David L. Bytheway Bio

July 12th, 2013

David Bytheway began work in the consumer audio business in the summer of 1973 when he became a technician at the House of Music and was factory trained by McIntosh, Bang & Olufsen, Nakamichi, Bose and Marantz. He holds a BSEE from the University of Utah where he graduated with honors, winning the IEEE Student Paper competition. He spent many years in broadcasting with 25 years designing broadcast television audio and video switching and audio processing hardware of all types. He does recording work, and custom audio design, has presented papers at SMPTE conventions and is published in several trade journals. He also holds patents for an audio measurement algorithm, large scale router design clocking and handling of synchronous and asynchronous audio signals in large size distribution systems.

Spring 2013 Pops Concert

April 18th, 2013

We will be performing on our Bells Bytheway Spring Pops Concert on Saturday, May 4th, 2013 at 7:00 PM. Please come and enjoy some light and different Bell Music

Click for PDF Version

-david BTW

Copyright © 2013 David L. Bytheway

Simulating the LX-521 ASP

February 12th, 2013

To help me learn about and consider the design trade-offs of the Linkwitz LX-521 ASP (the active filter based crossover) I have spend a bit of time creating a spice simulation in LtSpice4. This a considerable amount of time to create as there are a lot of parts in the design. I have also obtained models of the LM4562, the LME49990 and a few other op-amps just for fun. After removing my typos and running the simulation I have been able to re-create the response of the ASP as provided in the construction plans provided by Seigfried Linkwitz.

The circuit board is designed for thru-hole size components and as such the LME49990 op-amp, which is an SO8 surface mount package, will not fit but adapters can be built. The LME49990 is a newer design than the previous parts OPA2134 and LM4562 parts and at least published data shows lower noise and distortion for the LME49990.

Of course, all of this is a prelude to building the ASP and actually measuring the various stages and determining the optimum design. It just may be that there is little to be gained by changes or supposed improvements, but I intend to actually measure and listen to the thing and find out.

Copyright © 2013 David L. Bytheway

For the past year or two, as I have been building my North Creek speakers, I have also been following closely the Linkwitz Orion, which many consider is the best DIY speaker you can build. It is frighteningly expensive, however, and I thought it would always be out of my price range. As I read reviews and studied the design, it became evident that this speaker is something special, and the whole concept of open baffle presentation has slowly grown on me. Also my son recently build an open baffle system based upon the Hawthorne drivers, and I have had a chance to listen to them and learn more about the open baffle concept.

Just a few months ago (at the end of October 2012), Siegfried Linkwitz unveiled a new design called the LX521. These he considers "Monitors" and given my studio background what I prefer. I have been following closely the new design and the responses of those who have listened to and built them, some of which are just now finishing their builds, as the drivers were not available until after Dec 25th. I have been impressed so far with the responses, and given that the cost of the drivers is quite a bit less than the Orions, and also that I have the capability to build the amplifiers DIY I have been seriously considering a set.

Last week I purchased a set of LX521 construction plans and the ASP circuit boards. I am now working through what it will take to build and measure a set of them. I am hoping to chronicle the build process in this blog. A kit of drivers are available in the US from Madisound.

I am still finalizing the crossovers on my North Creek Kitty Kats, and Thunder subs, and will also update that work on this blog. They are almost in a state that I am comfortable using them to do some real audio production mixing and mastering. I am currently using them with a DCX 24/96 crossover that I modified to improve the analog performance of the DACs. While I am not totally happy with the sound of the DCX, where I suspect I am hearing artifacts from the sample-rate-converters as well as the less than state-of-the-art DACs themselves, I am learning what the analog crossovers I hope to build need to be.

Copyright © 2013 David L. Bytheway

A good book on Audio Design!

February 7th, 2013

Recently I purchased a copy of The Design of Active Crossovers by Douglas Self Also available at Amazon.com Here. While some of the information in this book can be found elsewhere, I am most impressed that Doug Self has presented measurements of some of the most recent audio op-amps, data that is hard to find anywhere else. This includes the venerable NE5532, LM4562, AD797, LME49990 and several others. Some of this data I have measured myself, but Doug has done a good job of exposing the pluses and minuses of these parts, especially as compared to some of the parts we have all been using for decades.

Copyright © 2013 David L. Bytheway

We will be performing on our Bells Bytheway Christmas Devotional on Sunday, December 16, 2012 at 7:00 PM. Please come and enjoy as we Ring in Christmas!!!

Click for PDF Version

Please come and join us!

