Low volume distortion during installation

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supraturbo94

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Joined: January 08, 2005

Posted: May 02, 2005 at 9:40 PM / IP Logged

I'm installing CDT components in the doors, run by a Cadence Q4000 and the stock HU. This is in a mkiv Supra using the high-level inputs (from after the factory amp) on the Cadence. I have one mid in the door so far and I wired it up to test the amp and wiring. With the gain on minimum and the HU volume relatively low, it is already distorting. If I turn up the gain, the distortion actually lessens. With the HU volume up and the gain at min (to set the gain according to Cadence), there is enough distortion that I don't want to turn up the gain any. Without music playing, there is minimal noise.

Any idea why I'm getting distortion at such low music volumes? Or why it improved when the gain was turned up part way?

kfr01

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Posted: May 02, 2005 at 9:54 PM / IP Logged

Here's my guess: it isn't quite distortion, but rather some sort of electrical noise. Increasing the gain just hid the noise. I can't say I've ever used high-level inputs, but I assume the gain setting procedure is the same as with RCAs. Pros? Set your gain and leave it. Then troubleshoot the noise problem. In my experience many noise issues go back to grounding problems. Check out the excellent grounding stickies at the top of the forum.

New Project: 2003 Pathfinder

supraturbo94

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Joined: January 08, 2005

Posted: May 02, 2005 at 10:09 PM / IP Logged

The only ground I've added is for the Cadence amp and it is grounded at the same point as the stock stereo. I did not sand off the paint at this location, should I?

There is also a ground wire in the little high-level harness on the amp (it has 5 wires: pos and neg for each channel and the ground). I have not connected this wire to anything, does it need to be grounded as well?

stevdart

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Posted: May 02, 2005 at 10:10 PM / IP Logged

The wire that you connected between the OEM wiring and the amp high level input may be picking up noise. A cure is to twist that signal wire, + and - around each other at 1 to 1.5 twists per inch.

And, the stock system might be "premium" which might consist of original low impedance speakers. If that's the case you should use a special adaptor to get a usable preamp level signal from the head unit.

The ground wire on the high level harness would not be used. It's there for use with common ground car audio systems. If you got no sound at all, then connected the ground, you would get sound if that were the case.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

supraturbo94

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Joined: January 08, 2005

Posted: May 02, 2005 at 10:28 PM / IP Logged

I used a shielded 4-wire 22awg from the OEM wiring and the amp high level input. Is having both channels twisted together a possible problem?

The stock HU puts out a low level signal (with one wire for each channel) to the factory amp, which then sends the high level signals to the speakers. As far as I know there's nothing special about the output to the speakers, so I have sent this signal to the Cadence amp. Ideally I'd get rid of the stock amp (5 lbs I don't need), but the power and other connections for the HU come from it and I'm not sure how I would set that up.

stevdart

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Posted: May 02, 2005 at 10:34 PM / IP Logged

The twisted wiring would not be a problem.

The grounding is a potential reason for the noise. If you can't fix it that way, try an aftermarket adjustable line output converter instead of the amp's high level converter.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

kfr01

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Posted: May 02, 2005 at 11:57 PM / IP Logged

Also, yes, strip the paint at your amplifier's gound point. It will thank you. :-)

New Project: 2003 Pathfinder

supraturbo94

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Joined: January 08, 2005

Posted: May 03, 2005 at 8:30 AM / IP Logged

I'll strip the paint and check the grounds tonight.

I'd like to use a nice LOC such as the PAC OEM and remove my dead weight factory amp, but I'm not sure how to do the wiring. Has anyone kept the HU and replaced the amp in a Toyota with a separate factory amp?

geepherder

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Joined: October 27, 2003

Posted: May 03, 2005 at 8:05 PM / IP Logged

Some Toyotas use the processors in the amps to do all the balance/fade controls. That being said, it may be easiest to take signal after the factory amps to connect your LOC's.

My ex once told me I have a perfect face for radio.

supraturbo94

Member - Posts: 9

Joined: January 08, 2005

Posted: May 03, 2005 at 8:57 PM / IP Logged

I ground off the paint down to metal at my ground. No difference. I installed the mid on the other side and have the same noise problem with that speaker. Could the high level inputs on the Cadence be that lousy?

According to the electrical manual, the wires in the harness from the stock HU to the stock amp are power, acc, FL spkr, FR spkr, RL spkr, RR spkr, mute, beep, fade, and antenna. Ground is in the shielding. This makes me think that the amp must be controlling fade, if not balance.

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