Layout is a big deal with these tubes for sure. Rather than using ferrite beads on the heaters, I've used MLCC snubbers with on cap between the heater pins and two more that go from each pin to the chassis.
Plate and grid stoppers are crucial, and I haven't noticed noise problems when using new production 100 Ohm 1/4W CC resistors.
Plate and grid stoppers are crucial, and I haven't noticed noise problems when using new production 100 Ohm 1/4W CC resistors.
Interesting. I called mine the quartet of quiet.
I'm with DF96 on this, long acquaintance with 5842/417A, D3A, 6S3P/6S4P indicates that a single stopper on one grid pin is generally fine. If you are really worried about the antenna effect (not a concern IMO) I would shorten the tag on the end of the pin to just above the crimp that keeps it from pulling out of the socket.
Metal films are OK provided there is not a lot of shunt capacitance inherent in the construction of the particular resistor used. (Some are worse than others)
On PCB layouts I usually use a single 100 ohm thin film 1206 SMD (!) stopper resistor within 5mm of the grid pin.
I use slip-on ferrite beads on wires close to the socket on D3A, placing one on the plate lead is not a bad idea, small 10 - 47 ohm resistors right at the plate are also helpful in some cases.
I'm moving away from P2P and doing more and more stuff on PCB as I get more proficient with the tools. (and with it these worries are mostly moot with careful layout)
Metal films are OK provided there is not a lot of shunt capacitance inherent in the construction of the particular resistor used. (Some are worse than others)
On PCB layouts I usually use a single 100 ohm thin film 1206 SMD (!) stopper resistor within 5mm of the grid pin.
I use slip-on ferrite beads on wires close to the socket on D3A, placing one on the plate lead is not a bad idea, small 10 - 47 ohm resistors right at the plate are also helpful in some cases.
I'm moving away from P2P and doing more and more stuff on PCB as I get more proficient with the tools. (and with it these worries are mostly moot with careful layout)
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