The Dayton iMM-6 Calibrated Microphone

When designing and building speakers I use OmniMic. It's perfect for that but when it comes to basic Blu-ray or Home Theater setup I rely on a much less expensive and much more convenient device, the $30 Dayton iMM-6 calibrated microphone. 

Dayton provides calibration files via their website which make this almost a laboratory piece of equipment. It works in your cellphone or tablet. I personally use it on an Android along with Audio Tool which will read the calibration file and adjust the levels accordingly.

One of the main benefits of this device is how deep and flat it goes and is therefore more accurate than the old SPL meter method. It's much easier to set your speaker levels, including your subwoofer using it and your tablet than any other way I know.  It also has outputs for a mini-jack so you can use test signals from your iPhone/Android device simultaneously. You can use a cable like this one to connect it to your stereo inputs.

If you are a DIY hobbyist and want to build your own speakers or want to do detailed acoustical analysis of your listening environment this is also the perfect front end for Room EQ Wizard but you will need an adapter cable from it to your PC or laptop.

The only real downside of this is that it's tiny and I'm constantly misplacing it after I use it.

Fix Ground Loops Quickly, Safely and Easily

What is a Ground Loop?

It is video noise or audible hum that plays through your speakers that occurs when multiple ground points with slightly different potentials are connected together through your equipment. More on this is available from Jensen Transformer's web site. It's called a loop because it's actually that, a closed circuit.  All we have to do is either connect everything to the same ground, or break the loop in the safest and most convenient location.

A clue to a ground loop is that the hum stays constant whether you play music or video or not. Sometimes equipment such as a TV doesn't even have to be on to help cause in the loop.

Note that this is not mechanical hum. If you hear the chassis or transformers vibrating and making more of a buzzing sound your problem is more likely DC on the line. I'll cover that in another post, but this is often caused by PCs, light dimmers, and modern compact florescent bulbs.

Ground Loops and Digital Signals

The usual "scientific" belief is that digital signals are immune or at least very resistant to noise. While it is true that digital circuits are resistant to many types of noise these circuits, including digital video, can participate in a ground loop which can cause enough jitter to be audible or visible. This includes HDMI, coaxial and USB circuits. Optical digital connections however are completely immune to all external noise, including ground loops.

Ground loops will not occur in Ethernet cabling unless there was a fault in the switches / routers. In other words, almost never since preventing ground loops was part of the design of the entire Ethernet eco-system.

Diagnosing the Cause

There are a few common culprits:

• Cable TV or Satellite Dishes
• External antennas like FM or television
• Audio or video cables from a Personal Computer
• Laptops! (Problem goes away when you disconnect USB or charger) See USB fixes, below.

The best way to find the root cause is to disconnect each suspect and listen for the problem to go away. Sometimes the problem is related to two devices interacting, which gives you a choice of where to break the loop. This process also works for finding noise sources in general. Turning lights off and disconnecting wall-wart supplies may solve other symptoms.

Lethal Fixes and Myths

One type of fix can be lethal to you and your neighbors. That's a "cheater plug like this one. Any attempt to defeat the ground pins in equipment that has them may be lethal. Do not do it. Do not rely on signal grounds to work the same way. They don't.

Pangea originally sold "high end" IEC cables with removable ground pins. Don't buy them, don't let your friends buy them. They appear to be discontinued, probably due to safety concerns. There is now a 2 conductor C7 version with a removable pin, but that's perfectly safe, and the feature is kind of useless.

I recently heard this argument:

I've been removing ground pins for years and never had a problem.

The problem is these pins are like safety belts. So imagine me telling you this:

I've not had a car accident in 20 years, so I no longer wear a seat belt.

That should sound dangerous to anyone who drives a car. That's how we electrically minded people think when we hear of audiophiles removing ground pins for that last bit of audio nirvana. There are better and safer ways. Another myth, spread by audiophiles who do not understand the safety ground or the life safety issues involved in UL certification and the National Electric Code:

Your system will be grounded by your RCA cables. No problem!

If no problem means dead and on fire, they're right. 

Free Fixes

If your problem is caused by a piece of audio/video gear, try connecting it all to the same power strip or conditioner. This ensures all the ground wires are at the same potential.

Another free fix may be to use XLR cables. XLR cables are not usually quieter in homes than balanced, BUT! there is a difference. XLR cables don't mix the ground and signal together. You avoid this contamination and XLR inputs often have a safe "Ground Lift" switch. It prevents the grounds loop from occurring at all.

