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