hey. finally got to work my hiraga class a amp. www.tcaas.btinternet.co.uk/hiraga3fig1.gif. its powered by rod elliots power supply +-24v. sound.westhost.com/p89-f1.gif. the problem is that the amp hum, the hum changes depending on engine revs, electric windows etc. where should i look for a solutution to my problem. thanks
maybe you have some guidelines to rerouting cables? here is the photo to make things more clear ImageShack® - Online Photo and Video Hosting
Try disconnecting the INPUT phono leads and shorting the INPUTs.
This will tell you wether the problem is coming from outside of the box.
I also note that the amp is not yet in a vehicle.
If you are powering it with a 115-24V adaptor, that could be the source of your hum. Try just using a car battery.
This will tell you wether the problem is coming from outside of the box.
I also note that the amp is not yet in a vehicle.
If you are powering it with a 115-24V adaptor, that could be the source of your hum. Try just using a car battery.
Sounds like you have a cabling problem as I originally intimated.
Check the cables carefully and make sure that the audio cables are run down the opposite side of the vehicle to the power cables.
You might also like to think about interconnects that don't use the shield for signal.
ie. Use a twin core screened cable, using the two cores for signal and signal return, connect the shield ONLY at one end to signal return.
Check the cables carefully and make sure that the audio cables are run down the opposite side of the vehicle to the power cables.
You might also like to think about interconnects that don't use the shield for signal.
ie. Use a twin core screened cable, using the two cores for signal and signal return, connect the shield ONLY at one end to signal return.
12V input is referred to power ground (- pole of the battery) but the signal ground cannot be referred to that.
You have a center tapped transformer, do you?
Your signal ground is the center tap, so the Higara's GND is the center tap of the secondary.
So you've a secondary floating ground. Good. Now you've to connect the signal ground (center tap) and the power ground (12V side) with 1k resistor // 100nF capacitor (in parallel).
With this solution, grounds are decoupled by 1k//100nF and you won't have any ground loop.
This method is use in every modern car amplifier.
See this:
You have a center tapped transformer, do you?
Your signal ground is the center tap, so the Higara's GND is the center tap of the secondary.
So you've a secondary floating ground. Good. Now you've to connect the signal ground (center tap) and the power ground (12V side) with 1k resistor // 100nF capacitor (in parallel).
With this solution, grounds are decoupled by 1k//100nF and you won't have any ground loop.
This method is use in every modern car amplifier.
See this:
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unfortunately the static noise didn't disappear after decoupling power and signal ground. the static noise starts right after the ignition is turned on, no matter if the head unit is turned on. ive also tried to wire power groud directly from my car battery, nof from th chasis and the noise became a little quieter
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