|
Posted by JimL on February 10, 1999 at 15:24:42:
In Reply to: Re: Mysteries of the "premium" DSP / AMP posted by Bob Hazelwood on February 10, 1999 at 12:03:06:
: Great information! Thanks for posting it. I have been dying to get my hands on one of these systems to investigate it for some time, but it has been hard to find any "take-outs" yet.
: I am very familiar with the Philips chip, as I evaluated and rejected it for a project I was working on some time ago. There is hope however for those who do not want to go inside the DSP "box" to get a reasonable signal to drive a sub amp. If the speaker output of the chip is unloaded by driving a high impedance instead of the specified 8-Ohms, then the distortion drops dramatically until it is in the <0.1% neighborhood. Therefore, connecting it to a typical external amplifier with an input impedance above 10kOhm should give good enough results for subwoofer use. The problem is that many of the "line output converters" that people insist on using simulate a speaker load, so this distortion reduction is often not realized in practical applications. A direct to amp connection without converters should work well with any amp with sufficient input level range.
You're probably right about this. Grabbing the low level signal is probably not worth it for most people.
Is BMW using a bridge configuration, or is it single-ended? I would imagine single ended is the way to go with this chip since it's not all that stable.
The TDA1560Q is internally bridged (BTL). The datasheet for this part is available on the web on the philips web site. It's a .pdf file. The "typical" application diagram in figure 6 is exactly what BMW uses. The charge pump caps (C1,C2) are 3300uF.
The subs are dual voice coil, so there are a total of 4 TDA1560Q's in the system.
Is it the same for all the channels?
The tweets are powered by TDA8566Q's, which are 2x25W BTL stereo amps.
: While in there, did you notice if they happen to have the operation software on a plug-in EPROM?
I was going to ask you about that. I forgot to write down the part number. THere is a custom control chip made by Motorola for BMW. It's called ZC... something or other. And it's labeled "BMW DSP-1". I assume that this chip decodes the I2C signals coming from the front of the car and tells the DSPs what to do. I think the 56004's are the ROMless parts, but I could be wrong.
I'll open the box again and post the exact part number.
Bob, about a replacement sub box. I was looking at the JL Audio Stealthbox for the Audi A4. http://www.jlaudio.com/stealthbox/audia4.html. Do you have anything like this for sale?
I haven't seen a good option for the E39 yet that gives good bass without sacrificing too much trunk space. I'm probably facing a custom install.
How would you recommend mounting a sub in this car? The factory bandpass box sits under the rear deck and fires through two small (approx 3") holes leading into the passenger compartment. The problem is, if I go to one or two 8" or 10" drivers, how do I position them for best sound and least waste of space?
A friend brought over his Hsu 12" sub mounted in a sealed box that we hooked up to a 600W MTX amp. We threw that in the trunk and it sounded GREAT. Tight, clean, powerful. I'm obviously looking for a more permanent and less "brute force" solution.
Any tips you can provide would be appreciated!
Thanks,
/JimL
© 1997 -
2010
Jump Internet Inc. All rights reserved.
