Anode stoppers

[Shoog]

Hi all,
I have recently started reviewing a number of my projects and adding 100ohm or 10ohm anode stoppers. This has been particularly effective with my RH807 amp, my Thorstens phono preamp and with a 5687 preamp. In all cases it has taken a slight edge off the top end and in the case of the 5687 preamp it helped remove a hum issue.
All these instances have involved flying leads to the load resistor or to a CCS.
What do other people feel about the need for anode stoppers ?
Everyone talks about Grid stoppers, but few people seem to use anode stoppers.

Shoog

 

[Zen Mod]

Hi all,
I have recently started reviewing a number of my projects and adding 100ohm or 10ohm anode stoppers. This has been particularly effective with my RH807 amp, my Thorstens phono preamp and with a 5687 preamp. In all cases it has taken a slight edge off the top end and in the case of the 5687 preamp it helped remove a hum issue.
All these instances have involved flying leads to the load resistor or to a CCS.
What do other people feel about the need for anode stoppers ?
Everyone talks about Grid stoppers, but few people seem to use anode stoppers.

Shoog

ferrite beads are helpful on all toob pins
in some cases they aren't enough ,so you must use resistors instead

 

[Wavebourn]

There are many options to try when the amp is unstable. Anode stoppers sometimes help. All depends on the path of parasitics.

 

[pchw]

Sorry for a stupid question, what is anode stopper? How is used?

Thanks!!

 

[Shoog]

Sorry for a stupid question, what is anode stopper? How is used?

When the load on the anode isn't right up on the valve base(ie in the case of a CCS or a heatsinked load resistor) - you add a small resistor onto that base at the pin.
This helps prevent the valve from going into radio frequency oscillation, which inevitably leads to intermodulation distortion and other unpredictable results.

Shoog