Power Mac G4 Cube Speakers help

Be sure you try that USB setup before you cut it up -- it may just work even though it's out of spec.

In the US, the answer to the question, "Where can I get a plug to match ..." is generally Radio Shack. The specs call it a 2.5 mm stereo speaker mini-jack.

The output is about 8 watts per channel into 8 Ohms, 20 to 20K frequency response, > 90 dB signal to noise and < 0.1 thd.

Hi,
You are referring to the 'eyeball' speakers I presume. They require a slightly higher USB output (the Cube's USB ports put out 500 milliamperes each at 5 volts) from the host computer and the Cube has upgraded USB ports to accommodate this.
Some have had luck just attaching them to a powered USB Hub attached to the host Mac computer.
I doubt a 'miniplug' would provide enough MA's to power the speakers. The USB powered Amp pushes the speakers.

Regards,
Dave

Of course you can cut the wires off the amp. The trick will be finding a suitable plug. I don't know what the plug looks like exactly, but if memory serves, it's similar to a 2.5mm cell phone headset plug. You might look at one of them and see if it matches and fits in the jack.

After doing some research, I found some stuff that may interest you...

http://www.macmod.com/forums/viewtopic.php?t=1381

According to this link ( http://support.apple.com/specs/powermac/PowerMac_G4Cube.html) I found this-

Digital amplifier and speakers with Harman Kardon audio technology
—Total power output: 20W
—Frequency response: 80 Hz to 20 kHz
—Single USB cable carries both power and audio; plugs into USB port on the G4 Cube or a display with ADC
—Removable covers protect speaker cones
—Digital amplifier module includes locking loop for theft prevention and minijack for connecting stereo headphones

And another link, selling them for nearly $300-

http://www.welovemacs.com/m7963.html

All of that being said, I wouldn't be too hasty to hack them apart.

Now one thing is for sure: the G4 cube had a more powerful USB bus. I am not sure how it works, I have looked around and can't find a voltage or amperage rating for the cube's USB. All we have a is wattage number, which doesn't help. The typical USB port can push out about 5 watts while the cube's bus could do about 20 (10 to each speaker). I'm not sure if the voltage required is still 5V (USB ports are 5V) but with a higher amperage rating or what.

Now I am sure of a couple things:

It is possible to get them to work with your machine without hacking them at all. First of all, they technically still work when plugged in, just at a really low volume (due to the lack of power supplied from the USB port). Apparently, the USB busses on most ADC monitors are similar to that of the Cube's. If you have an ADC monitor, just plug the speakers into its USB port.

Your other options before hacking the speakers are to either purchase an ADC capable monitor (with appropriate video card if you don't have one), or just sell them on ebay and use the money you make to get some speakers that actually work.

Now... you basically have two options when it comes to hacking. Theoretically, both are plausible. I wouldn't try them if you are a novice with electronics. You will need a good soldering station, flux, and a steady hand.

First, you can perform the hack that you suggested - cut the speakers from the amplifier and hook them up directly to the computer's internal amplifier. I'm not sure what the internal amplifier is rated at in wattage (its definitely not more than 20 W), but I don't think this is the best option. The speakers would surely be underpowered, and you'd be driving two speakers with a low powered amplifier which was meant to power one single internal speaker. Most internal speakers are rated at something rediculously low, like 2-5 Watts. All this to say, I doubt your sound would be much better with the cube speakers from the original internal speaker, because you are using the same amplifier. Ultimately, the amplifier is what will make the difference.

The second option is to hack the cube speaker's amp entirely. The USB connection passes audio and power, that's all. This means it is theoretically possible to open up the amp, separate the power from the audio, and make indivual connections for both. You would need some electrical training and experience. I could do it but I don't have the speakers to reference to guide you. If you were somehow able to separate the power input, and hook up an external power supply (say, a 5V adapter), and create a line level input for audio (typical 3.5 mm/1/8" input), you could power it from the wall and get sound from the headphone jack.

I don't know if that is too involved for you. Let me know if you are interested in this mod, I may be able to help you further...

Fangsuede - how is that number different than an ordinary USB port? Typically a USB port can output a maximum of 500 mA @ 5V. So what does the cube's USB ports measure? Where did you get that number from?

