Articles, Reviews and Measurements of Audio Products

This is a review, listening tests and detailed measurements of the 7Hz Salnotes Zero IEM. It was kindly donated by a member and costs US $22 ($20 on Amazon now).

The molded plastic looks cheep and the left and right markings barely visible. The included tip was extra soft/thin which may be a good thing for comfort but made for very difficult measurements. You could easily deform it to the point of it blocking most of the sound in the fixture. When I wore them on my ear though, the fit was excellent and with their light weight, I could barely feel them.

7Hz Salnotes Zero Measurements
Per above, I had a heck of a time measuring these IEMs but as if by magic, I toughed the off channel once and it created perfect fit and alignment with the other channel:

[ATTACH type="full" alt="7Hz Salnotes Zero IEM budget frequency response...

This is a review and detailed measurements of the 3e audio TPA3255 chip based stereo amplifier. It was sent to me by the company as a complete unit even though they only sell the amplifier modules.

As you see, it is a generic box which is something you can easily build yourself. I don't know what power supply is in there. Will fill in when I know. Same with the cost.

Back side of the reference design:


I believe the module name is: 260-2-29A or EAUMT-0260-2-A. Cost seems to be US $90 for the amplifier module.

The differentiation here is implementation of "PFFB" which stands for post-filter feedback design. Without this, the required output filter will interact with speaker load, varying the frequency response of the amplifier. High cost...

This is a review and detailed measurements of the McIntosh MC 427 (MC427) stereo car audio amplifier. It is on kind loan from a member. It has been discontinued but used ones go for about US $500.

Not much to distinguish the amplifier from other car amps other than the bright blue logo. Unlike all the others I have tested though, this one is class AB, not Class D.

There are two small fans which I don't like to see. Fortunately in use the amp ran very cool, barely getting warm and I don't think the fans ever came on.

McIntosh MC427 Amplifier Measurement
As usual we start with our dashboard of 5 watts into 4 ohm load:

Are you seeing what I am seeing? Distortion product at nearly -120 dB??? And in a car amp? Incredible. SINAD is noise...

This is a review and detailed measurements of the D'Amore E660.5 5-channel automotive amplifier. It is on kind loan from a member and costs US $299.

The E660.5 seems well built and as you can see, is in a rather large enclosure. I suspect that will let it run cool. In testing it did not even get warm. Power terminals are designed well with angled hex screws that bite wires quite well.

Company designer used to be at Fostex and currently builds a line of test instruments for automotive amplifiers so I expect good performance.

Note that my instrumentation is limited to 2 channels and that is what I tested. Power source is a custom Lithium battery bank with 100 Ah capacity (instantaneous power of hundred of amps). I was charging the bank as I was testing the amp so you will see rising voltage notations in the testing (ranging from 13.4 to 13.8 volts).

Note 2: I thought the amp...

This is a review and detailed measurements of the (SMSL) VMV D2R stereo balanced USB DAC with Bluetooth. It was sent to me by the company and costs US $999.

The DAC is quite heavy for its size and has pretty stout construction. User interface is similar to other SMSL products. A higher-end metal remote is provided:

Alas, no coin cell battery was included so I used the front panel for configuration of the DAC.

The DAC design is different than many other in that it uses a DAC IC from Rohm (BD34301EKV) instead of the usual ESS and AKM. Let's see how it performs.

If you are new to DAC measurements, be sure to watch my tutorial video.

VMV D2R DAC Measurements
Let's start with balanced output and use the default -2 dB on the volume control which generates our nominal 4 volts:

Noise performance is excellent...

This is a review, listening tests, EQ and detailed measurements of the Hidizs MP145. It was sent to me by the company and costs US $150.

The immediate impression of the shells is one of jewelry with its machined aluminum case. As you see, the included cable has 4.4mm balanced connection even though it doesn't need that (plenty sensitive to work fine with 3.5 mm unbalanced). Included in the case are three tip variants and nozzles (latter not shown):

As is typical, medium size tips match my GRAS 45CA measurement artificial ears best. But for listening, I have to go one size larger. I started with balanced tips but then tried to measure with the other tips. I found the process of swapping tips very difficult. The nozzle is large and the tips barely fit it. Good news is that once you get them on there, they going to stay. With some other IEMs...

This is a review, listening tests, and detailed measurements of the Dan Clark E3 closed back headphone. It was sent to me by the company and costs US $1,999.

As you see, the E3 has quite large cups which makes fitment on your ears quite easy. I used the headphone for about 2 weeks with good comfort. Compared to the Stealth, I thought it felt a bit heavier. On the looks, I find it kind of simple compared to the complex geometry of Stealth/Expanse headphones.

Let's measure it to see how it responds.

Dan Clark E3 Headphone Measurement
I expect compliance with our target and that is exactly what we have:

Indeed, it seems to comply a bit...

This is a review and detailed measurements of the Marantz AV10 Audio/Video Processor (AVP). It is on kind loan from a member and costs US $7000.

My picture doesn't do justice to the nice look of the unit. It is a massive step up from past Marantz AV products. I am still not a fan of the port hole and little information it shows but at least it now blends in with the rest of the unit. This thing is extremely heavy for a processor as well. I had to double check that it did not have amplifiers in it! The user interface is high resolution and relatively easy to use. One nit was that even though I had the HDMI out to my monitor, it would not bring up the full setup if I had it on CD with Toslink input. It required an HDMI input to do that. Strange.

An attractive metal remote control is provided. Usually these metal ones are not ergonomic but this one is.

Back panel shows the myriad of connectors due to 15.4 processing capability of this unit...

This is a review, listening tests, equalization and detailed measurements of the ZMF Caldera planar magnetic headphone. It is on kind loan from a member and costs US $3,500.

The Caldera is absolutely gorgeous to look at. It is lightweight and with its large cup, very comfortable to wear. Will have to find out from the owner which set of pads it came with.
EDIT: owner let me know that it has stock lambskin perforated pads.

The large cups allowed almost instant fit on my GRAS 45CA headphone measurement rig. I am always happy when that happens.

ZMF Caldera Headphone Measurement
As usual we start with the headphone frequency response measurement and comparison with our target:

OK, I get the flattish bass response but what is up with the three troughs...

This is a review and detailed measurements of the Sound Devices MixPre-3 II multichannel recorder and audio interface with headphone output. It is on kind loan from a member and costs US $895.

It is a cute, compact and rigid recorder. Gain control for Channel 2 has a stiffer feel which I imagine is designed to let you find it in the dark by feel. The LCD on the right is bright and touch sensitive. It is a bit small for comfortable manipulation but can be done. The user interface is a bit odd in that there is no scrolling and you have to learn to click on "..." to go to the next page. There are a myriad of inputs and a few outputs:



I dread testing this class of device as it takes hours to figure out how to do even simple things. The MixPre-3 was no exception. I installed its ASIO driver but it would keep complaining that it was not seeing it. Windows wouldn't recognize it either. Eventually found a...