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Products  Kearney Barton  Articles  DIY Stuff  Phantom Powering  PZM Stuff  Attenuator Pads  Theremin 
Sound Systems  Random Stuff  Ampex  MS Recording  Radar Sites  Bad Ideas  Lactose Intolerance  Laws for Audio Engineers 


Click on pictures for more information.

Universal Attenuator Networks

Universal Attenuator Pad 

Need to build a fixed attenuator pad for a project or installation? This handy circuit board can be configured for commonly used balanced or unbalanced configurations. Kit or Assembled, as you like it.

image linked to ubw

Universal Boom Weight

Back in Stock!

Does your Beyer/AKG/KM boom stand seem like it needs some Viagra? An add-on 2.6lb counterweight for these boom stands helps balance the boom arm, especially when using heavy microphones like the RE20 or U87.

image linked to pzm

An elegant solution to improving the performance of the RS PZM microphone. This board replaces the battery box and its crappy little transformer and it allows the microphone to be P48 phantom powered. Increased output level, and improved LF response.

Articles and Reviews

These are articles that I've written over the last 30+ years. Some have been published in magazines, some are excerpted from manuals that I've written, some are the result of email flurries, some were created as a result of need, and some just popped out.

Using Cine stands for Microphones 

RoHS — How the Rules of Hazardous Substances, an EU directive, affect you and me out here in the colonies.

What makes headphones loud? Find out here.

How to connect loudspeakers totalling 2-ohms to an amplifier that can only drive a 4-ohm load.

Neuman TLM-103 product review.

AKG Solidtube microphone product review.

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Passive Preamp A short article telling how to build your own "passive" preamp (which in reality is a volume control pot mounted in a box).

Radio Shack PZM microphone modification.

Power Supplies A short article about using 3-terminal regulator ICs to build small regulated power supplies. This is a companion piece to building a 48V supply for phantom powering microphones.

Design your own attenuator pads.

stdval A program for finding the nearest standard value of a resistor or capacitor.

AB Switch for Microphones 

Useful Information

Ampex Transistor Cross-Reference

Phantom Powering for condenser microphones.

T-Power. How it works, why it works, why it's not compatible with other microphones.

Sound System and Other Stuff

M-S Recording Resource.

Miscellaneous Stuff of various sorts.

Impdance Balanced Output Circuits. A rethinking of the problem of balanced outputs on TRS jacks. A better way.

Laws for Audio Engineers.

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Phantom Powering for Condenser Microphones

Sometime around 1970, Neumann introduced the Fet-80 series of condenser microphones that were solid state and remotely powered via the microphone cable. In typical German fashion, they decreed that these microphones were the be-all and end-all to microphones of any sort, and they promptly discontinued all of their vacuum tube microphones. Of course, nearly 40 years later, we know different, with the venerable U47 now selling for the price of a car. Here then, are a series of articles, that explain this important concept and how it works. BTW, Neumann "gave" the idea to the industry; apparently they trademarked the term, phantom power but gave the concept and the term to our industry. There! Something for free from Neumann!

Click Here. 

Radio Shack PZM Microphone modification

pzm/pix/img_0987_.jpg The Radio Shack PZM microphone is a low-cost microphone capable of fairly high performance. Many modifications have been published for this microphone; the simplest simply replaces the battery with two 6-volt smoke alarm batteries.

You can learn more about pressure zone and boundary microphones here.  

The RS microphone, no longer available new, is fair game for modification. Its puny unshielded output transformer is a magnet for hum and a source of sonic pollution. Uneeda Audio makes a kit designed to rid the microphone of these parts and make it work in a P48 environment.
The PZM Page 
The RS PZM Modification Kit 
Price List 
Assembly Guide (current rev 2800kb pdf) 
the RoHS Directive (21k pdf) 
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RoHS and A Plea For Conservation

In 2006, the member states of the EU placed into action a set of rules designed to keep certain hazardous substances out of the waste stream. Concurrently, they also placed rules about WEEE, Wast Electronic and Electrical Equipment and its disposal. The body of this legislation has come to be known as RoHS: Rules of Hazardous Suhstances.

