Modifying OEM head unit for un-eq’d line out

[utc_pyro]

On the P-203UE there is anothe mod you can do increse channel separation. it combines the four channels into a single one for the sub output (I presume you're not using) with a few resistors, you just need to remove those. I'll post up how to do it when I get home. It will help with the line level mod or using the internal amp.

[mars_volta]

Cool. Ive also come up with a quick and easy way to access the bottom of the board. Ill post up later.

[lopezi]

This is exactly the information I am looking for....it only took me two weeks....but I finally stumbled on it (maybe this should get stickied too?)

 

In any event, I'd like to perform this mod on my '05 OBXT factory radio. I'm assuming everything discussed up to this point is applicable? Also, do you just remove/de-solder the capacitors to eliminate the loudness circuit?

 

Also, in the above pics there is a mod done for line-in, I'd like to do this too while I have the unit open, could you expand upon the steps involved for that too?

[ean611]

This is exactly the information I am looking for....it only took me two weeks....but I finally stumbled on it (maybe this should get stickied too?)

 

In any event, I'd like to perform this mod on my '05 OBXT factory radio. I'm assuming everything discussed up to this point is applicable? Also, do you just remove/de-solder the capacitors to eliminate the loudness circuit?

 

Also, in the above pics there is a mod done for line-in, I'd like to do this too while I have the unit open, could you expand upon the steps involved for that too?

 

If you want line in, I'd recommend the Jazzy aux-in mod or go with a 07+ radio. As for the capacitors, just de-solder them, and you're good.

[utc_pyro]

I think I'm going to take the plunge and do the mod my self... I cant get my MS-8 sounding worth crap due to the loudness issues.

 

You guys that have done it, are you noticing any loud turn on/off sounds or ground loop noise? I'm having a LOT of issues.....

[mars_volta]

Yeah I get some noise when my headlights are on. Need better grounding...

[utc_pyro]

Do you think it's a bad ground to the trunk floor pan, or do you think the radio could use a better ground? I'm thinking about running 10gauge from the radio to a bolt on the transmission tunnel, but am unsure if that will help...

[ean611]

In my setup, I'm running the radio directly to a Rockford Type RF X4.C

 

I have no noise issues whatsoever.

[utc_pyro]

In my setup, I'm running the radio directly to a Rockford Type RF X4.C

 

I have no noise issues whatsoever.

 

Are you runing decoupoling capacitors on the signal leads? Also are you using an interal ground on the radio for the shield, or leaving that floating?

[ean611]

I am not running any decoupling caps.

 

I made sure that I'm using shielded RCAs for most of the run, keeping the wires soldered onto the radio as short as possible.

 

I also have an aux-in board from SVXdc which is grounded to the outer chassis of the radio.

 

The typical source of noise that I've seen is RCAs being run to close to amplifier power wire. My power wire is run down the left side of the car, while the RCAs are run down the center console to the trunk.

[utc_pyro]

My RCA cable is going down the passenger side with the power down the drivers side. I'm also getting pretty bad turn-off pop, especially if I use my custom line driver. The custon one SOUNDS better then the comercial one, but the pop is bad enough I'm afrad of blowing the tweeters.

 

Currentally I have a "tristed pair" rca cable going to the MS-8 and RG-59 coaxil cables from that to the amps. The MS-8 has difirential inputs, so the "ground referance" should be up from at the LOC without any ground loops. It also should conteract any noise. I'm not really finding this to be the case though.

[ean611]

I'm running without the line driver. With the JBL MS-8, I don't think you'll need any line driver. I'm running directly from the radio into the amp. have you tried that?

[utc_pyro]

The line lever is too low for the MS-8, thus I needed to get it up to 2.5vrms or so. It's only 3db, but the OEM integration wont work without it. The MS-8 is unity gain.

[ean611]

I've never used an MS-8....odd, as I tested my 3Sixty.2 on those voltages, and it works fine once calibrated (has pots to adjust)

[utc_pyro]

On my 3sixty.2 I could have turned the sensitivity all the way up an take care of it just fine as it has an adjustable input level. The MS-8 is fixed at 2.5(ish)Vrms. I could run it off the amp outputs from the head unit, but that would put all sorts of distortion back into the sound from those ~25 opamps we bypassed.

[SVXdc]

I also have an aux-in board from SVXdc which is grounded to the outer chassis of the radio.

 

The ground lead on my aux adapter board is strictly to the HU's aux enable input (pin 6 on the HU's i85 socket, which allows you to press the HU's aux button). It doesn't touch the audio ground.

