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Amp And Speaker

Hi All.

I need to put in a speaker for my full-sized Dr. Who K-9 robot (see my avatar). He is made of styrene and the speaker (about 3 inches or so in diameter) for his speech would go into the head. I'm also debating about putting in a 2nd speaker in the body for sound effects. The power will be from a 12v lead battery (which actually attaches to a power distirbution board that some of the R2 builders use).

I'd like to keep things as simple as possible with as little soldering as needed.

I have a few questions:

Is an amp needed? If so, how's this one? Are there ones that are any easier to wire-up? Specifically, it looks like I'd have to attach the raw EZ B output (I'll be removing the tiny speaker it comes with) to a plug to get the audio into the amp. It'd be nice to not have to do additional soldering.

If I do use 2 speakers, can the same amp power them both?

I won't be using a Sparkfun MP3 trigger now that the EZ B can take care of the sound files. Do I need a ground loop isolator anymore?

thanks in advance,



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I'll try to find the link or maybe Dave S can chime in. When the first batch of EZ-B's shipped there was a good discussion of hooking up external speaker vs an amp. I don't think you need to remove the speaker, I think if you attach an amp or speaker the internal one disables. You will need to do some soldering, but only two points for the speaker or amp connections (you will probably need an amp for anything but a very small speaker, certainly for two speakers, but likely one amp is all you need for both, although if you want different sounds to each, you will need to come up with some method of switching between them.. Maybe a Tip120 transister to switch between them with a digital port.

But, my reason for posting was to see if you can provide a link to the power distribution board you mentioned. I am building a "Steampunk K9" (actually, the farther I get with planning, the less like K9 it is turning out to be, and the more like just a big robot dog) and was going to build a power distribution system, but if there is something available that meets the needs for reasonable cost, I am always willing to save some labor.



Here is the tutorial for breaking out the sound on the EZbv4:

Also the product you picked I think would be a bad choice. For one it runs on 13 volt 3 amp, that's just way too power hungry for a mobile robot. I'd choice and amp more like the one in the tutorial or the exact same one.

Another option is to use battery powered "pocket speaker" amazon has lots of them.


My answer to this is to use a Craig Bluetooth sound system..Its has am/fm/ remote input which is use from EZB4 raw audio.and of cause bluetooth for you phone or tablet music and audio..The unit has a lithium rechargeable battery runs 3 to 4 hours on charge. Also has an infrared remote control...I dont know if the speakers that it comes with are too large for you project but they work great on my MOSHI robot(posted in project showcase..speakers are 3 inch diameter.You could use both or just one for single channel audio...Craig unit can be found on Ebay and some Walmart supercenters..around $25 .


Thanks. The pocket speaker was my orginal thought, but it won't fit well in the head. I saw the thread about the speakers, but I didn't know what the right amp was to use or if I still needed the ground loop isolator. If anyone can tell me about the isolator, please let me know.

I don't know if the power distribution boards are still being made, but you can contact Dan. He recently responded to an email question I had. The nice thing about the board is that it does have a USB port which will hook up to my digital picture frame on the side of K-9. Here's the link to the board:


Re: ground loop isolator.

They never hurt, and often help. If you can easily Leave it in, you might as well. I use on in my car when I hook up an iPod or my Android phone to the stereo and it prevents noise nicely.



Any bluetooth connected audio will work , using a direct connection sometimes has a hum in the audio line because the robots chassis is not grounded.


Thanks-- the bluetooth solution will make things easy if I can fit one of those in. I did find the Roker Sound Cannon on Amazon which is fairly small.

Will I still be able to sync LED lights to sound that's being sent to a bluetooth speaker? I've read a variety of threads on this and it seems like the easiest way is to directly hook the LEDs to where the speaker wires are. Will the built in speaker play at the same time if you're using a bluetooth speaker? I also found a thread by Rich describing use of the sound servo feature as an alternative. It looks like you'd need to hook up the LED a little differently (4 Route MOSFET Button IRF540?). Would that method work if using a bluetooth speaker too?

Thanks again!



The amp you point to is a quality amp but not a powerhouse. I'm useing two of these in my B9. That's how I get different sounds in each part of the robot but one is connected to a mini MP3 sound board that plays a constant sound loop of mechanical sounds. Justin may be right these amps may be to power hungry for battery power. I plug my B9 into the wall.

Also if you break out an amp from this board as I did you may need to remove the little speaker as you may experance an echo effect.


The bluetooth idea won't work after all. The small ones all seem to require you to press a button to turn it on and reconnect after a period of inactivity.

If I simply rewire the speaker to an unamplified one that's about 3 in in diameter will that still end up weak sounding? I may go back to my original idea about using a wired portable speaker, but it's a little hard to fit these in.


I used a small 5vdc stereo PCB to run two speakers using the mono non-amplified output from the EZB(4) The output is 3 watts and has a volume control pot also on the board. These PCBs can be found on ebay.

Here's a picture of a basic setup that can give you an idea of size.

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And another view. More details can be provided if needed.

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Here is a picture of just the Amp without the small header that can be soldered onto the board to provide a way to plug connectors onto the PCB.

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I finally found a tiny Bluetooth speaker that doesn't seem to need me to press an additional button to connect. Where in ARC do I tell the EZB V4 to use its Bluetooth to connect to the speaker? I can't find a project button to add a Bluetooth speaker.

Also, will the V4 directly connect to the speaker via Bluetooth? I don't want to use my PC to connect and I understand the iPhone's Bluetooth will not work with the EZB.

thanks again,



@ftlum ... As Mentioned earlier the EZB4 does not have Bluetooth.... The ezb4 uses wifi only... The EZB3 uses Bluetooth but only to connect to ARC (or the mobile android app) for the purpose of controlling it. .... The Bluetooth on your PC would connect to your Bluetooth speaker....


Thanks for the clarification-- maybe someone will add Bluetooth back for the V5.


Why? All processing is done in ARC... The computer is the brains, not the ezb... Even if you put Bluetooth back into the "ezb5" or whatever version, it won't be able to use it other than to connect to the software (ARC) that runs it...

Both your Bluetooth speaker and the ezb are both referred to as (for a lack of a better term) "slave" devices... Insofar they need a "master" device to control them. The ezb is the slave device and the master device is your pc with ARC... Two slaves can't control each other... That's why your ezb4 (even if it had Bluetooth) can't be used with your Bluetooth speaker.

Put your Bluetooth speaker on your robot... Now when you play sounds, mp3 etc out your pc speakers it will instead come out the Bluetooth speaker that is on your robot... Problem solved...:)