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Mac mini to car audio
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billb
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PostPosted: Thu Jul 26, 2012 4:07 am    Post subject: Two Displays VW Reply with quote

Also, do you have room for
two Displays in your vehicle?
You can run two displays from
the mini. Have your Mac Desktop
on one dispay with iTunes and
the other Display could have
Windows running your GPS Program.
Both with Touch Screens.
Talk about unbelievably cool!
I don't think anyone has done that.
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billb
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PostPosted: Thu Jul 26, 2012 4:11 am    Post subject: MonoPrice Reply with quote

Are you familiar with MonoPrice?
Great place to source most of your
cabls etc.
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cazzz
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PostPosted: Thu Jul 26, 2012 6:53 am    Post subject: Reply with quote

http://home.eeti.com.tw/web20/eGalaxTouchDriver/MacOSXIntelDriver.htm

I haven't tried this driver yet.
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cazzz
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PostPosted: Thu Jul 26, 2012 11:33 am    Post subject: Reply with quote

Installed the new Xenarc driver and the touchscreen works flawlessly.
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cazzz
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PostPosted: Fri Jul 27, 2012 6:43 am    Post subject: Reply with quote

Yesterday I spent some time testing the difference between using digital audio out and analog audio out on the Mac Mini.

Digital out has the advantage of being digital and if I were to play a DVD in my car, doubtful, I could take advantage of the surround sound. However. The digital out is not designed to have any volume control at the source. The volume control should be handles by the receiver. But. I don't have a receiver and it is imperative that I control the volume at the source (computer). I was able to achieve volume control using a utility called sound flower.

SoundFlower works but I found that it was not consistent enough for me at this stage of my lack of Mac knowledge.

Sewell DAC works great for the right application. It took the digital output from the Mac and processed the signal out to either 2.1 or 5.1. The kicker is that the source has to provide the channel for the sub to work or for 5.1 to work. That means the sub out does not provide a signal unless the mac mini provides a sub channel on the digital out. Same holds true for the 5.1. In essence I would have to wire for 2.1 and the sub may or may not work. In conclusion, the Sewell DAC will not work for my configuration.

Ground Loop Isolator, works as expected but it does cut the output signal in half. Hopefully there is still enough signal to the amp.

My near term plan is to use analog out directly to the amp.

I plan to add a miniDSP DAC in the future which will give me both digital and analog input options. So, I will take another look at digital when I get to that stage. MiniDSP does not have the limitations of the Sewell unit.
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cazzz
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PostPosted: Fri Jul 27, 2012 1:16 pm    Post subject: Re: Two Displays VW Reply with quote

billb wrote:
Also, do you have room for
two Displays in your vehicle?
You can run two displays from
the mini. Have your Mac Desktop
on one dispay with iTunes and
the other Display could have
Windows running your GPS Program.
Both with Touch Screens.
Talk about unbelievably cool!
I don't think anyone has done that.



Let me get one installed and then I will think about the second monitor. I dis run an HDMI cable. It would be simple to install a 7" on the dash for windows Nav.

Something to think about........later maybe.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:04 pm    Post subject: Reply with quote

My focus continues to be on the audio interface.

Using a TOSLINK cable and mini adapter, I plugged the mac mini into the Sewell DAC. Then plugged two speakers into the DAC.

It worked accept I had no volume control.

This won't work as I have no receiver to control the volume.

I installed an app called soundflower that gave me volume control.

Now will it work in the car?

I may have to rig it up and give it a try.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:06 pm    Post subject: Reply with quote

Today I read all the threads about the Monsoon amp. I also traces the wiring diagram in the service manual.

I verified that there is 6 volts on all the outputs from the radio. L/R F/B +/- when the original head unit is turned on.

I built a test box to inject 5 volts into the negative lead.



Now its time to apply 5 volts and test all the feeds on both sides of the ground loop isolator to make sure I am not throwing 5 volts back to the DAC.

Once that is tested I will connect speakers to the new interface box and see or hear the results.

Then I will move to the car and see if I can indeed power the amp with this configuration.

I am still not sure what to do with the ground from the power circuit.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:08 pm    Post subject: Reply with quote

I applied 5v from the ATX power supply to the negative side of the left speaker.



After testing for voltage I connected the ground loop isolator and behold, no current passed through to the source.

So I plugged the mac mini in to the GLI and the speakers into my interface box.

Everything worked. I did notice that the audio signal was cut down significantly with the GLI installed.

Will this work to power the amp?

It is time to pull the amp and wire in my test box.

I am still not sure how to wire the complete circuit. If I use a voltage regulator the positive and negative leads get connected to the VR and then the output of 5v gets connected to the negative speaker terminal. In my case I am running 5v directly from the ATX power supply. The negative lead is not hooked up. So, is there 5v present on the speaker lead without a ground to complete the circuit?

