Articles, Reviews and Measurements of Audio Products

This is a review and detailed measurements of the Monolith by Monoprice USB DAC (29512) portable DAC and headphone amplifier. It was kindly sent to me by a member and is on sale for US $60.

I like the volume control on the right. Other than that, there is not much else to it.

Monolith by Monoprice USB DAC Measurements
Let's start with our usual dashboard:

I must say, that is one odd looking noise floor! Company specifies output voltage of 2 volts but we are shy of that at 1.85. This is critical for headphone amps as that also sets the max power into high impedance loads. I don't know where their 117 dB spec comes from (datasheet for ES9018K2M chip???). We are nowhere in the same universe with SINAD of 82 dB.

Another major deviation is in dynamic range:


96 dB is OK for the application but why spec 122 dB that requires state of the art desktop DACs to achieve...

This is a review and detailed measurements of the Sennheiser HD569 closed back headphone. It is on kind loan from a member and costs US $80 on Amazon.

While the feel is a bit plasticky, overall comfort was good despite the rather thin pads. Speaking of which, they had deformed non-symmetrically which I think was partially responsible for wide variation in channel response as you will see later. A very long and silicone feeling cord is included along with a shorter one. I tested the longer one and while it was microphonic, I appreciated the length and rather low memory in it.

Sennheiser HD569 Measurements
I had a hell of a time getting consistent response and balanced results from the two channels. I suspect a lot of this is in the drivers but also the thin pads not holding their shape at all. So please don't micro analyze the frequency response measurements:


I was pleased to see a lot of bass but not...

This is a review and detailed measurements of the Schiit Magni Heretic headphone amplifier. It was sent to me by the company and costs US $109.

You can get it in silver or back. Either way, the side and back panels are in red which I like. As you see, there is not much to the functionality other than volume control and three stage gain settings which I appreciated. Previous Schiit Heresy model lacked this which likely hurt its performance in noise department. Back panel is as you expect:

As is typical of Schiit gear, the on off switch is in the back. There is no indicator on the front that the unit is on which is a miss. There is however a red LED inside which you can kind of see. Power is provided using AC transformer which is larger than switching units.

Operationally my only wish...

This is a review and detailed measurements of the Amazon Basics 4K HDMI extractor. Member kindly purchased and drop shipped it to me. It normally costs $22.89 but was on sale for just $5!!!

The case is the standard metal one for these kinds of adapters. Power is provided with a supplied USB-A to barrel (9 volt) connector. I powered it using the hub in my computer monitor. As you see a nice switch forces the digital output to be either stereo or 5.1.



Pass-through HDMI connector is naturally provided as well as Toslink, Coax and analog stereo 3.5mm outputs.

Amazon Basics HDMI Extractor Analog Measurements
I started testing by feeding it HDMI and capturing analog output:


Not very pretty but hard to expect...

This is a review and detailed measurements of the Schiit Modi+ stereo USB DAC. It was sent to me by the company and costs US $129.

There are three inputs and are nicely stepped through using the momentary switch. The white LED that indicates the selected input is nice but alas, there is some bleed into the other indicators.

Back panel is simple enough:


A USB adapter is included to power the unit although you could accomplish the same by using a USB port on your computer which is what I did for my testing.

Here are the specs:



Schiit Modi+ Measurements
Schiit implementation of USB defaults to 16 bit which causes trouble for my ASIO4ALL wrapper so for some of the tests, I had to use my Roon player to get...

For phase p and frequency f group delay GD is the negative of the derivative of the change in phase with respect to the change in frequency: GD = -dp/df. In general phase is a function of frequency p(f); that is, phase changes with frequency. That's the math behind it.

A change in phase is equivalent to a time shift, for example a 180-degree phase shift is like shifting the time by one-half cycle of the signal. The derivative is a fancy expression for the slope of a line, so it is a measure of phase linearity. A straight (linear) line has the form y = mx+b where every point x is multiplied by the slope m and added to offset b to produce a y value. For a straight line, m is constant (just a number, not a function of something else), and hopefully we remember this formula from school. Now replace m with GD so to get a straight line, that means the change in phase divided by the change in frequency...

This is a review and detailed measurements of Pass Labs HPA-1 headphone amplifier. It is on kind loan from a member and costs US $3,675.

The box is quite heavy which is "nice" given how much it costs. The look would be good if it were not for the locking headphone plug. A simple hole would have fit better with the rest of the input switches to the left. Volume control has substantial weight to it which is also appreciated.

Back panel surprised me by lack of balanced XLR input (and output for that matter):


When I attempted to power on the unit, none of the front panel LEDs lit up. I tried different cables, read the manual, etc. to no avail. So I took the top panel off. There are four hex head screws but the thread is cut poorly into the chassis, making them difficult to turn -- I...

This is a review and detailed measurements of the Topping E70 stereo USB DAC with Bluetooth. It was sent to me by the company and costs US $349.

I really like the new white multi-segment display with its large volume level indicator. Response is excellent as you rotate the encoder. A select button on the left turns on the unit and then selects the input in sequence. Or you can use the included remote control:

Nice to see 12 volt trigger being a standard feature on new Topping products, allowing you to turn on one unit and have it turn on the others like amplifiers automatically.

The output can be programmed to be nominal 4 volts (default) or 5 volts. I focused on testing the former.

Edit: forgot to mention that you have independent control over the outputs. You...

The story starts with me originally ordering a cloned Venu360 since some posters indicasted they seemed to be units which 'left' the DBX facility.

The seller did not have any VENUs (which was good after I saw Amirm's review) and the seller offered to sent two driverack PA2 clones instead.

They showed up and I was quite happy with them until...... Until I measured them. Damn you Cosmoas ADC!

The poor measurements, <60dBr multitone, <72dbR 1kHz FFT; left me shocked. I had to take a look inside. And inside I went.
There I found more Harmann markings, more obviously Harmann boards, genuine components, etc. ..... and also a ton of X7R or X5R resistors instead of NPO/C0G. The distortion was primarily due to odd-order harmonics which were MASSIVE.

This lead me eventually to this article. https://www.edn.com/signal-distortion-from-high-k-ceramic-capacitors/ (it has pictures!)

At this point I was about ready to get a miniDSP Flex, but my amps take balanced only...