Cap orientation again...

[Tdale]

There has been many posts about this, but i'm still not sure about all the caps.

For instance, outside foil should connect to the driving tube of a tone stack, since the impedance is smaller.. But what about the rocket, that has the tone stack after the cathode follower? And what sjikt the caps that connect to the grids of the PI tube? One is triumfer, the other is not. And what about the caps from the PI plates? It would be great if someones would specify the orientation of all the non electrolytic caps in the rocket...

[Jana]

Read my last post in this thread:

https://tubeamparchive.com/viewtopic.ph ... 2&start=75

[Tdale]

Thanks, that answers some og my questions. Still not sure about the two caps in the tone stack though...

[paulster]

Still not sure about the two caps in the tone stack though...

Outer foil to the 10K and 100K for the two caps.

[Tdale]

Ok, and the caps from PI to luring tubes has outside foil connected to the PI plates?

[Tdale]

...output tubes...

[paulster]

Yes. That's the driving side so that will be lower impedance.

[Tdale]

And finally, the caps before PI, the ond that is grounded has theoutside connected to ground, but what about the other ond?

[paulster]

To the treble pot side.

[Structo]

Here is a layout of a Dumble that someone oriented the caps on.
Lined end is foil end.
You should be able to translate to other amps.
Note: This amp does not have a cathode follower so the stack is plate driven.

[KT66]

Here is a layout of a Dumble that someone oriented the caps on.
Lined end is foil end.
You should be able to translate to other amps.
Note: This amp does not have a cathode follower so the stack is plate driven.

That was me. Here's a 50W plexi layout I posted which shows the orientation in a CF tonestack driver arrangement ( see page 2 ): https://tubeamparchive.com/files/50w_pl ... ut_431.pdf

[telentubes]

So, given this information, I'm seeing that some of the caps in my recently built Rocket Reverb are in backwards.

Can some one verify these observations...

Looking at the caps from LEFT TO RIGHT, and assuming that the lines on the caps (you can see them on the lower left of the cap) represent the foil end of the cap...

The first and second from the left are correct
The third and fourth are backwards
The fifth is correct
The sixth and seventh from the left are backwards

[KT66]

You are correct that the 3rd and 4th are backwards, but all others are correct I believe. The output impedance of the cathode follower is 56K, but the input impedance of those caps at their respective connections at the tone stack is higher than that because the "distance" to ground there is further so those caps are fine.

[martin manning]

I'd flip the 6th but leave the seventh. For the sixth cap, the end going to the bass pot sees 10k paralleled with the pot setting going to ground, so zero to ~10k. For the seventh, the way it is it sees the 100k slope in series with the Zo of the CF, so about 150k. The other way it's the upper part of the pot in series with the lower part paralleled with the 10k. The pot setting could make that anywhere from ~10k to 1M. With the bass pot at noon, it's ~800k. So, I'd leave the outer foil pointing at the CF.

[telentubes]

Thanks KT66 and Martin,
I'll make those changes and look for some tonal changes. This amp already sounds great, but subtle improvements in tone or feel are always welcome. Great to learn some more tricks of the trade.

Should I replace with new caps, or is it OK to just spin the old ones around?