz dashboard view with moving magnet setting:

Parasound Zphono Phono Preamplifier stage MM audio measurements.png


As with all good phono stages...

JBL SDP-55 Audio/Video Processor Review

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This is a review and detailed measurements of the audio performance of the JBL SDP-55 AVP home theater processor. It was kindly purchased by a member and drop shipped to me for testing first. It arrived about two months ago. The SDP-55 costs US $6000.

Note: our company Madrona Digital is a Harman (and hence JBL) dealer. Our business though is almost entirely custom installation in commercial and high-end real estate. So we don't do much business with them for typical products I review here (and the company is totally separate from this website). That said, we can source Harman gear and the member indeed purchased this through us. So assign as much bias as you like to this review.

The SDP-55 has a very elegant, modern and serious look:
JBL SDP-55 AV Processor Surround Dolby Atmos UH 4K Review.jpg


The menus and graphics are super responsive which is great. The large rotary volume control is nice but a bit too light for my taste. Then again it allows you to rotate it quick and watch the display...

Hivi 3.1A DIY Speaker With Sehlin Mod Review

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This is a review and detailed measurements of the Swan Hivi 3.1A DIY Speaker kit with modified crossover by Sehlin Sound Solutions. It was kindly sent to me by @Mudjock as tested. The kit by itself goes for US $300 including Prime shipping. Unusual for a speaker kit, it comes with everything you need including the speaker box. As built the response is too hot in the tweeter (I think) and hence the mod: https://sites.google.com/view/sehlin-sound-solutions/hivi-diy-3-1-modifications

I must say I like the white finish on a DIY speaker better than black:

HiVi - DIY 3.1 Bookshelf Speakers Stereo Review.jpg


Please don't mind the little nicks. The crossover had come loose in shipping and I had to take the speaker apart to affix it.

The mid-range throw me off as I first thought those two little wires are debris so I proceed to try to grab then with my needle nose pliers! Fortunately I realized in time and didn't try to pull them off. So if you have grabby hands around your...

Motu M4 Audio Interface Review

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This is a review of Motu M4 4x4 audio interface (DAC and ADC). It is on kind loan from a member and costs US $220.

The enclosure is heavy gauge metal and sturdy:

Motu M4 4 channel Audio Interface DAC 4x4 Audio Review.jpg


The front inputs are for microphones with higher gain. For my testing I used the Line in (and out) in the back:

Motu M4 4 channel Audio Interface DAC 4x4 Back Panel Inputs Outputs TRS Headphone Amplifier Au...jpg


For testing I installed the ASIO drivers which came with a nice little control panel that lets you set the sample rate and buffer depth. I had no difficulty operating the unit during my testing.

And oh, there is a headphone amplifier in there also which I tested as well.

DAC Audio Measurements
I started my testing with the M4 acting as a normal DAC using its balanced TRS jacks:

Motu M4 4 channel Audio Interface DAC Audio Measurements.png


I don't know why but I expected the performance to be worse so was pleasantly surprised by the sum (ratio) of the noise and distortion in the form of SINAD. This places the M4 firmly in the top bracket of all DACs tested regardless of...

Bottlehead Crack Headphone Amplifier Kit Review

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This is a review and detailed measurements of a (built) Bottlehead Crack Tube headphone amplifier. It was sold from one member to another and kindly sent to me in between for testing. The version I have has the "speed ball" current source which brings its cost up to US $430.

The original owner did a beautiful job of building this kit:

Bottlehead Crack Headphone Amplifier Audio Review.jpg


And here are the internals:

Bottlehead Crack Headphone Amplifier Kit Internals Speedball option Audio Review.jpg


Can't ask more in a DIY build.

I looked thorough the manual and it seems exceptionally well written and annotated.

I liked the feel of the volume control although as you will see later there is significant channel imbalance.

The tubes in the test unit are USA made 6080WC (output) and 12AU7 (driver).

Tube Headphone Amp Measurements
As usual we start with our dashboard:

Bottlehead Crack Headphone Amplifier Audio Measurement.png


It is a shock to the system coming from testing many solid state amplifiers to see SINAD (sum of distortion and noise) to be so low. That said, we have...

Selah Integrity DIY Speaker Kit Review

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This is a review and detailed measurements of the Selah Integrity DIY Speaker Kit. @Selah Audio designed this kit in memory of DIY designer, Jeff Bagby, who sadly passed away due to Covid-19. The Kit was kindly built by @Rick Sykora. Meniscus Audio will be selling the kit and a portion of the proceeds goes to family of Jeff Bagby. The kit cost starts at $630 plush shipping for a pair.

This is a three-way design and built out of ultra dense and thick MDF:

Selah Jeff Bagby Integrity DIY Speaker Kit Review.jpg


As you can see, there is an oval passive radiator in the back. It was a pleasure to have a pair of binding posts where I could get my fingers in there. :)

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and...

Tascam DR-100 MKiii Field Recorder Review

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This is a review and measurements of the Tascam DR-100 MKiii portable field recorder. It is kindly sent to me by a member and costs US $300 on Amazon including Prime shipping.

As one expects from the brand, the Tascam looks quite serious:

Tascam DR-100 mk iii studio-quality 192kHz 24-bit PCM Recorder Audio Review.jpg


The display is bland in black and white but does the job. Here is a bottom shot:

Tascam DR-100 mk iii studio-quality 192kHz 24-bit PCM Recorder XLR Inputs Audio Review.jpg


While there is a micro-USB jack on this unit, it is only for charging and moving files back and forth. It does not allow streaming of audio which made my testing quite difficult. The only thing I could do is feeding it a 1 kHz tone, record it, pull it back onto the PC for analysis. In order to create a familiar data to other devices tested, I played the resulting file using Audio Precision analyzer's DAC and analyzed that. This adds an extra DAC and ADC to the path but I suspect both are much cleaner than this device so impact is minimal.

Recording Audio Measurements
Per above, I recorded a few...

Zoom F6 Portable Field Recorder Review

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This is a review and detailed measurements of the Zoom F6 battery operated, multi-channel portable balanced field recorder. It is on kind loan from a member and costs US $650 from Amazon including Prime shipping.

I must say, the F6 is one sturdy feeling and looking recorder despite its small size:

Zoom Mulltitrack Balanced Portable Field Recorder Audio Review.jpg


There are six independent channels each with their own XLR input. They can all be configured as Microphone or Line inputs. I tested with the latter.

A camcorder/SLR style batter powers the unit but you can also use USB as I did in my testing:

Zoom Mulltitrack Balanced Portable Field Recorder XLR Inputs Audio Review.jpg


For my testing, I took advantage of the ASIO driver which allows the F6 to be used as an input-only audio interface. This allowed me to run full suite of tests on it that would otherwise be very difficult to do with first recording on a card and then shuffling that to the PC. It is possible though that the USB noise has interfered with operation of the unit to some extent as you see...
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