You may remember Southern GP7 2187, a Proto GP7 I finished last summer. Well in addition to fixing the railings and steps for my 1970 timeframe (black and white instead of yellow), I decided to install sound. Now sound is something pretty new and intimidating to me, but after running a couple factory-equipped sound locomotives, it was tough to go back to no sound. I finally decided to just jump in! There are many great sound decoders out there, and everyone has their preference. I won’t claim to be an expert, but after doing some research, I decided to start with some Soundtraxx Econami decoders. As you might guess from the name, these are “budget” decoders that run about 2/3 the cost of a full-featured sound decoder from any manufacturer. The Econami is pretty basic, but it does have the key features I need, and it uses the same basic sounds as the more expensive Tsunami 2s. Best of all, the Econami Diesel version allows the user to select from a handful of prime movers including everything I need for my first-generation fleet: the Alco 244 for RS3s and the non-turbo EMD 567 for Fs, GP7s and GP9s.

Soundtraxx makes two versions of the diesel Econami, the larger ECO-PNP and the smaller 21-pin ECO-21PNEM. I picked up a couple ECO-PNPs, one of which was intended for 2187, but once I got the decoder, it was obvious that it wouldn’t fit without major modification to the large metal weight–I needed something smaller. After installing the PNPs in an RS3 (just barely) and an F3A, I decided I was happy with the sound produced by the Econami and a pair of mini cube speakers, so I looked to see if I could install the smaller 21-pin decoder in the GP7. The 21-pin arrangement is newer, and I was surprised at how tough it was to find a cheap 21 pin harness I could wire into the locomotive. You can find cheaper ones in Britain, but it was going to cost me an extra $20 to get one in the states–what’s the point of using the Econami if a simple harness was going to eat up all the savings?

So, could I get the 21-pin Econami to work without a harness? While it was a little tough to find info, I finally figured out the mapping of the 21 pins (thankfully German shares some commonality with English…). I knew it wouldn’t be practical to solder directly into the decoder (the pin holes are tiny and close together), but I thought I might be able to shape the wires to act as pins, so I ordered up an ECO-21PNEM. What I found was I could tin the wires on the locomotive, cut the end so about 2mm of metal was exposed, and then carefully insert the wire into the correct pin hole. While the connection is not bulletproof, it’s snug enough that the wires don’t come out easily, and if you can push the wire in until the insulation is flush with the board, there’s little chance of a short. For the extra wires (e.g., speaker wires), I used 30 AWG stranded wire tinned with solder–I had to use a little extra solder to get a snug fit, so a 28 AWG wire would probably work as well. Once I verified everything worked, I used a piece of electrical tape to hold the wires down and in-place.

Now for the speaker. Unfortunately, I decided to use the large clear plastic blocks for the number boards and lights, so the little room that was left in the top of the shell was taken up. I decided the best course of action was to take the weight off and remove about 8mm of metal height from the nose section with a hacksaw. After filing the cut clean, I was ready to install the speakers. I’m using the 11 x 15mm cube speakers made by Loksound. You can find a lot of sources for speakers this size, but I love that the Loksound versions come with different baffle arrangements including both short and tall and a base to install two speakers side-by-side (my preference). I built a double baffle with the short walls using CA and connected the speakers in series (16 ohms impedence). Yes, the decoder is 8 ohms and the speakers are 16 ohms. My research leads me to believe this is not ideal but is acceptable as long as I don’t run the amp at max, which I don’t–if you have a good technical reason why this is not a good idea and will damage things in the long-run, please feel free to post a comment!

So, in the end, I was able to fit a sound decoder and two small speakers into the Proto GP7 with just a small, one-cut modification to the body weight, and I’m really happy with the sound! I’ve got a Soundtraxx Tsunami 2 EMD diesel decoder now as well, so I’ll do a comparison at some point and let you know how I think the Econami compares. For now, I’ll enjoy the chugging sounds of the EMD 567 and hauling coal hoppers interrupted occasionally by the chimes of a Nathan M5! St Charles is now a much louder place.