Filter caps

[sbirkenstock]

Hi there,

usually you should leave the amp on standby when you switch the amp off, so the filter caps can discharge.
Just figured out that this only applies to the main filter caps.
The filter caps for the preamp discharge themselves very quickly.
I just can´t figure out where the voltage goes? It´s mostly connected to plates...
Any explanation for this?

I changed my main filter caps to a totem pole setup, since my voltages were going up to 535V and the caps were 500V ones.
(2x 20mf at 500v parallel
changed to
2x80mf at 450v seriell)

I added two 220K resistors.
I actually believe the amp sounds better now.
Obviously this setup also makes sure that the main filter caps get discharged independently from the standby switch.

greetings,

Stephan

[cbass]

No the filters will drain faster if you turn the amp off while not in standby . even faster if you hit a chord after you shut it off.

[gui_tarzan]

Where does the electricity go? Think back to your high school physics class. VERY simplistically speaking, it gets converted into heat while it's moving through the circuit.

People used to ask me where network data packets went if they didn't make it to the destination, I just told them "digital heaven". I guess you could say the electrons go to "analog heaven" in our case.

[pdf64]

I changed my main filter caps to a totem pole setup, since my voltages were going up to 535V and the caps were 500V ones

Was that just at start up, ie did the VB+ drop down to 500V or below once the tubes warmed up?
If so, it may not have been a problem, as caps intended for this application should have a surge voltage rating to accommodate this, eg limit of 550V surge, 500V working.
So don't worry that your old caps may have been overstressed, they're likely still fine.

The filter caps for the preamp discharge themselves very quickly.
I just can´t figure out where the voltage goes? It´s mostly connected to plates.

The still warm tubes conduct it / discharge the B+ caps, to ground, ie the plates are the path to ground, until cool off.[/quote]

[sbirkenstock]

It went to 535 on standby, independently if the tubes were warm or not.
Standby on "on", the voltage went down to 500.
But there is no margin then.
And I believe it sounded better.
I have to add, all those values were only there with my variac.
I set it for filament = 6.3 volts.
Without there were 6.6 volts, all other values higher of course as well.

Is there any disadvantage to the serial totem pole approach?



So the discharge of the filter caps happens, because there will still be idle current after switching off?
Or more then idle if you hit a chord on your guitar?

Stephan

[cbass]

It went to 535 on standby, independently if the tubes were warm or not.
Standby on "on", the voltage went down to 500.
But there is no margin then.
And I believe it sounded better.
I have to add, all those values were only there with my variac.
I set it for filament = 6.3 volts.
Without there were 6.6 volts, all other values higher of course as well.

Is there any disadvantage to the serial totem pole approach?



So the discharge of the filter caps happens, because there will still be idle current after switching off?
Or more then idle if you hit a chord on your guitar?

Stephan

Your voltage drops when you go off standby because the tubes start pulling current putting a load of the PT.
You're right the charge left in the caps is why you can still hear your amp for a little while after you power off

[tubeswell]

Where does the electricity go? Think back to your high school physics class. VERY simplistically speaking, it gets converted into heat while it's moving through the circuit.

And a small amount of it gets converted into sound waves in the air, which ends up as vibrations in your inner ear canal. To remind you of tinnitus.