I have been thinking about the audio integration, while waiting for parts and components.
The audio integration will be in two phases.
Phase 1. Use the stock Monsoon amp and speakers.
Phase 2. Replace the monsoon amp and speakers.
Replacing the amp and speakers gives me the greatest flexibility but I'm not ready to drop the coin yet. Too many other things to buy first.
Lets discuss integrating the mac mini into the existing Monsoon system.
Monsoon amp turn on signal comes from 6v detected on the left negative input. Explained very well here:
Ground loop could be a factor.
Signal inout level to the amp
Here is my build design with questions and unknowns identified throughout.
Mac Mini audio output will come from the 3.5mm mini plug using a TOSLINK cable. Digital out that needs to be converted to analog. I have been researching several solutions and my initial design uses minidsp.com components.
The DAC will consist of a miniDigi which takes the digital inout from the mac mini and converts it to an analog output to the minidsp. The minidsp provides 4 RCA outputs. Two outputs for the monsoon amp and two outputs for the powered sub.
- Concern: this arrangement will not plug and play to phase 2 (new 2x two channel amps and speakers). To gain fader control I plan on using 2x 2 channel amps when I upgrade. So, I might consider using a 2 x 8 minidsp which gives me the addition outputs for both future amps.
- Question: how is the fader controlled on the monsoon amp?
- Question: how is fader controlled on an aftermarket 4 channel amp?
- I need this insight to determine how best to control the front to rear fade and to decide if the DAC needs to be 2 x 4 or 2 x 8.
Power for the DAC will come from the P2140 DC-DC power supply.
- Concern: the PSU will power both the Mac mini and the audio DAC.
The next step is to "wire" the DAC RCA outs to the monsoon amp connector. I have a connector and wire on the way.
I also have to inject 6v on the left negative amp input to turn on the amp. I would also like to delay the amp power-up to avoid the thump.
I plan on building a box with RCA inputs on one side and speaker connectors on the other to tie the DAC to the amp.
I will also provide 12v to this box and regulate it to 6v to inject power to the left negative to turn on the amp.
Question: could I use the 5v power from the PSU as the amp turn on signal?
Power to this circuit will be controlled by the miniDC isolator which creates a time delay for the amp to be powered.
- Question: the P2140 PSU has a delay circuit to start and stop the carpc. Can I use the delayed signal from the P2140 PSU as input to the miniDC isolator. This would ensure the the audio amp powers on after the computer.
I will install a ground loop isolator between the minidsp and the point I inject 5v into the negative left line. This will prevent the 5v from flowing back to the minidsp and will help with any ground loops that might develop.
Note: I will have a master volume control knob in the center console to control the carpc audio signal.
- no fader control
- no ability to "tune" front to rear speakers
- left and right control will be limited to preset values set in the minidsp.
Ok, I was hoping to get some help with the audio electronics but my questions have all gone unanswered on the following forums:
I guess I will try some hifi message boards.
While I like the minidsp product line I just can't seem to get help.
I may just fall back to a cheaper solution until I swap the amp and speakers. I wouldn't have to address power issues to the minidsp either.
I will give it a few days and see what turns up.
Here is my low cost, lets get the sound working, and upgrade the audio later, solution.
I plan on running the +5v line and connecting it to the negative terminal of the left input to the monsoon amp.
Question: since I am not using a voltage regulator to make 5v from 12v is there a need for a ground?
Any insights would be useful.
Keep in mind that this is not the ideal solution. That will come when I replace the amp, speakers and use a high end audio processor.
The Xenarc monitor has arrived.
Along with the GPS dongle and the wiring harness from a monsoon amp.
The Mac Mini is in and I will pick it up on Monday.
Unfortunately, I go out of town Tuesday for a week.
I hope to get the Mac Mini up and running with all the software installed and get it attached to the Xenarc LCD.
Lots of pics throughout the process.
Xenarc monitor test
I plugged the Xenarc 8" LCD into my desktop to check the functionality.
Wow! My first impression of the screen image.
I left the desktop resolution at 1290x1024 at 75hz and the image is nice. Certainly a little small but ok for the test.
Inserted the driver disk and selected WinXP.
The setup asked 2 questions that are not explained very well.
Install PS2 driver
Install RS232 driver
There is a note about a PS2 mouse still working.
I selected yes to both.
During the setup I got a message that no PS2 device was found. Ok, that makes sense because I have a USB mouse. So, next time I will not select the PS2 driver unless I have a PS2 mouse.
Drivers install and it is rebooting.
I asked to perform the 4 point calibration on the next boot-up.
4 point calibration started. In each corner it gives you a circled red X. Just place the pointer on the X and hold until the X turns blue and a blue circle is drawn. Repeat on all the corners. No directions were given but it was simple to figure out.
Touchsceen works with the pointer and my finger. At this resolution it is tough to get into the corners with my fingers.
Xenarc and a backup camera.
There are quite a few posts about the Lilliput monitors with a special wire that you can tap into so the backup camera when powered will cause the monitor to switch to AV1.
Well to my surprise Xenarc has made it much easier.
There is an on screen menu function that will do exactly that. If there is a source lied in AV1 the monitor will automatically switch the that source.
No wiring needed, now that is a nice surprise.
I see a backup camera in my future switched on and off the the reverse lights.
Picked up the Mac Mini.
Installing Fusion 4 and Windows7.
Gotta love windows, install failed the first time through. Deleted the virtual machine and tried again.
I would love to not have to install windows but I just need it for a few apps.
Windows7 installed using Fusion4.
Not impressed with the speed. Windows says, "your computer is low on memory!" go figure.
But Mcafee is updating and I am only running 4GB of ram. Hopefully 16GB will help and I have to get into the setup of Fusion 4.
Xenarc monitor is plugged into the Mac Mini and the resolution automatically went to 800 x 600 and looks good.
The Xenarc cd had an option to install the mac drivers bit the CD did not work on the mac. So, I downloaded and installed the driver from Xenarc.com.
Touch screen works. But the cursor position does not match. Horizontal scroll is ok, vertical scroll works backwards.
The OSx drivers did not include Lion 10.7. Could be the problem. Besides OS is new to me so I am learning as I go. Time to get help from Xenarc.
One more thing to try, open Windows 7 and install the Xenarc CD.
Tried and it didn't work. Same touch results in the windows 7 environment.
Time to research the issues.
Not much going in today. I need to pickup a few things at West Marine and radio shack so I can start wiring the DC power on the bench.
Still waiting for 1 wiring harness from Taiwan. This harness will allow me to remove the mac mini power supply and use it outside the mac mini case.
In the mean time, I plan on wiring the USB hub for testing.
I need a GPS software solution for OSx and a front end for OSx.