TOPIC:

My car audio have this output copy from manual is it going to over drive the minidsp ?
if yes is anything that i can do to make it work

Also my car audio says 20Kohms now that the minidsp says Impedance 6Kohms will this going to be a problem for me ?




hope it make sense not really good on electronics though i study them 20 years ago buut if my memory serves well it supposed that input and output impedance must be the same
Thanks in advance

Which headunit is it?

A few things:
A 20kohm load is VERY, VERY minimal. Adding a load to it is likely to cause the output signal to clip earlier and be lower.
It’s been my experience that the rated voltage is taken with a 0dB test tone. Your music is nowhere near this. A test tone is pure signal all the way. Music is much more dynamic.

In short, you should be just fine. If the output voltage does indeed register above the 2v input of the minidsp you’ll get clipping at the inputs.
In all actuality, you’ll likely be fine. A 4v rated output is much less when talking about music. And, the software has an input monitor which will allow you to watch the input signal to make sure it’s not too hot.

Let’s assume for a second that your headunit does output a higher input than the minidsp can manage… how do you fix this? Well, simple. Just note the volume at which you get input signal clipping (do this with pink noise at a -3dB tone) and make sure you rarely exceed that. Again, in real world use, this isn’t going to be a problem. The numbers from mfg’s is often highly exaggerated and given in ‘best case’ scenarios for them (test tone, 0dB output).

If you properly set up the gain structure in your system, you won’t have anything to worry about.

*sorry for the diffuse answer… typing on my phone and it’s hard to go back and move things around*

Check out my bit on the input voltage of the miniDSP in my review here:
www.minidsp.com/support/forum/7-car-audi...xcellent-alternative

Hello,

shouldn´t you be able to simply lower the input-sensitivity of the miniDSP with a voltage-divider?

Yes. I actually meant to suggest that, but typing from a BB is cumbersome and causes me to forget things.

Again, I don't think it'll be necessary. You'd be surprised just how little voltage a headunit's preouts spit out with music (same for amplifiers).


Here's a link to a voltage divider calculator:
www.raltron.com/cust/tools/voltage_divider.asp

If you want to drop the 4v output to 2v, use 560 ohm resistors.

And, again... I suggest you run this thing and watch the input meters before you go through the hassle of building a voltage divider. I promise, it's not as big a deal as you think.

The head unit is Jvc KD-SH909R and maybe i will change it for an kd-901 for the blue-tooth basically, you know to drive and talk with safety .

The initial setup i will do it with the 909 though , i am considering write a cd at 0 db
at 1 khz and check the input meters and thats all maybe i will be able to use a oscilloscope at work to measure the real voltage

Also i usually never go the volume knob more than the 50-60 % so maybe this isnt a real world problem for me

time will tell as the truth for now i am waitng the post office

Yes, you can test this yourself very easily with a 0db tone, 1khz and a DMM. Use the scope to watch for highest unclipped output.
I test every headunit I use this way, with a 560ohm load (and even 22kohm sometimes if I do get clipping at 560ohm). Every one has put out rated voltage, and only one has clipped at full volume. The DACs in most headunits today are very good.

The problem is, this isn't real music. A 0dB tone is nowhere near the signal that music is. Music is less constant and more dynamic. I'd put money down that the peak voltage on standard (ie: non-rap) music never peaks above 1.8v at full tilt, on a headunit rated for 4v nominal.

As I said, the easiest thing to do is to simply watch the GUI's input meters. That will tell you if you have a problem or not. And I bet that you won't.