-david BTW

Copyright © 2012 David L. Bytheway

We will be performing on our Bells Bytheway Spring Pops Concert on May 31, 2012.

Click for PDF Version

Please come and join us!

-david BTW

Copyright © 2012 David L. Bytheway

A Good Audio Blog

January 6th, 2012

Recently my son sent me a link to an audio blog that I find very good. This guy has covered the ground very much like I have wanted to do but not had the time to do so. Check it out!


Copyright © 2012 David L. Bytheway

One of the other things that we do at dlb Research is music. About 18 months ago, we began the organization of a family based English Handbell choir. On December 17th, we will be holding our Christmas Concert for 2011.

Click for PDF Version

Please come and join us!

-david BTW

Copyright © 2011 David L. Bytheway

On September 23rd, an article was posted on the LDS.org news room called "From Dirt Floors to Digital Delivery: 50 Years of General Conference Interpretation Technology"

We very much appreciate the nice explanation of our work!

Copyright © 2011 David L. Bytheway

Just received a Pure i20 iPhone4 doc that has digital outputs, both Toslink and Coaxial. The goal of course is to take the digital output of my iPhone 4 and feed it to my Benchmark DAC-1. At least in part, this is intended to be my headphone listening system at work. As soon as time permits we will also review and test the i20 and find out what it can really do.

So far, it sounds pretty good! The only surprise is that the device seems to have a volume control in the signal path. It appears to affect both the analog and digital outputs of the doc. A volume control screen comes up on the iPhone4, but no bar graphs is shown so it is impossible to know where it is set except by listening. In any event the hope is that at full volume we are getting bit-accurate SPDIF output.

Check back for more soon!

Copyright © 2011 David L. Bytheway

Today on the way to work, my 2002 Prius hit the 88,888 mile mark. While this is no large amount of miles compared to some, this is the first time the display in the dash shows all "8's" which is a bit unusual except for test mode.

My Prius has been a real gem, and I would buy another in a minute. I prefer the 1st generation cabin and view with larger windows and greater visibility. The 2nd and 3rd generation Prius models some how feel a bit more cramped and boxed in in the drivers seat. I would love to have the newer technology, with a 500 volt instead of a 250 volt system, electric A/C instead of gas-engine powered, and the Thermos bottle for the coolant which keeps the engine warm on those cold winter mornings.

The car is a perfect commuter car for me. It performs well for the 8-10 mile trip I make every day. Long road trips at full speed (75 mph) and fully loaded 3-4 adults, prove it to be less than perfect. The newer ones are probably better. I drove my 8.5 year old Prius to Wanship, UT yesterday, and maintained 70 mph all the way up Parley's canyon with no problem (so much for hybrids being underpowered). Got only about 40 mph during that climb, but the descent used no gasoline engine power at all and topped off the battery, with indicated 50+ mph. Round trip mpg was 48.

The car is much quieter and smoother than others its size and quite comfortable to drive. I only hope that battery holds out a lot longer as it is now out of its 8 year full replacement warranty. With the exception of a bit more tire wear due to the heavier front end, the car has been a maintenance dream with absolutely no problems at all during the life of the car.

The most common question I get now days is, "Have you replaced the battery?" The answer is no, as there is nothing wrong with the one I have. Lots of talk in the press about that, but my service technician, Bruce Belliston at Mark Miller Toyota, tells me they simply aren't replacing batteries due to just age, only crashes and rebuilds. Interesting huh?

Click for Hi Res Version

Copyright © 2011 David L. Bytheway

One of the other things that we do at dlb Research is music. About 18 months ago, we began the organization of a family based English Handbell choir. On May 14th, we will be holding our first Spring Concert for 2011.

Click for PDF Version

Please come and join us!

-david BTW

Copyright © 2011 David L. Bytheway

As the LDS General Conference once again approaches, we see references to the translation facilities in the press. We thought we would post some additional information for those who may be interested in more about the facility.

On March 25 an article was posted on lds.org called "Behind the Scenes At General Conference"

Part way down the page there is a video showing conference preparations in the Conference Center. At the 1:42 point our ATM-2000 Automatic Translation Mixers are shown in automatic ID mode, sending a pre-recorded ID message for each language enabling operators both inside and outside the Conference Center to check the language feeds.

An additional set of photos is also provided showing conference behind the scenes here.

We have downloaded Images #5 and #6 from that story which show our equipment in use.


This first image shows two interpreters wearing a headset/microphone combination similar to those worn by sportscasters. On the table in between the two interpreters one of our booth modules can be seen where the interpreters can turn on their individual microphones, adjust their headphone volume, and also contact the main control room.

