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Amp block - Triode Plate Frequency

javajunkie

Moderator
Moderator
Anyone know exactly what this parameter is. It seems to effect the HF response.

Does it have to do with Miller capacitance?
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
It sets the cutoff frequency of the resistor/cap combination on the plate of the last triode stage (the previous stages are not user adjustable).

Most amps have no cap on the last stage but a few do. You can vary this parameter to simulate increasing/decreasing the capacitor value. The frequency is only approximate since the actual frequency varies with the bias point/cathode impedance/drive/etc.
 

groovenut

Power User
It sets the cutoff frequency of the resistor/cap combination on the plate of the last triode stage (the previous stages are not user adjustable).

Most amps have no cap on the last stage but a few do. You can vary this parameter to simulate increasing/decreasing the capacitor value. The frequency is only approximate since the actual frequency varies with the bias point/cathode impedance/drive/etc.
Cliff are you referring to the cold clipping stage or the stage right before the cathode follower stage?

ps it totally rocks that you made this user adjustable!
 

symphx

Fractal Fanatic
It would be great to have the technical translated to actual sound ideas: yes I know I can adjust and listen myself, however with so many awesome parameters, I find I would like to know what to expect with one, or I try to dial in so many I dont know what does what (yes I do one at a time but still) thanks
 

groovenut

Power User
So... what does it do (soundwise)?
It will give you some control over the high harmonics that are created during clipping. The cap in question forms a low pass filter with the plate resistor on the triode stage. In English, it will allow you to control the buzziness that sometimes occurs with higher gain settings. It can also serve as a gain dependent tone control of sorts.
 

javajunkie

Moderator
Moderator
It will give you some control over the high harmonics that are created during clipping. The cap in question forms a low pass filter with the plate resistor on the triode stage. In English, it will allow you to control the buzziness that sometimes occurs with higher gain settings. It can also serve as a gain dependent tone control of sorts.
That is a good description of what it sounds like.
 

DNW

Power User
It will give you some control over the high harmonics that are created during clipping. The cap in question forms a low pass filter with the plate resistor on the triode stage. In English, it will allow you to control the buzziness that sometimes occurs with higher gain settings. It can also serve as a gain dependent tone control of sorts.
Was very confused until I got to this post, so thanks! :)



Not that it's at all relevant to me, with my lowly Ultra. :(
 

AdmiralB

Experienced
Are you talking about bypassing the last plate load resistor with a cap? That's typically done to stabilize an 'iffy' circuit, whether due to too much gain or poor lead dress/PCB layout. And some Dumble circuits use a cap to shunt highs from the plate back to the grid (through a huge resistor) - sort of local negative HF feedback, for the same purpose.
 
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