Not A Ground Loop

Some issues have nothing to do with ground loops but are caused by induced noise from other sources. This noise can come through the power lines OR be induced by proximity to interconnects and electronics. Things to try turning off, disconnecting, or removing from the environment:

• Compact Flourescent bulbs - VERY noisy! 
• Wall warts - These tricky bastards stay on, and polluting even if the device they are feeding is off.
• Wall dimmer switches
• PC and laptop power supplies (yes, again!). Disconnect your PC or laptop cables to your stereo, TV, etc. If the problem comes and goes with the PC/laptop being plugged in, then you have a noise problem and will need to relocate it.
• WiFi devices, including routers, streamers, receivers, modems, etc. If your Wifi device is part of your stereo, try moving the antenna or putting it on a different power strip/conditioner. 

 

Noiseless Cables

Sometimes the problem is noise our cables pick up. Especially problematic in apartments with a heavy concentration of WiFI signals or near transmission or cellular towers. Some electronics will help pick this up more than others.

Make sure your interconnects are 100% shielded. Most cheap and a lot of expensive RCA cables use a braided ground, which is more of a pick-up antenna than anything else. Regardless of whether you use RCA or XLR cables, the best use 2 conductors plus a foil shield. In essence they are built of conductors:

• Positive conductor
• Negative conductor
• A super thin and delicate foil shield
• The drain wire which is used to attach the foil to a ground conductor on the RCA or XLR jack

On RCA cables the drain wire should be attached to the negative conductor at the source. The destination end does not use it but instead uses the positive and negative wires. With an XLR cable all 3 wires are attached at both ends, unless the destination does not have a ground lift pin in which case the ground may go unattached at the destination.

My favorite brands for non-esoteric cables:

• DH Labs
• Connex
• Mogami
• Belden

I personally use Connex solid silver cables for everything, but they are delicate. Get the more expensive DH Labs varieties if you need rugged.

Cable TV & Antenna Problems

This problem can also cause Internet access issues. I use a dedicated Cable TV isolator like this one. You put it immediately inside the RF plug, unless you have a satellite dish.  More on that, below.

Satellite Dishes

Make sure the satellite dish cable is grounded before entering your home. Even though it is required by code, installers often fail to do this, and ends up in having your receiver or antenna getting fried by heavy wind causing static as it blows across the dish.

Unlike Cable TV and overhead local antennas, satellite dishes require DC power to operate the RF amps built into the little head. For this reason isolating them is a little trickier. Normal isolators block DC in all forms.

The trick is to buy a separate DC power supply for your antenna. Place the ground loop eliminator closest to your receiver, and your antenna power supply closer to the antenna.

HDMI

Your best / cheapest way to eliminate issues from your television over HDMI are to fix any connections going to it such as cable tv, satellite, a PC, etc.

USB/DAC

Early in the history of external DACs ground loops could occur through coaxial cables. Most good DAC's today provide what is called "galvanic isolation" meaning that there is no DC or ground loop path between the input plugs and the rest of the circuits in a DAC. This can be done by purpose built transformers or modern monolythic IC's. Unfortunately no magazine or agency I know of tests for this so there is no way to 100% guarantee a DAC's isolation. Of course, the way to test this is to disconnect your USB input and see if your hum goes away. There are also cases where you have very little ground loop noise. To fix either use a USB isolator like this inexpensive model designed for medical professionals, but works just as well with USB 2.0 DACs.

Another fix is to use a purely optical cable between your source and DAC such as the Audioquest Forest or Monoprice both of which come in a variety of lengths.  Check the size of the plugs, some may interfere with other sockets on your equipment. Optical cables are also a very good choice for going from PC to a DAC or receiver if the PC supports it since PC's are such noisy environments.

Of course, since the entire point is to avoid a current path, gold plated optical cables are kind of silly.

Audio Signal Isolators

Audiophiles hate putting anything in the signal path, and some fussy recording engineers may also, but pro's also know that it's far better to put in a transformer than delaying a show, so here are a couple of isolation products from Ebtech that are reasonably inexpensive.

I'm currently working on Cable Mittens, a new concept to warm up the sound of an amplifier while breaking ground loops and reducing noise.  Until then, the choices below are the best available!

The Hum Eliminator takes 1/4" jacks, but adapters are easily found. For a little more you can get the XLR version shown here.

The EbTech models, especially at their prices, are very good, but audiophiles who only want the very best turn to Jensen Transformers for the gold standard in high quality audio isolation. If that's what you need, I present the RCA Jensen Iso-Max for your approval. It's usually the best solution for PC audio problems.

The XLR Iso-Max, below, is also available for around $250.

