Articles, Reviews and Measurements of Audio Products

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...

NAD T778 Audio/Video Receiver (AVR) Review

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This is a review and detailed measurements of the new NAD T778 Home Theater AVR. It was kindly purchased by a member new and send to me and costs US $3,000. It is only sold through dealers and looks like if you contact them, you may get some discount from that price.

The NAD looks gorgeous and highly differentiated from your typical AVR:

T 778 AV Surround Amplifier AVR Dolby Atmos 4K  Review.jpg


The large high resolution display is a joy to look at. There are even "ear racks" included so you can mount it in an equipment rack!

A very fancy remote with motion detection and back light is included which even has a USB port. So I imagine it may be programmable. More on this a bit later.

The back connections are ultra modern, dispensing with yesterday's video inputs and such:

T 778 AV Surround Amplifier AVR Dolby Atmos 4K  Back Panel Inputs HDMI Pre-out Review.jpg


Despite using (modified?) Hypex class D amplifier modules, the T778 is fairly heavy, weight similarly to other AVRs. The class D amplifiers do bring a major benefit in how cool the unit runs. Only the...

DSPeaker Anti-Mode 2.0 Dual Core Room EQ Review

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This is a review and detailed measurements of the DSPeaker Anti-Mode 2.0 Dual Core Room Equalizer. It is on kind loan from a member and costs US $1,200. This review is only focused on electronic performance of the device. If I have time, I may test its correction ability later.

There is not a whole lot to look at as far as the design of the Anti-Mode:

DSPeaker Anti-Mode 2.0 Dual Core Speaker and Room Correction Review.jpg


The display is quite tiny but usable if you sit close to it. The back panel shows the good connectivity:

DSPeaker Anti-Mode 2.0 Dual Core Speaker and Room Correction XLR RCA SPDIF inputs and outputs ...jpg


For this testing, I focused on both analog XLR input and Toslink S/PDIF digital input. There are some lofty statements the company makes about the performance of this unit:

1598550505305.png


Well, I qualify as most demanding audiophile :) so let's see how the Anti-Mode performs with basic tests.

DSP Audio Measurements
I started my testing by feeding the unit via its XLR input. To my surprise, it complained about 4 volts input causing clipping...

KEiiD KD-W01 Streaming DAC

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This is a review and detailed measurements of the KEiiD KD-W01 streaming DAC and Bluetooth receiver. It was kindly purchased and drop shipped to me by a member. It costs only $69 from Amazon including Prime shipping.

I must say, as super budget products go, the look of this little streamer is not bad:

KEiid KD-W01 Wireless Stereo Receiver Streamer Audio Review.jpg


There is a remote control that I did not use. The M button selects between networking (wired or wireless), Bluetooth or Aux analog input:

KEiid KD-W01 Wireless Stereo Receiver Streamer Back panel input ethernet wifi SPDIF Toslink Au...jpg


The regulator tag is taped on the supplied USB adapter which makes it suspect as far as passing such a test. Fortunately you can use its cord with a more trusted option (from your favorite phone manufacturer).

For testing, the only option I had to talk to it over the network was Airplay. Airplay has a limit of 16 bits which limits SINAD to 96 dB. I was worried about this but as you will say, there was no reason to feel this way.

Streaming DAC Audio Measurements
I streamed a...

Definitive Demand D11 Speaker Review

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This is a review and detailed measurements of the Definitive Technology Demand D11 bookshelf/stand-mount speaker. It is on kind loan from a member who I think bought it used. The normal cost on Amazon is US $1,000 including Prime shipping.

I must stay, the enclosure is very attractive and well built. But I don't care for the look of the drivers:

Definitive Technology Demand D11 Bookshelf Speaker Review.jpg


The offset tweeter is supposed to reduce effect of diffraction but it bugs me and I don't even have ADD! There is a passive radiator on top which you can't see but is covered in nice fabric.

Back panel terminals are too close as usual but otherwise feel fine:

Definitive Technology Demand D11 Bookshelf Speaker Back Binding Posts Bi-wire Bi-amp Review.jpg


Speaker is built in China.

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...

Allo Volt+ D Amplifier Review

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This is a review and detailed measurements of the Allo Volt+ D class D amplifier. It was kindly sent to me by a member and costs US $129 in this "dual mono" configuration with stepped attenuator.

I am not a big fan of these clear cases but in this case, pun intended, it works!

Allo Volt+ D Class D Amplifier Audio Review.jpg


Hard to take a picture of it though without heavily accentuating dust and such that normally is not visible:

Allo Volt+ D Class D Amplifier PCB TPA3116.jpg


Dual TI TPA2116 class D amplifiers are used plus a front-end switching power supplies to generate the required plus and minus supplies.

Not that no power supply comes with this amplifier. You have a choice of what you put in there. I used my lab power supply at its max setting of 31 volts and 3 amps. It could use more than 3 amps with 4 ohm load as the power supply current limited near max power sweeps. It was fine with 8 ohm load though as that doesn't need as much current.