ATM-2000 MIxer

This second image from the lds.org website shows our ATM-2000 Automatic Translation Mixers in operation in the Translation Control Room. In reality the green displays showing the language name does not have the gaps in the letters which is an artifact of the digital camera used.

Conference Center Click for Hi Res Version

This photo shows the equipment rack holding 48 ATM-2000 mixers in the translation control room. Some of the units are used to service the 58 interpreter's booths that are present in the Conference Center. Each ATM-2000 mixer handles 2 languages. The balance of the ATM-2000 units support the in-country interpreters. The original program is sent over high speed network connections to the individual countries where native speakers interpret the program which is then sent back and inserted into the standard set of languages by ATM-2000 units. The output of these devices is the sent to headphones in the Conference Center, Recording devices, and to the master control room where it is then fed to the Satellites and internet distribution by another dlb Research device, the OAC-2000

Monitoring Station Click for Hi Res Version

This photo is the translation control room monitoring station. This Windows based control surface allows the operator to monitor all 96 languages, see at a glance the status of microphones and signal levels, as well as use a talkback system to speak to individual interpreters or all at once. Before dlb Research designed the first ATM mixers in 1991, individual operators were needed to manually adjust and check each language individually. dlb Research was formed as a business entity to design the first generation ATM-1000 mixers which were used in the Salt Lake Tabernacle from 1991 until 2002, when they were replaced with the ATM-2000 in the new Conference Center Building. The ATM-1000 mixers are now in use in the MTC in Provo, Utah.

The ATM-2000 mixers automatically adjust the microphone volume of each interpreter, fade the live program up and down for the musical numbers, and provide intercom to each interpreter's booth. They automate the creating of each language feed eliminating the need for manual microphone adjustments. With this monitor station one operator can easily handle a full broadcast replacing the dozens of operators that were needed prior to our work.

Conference Center Master Control

As part of the Conference Center broadcast facility, a master control room is used to control and monitor all the broadcast feeds to the Church Satellite system, broadcast facilities, other LDS Church campus buildings, and the internet. In 1999 dlb Research was also commissioned to design and build devices known as the OAC-200, which stands for On-Air-Controller. The purpose of these devices is to switch and condition the language feeds to the Church Satellite system and the internet. These new devices were designed at the same time as the ATM mixers, and use similar technology and software, but perform a very different purpose.

200 Audio Channels of audio processing for Master Control Room Click for Hi Res Version

This photo shows the four Satellite banks installed in equipment racks. There are 51 OACs installed in the Conference Center arranged in five banks, each handling 4 language feeds. The five banks of OACs are as follows:the Domestic Satellite, the European Satellite, the Pacific Rim Satellite, the Latin America Satellite, and the Internet. The Internet bank of OACs are located elsewhere. Mounted underneath the OACs are satellite encoders that combine the video and audio channels for each satellite transponder.

 Master Control Audio Monitoring Station Click for Hi Res Version

This photo shows the windows based central monitoring software workstation position. This is Windows based PC application that allows the operator to see the status of all 204 audio channels, as well as control and switch any language source as a group or independently. Switching is done by a single operator using the computers screens. Each monitor in the workstation corresponds to the banks of OACs mentioned above, with the Internet bank on the far right.

Simply clicking on the name of a language allows the operator to automatically hear the language feed or other sources for each output channel. The OACs also provide pre-recorded ID messages that are used for setup of the language feeds in each individual down-link location.

The ATMs were installed in October of 2002, and the OACs the next General Conference of April 2003.

Copyright © 2011 David L. Bytheway

Today we are posting a two set of sampless from a recording of the Sally Bytheway Chorale Christmas 2007 & 2008.

Sally Bytheway Chorale Christmas 2007 Sampler

This recording was created using Nuendo 4.2 with an RME FIreface 800 interface at 96 kHz sample-rate and 32 bit floating point sampling. This recording was done in the Waterford School Concert Hall in Sandy Utah. The microphones used were AKG-414 EB P48s, Modified Transformerless AKG-414EB P48's, Shoeps Omnis, etc.

Sally Bytheway Chorale Christmas 2008 Sampler

This recording was created using Nuendo 4.2 with an RME FIreface 800 interface at 48 kHz sample-rate and 32 bit floating point sampling. This recording was made in the Summit Academy Jr. High School in Draper Utah. The microphones used were AKG-414 EB P48s, Modified Transformerless AKG-414EB P48's, Shoeps Omnis, etc.