Simon Williams (DONTemail@luddite.ca) writes: > Anyone tinkered with replacing the IIe's crappy speaker with a line out? > I'm a little hesitant to connect the wires up to my stereo without first > hearing from someone who's already been electrocuted =8-O > > SW Unless the IIe changed it's circuitry from the II, it's not going to be just a matter of running a cable. I haven't looked at the II schematic in a while, but memory tells me the internal speaker is connected between the +5v line and the collector of a transistor. You don't want to run that +5v line to your stereo. And if the speaker is not there, that transistor will not be able to operate. You need to take the collector side of the speaker and connect that to the input of your stereo, using a capacitor to ensure that the DC voltage doesn't get into the stereo. And then connect the ground of the Apple to the ground of the stereo. And unless you are willing to leave the speaker in the IIe, you're going to have to put some resistor, maybe 100 ohms or so, between the collector of the transistor and the +5v line, ie between the two points that the speaker is connected to now. I suspect some have done this, and can provide specific values, but I thought it was important to warn you against just running the wires to your stereo. Michael Michael Black wrote: >Simon Williams (DONTemail@luddite.ca) writes: >> Anyone tinkered with replacing the IIe's crappy speaker with a line out? >> I'm a little hesitant to connect the wires up to my stereo without first >> hearing from someone who's already been electrocuted =8-O >> >> SW > >Unless the IIe changed it's circuitry from the II, it's not going to >be just a matter of running a cable. > >I haven't looked at the II schematic in a while, but memory tells me >the internal speaker is connected between the +5v line and the collector >of a transistor. You don't want to run that +5v line to your stereo. >And if the speaker is not there, that transistor will not be able to >operate. > >You need to take the collector side of the speaker and connect that to >the input of your stereo, using a capacitor to ensure that the DC voltage >doesn't get into the stereo. And then connect the ground of the Apple to >the ground of the stereo. And unless you are willing to leave the speaker >in the IIe, you're going to have to put some resistor, maybe 100 ohms or >so, between the collector of the transistor and the +5v line, ie between >the two points that the speaker is connected to now. > >I suspect some have done this, and can provide specific values, but I >thought it was important to warn you against just running the wires >to your stereo. This is a good approach. Another is to put a small audio transformer (like the kind found on any modem card) to AC couple the Apple output to a line output. I used this approach to couple the speaker jack of the Apple main board to a 100 ohm volume control and then to the speaker. I also inserted a phone jack in the speaker circuit, so that when headphones or a "line out" plug is inserted, the speaker is muted. -michael Check out 8-bit Apple sound that will amaze you on my Home page: http://members.aol.com/MJMahon/ Question to all electronics geeks. Would a transformer designed for audio circuits be used for isolation? Just wire one winding in parallel with the speaker and the other winding to stereo input. A resistor should be mounted in serie with the winding of speaker side to limit current when the transistor is ON. The ratio could be 5:1 to turn 5V into a 1V peak-to-peak signal which would be compatible with most line inputs... unless you want to connect to a phono input :). There are still impedance matters to sort out. Finding the right transformer could be a problem too but not impossible to solve if you have a electronic component junk box or some old audio equipment you can gut out. Electrocution could happen if you tinker with components inside Apple's switching power supplies, even if it's turned off. Nasty circuits with coils and 120V (or 220V) inputs ;-). Yves Joel wrote: > "Simon Williams" wrote in message > news:116059.PBUDTKEI@news.telusplanet.net... > >>Anyone tinkered with replacing the IIe's crappy speaker with a line out? >>I'm a little hesitant to connect the wires up to my stereo without first >>hearing from someone who's already been electrocuted =8-O >> >>SW >> > > > You do want to be careful. > > I had written an article on this back in the 80's. > The 2 wires to the speaker are from a darlington and +5V. > I f you had assumed they we're the more typical signal + ground pair and > connected them to an external device (like a VCR or monitor which also > connects the two devices grounds through the video connection) you can short > out the Apple's 5 volt supply. Not good! > > You need to isolate the signal with a capacitor. > This effectively becomes a high pass filter, so the capacitor value would > depend on the input impedance of the device your driving and your cutoff > frequency. > If you used 1kHz as your low cutoff and wanted to drive an 8 ohm load, you > would want a 22 microfarad capacitor. > 15V electrolytic will be fine. > > If you are driving a line input, the input impedance is much higher, and you > can get by with a smaller capacitor. > > There are actually a couple of ways to hook it up. > > 1. Make a ground connection to somewhere on the motherboard. (Ground does > NOT go to the internal speaker.) > Identify the signal line to the speaker (not the 5 volt line) and put the > cap between it and your signal out line. > > 2. If you want to be able to just hook it up at the speaker connection (or > at the internal speaker), use two caps. > Run one cap from the 5 volt pin to external sound ground. Run the second > cap from the signal pin to external sound signal out. > > Someone else said it wouldn't work without the speaker connected, but in the > //e there is actually an LED loading the darlington in parallel with the > speaker. > Though the load is less. > According to my ancient notes, if you connected signal out ground to +5v > through a capacitor, you will get a louder external signal if you leave the > internal speaker connected. > If you connect signal out ground directly to Apple ground (which you may be > doing without knowing it if you are connecting composite video out to the > same device), you get a louder external signal with internal speaker > disconnected. > > Boy, you thought it was going to be easier than all that, right? > > Makes you not even want to bother. > > > >