There is no remote control so this is really a desktop...

NAD M10 Streaming Amplifier Review

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This is a review and detailed measurements of the NAD M10 streaming amplifier and DAC. It was purchased and drop shipped to me kindly by a member. It costs US $2,749 from NAD dealers.

The M10 sports a very large touch screen LCD display that covers the entire front face:

NAD M10 BluOS STREAMING AMPLIFIER DAC Wifi Coax Review.jpg


Sorry for leaving the protecting plastic on. Like to keep things as new as possible for members.

As nice as the display is, it simply is not as responsive as your phone or tablet. What could be really cool such as the VU meter mode, becomes a jittery display that doesn't please much. A much faster processor with GPU would be needed to really make the display the star. Still, it is heads and shoulders above others that have small displays.

The back panel is notable for inclusion of HDMI ARC input:
NAD M10 BluOS STREAMING AMPLIFIER DAC Wifi Coax HDMI inputs ARC Review.jpg


Alas, I have no ARC capability on my workstation so could not test that feature.

In normal use the plastic case barely gets warm. Under heavy stress of...

Sehlin Helium DIY Speaker Review

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This is a (quick) review and detailed measurements of the Sehlin Helium DIY ultra-compact speaker kit. It was sent to me by the designer and member @Mudjock. Here is the cost factors as he provided me:

Drivers + crossover parts: $108.84
Cabinet kit and binding posts: $31.44

This is a very small speaker which literally fits int he palm of your hand:

Sehlin Helium DIY Speaker Audio Reivew.jpg


Needless to say, it was a joy to put on the measurement stand and bring up to my work area to listen. :)

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...

Denon AVR-X6700H AVR Review (Updated)

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This is an updated review of the Denon AVR-X6700H. I tested an early production 6700H a few weeks ago and found lower than expected performance. Denon Engineering traced this to a faulty capacitor( or capacitors) used in the initial run of this AVR. I requested an updated unit which the company was kind enough to send me.

AVR-X6700H AVR Surround HDMI Dolby Atmos Home Theater Receiver Updated Review.jpg


I have re-tested the DAC portion almost completely but for the amplifier I am just showing some of the highlights as the problem was not there.

EDIT: this is the serial number of the tested unit: DBCY032000007

Updated AVR DAC Measurements
The original AVR-X6700H returned a SINAD of just 87 dB which was well short of what the lower end models had achieved. I am pleased to report that this second unit nicely remedies that defect:

AVR-X6700H AVR Surround HDMI Dolby Atmos Home Theater Receiver Audio Measurements.png


This catapults the 6700H into the...

Polk Audio Signature S15 Speaker Review

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This is a review and detailed measurements of the Polk Audio Signature S15 bookshelf speaker. It was kindly sent to me by a member for the review and costs US $229 per pair.

If I did not tell you the price, you would think the S15 retails for $1000 given its very nice and "high-end" looks:

Polk Audio Signature S15 Bookshelf Speaker Review.jpg


And interesting cover an an inside out horn of some type adorns the rear port:

Polk Audio Signature S15 Bookshelf Speaker Back Panel Binding Posts Review.jpg


There is a genius at work getting a budget speaker to look this interesting and differentiated from a massive crowd of budget speakers.

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...

Pro-ject Pre Box DS2 DAC & Pre-amp Review

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This is a review and detailed measurements of the Project Pre BOX DS2. It is a multi-function device with USB DAC, headphone amplifier, analog pre-amplifier with Bluetooth, and phono stage. It is on kind loan from a member and costs US $899 although I see some open box ones for US $699.

The DS2 manages to come across as elegant in a sea of same looking desktop audio products:

Project Pre Box DS2 Digital Phono USB DAC Preamp Audio Review.jpg


The controls are microprocessor based and have a good feeling to them. LEDs light up to indicate what mode the device is in.

The back panel better shows all the functionality:

Project Pre Box DS2 Digital Phono USB DAC Preamp Back panel adapter remote control Audio Review.jpg


I don't care for membrane based remote controls but that can be easily replaced with another remote. The power supply is nice and light although has those adapters for mains socket which I don't fond of. But I understand the usefulness of it instead of stocking multiple versions of the unit.

USB DAC Audio Measurements
As usual, let's start with our dashboard view...

Choosing between Denon X8500H, X4700H and X3700H AVRs

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The power differences between the X8500H, X4700H and X3700H are about 1dB. If the requirement is for an AVR with only the internal amplifiers used, and with the number of power amplifiers that the X3700H or X4700H provide, then the lower price products provide a little cleaner power with about 1% less output. While the preamps of the X8500H are very clean, the good (actually a little disappointing), but not great distortion performance of the power amplifier channels is the limiting factor in the X8500H power amplifier performance. There is little to no reason in this use case of 100% internal power amplifier channels, to choose the X8500H unless based on features important to a specific user. This is good news. It means that there are low cost options with excellent performance.

