Got a new car! And sadly, its not in the Nissan Family...a competitor*

[pfarmer]

have question for you re your g37s--- I've got the similar g35s-2007... I've also driven a TL, and wife's got the new tsx. My G seems to be really rough* riding compared to these other cars. I do love and appreciate the handling- do you find the same?

And yes, my guy from SoundWorks will tell how he installed the sub- exactly... But- I THINK it is put in with splitting rear stock sub's feed, (high level input?) into my Rockford Fosgate mono 200m-amp with a kicker comp vr 10" sub- with ported box

Modified by lucidd at 3:24 PM 8/19/2009

When I took the 'G's out for test drive (all 2008s) I found the Coupe S to be a little bit 'crisp' compared to the XS, and the XS a little bit 'crisp' compared to the both the X and base versions of the sedan. I did not take an S sedan out.

I haven't really looked at my stock sub yet but since it recieves an 'amp on' signal then it sort of gives away what it is. Depending on several factors it can make a difference to the rest of the system on how it was connected to the Bose or woofer amps especially if the new amp uses non differential inputs (inductive inputs like many) or just straight rca level inputs.

Perry

[pfarmer]

I looked at the FSM. I now know what you mean by +1 and -1. I see they use a voice guidance signal as the audio reference. They call the condition: voice output. The pictures look as if viewed on an O – scope. We (electronic technicians) don’t usually say + and – “X” volts. It’s widely stated: Volts peak to peak (Vp-p). That’s where I was confused. Just to clarify, the +/- 1 V is only a reference for the “voice” In reality, that voltage or should I say amplitude of the audio signal would be much higher or lower depending on the level set when using real program sources such as a CD or iPod. It could be very low in the mV region say for the head units output to the amplifier(s) or many AC volts if monitored on the main or sub amplifier outputs to the speakers. So stating “The audio signals to the amp is +1v to -1v” can be misleading. Although it can be +1 to –1 it also could be + 4.2mV to –4.2mV or +9.8 V to –9.8V and anywhere in between.

Actually it could be that it maxes out at +1 to -1. The reason I did not use the peak to peak term is that this appears to be a differential with a reference to zero (note the time base reference as well). Normally when using peak to peak you would state 2 volts peak to peak and the reference could be anything for example +1.5v to - .5 . I have a small scope so have been thinking of looking at it at the inputs to the amp to see if the signal level (plus and minus 1 volt) stays the same and this is modulated such as phase modulation (hence the time base). Based on other reads however it looks like a typical balance differential output. I have a reason for this as I am looking at a concept similar to how the nav comes into play with another source in service.

Perry

[pfarmer]

Yesterday I checked the inputs to both amps and their respective outputs with my inexpensive but fairly accurate hand held digital O - Scope. I was not going to drag my Tektronix 465 from my shop. What I found was what I expected. Using a reference CD with various sines waves @ 0db and -10db depending where I set the level on the head unit the AC varied from 0 V on up. Of course the speaker outputs went much higher. If I can remember at least 6 or 7. I was not about to push the system but if I would I'm sure I would have seen double digits. Heck when I repaired pro sound amplifiers such as Crown and QSC those units could easily hit 60 - 70 V on the outputs. On a side note, I have repaired many audio power amplifiers and have never run across a unit that used phase modulation. I have thought worked on RF equipt. that did use it. Finally, about the scopes reference point. In the past 20 years of repairing electronics, I have only had to use a value other than 0 (earth or signal ground) one time. That was when I was working as an asst. engineering technician dissecting circuits that the real engineers designed on paper but when bread boarded didn't work.

You are correct about what you would normally find with peak to peak using 0 reference, but that is not always the case. One example is where you are using a system to detect signal to ground exceedence such as alarm panels. Basically you have a voltage of lets say 10 volts peak to peak with your reference on a floating ground of lets say -1 volt. This leave 9 volts to ground under normal conditions (or +1 to the reference) it either one of these changes you have a signal to ground issue. An alarm will pop up and let you know this. I think you would be surprised at how effective and how sensitive this is. A couple of milliamps on a plant wide grounding scheme will show up. This allowed you to go looking into various panels for something like a drip of water leaking on to a circuit board, etc.