[HokieMike]

Greetings all. I am new to this forum, but have been around car Audio for a long time. First off, thanks to utc_pyro and ean611 for their work.

 

As the owner of an 07 outback limited, I am eagerly following this thread. I am about to begin an install, and was debating how to take care of the volume dependent EQ in the factory head.

 

I am not at all opposed to snipping a few solder paths to get good sound, but I was hoping someone could condense the directions into something easy to print and read. Also, how many people have tried this? Can others post their experience to give those of us who are interested a better idea of what to expect?

 

I am thinking of using this technique to defeat the EQ, and then running speaker-level wiring to my MTX Re-Q5 to provide the line conversion and some gain. I was hoping to get away with speaker level to the back of the car, and converting to RCA there. If this mod drops the speaker-level output to 2V, that might not be a good idea. Any thoughts about how that would work?

 

Thanks. Mike

[ean611]

The ground lead on my aux adapter board is strictly to the HU's aux enable input (pin 6 on the HU's i85 socket, which allows you to press the HU's aux button). It doesn't touch the audio ground.

 

I agree this shouldn't matter, but I was including it for completeness, as there is noise in UTC_pyro's system that I'm not seeing.

[utc_pyro]

I am thinking of using this technique to defeat the EQ, and then running speaker-level wiring to my MTX Re-Q5 to provide the line conversion and some gain. I was hoping to get away with speaker level to the back of the car, and converting to RCA there. If this mod drops the speaker-level output to 2V, that might not be a good idea. Any thoughts about how that would work?

 

Thanks. Mike

 

This does not defeat ALL of the EQ, just the loudness compensation. There is still a whole mess of EQ (including sharp notch filters) after the point we did this modification. A Clean Sweep, 3sixty.1/.2, or MS-8 can take care of it after that point, but it's not "de-eq'ed" at the speaker level outputs. It just has a consistant EQ there.

 

If I can find another radio, I'm going to do a step-by-step guide. I just need another radio first...

[HokieMike]

UTC - I understand what you are saying. I think that eliminating the loudness curve will do the trick for me at this point. While I don't have the MS-* that I would like to have, I do have parametric EQ that will help the siutuation. Have you by chance plotted the problem spots for the remaining OEM EQ/filters? Thanks again.

[utc_pyro]

UTC - I understand what you are saying. I think that eliminating the loudness curve will do the trick for me at this point. While I don't have the MS-* that I would like to have, I do have parametric EQ that will help the siutuation. Have you by chance plotted the problem spots for the remaining OEM EQ/filters? Thanks again.

 

No, I haven't plotted it as I was never planning on using it. Though I guess you can use it to get a ~5vrms balanced output if you bypass enough stuff. There are ~10 op-amps applying filters to the signal you'd need to bypass

 

If you look at the attached, you could put that into Spice and see what sort of responce it has. I only have an educational version, so I can't modle something with more than ~3 opamps. The pink and blue lines are are how to wire the bypass, the red ones are "cut" lines.

[HokieMike]

UTC - I guess I should have been a little more specific with my question. I was wondering of you knew where the problem EQ frequencies were acostically - as in "6dB notch filter at 3500hz" rather than attacking it electrically by bypassing the internal EQ. I have no intention of modding the factory head that much! I was just hoping to dial in my parametric EQ to the most noticeable problem areas and calling it a day!

[ean611]

hokieMike: You're over thinking things as far as analysis of the radio.

 

Grab a reference microphone, play some test tones, and use some RTA software if you're looking for peaks and valleys for PEQ setup.

 

I'm running the radio with loudness kill to an amp, and the frequency response is smooth enough for what it is. Most of the stuff you'd be fixing would be more related to the car's acoustics anyway. In addition, this means that your specific speakers matter for that equation, so go measure.

[HokieMike]

ean611: You are probably right. I will definitely do my regular tuning routine. it's just that when utc mentioned that the head still had lots of EQ issues, I was hoping that those might be overcome as well. If this fix bypasses the loudness curve, then I should be able to take it from there. Again, thanks to both you and utc for your work!

[sjwelna]

Has anyone attempted this on an essentially stock stereo system yet? I have an 08 limited that I am thinking of just trying the loudness kill by taking out the listed capacitors. If im understanding you correctly I could then run line level inputs to an eq and to amps from there and be good to go? I wasn't planning on doing a big stereo in the lgt but this has my interest peaked.

 

-Steve