Can someone please explain to me what it is that two resistors do in parallel that one resistor of the same value can’t do in controlling excessive current?
As in r702. 703, 704 and 705.
Thanks in advance.
Explanation for this.
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Stevem
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Explanation for this.
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pdf64
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Re: Explanation for this.
The schematic is nonsense.
The screen grid g2 is connected to the cathode, suppressor grid g3 connected to HT, via 25.5k resistance. WTF!
But then the suppressor grid is shown as being pin4, the screen grid.
Whatever, the design is certainly not relevant to any valve guitar amp.
The screen grid g2 is connected to the cathode, suppressor grid g3 connected to HT, via 25.5k resistance. WTF!
But then the suppressor grid is shown as being pin4, the screen grid.
Whatever, the design is certainly not relevant to any valve guitar amp.
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Re: Explanation for this.
I've done it on other things. It allows you to make up higher power equivalent resistors with possibly cheaper or easier-to-lay-out smaller parts. It can add a tiny bit of fail-soft, as in there'll still be one there if one fails. Maybe.
It might let you spread out the heat density into a wider space of PCB and not heat one spot so intensely.
It won't help in this application, but it can be a way of fudging parasitics so the capacitance gets spread out; likewise, two smaller devices might be obtainable as lower inductance, or get you a lower inductance by paralleling.
All of these are only useful when your design is already near the edge, though. I don't think that's what drove this design.
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Re: Explanation for this.
Guy just really, really wanted "675Ω" as the cathode resistor, and "25.5kΩ" as the dropping resistor for the screen filter cap??
I don't think the circuit-values are so critical, so the above doesn't make sense.
Then again, providing the very-high dropping resistance to the screen node because of "protection from excessive screen current" but then adding a 50µF filter cap that will "supply excessive current on demand" also doesn't make sense...
I don't think the circuit-values are so critical, so the above doesn't make sense.
Then again, providing the very-high dropping resistance to the screen node because of "protection from excessive screen current" but then adding a 50µF filter cap that will "supply excessive current on demand" also doesn't make sense...
Re: Explanation for this.
pdf64 wrote: ↑Sun Mar 08, 2026 6:20 pm The schematic is nonsense.
The screen grid g2 is connected to the cathode, suppressor grid g3 connected to HT, via 25.5k resistance. WTF!
But then the suppressor grid is shown as being pin4, the screen grid.
Whatever, the design is certainly not relevant to any valve guitar amp.
The tube (valve) is drawn wrong with screen and suppressor swapped, but the pin numbers are correct.
Like RG said, sometimes there are reasons to use two resistors in parallel.
Don't know the context of the article or what they were trying to accomplish.