Additional filter caps....

[trem]

If you want to add filter caps to a circuit, but do not want to drop any (appreciable amount of) voltage; how do you determine what value resistor to use.? I have mulled this over in my head, but I am not sure what to do.
For example, in the schem below, if you want the plates of V1 to have their own filter cap, what value (how do you figure it out.?) resistor would you use to separate the nodes.? Could I just use a 1 ohm, 10 ohm, 100 ohm resistor.? I just want to separate the caps, not drop voltage. Hope you guys understand what it is I am trying to ask.
Thank You

[Enzo]

Ohm's Law.

ANy resistor you stick in series with the current will cause a voltage drop proportional to that current and the resistance.

VOltage equals amps times ohms.

[trem]

Hey Enzo -
I understand and appreciate your response.
But what I am wondering is, if all I am trying to do is isolate the plates from each other, so they have their own filter cap....What resistor do you go with.? Is there a minimum value I need to use.?
If I do not need a voltage drop of any particular value (I do not need the voltage to change at all) do I just pick a resistor and make sure it has a wattage rating that will handle the ohms law formula.?
For example.....If I go with a 820 Ohm resistor, is that OK as long as its wattage rating will handle whatever voltage drop there might be.?
Thanks

[mooreamps]

I just want to separate the caps, not drop voltage. Hope you guys understand what it is I am trying to ask.
Thank You

They may not, but I think I do..But, it will cost you some money.. Pull those two resistors out, and replace them with a couple of 60 Henry chokes.
That will give you the most filtering with the least lost in voltage...


-g

[R.G.]

Hey Enzo -
I understand and appreciate your response.
But what I am wondering is, if all I am trying to do is isolate the plates from each other, so they have their own filter cap....What resistor do you go with.? Is there a minimum value I need to use.?

Enzo had it dead correct. What you're missing is that there is already a resistor in series with them. It's that 22k/1W before the filter for the V1 plates and the phase splitter plates.

As it, all the plates of V1 and V3 suck current through that 22K, and the voltage dropped across the 22K is V = I *22000. You're a little stuck, not knowing what I is. But you can figure it out, using Ohm's Law again. You find the voltage at that 20uF cap to ground, then the voltage on all four plates. By subtracting the plate voltage from the supply voltage at the 20uF cap, you can find the current in each plate. This should reasonably be equal for both halves of V1 and again a different for V3's plates.

Once you know those voltage differences across the four plate resistors, you can do the math: I = V/R where V is the voltage difference you measured, and R is the plate resistor. The four values you calculate have to add up to the current out of the 22K dropping resistor. Well, OK, any leakage in the 20uF cap is in there too, but let's say it's zero just to keep the mental model clear.

So after this, you know the current into each plate, and also know that the sum of all four of these currents have to come through that 22K. If you take out the 22K and put in three resistors, one going to the B+ supply for the phase inverter, and one each going to the halves of V1, you can make that resistor drop exactly the same voltage as the 22K used to drop by just setting the resistance value, using the currents you calculated earlier. Now you can put a filter capacitor to ground on each one of these points, and have the same voltage as you started with when they were all combined, but now they're isolated from each other by the resistances and the new filter caps.

The thing is, those resistors will all be bigger than the 22K that was in there, in proportion to how much smaller each current is compared to the total. So each half of V1 might get a 47K resistor (I just made that up) and the phase inverter might get a 33K.

They may not, but I think I do..

What a surprise. Once again you think you're the only person in the world that understands electronics. Calculated any fuse values lately, Gary?

But, it will cost you some money.. Pull those two resistors out, and replace them with a couple of 60 Henry chokes. That will give you the most filtering with the least lost in voltage...

Maybe. You can actually do better with an active regulator, and at a far lower cost. However, splitting up the power supply distribution before that last filter cap into three resistors instead of one is far cheaper. A choke will give you higher attenuation of ripple and crosstalk than a resistor, but you pay a very large price for that. Far, far simpler and cheaper to split the power out a bit higher up in the dropping chain.

[Enzo]

Oh, a lot less expensive in both money and space would be to create a new B+ node. Branch off the existing string.

