I am designing a PCB for a tube compressor with a max gain of about 40dB
The heater supply requirements is 6.3V 1.6A. Initially I thought to make it DC regulated, but the power transformer gets too big for the chassis I'm using.
I am wondering if there is a way to run the AC heaters on the PCB without causing too much noise.
Perhaps running the connections on the edge of the pcb away from grid circuits would be safe enough, or maybe some kind of heater elevation would help ?
I am seeing a few diy projects that run the heaters with the classic twisted pair off board but I am also seeing commercial units that seemingly run the heaters AC on the PCB. So I guess in some way it's possible.
Wondering if someone has any experience with this.
The heater supply requirements is 6.3V 1.6A. Initially I thought to make it DC regulated, but the power transformer gets too big for the chassis I'm using.
I am wondering if there is a way to run the AC heaters on the PCB without causing too much noise.
Perhaps running the connections on the edge of the pcb away from grid circuits would be safe enough, or maybe some kind of heater elevation would help ?
I am seeing a few diy projects that run the heaters with the classic twisted pair off board but I am also seeing commercial units that seemingly run the heaters AC on the PCB. So I guess in some way it's possible.
Wondering if someone has any experience with this.
I only use on board filament wiring for DC. With AC filaments, I always run them off board using twisted pairs.
Commercial would be on board for cost savings and less labor.
Commercial would be on board for cost savings and less labor.
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I use an ABA style layout in my valve DAC, see https://linearaudio.net/design-data-package-marcel-van-de-gevels-valve-dac-vol-13
Twisted wire ( very tight) then put a reference to ground
Never seen ac filaments on pcb
Walter
I think it was standard practice when PCBs were first introduced. At least the valve radio with PCB I repaired a couple of years ago had no heater wires, as far as I remember.
I always use AC heater power.
So long as it doesnt run next to high impedance signals on the pcb it should be ok.
In my experience I have never found DC heater supply to fix hum problems.
Any hum problems I had was caused by something else.
But thats my experience.
So long as it doesnt run next to high impedance signals on the pcb it should be ok.
In my experience I have never found DC heater supply to fix hum problems.
Any hum problems I had was caused by something else.
But thats my experience.
Not only phono: my silver face Fender Champ hums audibly. With the stock trafo, a single diode and a simple CRC filter on the 1st stage heater make the hum go away, much lower in level than the hiss of the tube. The ripple doesn't look great, but hey, it works. Rfan is just a starved PC fan to cool the internals.
This is the ABA style layout I use for the AC heater traces on the four-layer board in my valve DAC.The idea is that the magnetic field of the left loop compensates that from the right loop. Unfortunately I didn't manage to keep it in ABA style close to the valves, where it actually matters most, but then again, twisted wiring also isn't twisted right at the valve holders.
My DAC doesn't hum, but then again, it's not that sensitive to hum fields anyway compared to a phono preamplifier.
I also don't have any problem with hum from the AC heater wiring in my valve phono preamplifier, but that is a point-to-point wired circuit with shielded twisted cable for the heaters.
My DAC doesn't hum, but then again, it's not that sensitive to hum fields anyway compared to a phono preamplifier.
I also don't have any problem with hum from the AC heater wiring in my valve phono preamplifier, but that is a point-to-point wired circuit with shielded twisted cable for the heaters.
The logic behind tightly twisted wires is to keep them perfectly parallel and as close to each other so that magnetic fields are canceled. Another efficient scheme is plain power cords. Easy to implement on a pcb, just run the lines one next to the other with the smallest possible clearance. However, hardwiring might excel because it could take these lines away from the rest of the circuit.