The Directive  and WEEE have a far reaching effect: any manufacturer who hopes to sell their product within the EU must conform to RoHS. Without so much as a filibuster, they have more or less forced us to comply. This is actually good, because Congress is so completely hamstrung by special interests that this would never have made it out of committee within our lifetimes.

Cynical, me? NOT! Realistic? YES!

Here then, is my plea  for some moderation in our love affair with cheap goods, abandonment of the bean counter's mantra about repair cost, and a more common sense approach to keeping old gear out of the landfill.

Don't toss that old thing! Repair it, FreeCycle it, E-Cycle it, or Re-Cycle it!


The theremin continues to interest people year after year. Here is a reprint of Lou Garner's DIY project that appeared in Popular Electronics over 40 years ago(!).

Arthur Harrison's  way-kewl Theremin pages. DIY Here zzounds -- More Theremin info 

Sound System and Other Random Stuff

M-S Recording Resource

This is a collection of files describing some of the hardware used for M-S recording. There is a short discussion of the theory, several decoder circuits, and a bibliography.

  • Bibliography - Revised 2006
     An overview and bibliography of articles and papers about MS-Stereo technique along with brief descriptions of the three MS decoder circuits.
  • Circuit 1 Simple decoder #1, viewable gif.
  • Circuit 1 (pdf) Simple decoder #1, PDF format.
    This is a simple decoder circuit using two opamps to perform the sum and difference operation. Good for conceptual understanding.
  • Circuit 2 Simple decoder #2, viewable gif.
  • Circuit 2 (pdf) Simple decoder #2, PDF format
    This is a slightly more complex circuit using four opamps to perform the sum and difference operation. This circuit does not use a diff-amp to perform the sum and difference operation.
  • Circuit 3 Complex Decoder, viewable gif.
  • Circuit 3 (pdf) Complex Decoder, PDF format
    This circuit has a stereo spread control, which varies the output's separation from mono to normal stereo to super-stereo.
  • The classic Neumann passive MS-matrix circuit
     A blast from the past, this circuit shows how it used to be done.
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Radar Sites I Have Known

I spent four years in the US Air Force, during the time that young men were being sent to VietNam to die in the name of democracy. That's a statement of fact, at least how that fact was sold to the American People. For me, joining the Air Force was my countermove to being drafted and a becoming an unwilling member of the Army, which would have nearly guaranteed me a free trip to VietNam.

Instead, as a voluntary Air Force enlistee, I got to spend the majority of my enlistment stateside, with my last major tour being in South Korea, at Osan Air Base. My job title (AFSC) was 30454, Ground Radio Communications Equipment Repairman. It was nearly all tube gear, mostly UHF AM, 225-400mHz, about 100W output. There was some prehistoric digital gear, all discrete, with germanium transistors everywhere. You had to go to a special school to learn about that gear, and I believe that one of the selection criteria was how well they (the ruling class) believed you were likely to stick around after four years. I guess I could have played their game to try to go to the school, which meant going TDY (temporary duty) to McChord for several weeks. But I didn't, so I never got to go.

I got my induction notice telling me to appear for induction into the armed forces of the United States. This would have been late summer 1967. It was clear to me that letting the Army have me would be a guaranteed tour of Vietnam. I had from then until early November to find an alternative, which could have been leaving the country, disappearing, or joining another branch of the military. I chose the latter. In my last year, I got to go TDY to an army outpost in the area just south of the Korean DMZ. I got confirmation that I'd made the right choice 3 years ago.

A helpful Air Force recruiter led me thru the requisite testing, and I scored highest in electronics (DOH!). I didn't understand it at the time, but your entry to a given school was based on a class beginning on some date, and then your enlistment would be that date with basic training time backed out of it. With the window that I had, there were no electronics schools openings. The alternative was some other job, in a different career field. There were administrative openings (clerks). Since I knew how to type, I said yes, let's do that! Since I had my induction notice, there really wasn't much choice in the matter.

