More than one speaker?

There are only four wires in the tether, no wires for an additional speaker.  As for how to put a speaker in, I'd use two 16 ohm speakers in parallel, that gives you the correct impedance match of 8 ohms.  In addition, if you disconnect the rear unit, you still have a speaker in the lead unit.

Personally, I'd consider something like this wireless rig, add a $2 amplifier module and a 5V power supply and you have a wireless link that doesn't need an added tether.  Go to AliExpress.com and search for item: 3256804229604343

Again, thanks John for a great idea.  Since they were so inexpensive, I ordered 3 sets to liven up another ABA set plus an AA set I bought another unpowered B for.  I build my own 7805 5 volt regulator circuit to run stuff, so powering them is no issue.

I don't know how much drive the output has, that's why I mentioned the amplifier.  You can buy simple amplifier modules for a couple of bucks, so that's not a major impediment.

Interesting, John.  Since this isn’t my field of expertise, I have a couple of questions.

Like CALNNC, I have an MTH PS2 A-B-A which has a dummy B and a powered slave A.  I would like sound in both the B and slave A.

Is this thinking correct?  The speaker leads in the master would also connect to the mic 1, or 2, input of the launch module.  The receiver modules in the B and slave A units are connected to an amp and then to the speaker.  I see that the modules are programmable; does that mean that a single launch module in the master could support receivers in both the B and slave A units?

Is it fair to assume that volume would be controlled by the settings of the master unit?

Thanks for your help and ideas.

Yes, the speaker leads connect to the microphone.  I'd suspect you'll need a resistor network to cut down the voltage levels to microphone sized inputs.  A series resistor of around 1K into a selected value resistor to the amplifier common (not frame ground).  The resistor is selected to give you microphone level voltages, since I've never actually used this rig, I can't say for certain what the exact value of the resistor to ground might be.

Also, since the speaker leads float with respect to frame ground, you'll also need a fully isolated 5V supply to feed the transmitter module, there are a number of DC-DC fully isolated converters available for a few bucks.

Here's one at Aliexpress.com that's a 12V to 5V DC converter and puts out 200ma of 5V, more than enough for the transmitter, search for item 3256804874735956

Receiving side.

The good news is, you don't need isolation for the receivers since they're really stand-alone an just receive the over-the-air audio.  Just a three or four component 5V supply will do the trick there.

Item 2255800209759634 is a suitable amplifier module, it also runs on 5VDC and will drive your 8 ohm speaker directly.

Thanks for info, John.  Maybe I’ll tinker around with this.  For power I was thinking of using track power with a rectifier and buck converter.

@Danr posted:

Thanks for info, John.  Maybe I’ll tinker around with this.  For power I was thinking of using track power with a rectifier and buck converter.

For sure you want to use track power!  Batteries are such a PITA in the long term for operating.

I make my own power modules from an eBay 70 cent switching module and a little sandwich board for input power conditioning.  It supplies 300 or so milliamps at an adjustable voltage of my choice.  The whole package is 5/8"W x 3/4"L x 3/4"H, being a switcher, it doesn't get hot like a linear supply would.

Assembled Power Supply

eBay switching module

FWIW, when I contemplated doing this (using wireless audio) I planned on using an automotive speaker level to line level device that solves multiple problems- one huge one being that common or ground isolation issue. Again, the idea was use an off the shelf and relatively cheap design that contains voltage dividing resistors, and then a specially designed audio level transformer and also adds a potentiometer to adjust that line level output and sensitivity to input.

While the device is stereo, I found you could cut the circuit board right down the middle to get 2 mono units- to put into 2 different trains.

But here is the catch22 I ran into- Latency. The problem what that the electronics (I was using off the shelf Bluetooth transmitter and receiver modules) transmitting and receiving add a slight delay (in some cases- more than a "slight" delay) making it unsuitable. Again, if the intent was to copy and add to the original sound of the speaker in the lead engine- the problem was your second output was delayed and sounded minimally like an echo and worse, was even more delay.

@gunrunnerjohn is doing a great job of pointing out to you the power supply and other requirements to do that isolation.

Again, my concern is that I've yet to find modules with no delay. I've seen claims of no delay, but none thus far actually could play in concert with the source and not have a delay.

Being honest, I would just run a tether- the smallest I could find for 2 wire for speaker, and call it good.

Wire= no latency and way, way, way, simpler.

Nice black connector latching pairs- easy to put heatshrink over the wires to make them black too and hide better.

@Vernon Barry posted:

Again, my concern is that I've yet to find modules with no delay. I've seen claims of no delay, but none thus far actually could play in concert with the source and not have a delay.