Last Ditch Efforts

If your problem is your electronics and the single power strip idea doesn't work, the only remaining almost safe way to prevent the problem I know of is the Ebtech Hum X. The Hum X is only rated for 6A which limits it to line  level electronics. You cannot use it on power amps, which is not really a problem because we can prevent the ground loop at either end. You will find it just as effective by putting this on a preamp, TV or source as on the amps. It should also be effective on PCs, but I'm not sure if it could cause other problems.

I say it's "almost safe" because it has not yet been UL approved. The 6A rating is probably why, as there's no way to guarantee users will only plug-in 6A devices.

Iffy Solutions

If you are an audiophile you might have gotten to the end of this article wondering why the real "power conditioners" weren't mentioned. The truth is that the solutions provided above are the most effective in solving ground-loops than almost any high-end power conditioner.   Balanced power conditioners, which are often touted as the best solution for this, may or may not fix actually fix a ground loop problem.  Bill Whitlock and Jamie Fox of Jensen wrote a great paper for the Audio Engineering Society on the matter. Balanced conditioners ARE completely effective at removing DC from an AC line however, and very effective at reducing other types of incoming AC line noise.

Other types of power conditioners will have no effect at all on ground loops but may reduce other types of noise or provide surge protection and, as mentioned, connecting all your electronics to a single strip or conditioner may also eliminate the problem but don't go spending big bucks on them trying to fix ground loop issues, or ignore the solutions above because they don't seem high-tech or expensive enough.

The LM-1 vs. Home Theater

As mentioned The LM-1 is most at home on a bookcase, with the back panel wall within 6" to 12" of the rear wall. For the all-analog audiophile that wants a purist system this is perfect.

However, if you are more progressive, and have access to room-correction then you can use the LM-1 pretty much anywhere.  Of course, this usually means a home theater.

If you are going to use them with a sub you may wish to plug the ports though, as that will give you the most dynamic range and make for the easiest crossover matching.

Good listening!

The LM-1 vs. Stock

Unfortunately it seems my designs are so popular that in the US the LM-1 and its sibling the LM-1C have caused Madisound and Parts-Express to run out of stock. Fear not, Parts-Express expects more in February of 2017.

If you absolutely cannot wait, the Peerless 830860 will substitute. Same motor with a polypropelyne cone. Probably won't be as transparent, but I've not heard or measured it. Specs say it's going to be very close.

Lepai 2020A Micro Amplifier

I purchased a Lepai 2020A 20 watt micro amplifier to power the LM-1 speakers I recently put on my desktop.I used the micro plug for the PC sound and the RCA inputs are being fed from my Logitech Squeezebox Touch.

The Lepai 2020A is part of a family of amps that visually look identically but are based on different chipsets or have higher power ratings.  The "A" variant is based on a Yamaha chipset. Yamaha has been making professional amplifiers for decades, including very high efficiency models for studio and touring use.  The 2020A uses a 12V/3A supply.

Based on a variety of reading material, I doubt the 2020A does 20 watts/channel. It's probably closer to 7 when you limit power rating to 1% THD. Still, sounds very good.

For the price, it's really kind of ridiculously good.

The next model up, the 2020Ti takes up to a 24V/3A supply and gets closer to 14w/channel at 1%. Sort of.

The sound is smooth, very quiet, and not fatiguing at all. It has plenty of power for watching Hulu while in bed or playing games, as well as listening to Jazz FM 91 via the Internet.

The tone controls are subtle! They may not do it for you if you are looking for big changes, but if you like to gently adjust bass and treble they'll be great for you.

Some users report even better performance with beefier power supplies which I did not try. In my case small and hidden is key! Plus I never really felt the amp was too small. One thing though, the LM-1 speakers are VERY easy to drive. Your success with speakers that have lower impedance may not be as good.

The Lepai 2020A does not have any input switching. Both the RCA and mini jack inputs are live at all times. Sadly they are mixed through a resistor, not buffered. and then mixed together. This means that if two devices are operating, you'll get half the volume of either. Turn one off and the volume doubles.

If you don't intend to head bang, but are looking instead for a solid mini-amp to put under your desk, or in a boat or RV, I highly recommend the Lepai 2020A. 

The amp runs ice cold at all times. The one negative thing is this desire for Asian manufacturers to put blue LED's on every damn thing. In this case it's around the volume control. It's big, bright and blue, so you can forget about sleeping with it on nearby.

Stereophile Hatchets the Crystal Cable Arabesque Minissimo Diamond

This is kind of a follow up on my original article Stereophile - The Data Doesn't Lie and, to be honest, this is a tempest in a teacup as well. It's just one sentence that lit a fire under me.

First, I've never heard the Arabesque Minissimo, nor can I really morally justify the purchase of small home speakers that cost $20,000, whether from Crystal or Magico.

