How To Use a Stereo Audio Power Meter on More Than One Pair of Speakers.

November 10, 2018

#287

Gentle reader,

My last post was about the various kinds and types of meters one can employ in their stereo system. It can be read here:

Stereo VU Meters dB Meters Audio Power Meters Watt Meters See Your Music!

My closing remark was along the lines of, "Now which pair of speakers to use it with...."

It occurred to me there was a solution to a question I had not asked myself: "Why not use it on both sets of speakers or even more?" The answer, while not "Genius!" was to me, a great idea.

The epiphany I had was this, "Why not use my speaker switch, but in reverse. That way, I can switch the meter to the speakers I am listening to." Brilliant!

I prefer binding/banana speaker terminals over the cheap, minimal contact spring terminals. After much searching I found this economical speaker switch years ago.

LEGEND LE412 is what they called it. I can find NO information on them now. Not even a single picture. How is it I am the ONLY person to buy one of these? 

I did a number of modifications on it, including adding those weights to the front of it. The cables I use are heavy and it doing "wheelies" was a no go. I also used BluTak reusable adhesive (available under many brand names) to secure the switch.

Here is what the back of it looks like now, after my modifications.

The company made it with the three-way terminals having the industry standard of 3/4" apart so that double banana plugs can be employed. BUT, they did not arrange them as you see them here. Nope. As you can see it is marked as having the Right channel on the top and the Left on the bottom.

I took it all apart and rearranged all the terminals and internal wiring so that they are as seen above. The terminals on the left are originals. Sadly, they were not sturdy. I had to replace the eight on the right, since the metal inside was too thin. The ones I installed are more robust, but were too thick to be placed so closely together. Thus the "rounding" I had to do to each plastic nut to make them fit. Attractive, it is not. Effective, it is.

Below shows the wiring solution I came up with. It may not be pretty, but from where I sit, all I see are the faces of the meter and switch-box. And it works.

In the previous article, (linked at the top of the page) I introduced you to various audio power meters. All but one were made and sold by Radio Shack. This one is new to me and extremely well made. Albeit with spring terminals. It is a   Realistic AMP-300. Of the four series they made, the finest construction.

Below is the first step for mine, since I needed banana plugs.

I have had these double banana plugs for decades. They are ugly, but well made, right here in the USA. No 24 karat gold plating, not red or black. (See the raised bar on the sides facing each other? I chose that side for all negative wires.)  These plugs were employed with signal cables. I rescued them and the cables from the dumpster. Unlike the ones available today, they still hold strongly, the bananas have never lost their spring tension. I had exactly SIX of them, five purple, one brown. $0.

Also in the previous article, I showed you the colorful red, white, blue and black cable (left, above) I made by twisting them together. For this, I put yellow shrink tubing on each to mark where they will go. I added large ring terminals trimmed to slide onto a binding post terminal, or four:

Obviously, I needed a second set and chose two shades of green for left and right, positive, along with dark blue and black for the negative wires.

I HAD written a long explanation on how one sets up and employs double banana plugs like these. But decided it was unnecessary to the article. 

Please pay attention to polarity ( + and -) for each set of wires. Otherwise you may inadvertently cause a problem. And, no, one does not have to twist them.

As I have a bunch of objects for cleaning records next to my turntable, it made sense to stack the two units.

This photo shows how I used the wires bare, stripped about 5/8" long, to attach to these are two-way binding/banana terminals, Sadly, my eight ring/spade terminals were wasted. 

I needed to mark the speaker cables (Monster Cable Z-Series) as to which terminals they plugged into on my amp. You can see my simple solution above.

Yes, that IS a Swiffer 360. It is very effective for cleaning records that are just dusty.

Here is how they look from the front. The APM-300 has lots of red LEDs to show the music in action.

This meter can be set to read 0-2.0 watts or 2-200 watts. It can also show RMS (moving constantly) or PEAK which means it will display the highest (loudest) moment of the music which would show whether the amp had been driven to "clipping". A term that means the music was distorted.

The bottom speakers are Klipsch KG-4s which my digital meter shows are five Ohms. 
The top speakers (Advent Baby Advent II) are employed along with a pair of Dynaco A25XL speakers through the QD-2  device shown below. Together, they read 4.5 Ohms. So, I switched the meter to the 4 Ohm setting.

