I've found this amp, opened it up and found that it has no filter coil on the 12v input... The other jensen that i have has one. Also this amp has a 22ohm resistor in series with a 10nf cap between gnd's. As far as I can remember this never had a problem with noise. Is your alternator and engine well grounded?
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Inductors are not necessary on the B+ input to prevent noise. They wouldn't have any significant effect on the low frequency noise that's produced by the alternator.
The isolation of the secondary ground is what prevents noise in most of these budget amps.
The 22R in series with the 10nF cap is a snubber. It's connected across the transformer's windings to damp ringing on the square wave.
The isolation of the secondary ground is what prevents noise in most of these budget amps.
The 22R in series with the 10nF cap is a snubber. It's connected across the transformer's windings to damp ringing on the square wave.
the resistor between amp gnd and pwr gnd is definitely 10R, thats what i measured and it says 10 ohms on the PCB. Perry, if i change the 10r resistor with a 100R would that be ok? or would it disrupt the whole design? cos i also got another amp here - a 250 W sony xplod amp - the resistance from amp gnd to pwr gnd is about 5Kohms.
there is a large inductor by the pwr input in the Jensen amp.
i just measured the resistance from the rca shield on the cable (disconnected from amp but connected to frontloader) to pwr gnd of amp, it measured 2 ohms (about)
as far as i know the alternater is well grounded - its a 96 model nissan sentra and i have no other electrical problems with it (charges fine too)
i have the pictures on my computer but they are too big to put as an attachment (about 300kb)
there is a large inductor by the pwr input in the Jensen amp.
i just measured the resistance from the rca shield on the cable (disconnected from amp but connected to frontloader) to pwr gnd of amp, it measured 2 ohms (about)
as far as i know the alternater is well grounded - its a 96 model nissan sentra and i have no other electrical problems with it (charges fine too)
i have the pictures on my computer but they are too big to put as an attachment (about 300kb)
There isn't much noise in an amp that's properly designed and in good working order. The filter caps across the B+ and ground terminals filter most of the noise. The inductance of the power wire is enough to stop anything that's left.
For the most part, Rockford, SoundStream, MTX and Zapco don't use filter caps on their B+ input.
For the most part, Rockford, SoundStream, MTX and Zapco don't use filter caps on their B+ input.
I don't see a problem with changing the resistor to a higher value.
With no RCA cables plugged in, confirm that one end to chassis ground is 0 ohms and the other end to the RCA shield is 0 ohms. That will confirm that this is the resistor that connects chassis ground to secondary ground.
After you change it, mount the board back into the heatsink and clamp the transistors down tightly to the sink. Insert a 10 amp fuse in the B+ line in case the amp has a problem with the higher value resistor.
If the engine noise was relatively minor, this may solve the problem. If the noise was extremely loud, this probably won't solve your problem.
With no RCA cables plugged in, confirm that one end to chassis ground is 0 ohms and the other end to the RCA shield is 0 ohms. That will confirm that this is the resistor that connects chassis ground to secondary ground.
After you change it, mount the board back into the heatsink and clamp the transistors down tightly to the sink. Insert a 10 amp fuse in the B+ line in case the amp has a problem with the higher value resistor.
If the engine noise was relatively minor, this may solve the problem. If the noise was extremely loud, this probably won't solve your problem.
i recently got a new set of front speakers, and decided to try and fix my amp so there would be no engine noise. i replaced the 10 ohm resistor with a 100 ohm, and it did nothing. then i pushed the resistor to 2k2 ohm, stil tons of noise. then i went back to the head unit to check the RCA output grounds - this is where its gets interesting:
measuring the the RCA ground to head unit chassis -> 0 ohm. this seemed right, but as a last resort i physically tied the RCA ground to the chassis with a piece of wire and the noise went away!!!!
so for anyone reading this with the same problem, do the mod that Perry suggested - even if your measurements look right.
thanks again to everyone for your input.
measuring the the RCA ground to head unit chassis -> 0 ohm. this seemed right, but as a last resort i physically tied the RCA ground to the chassis with a piece of wire and the noise went away!!!!
so for anyone reading this with the same problem, do the mod that Perry suggested - even if your measurements look right.
thanks again to everyone for your input.
I just put a refurb pioneer HU in and took an alpine out, now at low volume the alternator comes in. Had this with pioneer 20yr ago and they still can't get it right.
It does seem to be louder on the right than left, I'll have to find time to test it out. Reconnecting the RCA made no difference.
It does seem to be louder on the right than left, I'll have to find time to test it out. Reconnecting the RCA made no difference.- Status
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