Even then I am nothing if not a hero for truth and justice so it was inevitable that the latest online review from Stereophile would completely piss me off. For the most part, it's a too crappy and short for a pair of speakers with such pedigree.

Stereophile Listening Tests 

The listening section is only one page, and very little devoted to actual music listening. Also, John Atkinson seems to write that he relies on test tones and his ears to tell "tonality" instead of oh, I don't know, music? I mean, your ears are for music, not test tones. If you have the gear, you don't need to be using test tones and aural guessing.

The biggest problem is that by JA's own admission, the speakers could not be placed optimally in his room. Instead of realizing there was significant "operator error" JA goes on to blame the speaker's and claims "treble tailoring" will only play nice with some music.

So what happened? Speaker/reviewer mismatch.

To have the maximum possible sensitivity and simplest crossover it seems that the Minissimo foregoes "baffle-step compensation" or BSC, and requires close wall placement. I have highlighted this region under the line in the chart at the left. This rising bass effect happens as the woofer's output goes from omni-directional to half space, and is related to the woofer and the baffle width. Notice it does not show up in his near field graphs...that's a whole other story of mess too long for this post. 

You might look at that and say "what a crappy speaker!" but you'd be wrong.  There's nothing wrong with designing a speaker for a specific environment, and we need more speakers that don't try to dominate your living room. This kind of design approach can yield exceptional results. Unlike almost all "high end" speakers, the Minissimo's were never designed to be a "one size fits all" model. They are ideal for a salon where discretely beautiful speakers could play wonderfully while leaving space for everything else. Listening to the Minissimo's in the middle of the room will sound like a mosquito orchestra, which seems to be just what happened.

JA rigidly reviewed them as middle-of-the-room stand mounts and blames the speaker when he should be blaming his closed mind and lack of understanding. With these measurements in hand, JA should have stopped or found a better place to listen to the Minissimos, or held of on publishing the review. Instead he attributed the weak response to the "tailored treble." His excuse that his furniture did not allow him to place the speakers correctly is the height of professional whinery. Either move them to the right place, or let some one who can and wants to them properly so. Don't compromise by writing a half-ass review with the speakers in a poor location.

The Bottom Line

The Crystal Cable Minissimo designers took truly refined components with a minimalist design aesthetic and made a high quality, beautiful looking pair that will stay out of your living space. Comparing the Minissimo to the slightly less expensive, but equally insensitive, Magico S1 Mk. II, the S1 requires much more floor space to sound it's best. To me, a small speaker that actually needs so much space is kind of a weird situation. On the other hand, the Minissimo is small (for a speaker with a 6" woofer) and perfectly happy to get cozy to the art on the wall.

With this in mind, if you are a music lover who wants top tier, beautiful speakers made from rare materials that don't take over your room I strongly encourage you to listen to them for yourself and pay no attention to the critic behind the curtain.

Ubuntu Mytek Brooklyn DSD Setup Guide

Update August, 2018:

These instructions are still valid, but I've gotten direct DSD working as well.  Please visit my updated post here:

http://pqltd.blogspot.com/2018/08/mytek-brooklyn-and-manhattan-dsd-with.html

I'm happy to report that the Mytek Brooklyn DAC is not only great sounding but it's a real treat to set up with Ubuntu. Why would you care if you are an OSX or Windows person? Because it's really inexpensive to set up a music server with Ubuntu.  From under $100 Raspberri Pi 3 to my own mini box which was under $500. In all cases, an Ubuntu server competes very well with $2,000 or more dedicated streamers. 

One major feature that is missing from a lot of "audiophile" solutions is Android app support.  This is something we will overcome quite easily.

Also, since this is really a driverless installation, these instructions will probably work for any other modern USB 2.0 DAC that claims to be "driverless" for OSX and Linux. The catch will be in setting the right device (SL_SOUNDCARD, below) but that part is easy.

There is a known limitation. Currently Squeezelite only supports DoP, which is horribly bandwidth inefficient. DoP is DSD over PCM. It is not the same thing as direct or native DSD play.

It's not my code, but I'm working on it.

Introducton to the Logitech Media Server

There are a lot of Lunix music players out there, I'm going to go with the easiest one that gives me bit-perfect playback: Logitech Media Server 7.9 and Squeezelite.  You need at least 7.9 to get DSD player support as it's a fairly recent feature. I think it was introduced in 7.8, but I never tried it.

Originally developed for the highly regarded streamers created by Squeezebox and bought by Logitech, LMS has pretty much transcended Logitech AND Squeezebox and now has a robust and active Open Source development community. It's easy to use, convenient and free, and has Android and iPhone apps available. On Android I use Squeezer but on iPhone you can try the original controller app or SlimLibrary.