The QD-2 is an update on the original 1970's Dynaco Dynaquad device. It reveals ambiance and echoes which makes one feel as though they are sitting listening in the recording studio or concert hall. Works great and I love it. Previous QD models have spring terminals.

I have been fortunate to find and buy the Dynaco ST-200 power amplifier, QD-2 and PAT-6 Tuner-Preamplifier, all from the late 1990's. When Panor (originally Pan Orient) Company started making new products with the Dynaco brand name.

If you are interested in the products they made, good luck finding anything. I scoured the Internet and wrote about what I had found here:
Dynaco Given a Second Life. Pan Orient Company: Panor for Short. A Photographic History PART ONE.
And, here:
Dynaco: Panor for Short. History PART TWO Plus ODD Dynaco Speakers.  
And for more on the QD series:
Quadraphonic Adventures: 1990's Dynaco QD-2 Passive Surround Sound Device Tested.
 
So, there you have it, a way to use one set of power meters with countless pairs of speakers. As many as your speaker switch will handle. 

I thank you for taking the time to read my words and view my photos. Your kind words make all the effort worthwhile.

Scott
November 10, 2018
#287

Stereo VU Meters dB Meters Audio Power Meters Watt Meters See Your Music!

November 8, 2018

#287

Gentle reader,

Who doesn't love big meters on their amp? No one! Come to think of it, of all the integrated amps and separate power amplifiers I have owned, only a small handful had any kind of meters. The most obvious was this Mitsubishi unit. But, there's a catch.....

This is not an amplifier. It is a pair of meters that can be physically mated to one of Mitsubishi's Dual-Audio power amplifiers. 

As I recall, one ran the RCA interconnects from the preamp to the inputs on this meter. Then from the meter's output RCA terminals, another pair of interconnects to the inputs on the power amplifier. Here's a series of photos showing how they "mated".

All of these large and heavy "DA" components had carry handles on them. 

This view shows how these handles are inset compared to the ones on the front of the meters and the rest of the series.

See the notched in sides of the meters, above? The handles on the amp slide right in those places.

Right now, it's just foreplay. But keep watching.

Oh, yeah! Drove it home. If you are fortunate enough to get some of these Mitsubishi "DA" components, do so. They are awesome. I should never have sold them. But be prepared they are very heavy. I mean, just look, TWO transformers, because they are Dual Mono. Two separate mono power amplifiers in one chassis. They came in several outputs, this one was 150 WPC.

So, what is one to do if they cannot afford a nice amp with those big VU or watt meters?

Radio Shack had your answers. Actually four answers. It all started with a little plastic box with two meters in the face of it. Like this:

Totally passive, no power needed. Just hook them to your amp or receiver's speaker terminals. 
I had two of these. This was the second one. The first, I removed the meters and installed them, along with a new faceplate, in my Dynaco Stereo (ST for short) 150 power amp. Dynaco meters were an expensive option on the 150 and 400 power amps. 

This one, I couldn't leave alone either. I dissected it and attached it's face to this black plastic box (also from Radio Shack) and added six pairs of 3-way binding/banana terminals and a DTDP switch. Double Throw, Double Pole is what that stands for. Could be written DPDT, also.

If I'd owned a label maker, it would have labels as to what plugged where on the back. But I didn't. 

So, I transformed a humble Realistic APM-100 (Audio Power Meter, 100 watts) with a speaker switch. Genius!

The APM-100 was so successful that Radio Shack improved on it and made the APM-200.

It is larger than the original, has power inside to light the meters and to power the FIVE red LEDs that also flash on and off with the dancing needles of the meters. Plus, the meters go to 200 watts! What's even cooler, is they can be switched to go from zero to 2 watts, or 2 to 200 watts. Genius!

Go ahead and check on eBay after reading this article to see what this family, especially the APM-200s, sell for. 

The one above, was one of FIVE I bought as a lot for $20.00! Had I a crystal ball to gaze into to the future to see what things would sell for USED years later, I would have hoarded all the stuff I have bought and could retire when I sold it all. But I did not. Nor does anyone else.

Radio Shack went high tech and dropped the meters opting for just LEDs with more than the number in the APM-200s. This is the APM-500.