For the prime mover, a slight delay would be fine, and even the horns wouldn't be a problem..  However, as you correctly point out, for the crew talk, it's not super.   It's the same as sticking a bunch of identical Legacy engines on the track and addressing them with #99 so they all run together, the crew talk sounds like they're yelling into a sewer pipe.

FWIW, the audio delay is stated as 15-20ms, and since this isn't a complex protocol but a 1:1 connection, I suspect that's probably about right.  I'm guessing they're digitizing the audio, maybe a transmitter than just repeats it in an analog form would cut down the delay.

All good thoughts and ideas on this issue.  It was a whopping $11 for the whole order so whether it works or not won't break the bank.  I did think of one more thing concerning multiple use, in that the units may work on the same frequencies so running 2 loco sets might be a problem.  I doubt they have the circuitry to pick an unused channel like routers can do.  While we are at it, this whole project started because I had to replace a lamp in this MTH set, and after spending a day removing screws from the the chassis, (it seemed)  I learned MTH wanted $4 not including shipping for a 3mm incandescent lamp for this loco.  I took a chance on a bundle of 10 for $15 including shipping from within the US off epay.  They fit in the MTH holder, and work perfectly, they are rated at 6.3 at 70ma which is about 90 ohms and the MTH bulbs are rated at 6 V at 60 ma, which for a 90 ohm bulb in this replacements case, would draw 66ma with the 6 volts from the loco and only 30mw different in heat.   They are probably all the same bulb.  The only issue for some,  is you have to cut off the old dead bulb and splice the leads from the new on into the leads coming from the connector.  The new bulbs come with a generous lead length and their attachment point at the bulb is sealed.

If they don't work on the same frequency (can't tell from the ads), just use two transmitters and the problem is solved.   I couldn't find anything about how you pair the transmitter/receiver.  They do have a statement that seems to indicate it's strictly 1:1 pairing.

Transmission method: one send and one receive

Another question on adding a speaker.  The engine has an 8 ohm 2W baby Fat Boy speaker.  Using two 16 ohm speakers in parallel, one to replace the original 8 ohm in the lead unit on one in the B unit, will keep things even.  The question is will running the lead unit by itself hurt the 16 ohm speaker?

So I ordered the transmit/receive modules and couple of amplifiers along with some other things I needed.  We'll see what happens.

I thought about a tether awhile back but I didn't want the extra tether because I was thinking I could run them as just the A, an AB or AA.  Reality is they have been and ABA since I got 10 years ago.  Would the PS2 audio amp support 3 speakers?

Latency could be an issue for sounds other than the prime movers.  I don't use most of the sounds but I can see, or hear, that 3 horns or 3 bells sounding in each unit would not be very prototypical, even more so if they were out of phase.

The description and instructions for the send/receive modules is pretty thin.  We will find out when we get them just how flexible, or inflexible, they are.  I always loved products that came with instructions that said: "Congratulations, you buy nice product".

Keep in mind that I am not an electronics guy - ask me about a watch instead, but I'll let you know what happens.

@CAPPilot posted:

The question is will running the lead unit by itself hurt the 16 ohm speaker?

Nope, it'll work just fine, just a bit lower in volume.

@Danr posted:

So I ordered the transmit/receive modules and couple of amplifiers along with some other things I needed.  We'll see what happens.

I thought about a tether awhile back but I didn't want the extra tether because I was thinking I could run them as just the A, an AB or AA.  Reality is they have been and ABA since I got 10 years ago.  Would the PS2 audio amp support 3 speakers?

Latency could be an issue for sounds other than the prime movers.  I don't use most of the sounds but I can see, or hear, that 3 horns or 3 bells sounding in each unit would not be very prototypical, even more so if they were out of phase.

The description and instructions for the send/receive modules is pretty thin.  We will find out when we get them just how flexible, or inflexible, they are.  I always loved products that came with instructions that said: "Congratulations, you buy nice product".

Keep in mind that I am not an electronics guy - ask me about a watch instead, but I'll let you know what happens.

Yep, it's always fun to find information on these products.  That's why I looked around and posted some basic information that should get you close to running.

I don't know if the PS/2 audio amp would be happy with three speakers, but probably if they were all 16 ohm and it's a 3V board.  OTOH, sticking an extra little amp in shouldn't be that hard.

The latency can be an issue, not so much for the horns but probably the crew talk for sure.  I just fired up six Legacy F3 units, all with sound using #99.  The crew talk is comical as they all react at slightly different rates.  The prime mover, OTOH, sounds outstanding, and it shakes the walls with six units running at full volume!  The horn is great as well, it's a 12 chime horn it sounds like.

I imagine that multiple crew talks at the same time would equal TMCC cab chatter.