The one thing that is missing from LMS is a music management feature. It doesn't tag, organize, or do much else but play music. On the other hand, it does this VERY well and without complications. For this you'll have to find another application of which there are legion.

Also, LMS has fantastic and simple Internet radio discovery and playback. It's a real marvel in this manner for which on Linux I have no better alternative, nor do I want one.

Preparation

First, you must have Xubuntu/Ubuntu 14 or greater set up. I am on 16.04 LTS, but 14.04 LTS was identical.  If you have another Linux distro, see the link to the details, below. I will say in the past I used to run Fedora and LMS was one of the main reasons I quit it, so if that's your distro and this is difficult, you have my sympathies. May the gods have mercy on your heathen soul.

Decide where your music and playlists are going to be. I prefer to put public media in /opt, so:

cd /opt
sudo mkdir Music Playlist log
sudo chown bob:bob *

Replace "bob" with your user account name.  Notice we are creating a log directory as well.  This is where any messages from the player (squeezelite) will be put.

Server Installation

First, install LMS from the public repo.  There are only nightly builds but seem pretty stable. You'll find detailed instructions here.

I used this script:

url="http://www.mysqueezebox.com/update/?version=7.9.0&revision=1&geturl=1&os=deb"
latest_lms=$(wget -q -O - "$url")
mkdir -p ~/sources
cd ~/sources
wget $latest_lms
lms_deb=${latest_lms##*/}
sudo dpkg -i $lms_deb

Mine is just a little different because I don't like cluttering up the root directory. This will look for the latest build, download to ~/source and install it.

After it's installed LMS should be running and available on port 9000. So open up firefox and click here:

http://localhost:9000

Follow instructions on the screen.  You'll need to setup your directories. Click on the lower right of the page, "Settings." and setup your music and playlist folders. The only tricky part left in LMS now is to enable the DSD player.  Click on the "Plugins" tab and enable "DSDPlayer."

Very cool part of this is that DSD files will be automatically transcoded if your player doesn't support DSD directly. I have a Squeezebox Touch that does not, so that gets transcoded to 88.2kHz PCM automatically for me.

Make sure your music and playlist folders are universally readable.

Player Installation

OK, that's it for the server.  Now we need to get your PC to talk to the DAC. This is even easier since the Ubuntu distribution includes squeezelite. Let's install it:

sudo apt-get install squeezelite

I've tried the distro version with Ubuntu 14 and 16, and both work great with the Mytek Brooklyn. DSD and HiRes PCM played without a hitch on both so don't feel put out if you don't have the latest version. It's not worth the trouble to get the nightly or the source and build.

Make sure your DAC is now plugged in and turned on.

You'll find the configuration file for Squeezelite in /etc/default/squeezelite.

Here is how I configured it:

# The name for the squeezelite player:

SL_NAME="Brooklyn_DAC"

# ALSA output device:
SL_SOUNDCARD=""hw:CARD=DAC,DEV=0"

# Squeezebox server (Logitech Media Server):
# Uncomment the next line if you want to point squeezelite at the IP address of
# your squeezebox server. This is usually unnecessary as the server is
# automatically discovered.
#SB_SERVER_IP="192.168.x.y"

# Additional options to pass to squeezelite:
SB_EXTRA_ARGS="-D -f /opt/log/squeezelite.log -d all=info"

# As above, but without the log file

# SB_EXTRA_ARGS="-D"

The key part is the SL_SOUNDCARD setting. If you aren't using the Brooklyn, I'm not sure this will be right.  I found it by using "squeezelite -l" and looking for the entry that said :

USB Audio - Direct hardware device without any conversions

There were other entries that worked, but I found they would convert whatever I played to 48/32, no matter the original.

Another important switch is -D which enables playing of DSD without transcoding to PCM.  Without this switch your DAC will always get PCM.

You'll see two versions of SB_EXTRA_ARGS. The first adds a log file, but really once you've got it all working it's not very useful. Once you are happy it's working comment it, and uncomment the last line, then restart.

One last command and you should be running:

sudo service squeezelite restart

Assuming all went well, you should see "Brooklyn_DAC" (set by SL_NAME, above) appear as an available player in LMS on the top right.  Select it and play some music! If you have music but it's not showing up you need to scan your library. Click on the bottom right "Settings" and in the "Basic" tab check the media folder is correct, then click "Rescan" and your files should get imported quickly.

If you need to free up your DAC for movies, or games use the player OFF switch in the LMS screen on the top right.

Now of course it is time to download some good sounding DSD music, for which I highly recommend Blue Coast Records.


Happy Listening!