If more power amplifier channels are required than the X3700H or X4700H provide then of course the X8500 is the obvious choice.

The real advantage of the X8500H is when the preamp outputs will be used...

Headphone Measurements Using Brüel & Kjær 5128 HATS

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This is an investigation thread into feasibility of ASR adopting the Brüel & Kjær Type 5128 "high-frequency" Head and Torso Simulator (HATS). It is on kind short-term loan from the company. As configured, it costs around US $41,000. This is quite a bit more money than competing solution. The premium comes from the 5128 benefiting from a more accurate representation of our hearing system. How much difference this makes in real life is something we need to determine in short order before I have to return the unit in four days.

Not that it matters but I like the somewhat friend/crash dummy look of the 5128 :)
Brüel & Kjær Type 5128 HATS Headphone Measurement.jpg


There is an external CCLD signal conditioner model 1704 which can operate on internal battery for USB. Using the latter, I saw a noise spike in upper band of the audible spectrum. Not an issue for frequency response measurements but will...

ARX RS-1 XLR AB Switcher Review

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This is a review and detailed measurements of the ARX RS-1 Remote Switcher. Strangely the back says "Remote SwitcherAB-19" so not sure what is the right model number. It was kindly purchased and drop shipped to me by a member. The RS-1 costs US $273. The website says "HANDMADE IN MELBOURNE, AUSTRALIA."

This is an industrial looking piece which hints at their traditional market:

ARX RS-1 Remote Switcher Channel B Audio Review.jpg


It is nice that by default Channel A is active so if there is a power loss, etc., you can count on that input being live. To switch to Channel B, you must supply power for the internal relay. There are two methods: that power input and then shorting the two left terminals. I tried that but it did not switch. I had to string together different connectors so maybe that was the issue. The alternate method of just feeding 12 volts to the right two terminals worked. Note that it drew about 40 milliamps so make sure your source can supply this much current...

Hagerman Bugle2 DIY Kit Phono Preamp

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This is a quick review and measurements of the Hagerman Bugle2 DIY/Kickstarter Phono prempalifier/stage kit. It was kindly sent to me last year believe it or not! Alas, I am in the midst of evaluating a $40K headphone measurement gear so can't spend a lot of time on it. But thought I test it at least at high level. The PCB for this kit costs $39. Fully assembled kit during kickstarter was US $150. There seems to be a version 3 now.

The assembled version I received is in opaque housing which doesn't make for good pictures:

Hagerman Bugle2 phono preamplifier audio review.jpg


Here is a shot from kickstarter page:

Hagerman Bugle2 phono preamplifier PCB Kit audio review.psd.jpg


Phono Stage Measurements
Here is our usual dashboard with 5 millivolt input:

Hagerman Bugle2 phono preamplifier audio measurements.png


Distortion is very much under control but one channel is a lot more noisy than the other. I tried different grounding schemes but did no good (red channel). That pushes the SINAD for that channel way low. The other channel has lower noise but...

Denon AVR-X8500H AVR Review

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This is a review and detailed measurements of the Denon AVR-X8500H Flagship 13.2 Audio/Video Receiver (AVR). It is kindly loaned to me by a member and costs US $3999.

The 8500H is a beast: it is both deep and heavy. Thankfully the transformer is centrally located so as manageable as 51 pounds can be:
Denon AVR-X8500H Surround Sound AVR Audio Video Review Home Theater.jpg


If RCA connectors were Christmas lights, you would have the best one in the entire neighborhood with this AVR:

Denon AVR-X8500H Surround Sound AVR Back Panel Inputs HDMI  Audio Video Review Home Theater.jpg


In use, the AVR-X8500H ran a bit cooler than its lower end siblings. I think I measured a post-testing temperature of 45 degrees C. Still, I highly recommend ample cooling as once again, there is a fan under the heatsinks but it does not turn on in normal usage (ECO mode off).

If you have read my previous reviews of AVRs, you know that I test the pre-amp output with and without amplifiers active (if there is such an option). I tried to do this with the 8500H but at first failed miserably. I set the amplifier...

Schiit Magnius Balanced Headphone Amp Review

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This is a review and detailed measurements of the new Schiit Magnius Balanced (input and output) headphone amplifier. It was kindly sent to me by the company and costs US $199 direct plus shipping.

The sample I received is in black which gives a serious look to the new amp:
Schiit Magnius Balanced Headphone Amplifier XLR Audio Review.jpg


There is an input selector (balanced or XLR) and gain with dual settings.

The volume control is a bit stiff but not a problem.

Back panel shows what you expect:

Schiit Magnius back panel inputs outputs AC transformer review.jpg


The AC transformer is hefty in size and gets a bit warm in use. Do not attempt to replace it with a DC power supply. AC power is used so that it is easier and higher quality to generate both positive and negative voltages needed for the amplification. So you need to get the right one for your country's voltage.

Headphone Amplifier Measurements
As usual we start with our dashboard of 1 kHz and see what comes out of the unit. I started with 1/4 inch headphone output while feeding...
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