Paraphase inverter question

[Helmholtz]

Ok, I tied the inverter back to power grids and this is what I get in differential mode:

This is with 47nF interstage

[ATTACH=CONFIG]55131[/ATTACH]

This is with 470nF interstage

[ATTACH=CONFIG]55132[/ATTACH]

To be honest I don't see any difference

Where is the perfect sine coming from? I expected to see the bias ripple? What is the strange oscillation in the difference signal? Did you connect earth clips to chassis?

[catalin gramada]

Ripple has nothing to do with the (para) phase inverter.
Ripple is about 100 mV / 50Hz, and the amplifier is without any signal from the generator.
Don't you think about ground loop?

EDIT 190909
Just remember the experience from the studio when the amplifier connects to the processor and puts it all together on the mixer.
All devices are earthed via the power cord.

Silence in space only when all earthing is at one point.

The source of noise is the ripple from bias supply as it was confirmed. The problem is why is not cancelled in power stage. Is not a subject of any ground loops as it is very simple, but I.ll check one more time. Thanks

[Dave H]

Ok, I tied the inverter back to power grids and this is what I get in differential mode:

This is with 47nF interstage

[ATTACH=CONFIG]55131[/ATTACH]

This is with 470nF interstage

[ATTACH=CONFIG]55132[/ATTACH]

To be honest I don't see any difference

By interstage do you mean the cap connected to the virtual earth triode's grid? When I did the sim that one didn't have much effect. Try increasing the value of the caps to the power tube grids and measure at the grids.

[catalin gramada]

No, this was done with ground clips floated, seems it is not right. Post other pics in minute

[catalin gramada]

470n



47nf



This was picked up with ground clips to chassis. Previous was with ground clips floated, and also I used a digital filter to smooth the traces.

[Helmholtz]

By interstage do you mean the cap connected to the virtual earth triode's grid? When I did the sim that one didn't have much effect. Try increasing the value of the caps to the power tube grids and measure at the grids.

Seems I misinterpreted your sim results. I thought you had increased the second triode's grid cap. Having problems to see why increasing the power tubes' coupling caps would change phase difference in a symmetrical arrangement.

[vintagekiki]

[ATTACH=CONFIG]55104[/ATTACH]

Why did you put in an independent bias. Even the slightest imbalance of the bias manifests itself as a hum.

Tip.
In order to do custom any amplifier, you must first bring in 100% mint condition.

[Dave H]

Seems I misinterpreted your sim results. I thought you had increased the second triode's grid cap. Having problems to see why increasing the power tubes' coupling caps would change phase difference in a symmetrical arrangement.

Green and blue power tube grids wrt ground, red grid to grid differential.
First plot 47n, second plot 470n.

[catalin gramada]

I posted wrong pics from rush, Now there are the right one , Sorry.
I just changed the capacitor between first and second triode 47nf and 470 nf. Didn't see any changes

[Helmholtz]

First plot 47n, second plot 470n.

Which cap(s)?

[Dave H]

Which cap(s)?

Sorry, they are the caps between the PI plates and the power tube grids.

[Helmholtz]

Green and blue power tube grids wrt ground, red grid to grid differential.
First plot 47n, second plot 470n.

[ATTACH=CONFIG]55135[/ATTACH]

[ATTACH=CONFIG]55136[/ATTACH]

I don't see much change in the differential signal.

[catalin gramada]

No , there is one cap which goes to second triode grid, This was changed. The couplings to power stage are the same 47nf

[catalin gramada]

I don't see much change in the differential signal.

It is not, take a look at the pics in post 95

[vintagekiki]

I see a lot of pictures from the oscilloscope, various numeric values from the screen, who it mean nothing.
We just don't know what we want with a bunch of data.
I am afraid that we will stray because proposals and results do not indicate constructive debate.

Let's go back to the beginning

https://music-electronics-forum.com/showthread.php?t=49645&p=537990&viewfull=1#post537990

and to define what we want from thread.