I was still wondering how I could get things changed from being a clerk to being an electronics tech. The recruiter said to take my license with me and wave it around and maybe someone would notice. In retrospect, that was a long shot, but someone did take notice. A few weeks later, I was summoned to appear to take a test. This was apparently (unbeknownst to me) the final exam for the 304x4 tech school. At the time, I thought it would just get me into one of their electronics schools. Ha! I must have passed, because a few weeks after that, I received orders to report for duty in Charleston WV. No tech school. Instant job. DDA (direct duty assignment) So much for the know-it-all in my flight (Airman Jones) who said, "They never give DDAs in electronics." I don't recall getting a chance to rub it in. Little did I know what I was missing out on by not going to tech school. 40 weeks of merde de poulet with lots of military stuff mixed in, marching, inspections, power-hungry ropes (airmen put in positions of authority over you), etc. Oh and let's not forget Biloxi Mississippi, deep down in the south, in the late 1960s, during the Vietnam war. Remember that all Asians look alike. Chinese, Japanese, Vietnamese, Singaporean, etc. They all look the same. Not so good in the deep south!

The gear that my AFSC qualified me to work on was in use at Radar Sites, and there was a network of them all across the United States, and a few other places as well (like Vietnam). Each site had search and height radars and radio gear to communicate with military aircraft in their sector. The purpose was to look for bad guys (Russians) flying over the horizon to do bad things to the capitalistic Americans. I don't know if we fed radar coverage to the FAA for commercial aircraft but we definitely used it for national defense purposes. The time I spent at three different radar sites in the continental US was great time, away from the pomp and circumstance of the big bases, with their collection of military brass and the merde de poulet associated with them. At the radar sites, it was mostly just do your job. Inspections were infrequent, as was the time doing seemingly meaningless duty, like painting rocks. The mess halls were run by a military cook, but staffed by civilians, so there was no KP. Really, it was not a bad gig. In the final analysis, I lucked out!

I spent my stateside time at three different radar sites (which are now all closed/deactivated):

  • 783rd Radar Squadron, Charleston, WV
  • 776th Radar Squadron, Point Arena, CA
  • 757th Radar Squadron, Birch Bay, WA

I haven't had the opportunity (or the desire) to return to Charleston. It was closed within six months of my arrival. Point Arena is on the Northern California coast, on Hwy 1, and that is without a doubt, my favorite stretch of road in the world. I've been up and down that road many, many times, and I've stopped in on occasion to see what's left of the radar site. I last visited the site in October 2008. It's a remote location (150mi N of San Francisco), so if you're stationed there, your off-duty times are spent on site, or in one of the neighboring towns. You need a weekend to get there from San Francisco, because it's about 3.5 hours one-way to get there. The site is decaying, and some of the buildings are falling in on themselves. It's the gravity of the situation, y'know?

n.b. If you just drive up there, you'll get as far as the main gate. If you want to look inside, that requires an appointment with the caretaker. 2020 note: I think the caretaker who was there in 2008 has retired now. He was getting on in 2008, and it's 12 years since. There might not be a caretaker now, and the neighbors who are into agriculture in varying forms, are not particularly sociable to strangers. If you should venture up there, I'd not just go wander around exploring, and I'd definitely not recommend knocking on doors, especially if you look establishment.

The site at Birch Bay, WA was a mile from the beach. A far cry from the usual location for a radar site. 60 minutes to Vancouver Canada, 20 minutes to Bellingham WA. A real peach. If you had to go to a radar site, this was the one. It turns out that for me at least, this was a parking spot until an overseas billet opened up. Instead of a year at Blaine, I got about 9 months, and then I got orders for Korea. If you do the math, I was supposed to get out around Halloween 1971, and my orders arrived about the end of July, with me to appear at my new duty assignment somewhere in early September. The tour there was a year, and I would separate (be discharged) when I returned home in early September. The 4-weeks or so between then and the end of October would be overlooked as being for "the convenience of the government." I didn't argue. It's a Whatcom County park now.

757th Radar Squadron Reunion

17 Sep 2016 at Bay Horizon Park (formerly the 757th Radron).
More details at 757th Radar Squadron page 

There is also a Facebook page or two.

