Bose sound system

Hello dear community and dear Bose(with)damaged,

A few weeks ago, I already announced that I would
will deal with the architecture and the conception of the Bose sound system. This I have done in my spare time in the last two weeks
and now wants to announce my preliminary results, not
Finally, to give some here in the forum a little courage and courtship, if
I'm going to die another final.

First of all, the principle of the final stages. If you ever have one of the Bose-LS
unscrewed, then in the first moment you are very surprised
about the tiny common heatsink, which is shared by all four
Power transistors are used and at the same time also the shield plate
the final stage. Furthermore I was at least very much about the compact
Design of the final stage surprised.
A first measurement at the final stage transistors then brought light into the dark
of the end stage architecture: Digital end stages, i.e. end stages of the class D!
So if you ever expand and miss such a final stage, you shouldn't
wonder if it only measures rectangular signals over the end-stop transistors,
that must be so.
Well, of course, now you're wondering what the special thing about class D power amplifiers is.
Class D amplifiers have the great advantage that they have a very high
Have efficiency up to over 90%. This is because the transistors of the
Power amplifiers are operated as switches, i.e. on or off. Conventional End-
the most often work in AB operation and thus have a maximum
==References== 78%. The high efficiency of the class D amplifiers
allows the use of very small heat sinks. The disadvantage of these end stages
is the distortion factor which is significantly higher than the conventional end stages in the
AB operation. This has ultimately also been the reason why
the class D amplifiers on the HIFI market could never prevail. Now,
many BOSE opponents certainly shout out:"Ha, that we have always been
Well, I'll leave this claim in the room.
If you consider how many acoustic sources add up in the car, then
One may rather neglect the small proportion of the distortion factor.
In the appendix I have the frequence of a power stage for the front doors
Annexed. The frequency response is not completely clean in measurement technology
and not, as is actually necessary, with the
the relevant impedance has been included. Since the output signal of the
This has been taken up after the output filter, this has to the
The Commission's proposal is based on a number of considerations. The frequency response is at an impedance
At the output, it is probably even more linear.

Now to the previous results of my measurements at defective final stages:
There is hope!!!!
The typical phenomenon, which can be observed at a final stage, is the
"Flattersound" is that she gives away. That flutter--
noise is derived from the switching frequency of the AD converter of the power stage.
I have succeeded in identifying the components responsible for this
To eliminate fluttering noise. What is to be solved now is the problem that
the gain of the final stage has dropped. The components which are responsible for this effect
I have not yet been able to figure out, but I have not yet been able to
Work on it.

When I get new results again, I'll get back to you. The
But it may take a while.

Greeting from Kiel

Maadin