MyrkridianRhapsody,
I got it from Cubeowner.com, the place for all things Cube.
Cube Sound Spec's:
+The Power Mac G4 Cube comes with a pair of stereo speakers and a separate digital audio amplifier. The connection from the computer to the amplifier is a single cable that carries USB signals and power. Power is provided by the USB ports on the G4 Cube or on an Apple display that uses the Apple display connector (ADC).+
+The digital amplifier module supplies up to 10 W per channel.+
+The speakers have a frequency response of 80 Hz to 20 kHz.+
+Headphone Jack+
+A headphone jack is located on the digital audio amplifier module. The headphone jack is a stereo mini-jack for connecting a pair of low-impedance headphones. It can also be used to drive a 10K-ohm audio line input.+
+The recommended minimum impedance is 32 ohms. Headphones with lower impedance can be used, but with some degradation in performance.+

.. and from the Cube's User manual:


Compare a Cube USB ports to other PC's?
Again, from Cubeowner.com's FAQ's:
+These special USB ports are sometimes called 20-watt ports by Apple, because the two ports share a single 20-watt supply of power, however, the Cube Speakers only use 10 watts per channel. Regular USB ports only supply 2.5 watts - so don't bother trying to run your original Cube speakers off your USB hubs or keyboards.+
+The Apple Pro Speakers, which look identical to the Cube's USB orb speakers, use a proprietary digital audio connector rather than USB; this connector is found only on G4 towers (not Cubes) made January 2001 and later. In other words... no, they are not interchangeable.+

Regards,
Dave

Fangsuede - thank you for the reply. Unfortunately, I don't see how any of this makes sense. I read all of what you posted before on cubeowner.com, and I don't see how it can be. I didn't however, read the cube manual. That makes it even more confusing.

As far as I understand it, the typical USB port supplies 5V at a maximum of 500 mA. That is what the Cube manual that you quoted says about its ports. How can that be correct if the Cube supposedly can supply 20 watts of power? If you remember back to high school physics, voltage x current = power. This is why the typical USB port supplies 2.5 W (5V x .5A = 2.5 W). So if the Cube can supposedly supply 20 W per port, and the 5V value is fixed (it has to be in order to run other typical USB devices), then it has to supply more than 500 mA, correct? Every place I go to on the net suggests that the Cube outputs 500 mA through its USB. This makes no sense. If it can run 20 W to a device @ 5V, then it would have to give a current of 4 Amps! I highly doubt it can output 4 Amps. So where is the power coming from?

You can run a cube's amp & speakers off most any Mac's USB port, but it won't play loudly. I tried the idea of using a powered hub with a beefy 5V adapter on one, but it didn't get any louder. Dunno what I did wrong. Inside the amp case is one of the fabled Tripath Class T amp chips. Supposed to be audiophile grade digital amplification.

One thing that may be a hangup using the cube speakers with a G4 Digital Audio is that Apple claims the G4's speaker plug is proprietary, so it may not be exactly like a 2.5mm stereo headphone plug. Try a test fit before hacking things apart.

Well if we can figure out just how many Amps this thing uses then we should be able to hack it correctly as long as we have 5V and a line level audio. That seems to make sense to me.

I just measured the current draw on mine, and it definitely peaks over 500mA. I never saw 4 Amps, but I think that's what it does. I also scared myself by shorting the probes together and the monitor's USB went dead. Luckily, power cycling the cube reset something inside. I thought I was going to have to find a blown fuse or worse!

There's no line input I can see. The Tripath chip takes digital input directly off the USB. I had the idea of using it with an iPod, but it doesn't look possible.

It has to be possible... the USB can only send a line level audio signal. If it could send a full powered audio signal then there would be no reason for an amp. If you can find exactly which type of Tripath chip it is (check on the circuit board for a number or something...), then we may be able to find a pinout online. Unfortunately it looks like Tripath went out of business last year so it may be hard to find information.

.. the USB can only send a line level audio signal.

The USB does not send an Audio signal AT ALL. It sends serialized packets of digitized sound. The chips in the so-called "amplifier" act mainly as a Digital to Analog converter AND boost up the levels.

Remember that ratings for Amplifier outputs are not straight conversions to Amplifier input power. In ratings like "8 watts RMS" the RMS stands for means Root Mean Squared -- a complex analysis of the power supplied in the output signal, and cannot be directly compared to power supply power.

Okay I understand... but there still has to be some place on the amplifier board which is post digital-to-analog conversion and pre-amplified signal, correct? Or in other words, a line-level signal?

And as far as power is concerned, all we need to know is the MINIMUM current draw needed to power the speakers, correct? We can supply as much current as we want, but the load will only use as much as needed, correct? It's been a while since I went through this stuff...