About the same width of the APM-200, but much lower. No switch for 4 Ohm or 8 Ohm, on this model.
Well, like so often happens, I sold it, the novelty of "Das blinken litez" had worn off. 

See? The whole thing, except the back, is plastic! And made in China, not Korea like the 200.

I had an ongoing search on eBay for an APM-200. But refused to pay those prices. I decided to change my search by dropping the "200" and to my surprise there was an APM-300. (There never was a 400 for some reason.)

The entire APM-300 unit is metal. The LEDs are behind a window. It has a switch to choose between RMS or PEAK. Root Mean Square, is how amplifier output is measured. Peak means the LEDs will stay lit to show you the highest wattage level reached.To show if any clipping might have occurred by too high a volume level.
Since I have no 500 to compare it to, take my word for it. The 300 is quite a bit larger, better made and heavier than the 500.

For an idea, scroll up and look at the picture of the back of the 500 and then back down to the photo below. Same terminals for scale. See? ".....bigger, stronger. We have the technology!"

This particular one is in exceptional condition. When I saw how nice it looked in the pictures, I didn't hesitate to buy it. When Jerry the mail carrier handed me the box, I was surprised how heavy it was. Remembering how small and light the 500 was, I was intrigued.

It even came with the factory manual which has a schematic! I photographed it for those that like such things.

I made up this cable of four wires. Red and black (red is right) and blue and white for the left channel. I twisted them, because I can.

The manual shows the meter in series with the amplifier, but that is not necessary and it is not equipped with two sets of terminals, or larger, better ones to accomplish that.

I needed large ring terminals, spades lugs would be better, but I had no spades large enough. I cut out a section on each. Below, the other ends are stripped to insert into the spring (Grrrr) terminals on the meter.

Like such, above. 
I hooked the ring ends to one set of terminals on my Fisher RS-1035 vintage receiver to test it. I upgraded the receiver with these proper speaker terminals. Why? I hate spring terminals and I use 12 gauge speaker cables, no way they would fit in those tiny things it came with.

The no-longer-ring terminals slip under the nuts of the 3-W-B-B terminals and do not interfere with the banana plugs.

I chose the Fisher to test them because it is right next to me, watch, I can touch it from here. See? Way up on top, you can spy the green LED that shows it is on and three illuminated red LEDs. It has a LOT of them!

It will be used with my Dynaco ST-200 power amplifier in the listening room. Seen below is my system rack/table/shelf. I never know what to call it.

Of course, I can only attach it to one set of speaker terminals. Which will it be, Klipsch or the surround sound set?

I mentioned VU meters in the title of the article. And, yes, there are some on the Fisher cassette deck. But like Darth Vader realized, "There is another. A sister!" 

OK, so this is not a VU meter (Volume Units) is is a Decibel meter. Also made by Radio Shack. Why A and C weighting, why no B?

Cleverly they added a 1/4"-20 threaded hole so that one can mount it on a tripod! Genius!

Lastly, since It was made clear to me to add a lightning arrestor in line with my dipole FM antenna above our roof, I decided to go ahead and by a better antenna.  

This photo is from Winegard. This is their 6010 omnidirectional FM and HD Radio antenna. It is praised for pulling in distant stations. Below is what I was using.

I had this dipole FM antenna an eBay seller makes up from two car antennas. It's well made and really works well, but since the Winegard 6010 sells for under $30.00 in some places, and since I was going to the trouble of adding the arrestor, a new antenna seemed like a good idea.

It pulls in all kinds of channels from all over. The rule is no two FM stations any closer than four points,  to prevent cross-talk. Well, it picks up ones that are next to each other: 93.5, 93.7, etcetera.

It also acts as a TV antenna. I have it hooked to a small HDTV my wife uses in here woman cave. The dipole gives clear HD pictures and she said she is now getting all kinds of channels. 

I am going back up to rotate it so that it points due north towards Washington and Baltimore. There is a second FM classical station in Baltimore that the Fisher already pulled in, but now the Yamaha does as well. Just not quite strong enough. The directions, show that the bottom antenna piece (that points away from the mounting pole) should be aimed in the direction of the stations one wishes to listen to.

Thank you once again for taking the time to read my words and view my photos. You kind comment are so heart warming.

Scott
November 8, 2018
#287