Hello there,
I am building my first point-to-point amp (a Bugle 45 by G. Rankin, with some mods suggested by him). I decided to use a dual-panel chassis with a wooden frame separating the power supply section from the signal one, and two heavy (1/8") aluminum panels.
I built a ground bus for each section with 10 AWG bare wire. All components that should go to ground are connected to it. See picture (note that I haven't received my power and filament transformers yet so some connections are missing, but you get the idea. I also added a wire from the mains earth to the PSU ground bus). The chassis is not connected to the ground yet.
Does my wiring make sense so far? I am not sure what the best way to connect the two buses and the chassis would be. Shall I run another piece of 10 AWG wire between the two buses, making an "H", and connect the two chassis panels to the closest point in the bus? Does the connection point or the wire gauge make a difference?
I'd appreciate any help. Thanks.
gm
I am building my first point-to-point amp (a Bugle 45 by G. Rankin, with some mods suggested by him). I decided to use a dual-panel chassis with a wooden frame separating the power supply section from the signal one, and two heavy (1/8") aluminum panels.
I built a ground bus for each section with 10 AWG bare wire. All components that should go to ground are connected to it. See picture (note that I haven't received my power and filament transformers yet so some connections are missing, but you get the idea. I also added a wire from the mains earth to the PSU ground bus). The chassis is not connected to the ground yet.
Does my wiring make sense so far? I am not sure what the best way to connect the two buses and the chassis would be. Shall I run another piece of 10 AWG wire between the two buses, making an "H", and connect the two chassis panels to the closest point in the bus? Does the connection point or the wire gauge make a difference?
I'd appreciate any help. Thanks.
gm
Attachments
I installed a new browser and now I can zoom out thumbnails so---
Good job of carpentry Gattu but keep the earth buses separate to terminate on a star earth point that is where the mains earth is terminated at the input --or as near to it as possible to keep the mains earth as short as possible .
Center tap of the secondary of the mains transformer is taken directly to the star earth --separately.
Good job of carpentry Gattu but keep the earth buses separate to terminate on a star earth point that is where the mains earth is terminated at the input --or as near to it as possible to keep the mains earth as short as possible .
Center tap of the secondary of the mains transformer is taken directly to the star earth --separately.
Thanks @duncan2. I'm not sure I understand correctly... I assume the star will be on the chassis, do I need one for the power side panel only, collecting the mains earth, the ground bus, and the power supply CT? And then, separately a wire running from the signal bus to the signal chassis, with no connection with the other panel or bus? Thanks again.
Basically yes Gattu --only one star earth otherwise you have two sources of earth return currents running round a single amplifier .
If you want to be particular about it then the output return should be on its own and not connected directly to the input signal earth return or if that doesn't look so good to you then connect a 10 ohm resistor between the input signal earth and the output earth return and independently on the signal earth side run a separate earth return to the star earth .
I realize you want to keep it "looking nice " I rather concentrate on getting rid of noise quicker rather than let it "float around " .
If your input has a potentiometer input then run the input signal earth to it and then a separate earth return ,this works for me and its worked for JLH .
If other ways work for other people good luck to them but I managed to get noise down to minute levels
and as a bonus the design became more stable with a lower value of compensation capacitor.
If you want to be particular about it then the output return should be on its own and not connected directly to the input signal earth return or if that doesn't look so good to you then connect a 10 ohm resistor between the input signal earth and the output earth return and independently on the signal earth side run a separate earth return to the star earth .
I realize you want to keep it "looking nice " I rather concentrate on getting rid of noise quicker rather than let it "float around " .
If your input has a potentiometer input then run the input signal earth to it and then a separate earth return ,this works for me and its worked for JLH .
If other ways work for other people good luck to them but I managed to get noise down to minute levels
and as a bonus the design became more stable with a lower value of compensation capacitor.
Hi there,
Reviving this thread after putting off my project for several months.
I finally completed all my ground connections, plugged in the tubes, added a dummy load, put a lightbulb current limiter before the amp power, and powered up.
Nothing blew up, which was good. But on power up I can hear a faint (60Hz?) hum coming from the transformer, that gets very loud after about 10 seconds. If I disconnect the power transformer center tap from the ground the hum goes away, but that can't be a solution, in fact I switched the amp off soon after that.
I suppose that there is some ground loop but I thought I followed directions both from this thread and Grounding and Shielding for your DIY Audio Projects
My grounding, in summary, looks like the following:
- Star earth: I used a piece of 10AWG bare copper, connected my 3 input channel grounds (6x RCA) together with it, and left a piece sticking out so I could wrap all the other wires around it.
- Power supply components to power ground bus, except for power transformer CT.
- Power supply chassis to power ground bus.
- Power ground bus to star earth.
- Power tx CT to star earth.
- I have a separate 2.5V filament transformer with CT that I join to the main tx CT and to the star earth.
- Signal section components (including power tubes, output tx) to signal ground bus.
- Signal wire is shielded and I connected the shields together on the RCA end and to the star earth. I cut the shield flush with the jacket on the other end and only connected the hot L/R wires to channel selector and volume.
- Ran a wire from volume neutral to ground bus (signal reference).
- Signal bus to star earth.
- Signal chassis to star earth.
- Star earth to mains earth via a low-impedance cable (double OFC speaker wire).
Does anything look suspicious to you?
Thanks again.
gm
Reviving this thread after putting off my project for several months.
I finally completed all my ground connections, plugged in the tubes, added a dummy load, put a lightbulb current limiter before the amp power, and powered up.
Nothing blew up, which was good. But on power up I can hear a faint (60Hz?) hum coming from the transformer, that gets very loud after about 10 seconds. If I disconnect the power transformer center tap from the ground the hum goes away, but that can't be a solution, in fact I switched the amp off soon after that.
I suppose that there is some ground loop but I thought I followed directions both from this thread and Grounding and Shielding for your DIY Audio Projects
My grounding, in summary, looks like the following:
- Star earth: I used a piece of 10AWG bare copper, connected my 3 input channel grounds (6x RCA) together with it, and left a piece sticking out so I could wrap all the other wires around it.
- Power supply components to power ground bus, except for power transformer CT.
- Power supply chassis to power ground bus.
- Power ground bus to star earth.
- Power tx CT to star earth.
- I have a separate 2.5V filament transformer with CT that I join to the main tx CT and to the star earth.
- Signal section components (including power tubes, output tx) to signal ground bus.
- Signal wire is shielded and I connected the shields together on the RCA end and to the star earth. I cut the shield flush with the jacket on the other end and only connected the hot L/R wires to channel selector and volume.
- Ran a wire from volume neutral to ground bus (signal reference).
- Signal bus to star earth.
- Signal chassis to star earth.
- Star earth to mains earth via a low-impedance cable (double OFC speaker wire).
Does anything look suspicious to you?
Thanks again.
gm
Never mind... I guess that I got worried about something not sounding right and didn't wait for the system to warm up. After 5 minutes the hum subsided, becoming only audible from less than a foot away.
Regardless, does the previously mentioned grounding sound OK?
Thanks,
gm
Regardless, does the previously mentioned grounding sound OK?
Thanks,
gm