Phoenix Gold Phorum

I've had a ZX450 in my car for about six months now. When I turn the stereo on, now the right front channel is much louder than the left channel, like 10dB more. After maybe 10 minutes it settles and sounds right. Keep in mind its winter here and temperatures below freezing.

It doesn't seem like a gain pot problem. I've twiddled it around but no help.

Out of curiousity, when this happens turn the volume knob on your headunit up to 60%-70% max for a few seconds then turn it back to your normal listening position and see if it goes away. I have noticed a similar issue with my Roadster 66 amp and doing this seems to fix it temporarily. In colder weather, I notice my Roadster 66 channels will take a lot longer to turn on than normal and each channel comes in at different times.

bias settings.... not more not less...

had this problem years ago on a zx450....

but stranges it settles after 10min....

but almost sure this is the problem/solution....

I have a friend that complains of similar problems on his.

Sure enough if I turn the volume up loud, then the gain settles much faster, maybe less than a minute. And then its fine. But if I turn the stereo off and on again, the right gain is louder again.

SO it seems like the amp needs to warm up to settle into its normal operating point.

I've never had this problem with an M or MS amps. I prefer them over the more complicated ZX-series. I'm only using the ZX because its four channels in a small space.

Mr. Wild wrote:Sure enough if I turn the volume up loud, then the gain settles much faster, maybe less than a minute. And then its fine. But if I turn the stereo off and on again, the right gain is louder again.

SO it seems like the amp needs to warm up to settle into its normal operating point.

I've never had this problem with an M or MS amps. I prefer them over the more complicated ZX-series. I'm only using the ZX because its four channels in a small space.

My Roadster is similar except when I turn the volume up it will go away and won't come back unless the vehicle has sat overnight or longer and the temperature is around 20F. Even then it only does it 5%-10% of the time. I'm not sure why this occurs. Maybe it's something to do with the electrolytic fluid in the caps? The higher input signal when you turn the volume up seems to send enough juice to "jump start" the amp.

These issues are not normal, and indicate something wrong somewhere.

To start with swap the right and left outputs, and right and left inputs on the amplifier. Does the problem move to the left side, or does it stay on the right side?

Another question is, are the channels experiencing issues...do they have the amp's xovers activated? I notice that the xover pot is a little tedious when near either end (fully clockwise or counterclockwise), if it's set at ByPass then never mind my comment, lol.

on my guys we tried that and then I tried just sweeping the gains back/forth in case they had got dirty but I think the problem I had was more in that we were never able to recreate the problem with me in the car. Its the curse of a tech, sit one in the car and everything works. I half way thought he was making it up because he is my old install groupie that just liked to hang out and talk car audio... I need to go back and will try swapping them although I am pretty sure I swapped them both front/rear at different times to see if it moved with either thinking the cables could go bad. I installed this system back in 1999 after all.....

As of lately this issue has been getting progressively worse with my Roadster. Just about every time I shut the vehicle off and turn it on again the left tweeter is very quiet. I'm running the amplifier fully active to a set of Rsd components and RsdC subwoofer. The 500.4 section crossovers are all set to bypass/flat and I'm using my Pioneer P880PRS crossovers for processing. The 600.1 section of the amp cannot bypass the crossover, but it's set as high as it will go and then I use the headunit to fine tune it. I switched the RCA's on the front section that is sending signals to the tweeters and the issue stays on the left side. Any idea of what could be causing this? I hesitate to turn the gain knobs to see if they are the issue as I've got them set right where I want to.

dwnrodeo wrote:As of lately this issue has been getting progressively worse with my Roadster. Just about every time I shut the vehicle off and turn it on again the left tweeter is very quiet. I'm running the amplifier fully active to a set of Rsd components and RsdC subwoofer. The 500.4 section crossovers are all set to bypass/flat and I'm using my Pioneer P880PRS crossovers for processing. The 600.1 section of the amp cannot bypass the crossover, but it's set as high as it will go and then I use the headunit to fine tune it. I switched the RCA's on the front section that is sending signals to the tweeters and the issue stays on the left side. Any idea of what could be causing this? I hesitate to turn the gain knobs to see if they are the issue as I've got them set right where I want to.

I think there is a very good chance the gain controls are the issue.

I was hoping you wouldn't say that. I guess I'll give it a try.

I've got a ZX475Ti that does the same thing. In my case it is definitely the gain control, YMMV.

It would be very rare for the bias circuit to be responsible for this. Bias has very little to do with the overall gain of the amp.

Good Luck,
Jason

I rotated all of the potentiometers, exercised the switches and no change. I haven't swapped the speaker outputs to see if the problem follows.

The problem has got worse. When I turn up the volume, the channel with the gain fluctuation distorts quite badly.

One of the transistors in the voltage gain section of the bad channel may have failed. Or you might have a broken trace so you are only getting half of the output signal (which will sound like bad distortion). Just some guesses.