So you have 10 RCAs coming from the HU. Why do you then send the signal to the OEM amplifier. Why not connect the front 6 channels to the summing device (assuming the summing device can accept RCA aka line level signals)? Why use the OEM amplifier at all? Unless the summing device does not accpet line level inputs.

This (speaker level input of summing device) is most likely where the hiss is coming from.

So your summing device converts 6 channels to 2 channels then these 2 channels and the other 4 channels are DSPed by the 441dsp! OMG this is nuts. Brave but nuts. (I mean this in a nice way).

Typically a HU will output 2V rms at about 10-20Kohms. Unfortunately your HU outputs 10 such channels and we need to DSP all of them to get time correction. Most DSPs provide for 6 or 8 inputs not 10.

It might be beter to get a summing device that can accpet line level inputs. This will give you 6 channels of line level audio. The other option is to Juggad the HU and bypass the crossover in the HU. Time to break out the soldering iron!

Do you know of this device?
http://www.zapco.com/zapcoprocessors.html

There are NO RCAs coming from the stock HU. Infact, the HU is a mere transport device for reading from CDs/SD card or Radio. The stock wiring harness connects the HU to the Stock amplifier. Its the stock amplifier that manages the volume, Bass/Treble & other effects. This is the reason why I had to tap from the door speaker wires (3+3, for L & R doors, front only). I've not tapped from the rear door.

The hissing comes from the DSP. The DSP 441 has two modes, first for receiving signal from the SSI and the second for the Aux mode. The DSP also has aux ports. The hissing is only heard when set to receive from the SSI (even with the ssi disconnected).

Yes, apparently, that's the only way out, if I wanted to use the stock HU the way it is. Else I can connect the DSP directly to the HU and use the DSP volume control to manage the music volume, however, in this case I wont be able to have any control on the Bass/Treble.

One alternative is to install an equalizer and connect it to the HU or to use a separate HU (single DIN). In latter case I wont be able to use the steering volume controls.



I repeat, the HU has only 4 stereo outputs which is fed to the stock amplifier. I'm also attaching the HU connection diagram.

The CL-SSI I'm using accepts both line and speaker level signal. There is a selector switch.

The edit function is not working, so I have to upload the wiring diagram separately.

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Thanks Nitin. I hope you are not getting frustrated answering my questions. My only intention is to find some way to shorten the signal path and hopefully remove that hiss.

That diagram explained a lot. I assume that even if we find a DSP that has bass and treble controls these controls will not be usable from the stock HU??

No not at all. All suggestions are welcome

If you're using the input to the DSP from the speakers (woofer, tweeter & mid-range) then you can use the stock controls - that's the only way. However, if you take the input from the HU instead of the speaker wires, the controls would be invalid. However, you can use the DSP volume and other controls.

I'm now trying to troubleshoot the hissing problem; looks like the dsp is defective.

This weekend was when things took a sharp turn to a different direction altogether. I was browsing the net and came across a similar HU & stock amp and the connector diagrams. I had a bad hunch to open and see what exactly is inside and how all of this works.

The first thing I did was to remove the Skoda amp at the bottom of the left passenger seat. The build was quite solid and there was just a single connector for power, inputs and outputs. No turning pots/switches provided. The label mentioned the make to be Panasonic and there were symbols of VW & Audi, which told me they share parts.

The next was the stock HU, Bolero. Previously, I noticed that the entire volume was controlled through the amp so I wanted to find out how. I was surprised when I took the HU apart, the CD changer was quite identical to the ones used in Pioneer and the entire HU was made by Blaupunkt! The board was quite clean with the single IC power stage.

I powered on the HU and using a headphone tried to trace the signal path. Wow, I noticed that I could control the Volume, Bass & Treble independently without the amp! How was this so, as the last time, It appeared not so! I connected the amp and noticed the volume is now controlled by the amp, while the HU outputs the full output. IC., so with the amp, the canbus takes control and with the HU alone, its through the HU volume control.

