phase splitter issue

[SY]

Originally Posted by CPaul

Your circuit which purportedly tests P & K to ground impedances by simultaneously shorting plate and cathode to ground draws no ground current. So there can be no current through ground referenced impedances. So they can't possibly be tested by your circuit.

I can't answer a nonsequitur.

[CPaul]

Please don't. Just respond to my comment.

[SY]

That's even stranger. "Don't answer me, but answer me."

[CPaul]

Originally Posted by dave slagle

Every test you have proposed to prove unequal plate and cathode impedances has unbalanced the loads. I do not accept braking the model to prove it wrong acceptable.

To test an impedance, you run a current through it, observe the resulting change in voltage across it, and divide. Since the impedances in question are connected to ground, as you test each one individually, the current must go into ground from one path and out through another. There simply is no other way to test the impedance. If that's all it takes to break the model, it's a pretty brittle model. But I think you find your way through this a little later on in this post.

Originally Posted by dave slagle

In the case of the dual LCR's the only correct answer is ~5800 ohms in both the plate and cathode...

I agree in this case there will be no current flowing through the ground node. I will also accept that we need to call this the differential output impedance.

The problem was the demand, per SY's grounded two source model, that each load be driven by a separate source of impedance 6K rather than a single differential source of impedance 12K.

Originally Posted by dave slagle

I think the key here is to draw the current loops and treat each loop impedance as it should. Currents common to the plate and cathode must have the differential output impedance. Currents common to just the plate or cathode loop (through ground) will have the respective plate or cathode impedance.

Dave, I agree completely. Not sure I could have said it better myself. (SY, take note!) Consensus is nice!

[CPaul]

I'm sure you're chortling about what you consider to be a non-sequitur. Perhaps you'd care to explain yourself so the rest of us can have something to laugh about.

[SY]

Consider symmetry and current cancellation under the specified constraint. You might call it "brittle," but it was successfully applied in some of the most popular and high performing tube amps ever made (Williamson, Dynaco, Heathkit, Eico...).

[CPaul]

?

[dave slagle]

The problem was the demand, per SY's grounded two source model, that each load be driven by a separate source of impedance 6K rather than a single differential source of impedance 12K.

here is where I have a problem. The only way for the circuit to provide the proper results is with 5800 ohms in the plate side and 5800 ohms in the cathode side. This suggests that the differential output impedance of the cathodyne is 200 ohms to make up the needed 12K impedance.

If it were just the differential output impedance that we care about, you should be able to divide up that 11K8 series resistance any way you want and still get the 12K differential output impedance, when you do this the low frequency behavior tells us we are not providing the proper source impedance.

dave

[CPaul]

I understand why this bothers you.

The best simple answer I can think of is that the Cathodyne is a bit more complex than either a single floating differential source or certainly a pair of ground-referenced opposing sources. That’s one good reason not to think of it in terms of either of these models, because doing so is sure to trip you up.

To get an understanding of a circuit, I always recommend doing a full circuit analysis rather than assuming shortcut models. Short of that, you could play around with a lot of simulations, but I still prefer the former approach.

[DavesNotHere]

Originally Posted by grungeman91

Has anyone ever built a concertina phase splitter and have the signal be perfectly split but they differed in amplitude?

I had that happen is when I used too small of a grid stop resistor on the input of the splitter.

And another time I tied too many output tubes in parallel. I increased the grid stoppers on the output which did fix it however, I went back and added a 6sn7 as a buffer between the outputs and phase splitter to provide a better drive signal.