I test for voltage by completing the circuit to the negative lead from the ATX power supply and of course there is voltage because I complete the circuit.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:09 pm    Post subject: Reply with quote

Yesterday I spent some time testing the difference between using digital audio out and analog audio out on the Mac Mini.

Digital out has the advantage of being digital and if I were to play a DVD in my car, doubtful, I could take advantage of the surround sound. However. The digital out is not designed to have any volume control at the source. The volume control should be handles by the receiver. But. I don't have a receiver and it is imperative that I control the volume at the source (computer). I was able to achieve volume control using a utility called sound flower.

SoundFlower works but I found that it was not consistent enough for me at this stage of my lack of Mac knowledge.

Sewell DAC works great for the right application. It took the digital output from the Mac and processed the signal out to either 2.1 or 5.1. The kicker is that the source has to provide the channel for the sub to work or for 5.1 to work. That means the sub out does not provide a signal unless the mac mini provides a sub channel on the digital out. Same holds true for the 5.1. In essence I would have to wire for 2.1 and the sub may or may not work. In conclusion, the Sewell DAC will not work for my configuration.

Ground Loop Isolator, works as expected but it does cut the output signal in half. Hopefully there is still enough signal to the amp.

My near term plan is to use analog out directly to the amp.

I plan to add a miniDSP DAC in the future which will give me both digital and analog input options. So, I will take another look at digital when I get to that stage. MiniDSP does not have the limitations of the Sewell unit.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:12 pm    Post subject: Reply with quote

Had some time to tinker.

I took the ATX power supply out to the car and powered it up.

I connected the ground to the radio harness ground pin which is grounded to the chassis.

I then touched the 5v output to each of the speaker negative pins in the connecter that leads to the monsoon amp.

It worked!!!!!!!!!

When I applied 5v to the left front negative speaker line feed to the monsoon amp the amp came on and the speakers were alive. No music yet just a pop like I expected.

So, that confirms everything I have read thus far. I plan on applying power to the left front negative speaker terminal and ensure the ground is to the chassis.

Now I need to pull the monsoon amp and replace the input feed with my replacement cable.


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cazzz
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PostPosted: Fri Jul 27, 2012 8:13 pm    Post subject: Reply with quote

I finished the temporary interface box.



Molex connector goes to the ATX power supply. The grey connector goes to the amp. The black wire goes to car ground.

Now I am ready to hook it up with the mac mini and see if I have sound.
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cazzz
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PostPosted: Fri Jul 27, 2012 8:16 pm    Post subject: Reply with quote

Success!

I connected the mac mini via 3.5 to L/R "Y" cord and ground loop isolator (GLI) to my experimental box.





The box splits the 2 outputs to 4.

5v was input to the LF negative line only.

I had music but I also had a buzz. Since the Monsoon amp is looking for a balanced signal I decided to connect all the negative leads and apply 5v across the board. This eliminated the buzz.

The only thing that remains is a faint buzz or hum when there is no sound output from the mac mini.

It doesnt happen when I mute the source only when I turn off all sound sources, iTunes, internet radio, sirius, etc.

This may be related to the fact that there isnt 5v on the positive inputs.

However, when the stock head unit is installed the 5/6v is only applied when the radio is turned on. So when there is no source there is no current to the amp.

I think the safest and easiest solution is to install a switch on or near the center console that lets me apply the 5v and turn on and off the amp.

I would like some help figuring out the buzz with no sound signal.

One other issue, when the key is turned off there is no head unit to turn off the amp. It just keeps playing. This will be handled by the P2140 PSU.

At least I can have sound for now and the quality is much better than the stock tuner.

Once the system is installed I will readdress the audio to include a miniDSP that allows me to control the output signals via software. I can the control the speakers independantly and create a sub out.

This will likely coincide with a new amp and speakers.

I can move past the audio and start modifying the mini. This is where it gets tricky.
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cazzz
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PostPosted: Wed Aug 01, 2012 6:50 am    Post subject: Reply with quote

Found 2 components that should do the trick with the audio interface.

Pac-Audio TR-4 and LD-10.

TR-4: The TR-4 senses low voltage, as low as 0.8 volts, and turns on a 12v line when the voltage is detected. This should work for me. When there is an audio signal out of the mac mini the TR-4 will turn on a 12v line which I will run through a 5v voltage regulator and apply this to the negative leads. So, with an audio signal there is voltage to turn on the amp. When the audio signal is not present then the amp will be turned off.

LD-10: This is a ground loop isolator with an signal amp built in. So, this should be a better solution then the GLI I am using. I need a little more signal to the amp.
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