In May 2009, I was able to return to Birch Bay and see what is left of the site. This site is far less remote, being about 30 minutes north of Bellingham and 60 minutes south of Vancouver BC. The DOD gave the site to Whatcom County, and they in turn leased part of it to the Lions Club, who turned it into a camp for people with special needs, Camp Horizon. I've been back many times since. The old buildings keep disappearing; only the 24-tower remains of the radar towers. The barracks building are still there, because they're used by the Lion's club. The county uses the gym for public recreation programs. The Lion's Club uses the orderly room for an office and meeting space. It's a wonderful way for the old radar site to live on. Since it's now a park, you can just drive on up and in. The Gym is usually inhabited; you should stop in and say hi. Veterans who served there are always welcome.

A group of veterans who were stationed there have a reunion roughly every other even-numbered year. 2020 got cancelled because of Covid-19. We haven't decided to try in 2021 or to wait for 2022. The 757th page will be updated to reflect this.

These links take you to sites created for each of these former radar sites. I don't know when I'll get back to Charleston. Probably never.
783rd Radar Squadron. Not yet. Highly unlikely.  776th Radar Squadron. Online. Pictures added Nov 2009.  757th Radar Squadron. Online.  Return to top 

Bad Idea Dept.

Have you ever had the idea of making adaptors to convert a common-ordinary extension cord (with NEMA 5-15 connectors) into a speaker cable? Did you shelve the idea quickly after the briefest reconsideration? I hope you did!

These guys got the same idea and actually tried to take it to market, but I guess they never thought twice about what they had really done. These are two separate instances of the same idea, almost 10 years apart.

Click on the pictures!
image linked to images/jcon.jpg image linked to bad_idea/pe1.jpg image linked to bad_idea/se1.jpg image linked to bad_idea/speakerlinx.jpg

Don't even think about trying this. Do you know the expected lifespan of a 8-ohm loudspeaker that has been connected to 120VAC? Yeah, I know about Cerwin-Vega (who used to do this); that's a special case.

These are real data sheets. At least the developer/inventor(?) of these products thought so. I picked the J-Con one up at the 1996 AES convention. A friend picked up the SpeakerLinx one at the 2005 NAMM Show. The product pictures were taken at that NAMM Show.

Talk about a bad puppy that keeps coming home!
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Privacy Notice

I respect your privacy. That's it, period. Nothing more, nothing less. It doesn't get much simpler.

This site does not use cookies or any other fancy/wierd stuff to harvest, collect, or otherwise obtain any information about you, your computer, your ISP, your wife, kids, or pets. People or companies who engage in this practice are some of the most reprehensible slime to inhabit our planet. It's sad that the Internet is rife with this sort of behavior.

If you communicate with me, I'll likely save the email, but that's the extent of it. I don't compile mailing lists from this information. I don't send spam. The information goes nowhere.

I find it a sad commentary on the business world that I must make this disclosure. I consider our right to privacy to be sacrosanct. Obviously others do not.

This is the best that I can do: I respect your privacy. Please respect mine.

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Copyright Notice(s)

© 2004-2023 by Rick Chinn. All rights reserved.

The materials on this page and pages linked to it (including any drawings or photographs) are copyrighted and I am the copyright holder unless otherwise noted. I reserve all rights to this material. If you want users on your site to access this material from your website, please ask for permission to link to this site.

The article on the Theremin appeared in Popular Electronics magazine in 1967 and they or their successors hold the copyright on it.

The article, Equalizing for Spectral Character appeared in an old (~1964) Langevin Recording Equipment catalog. They, or their successors, are still welcome to the copyright for the article.

Christopher Hicks holds the copyright for the PZM modification page bearing his name.

The acronym "PZM" is a trademark owned by Crown International, a Harman International company, now part of Samsung. Its appearance here in no way alters their ownership of same. Radio Shack is a trademark of General Wireless. They were formerly a trademark of Tandy Corporation. Today (2021) they are owned by Retail Ecommerce Ventures. They own the trademark; why would I even think I wanted to own it?

Other trademarks used are owned by their respective owners.

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Last modified 09/04/2023 24:38:56.