Rockford Fosgate 500X, PC-3084B. Rebuilt channels 1, 2, & 3. Everything appears to be good, but with the input switch on 2 channel input, 3 & 4 emit white noise with either no input connected, or in addition to input. There's no noise from 3/4 with input switch on 4ch and 3/4 produce clean output. Channels 1/2 never have any noise regardless of switch position, and switch seems to be fine (cleaned with deoxit as well).
How is it picking up noise if it's getting signal from 1/2 which have no noise?
How is it picking up noise if it's getting signal from 1/2 which have no noise?
The diagrams sometimes have an I and a J shield ground for front and rear. They sometimes appear to be directly connected and sometimes through a resistor.
With no jumper, what's the resistance between the shields?
With no jumper, what's the resistance between the shields?
That's right for some of the 4ch amps.
I generally recommend recommend using y-cables to drive all 4 channels and have the RCA shields directly connected. You could jump them internally. The only time that the internal jumper might cause a problem is if you have two different sources for the front and rear channels like directly from the head unit and the other after passing through an EQ or other signal processor (rare).
I generally recommend recommend using y-cables to drive all 4 channels and have the RCA shields directly connected. You could jump them internally. The only time that the internal jumper might cause a problem is if you have two different sources for the front and rear channels like directly from the head unit and the other after passing through an EQ or other signal processor (rare).
So you think it's normal and if I hooked up front & rear RCAs from the same head unit that would ground the two together? I'm looking at the 400a4/200a2 schematics and they just show all shields going to the "I" ground and no mention of the 100ohm resistor
This is an amp with the 100 ohm resistor.
You can run two stereo patch cords if you need a fader. That would ground the shields together in the same was as the y-cables.
You can run two stereo patch cords if you need a fader. That would ground the shields together in the same was as the y-cables.
Funny how that schematic omits the 2/4 channel switch. It makes sense that I should have been looking at, say, the Power 400a4 manual as the punch versions don't have the channel switch or passthrough RCAs. The Power 400a4 schematic doesn't have the 100 ohm I/J resistor, though.
Still confused as to why switching the input causes the noise, though
Still confused as to why switching the input causes the noise, though
The extra 100 ohms between the RCA shield ground and the ground that the amp has for channels 3 and 4 is likely the problem.