you know what? the hiss goes away within 60 seconds, once it has fully warmed up. after adding the second ground wire, its seems to have gone away almost completely, and once the car starts, with the sound of the engine, maybe the fans, it cant be detected.
i will take a photo when i have an opportunity, and draw on the image to show where it is all going. it really sounds quite nice now
i will take a photo when i have an opportunity, and draw on the image to show where it is all going. it really sounds quite nice now
adding the second ground had fixed the hum practically completely. (you have to hold your ear to the speaker with the car turned off on a quiet day to hear it)
the only problem left is a hissing i get that lasts for around 60 - 100 seconds when you first fire it up cold. if i turn it off and then back on again within 10 minutes, the hissing takes 20 - 30 seconds to dissipate. this is really not much of a problem to me, but i guess if someone has any suggestions with the very limited infomation i have, then go for it. all i can offer is what has already been said, and this photo:
the only problem left is a hissing i get that lasts for around 60 - 100 seconds when you first fire it up cold. if i turn it off and then back on again within 10 minutes, the hissing takes 20 - 30 seconds to dissipate. this is really not much of a problem to me, but i guess if someone has any suggestions with the very limited infomation i have, then go for it. all i can offer is what has already been said, and this photo:
Attachments
nothing is connected to the chassis on this pcb. if i attach from chassis to the on board ground i get a heck of alot of noise. so i dont connect it. obviously the audio grounds are connected from source>input then output>power amp. none of the power windings from the transformer (150v,0v,150v and 6v,0v) are connected to the chassis.
one of the terminals/pads for the volume control also connected to ground on the pcb, so i made that terminal/pad the shielding for the cable volume control.
one of the terminals/pads for the volume control also connected to ground on the pcb, so i made that terminal/pad the shielding for the cable volume control.
That's good. So the only connection from pcb wiring of any kind to ground/chassis is through the source/input via the signal cable shielding? That's an appropriate single point earthing.
Sounds like a good setup is for the inverter and power transformer to be close together and bolted to the chassis. If the transformer had a shield then that would assist filtering some of the switching noise from the inverter back to it directly. The inverter should also have extra DC terminal capacitance if possible to localise switching current as much as possible.
Sounds like a good setup is for the inverter and power transformer to be close together and bolted to the chassis. If the transformer had a shield then that would assist filtering some of the switching noise from the inverter back to it directly. The inverter should also have extra DC terminal capacitance if possible to localise switching current as much as possible.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.