Now things are easy and I could just trace the signal path to the preamp section and take the preouts! Neat!

Got hold of a couple of RCA connectors and soldered them towards the output of the preamp. I also used a couple of resistors and caps just for safety in case the preouts got shorted. I am now able to get clean preouts from the very same Bolero HU!

The next step was to test by connecting the amps and I was so happy with the clean output and fidelity.

Here are the pics. I would today purchase some good quality RCA wires and wire the entire amp freshly! The DSP and SSI are now on sale!

Now do you agree with the title, "where no one has gone before"

The stock amp is now bolted back to its original location but kept disconnected.

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I expected this. Blaupunkt makes HUs for many VAG cars. Apparently what the HU does is offer full line out and a controlled output (many devices like iPods also do this). The controlled output is used when no amplifier is used or when the amplifier used does not have it's own control section. Hence the OEM amplifer used only the full line out of the HU and ignored the controlled output.

It could even be that the controlled output must have a low output impedance (low enough to maybe drive speakers) while the full output would have a higher output impedance meant to drive amplifiers and such.

Anyway now that you have in effect eliminated the OEM amplifier you can live without the DSP (unless you are looking at Time Alignment and/or EQ).

Unfortunately there is no DSP processor I know of that can offer you more than 8 channels of output. Do you still need 9 or 10 (front low, front mid, front high, rear and sub - either mono or stereo) channels of output? If you can live with 8 channels I would stronggly recommend looking at the Bit One or the latest DSP to arrive - Arc Audio's PS8. If you are on a budget look at Zapco's DSP-Z8 or Helix's P-DSP.

If you need to know more about these products PM Gunbir or Bass & Trouble (both BHPians).

I've already taken two pairs of Line Outs, L/R for F/R so no need for any DSPs now, can feed directly to the amplifiers.

Sir, DSPs I was refering to offer you various other functions like Time Alignment and 1/3 band parametric EQ (and even auto tune).

If you find the bass coming from the rear and the mids coming from the front then you might need a DSP.

Oh Yes, you wont have those functions. The DSPs you're talking about cost alot - not willing to spend as of now.

The JL that he had couldnt do this anyway, so he's better off getting rid of it.

I know that B&T. After getting TA (on the first Alpines) in 2003 I wonder how we lived without it (sorta lika a microwave ).

Wow.... the hissing, cracking and alternator whines came back for some unknown reason. tried everything, changing the RCAs, testing the ground at different points, noise filters etc., but all of these were only temporary solutions.

I finally decided to have an Alpine CDA-117 installed with the stock HU connecting to the Alpine HU through the AUX, so that I can use both the HUs.

The sound quality with the Alpine is definitely great, though it lack the "loudness control" which boosts the bass & treble at low volume levels. :-(

The sad part is that the hissing, cracking & alternator while still persists when you start the car for the first time in a day or after a long break. They slowly disappear after some use! Strange indeed.

MODS: The pics which we normally have nowadays easily exceeds 3-4MB, so having the 1MB limitation is a real problem as its such a task to down-convert them. Please increase the attachment size limits, atleast for pictures.

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Interesting ICE now

The noise issue can only be a install/bad component issue. Hope you can get it sorted soon.

About pix, resize and post since there is no point posting 3MB pix anyway.
If on windows 7, google for "powertoy windows 7 resize image".

Wrong thread,still Why did you sell the Fortuner ? And why Laura?

I'm trying to put new RCAs, I believe the current RCAs are counterfeit.

I sold the Fortuner because having used both the Innova and Fortuner, I feel Toyota vehicles are more targeted towards the Taxi/commercial vehicles segment, whereas the Skoda, VW, Audi or BMW are targeted more towards the driver and passenger comfort and safety. The build and quality of materials are way above superior. So are the features and specs. I really dont know how to praise the drivability of the Laura!