I have worked on several signal systems that use phase modulation but like I posted I doubt they would do so here since others have tapped into the line and put in aftermarket amps. I am thinking there are a few who have then had some issues after doing so without realizing they are not really looking at a normal rca style output assuming the - is actually ground.

What type of hand held scope are you using? I have a small scope and a couple of old large ones but have been looking at getting a hand held. The other option is a pc scope for my laptop.

Perry

[pfarmer]

Yesterday I checked the inputs to both amps and their respective outputs with my inexpensive but fairly accurate hand held digital O - Scope. I was not going to drag my Tektronix 465 from my shop. What I found was what I expected. Using a reference CD with various sines waves @ 0db and -10db depending where I set the level on the head unit the AC varied from 0 V on up. Of course the speaker outputs went much higher. If I can remember at least 6 or 7. I was not about to push the system but if I would I'm sure I would have seen double digits. Heck when I repaired pro sound amplifiers such as Crown and QSC those units could easily hit 60 - 70 V on the outputs.

Not sure what the stock Bose amp delivers rms to each channel but you can figure on just under 10 volts you can get close to 48 watts assuming push pull outputs, non bridged, with no dc-dc power supply since you are limited to the system voltage times 2. If you had 70 volts on the output of the higher powered amps then chances are you had just under 150 watts and the amp was using a dc-dc power supply of about +- 35 volts.

Perry

[pfarmer]

Stereo Specialties in Spring Hill Fl would have to answer that for you.

They handle all my equipment.

As I stated... I trust them with what they know best.

I simply pay and drive.

Unless it's my Harley... then we can discuss every bolt..

TD

You stated you had a vette with an aftermarket sound system. What year? I am asking as I am looking at an 06. While I am satisfied with the sound system as is, it is missing the rest of the features I would want, one of which is the blue tooth. So far everything I have read about this is that the work arounds sound like a pain in how well they integrate.

Haven't played with the vette too much so am wondering about the negatives of replacement, that is does it use the stock display for other things that could come into play like the 'G' uses the display for various settings of the car in general?

Perry

[pfarmer]

I've worked on everything from QSC's that output 4000 watts/ch stereo into 2 ohms. They use class AB / H topology. The Vcc rails are +/- 82 (Med.) AND +/- 134 (High) Those type H SMPS have very interesting circuitry. Much different that your standard switch mode. Lately, I have not repaired many car audio amplifiers but when I did most either used inexpensive IC based outputs running 12-35V rails or MOSFETS typically running 35-75V volt rails.

In the case of the 70 volt figure I presented that was just below 150 watts per channel without knowing anything about the particular amp in question (nor the speakers). While I haven't worked on amps of this size for awhile (other than installs) one thing that counts in the higher rail voltages is the ability to maintain it with changes in supply voltages to the unit since the supply can be regulated.

For example running a 13.8 volt system using push pull may get you just over 23 watts, but it will vary based on system voltage. I think this is a good indication of what you often see with amps imbedded in many standard head units which list the magic 22.5 watt values.

Perry

[pfarmer]

The portable scope is a Velleman HPS50. It's no Le Croy or Tektronix but for audio it's fine.

Well beats my BK 2120 or my Echo (out in the garage someplace which is now storage) and whatever is out there. For multimeters I have probably a dozen, I grab whatever I happen to be near for most things. I do have a couple of small bench ones, an older Fluke 8050a and a minimal Hickok 334. Basically these all do what I need right now but with the rc helicopters and so on that I am getting more and more into I am looking at something a little bit newer (like this decade), the Echo is now about 50 years old. The Fluke was actually made in the U.S.

But then each of these cost about 5 bucks each (except the Echo was free a long time ago) and came for the ride when I also bought a 1938 Zenith shutter dial floor radio for $150. My friend has a rare robot shutter dial which has to be seen to be believed (over 3 grand invested). If anyone has not seen one of these - when you change bands the dial is actually a set of dials that are two parts. One set splits in two and moves off to each side and another set comes together to take its place. On the robot shutter you push a station button and the thing takes off hunting it down, the dial is motor driven. It starts spinning and then settles in on the correct station. Works great and remember these were made in the 30s. Great fun to work on, just turn up the air condition.

Perry