Look at the junction of the 1k and 22k resistors at the second filter cap. From that node, run a new resistor to a new cap, and wire V1 plate resistors to that. V3 remains wired to the old resistor.

SInce the new node will only be powering the one dual triode, the current through it will be less than the original 22k resistor. So if you use a new 22k resistor, the voltage will wind up a little higher than it was. If that is OK, fine. If you want the voltage the same as before, make the new resistor larger - 33k 47k, whatever it takes. Likewise, the original 22k is now only conducting current for the one tube, V3, so the current through it will be less, and thus the voltage drop across it will be less. SO if you want the V3 voltage to remain the same, the original 22k would probably have to increase too. Again 33k 47k, whatever.

[R.G.]

Oh, a lot less expensive in both money and space would be to create a new B+ node. Branch off the existing string.

Look at the junction of the 1k and 22k resistors at the second filter cap. From that node, run a new resistor to a new cap, and wire V1 plate resistors to that. V3 remains wired to the old resistor.

SInce the new node will only be powering the one dual triode, the current through it will be less than the original 22k resistor. So if you use a new 22k resistor, the voltage will wind up a little higher than it was. If that is OK, fine. If you want the voltage the same as before, make the new resistor larger - 33k 47k, whatever it takes. Likewise, the original 22k is now only conducting current for the one tube, V3, so the current through it will be less, and thus the voltage drop across it will be less. SO if you want the V3 voltage to remain the same, the original 22k would probably have to increase too. Again 33k 47k, whatever.

Yep - that's what I was trying to say! Dead right again, Enzo.

[trem]

10-4
Got it guys.
Thank You

[Enzo]

Hey RG. Your post wasn't up there when I wrote mine. I was responding to Gary's plan.

Otherwise looks like we were on the same wavelength.

[R.G.]

Hey RG. Your post wasn't up there when I wrote mine. I was responding to Gary's plan.
Otherwise looks like we were on the same wavelength.

Actually, I was impressed with how much clearer yours was!

[mooreamps]

What a surprise. Once again you think you're the only person in the world that understands electronics. Calculated any fuse values lately, Gary?

Hey, RG ???

F*CK U....

[Chuck H]

Smooth
Wouldn't it be better to ignore such jibes. That one was ill placed and unsolicited. I hadn't passed any judgement based on R.G.'s jibe because of this. But as it happens, this is the first time I've seen one forum member respond to another with simple profanity. I personally don't think it suits the forum or you at all. I thought the same of R.G.'s jibe too but this post is somehow more offensive if only because it required absolutely no brain activity.

In a perfect world R.G. would have skipped the jibe and you could have recognised his more eloquent solution to the OP's issue.

If I look back at previous threads I can see where the trend shifted from Gary accusing other members of circuit plagiarism and stubbornly insisting his innovations, including attacks on respected forum members, to a rash of valid arguments about prior technologies and finally Merlin and R.G taking any chance to poke at Gary as he becomes slowly more bitter. Culminating in this crude post. The three of you should get a room.

[trobbins]

Trem, did you have a reason for wanting to isolate the HT to each section of V1? Interactive topics that crop up may include hum reduction, voltage sag on preamp stages, operating HT voltage level, and common cathode bias.

Ciao, Tim

[trem]

Trem, did you have a reason for wanting to isolate the HT to each section of V1? Interactive topics that crop up may include hum reduction, voltage sag on preamp stages, operating HT voltage level, and common cathode bias.

Ciao, Tim

I was going to address it in another post....but as a way to reduce noise/hum. Not sure what happens with an octal preamp tube....are they more susceptible to hum because of their construction.?
Thanks

[R.G.]

In a perfect world R.G. would have skipped the jibe and you could have recognised his more eloquent solution to the OP's issue.

I do apologize to you and other gentle readers, Chuck.

The lack of insight and unjustified arrogance some people display kick off an almost reflexive response in me. I had to work with people like that for a long time, and I'm dealing with someone who has that set of personality issues now on a more personal level. It makes me intolerant of that approach in places I care about.

I'll try to control it. Sorry to offend you, Chuck.