Do resistors block voltage

[RDK]

Im reading the guitar amp handbook. Starting with signal chain. I am curious about something. It shows that on pin 6 of the 12AX7, 150 volts is being supplied. It's the power source to operate this tube. But right before it gets to pin 6, there are to 100K resistors linked together that are connected to the signal chain. What's to keep that voltage from going Into the signal chain. Is it the resistors?

Thank you
Corey

[RDK]

Disregard that. I can see obviously that it was 260 volts and the pair of resistors knocked it down to 150.

[Chuck H]

It may help you to know what is actually going on in the circuit. If you can give a page reference, or even better, a link or picture, we can describe the circuit and it's function. It sounds like you may be misreading a preamp plate supply. And if so then there shouldn't be any resistors attached directly to the signal from the HV rail without a coupling capacitor to block that voltage from ground or another preamp tube grid. Further, resistors cannot, by themselves, reduce voltage. There must be current passing through the resistor in order for voltage to be reduced. I know that may seem nit picky, but it's an important distinction.

[Enzo]

The most fundamental concept in electronics is, in my view, Ohm's Law. It is the simple relationship between voltage, current, and resistance. Current flowing through a resistance causes a voltage difference between the ends of the resistor.

I have been in electronics well over 50 years, and believe me, I still use Ohm's Law every single day.

[tubeswell]

To re-state what enzo said

Volts = Amps x Ohms (and Amps = Volts/Ohms, and Ohms = Volts/Amps)

If current flowing through a wire is like water flowing through a garden hose, then a resistor is like a section of garden hose that is skinner that the rest of the hose, and this makes it more difficult for the water to flow through it, resulting in a rate of water flow which is constricted (compared to the rate of flow at the inflowing end of the skinny section of the hose).

To carry this analogy further, if you elevate the inflowing end of the garden hose so that it is higher than the outflowing end, then the water will flow through the hose with more impetus. The higher you elevate the inflowing end, the more impetus/potential energy the water will have. The difference in impetus of the water flow is like difference in voltage (higher potential = more voltage). The flow itself is like current (less volume of water = less current). The skinniness of the hose is like resistance (skinnier = more resistant).

Lifting one end of the hose is like giving the current more 'charge' (which in voltage terms is more potential energy) because of the resultant increase in water pressure from the higher water column. However if both the input and output ends of the hose were kept at the same level, then there is no increase in potential as such, only a reduction in current flow because of the skinniness of the hose outlet point.

[hasserl]

To carry that analogy further, pressure in a hydraulic system (your water hose for example) is caused by resistance to flow; if there is no resistance to flow there is no pressure. You can have a lot of current flow at very low pressure if the resistance to the flow is low. Increase the resistance while maintaining the flow and the pressure will rise. But the pressure rises on one side of the flow restriction, the side facing the current supply (i.e. pump or reservoir), and the pressure drops on the other side of the restriction, so there is a pressure drop across the restriction. Now carry that over to electricity current flow, voltage is caused by resistance, with no resistance there is no voltage; and you can have a lot of current flowing with very little voltage, if there is low resistance to the flow. Inserting resistance into the flow path while maintaining the same current flow and you will see voltage rise on one side of the resistance, and it will drop on the other side of the resistance, so you get a voltage drop across the resistor.

So resistors don't block voltage, they create it; but you will see a voltage drop across them, which is what was described in the OP.

[Enzo]

And to make it even more realistic, we now also have to start arguing whether rubber garden hose is better than the vinyl. Then someone would suggest thinwall pipe.

[Chuck H]

Thin wall pipe doesn't have the same "sag" as hose. Of course some hoses sag more than others. You can experiment with different hoses for a slightly different effect. But some sag adds a more natural "feel" to the gardening experience. When opening pressure on attachments you get a softer "attack" that some gardeners prefere. The spray seems to "swell" and "bloom" with a very natural compression. Some guys that use pipe add a chamber to the line that simulates the sag of garden hose. But it's not exactly the same as the real thing.

[tubeswell]

Well I suspect that metal film hoses are going to be quieter, but carbon comp hoses will probably have more of a pressure gradient depending on the conduction angle of the hose, while carbon film hoses will be somewhere in between

[Enzo]

I have the hardest time understanding Single Ended hoses.


Damping, I understand that.

[MikeH]

I always make sure to use NOS rubber hose with silver connectors.