RC parallel circuit

[KrishnaphatM]

Hi all

I saw a circuit in Friedman be-100 that power section a RC parallel circuit ( C1//R2 ) from source to anode 12ax7

** Please see in the attach

My questions : What is it purpose?

Thank for comment.

[tubeswell]

Plate (anode) bypass cap.

[fred.violleau]

Hi all

I saw a circuit in Friedman be-100 that power section a RC parallel circuit ( C1//R2 ) from source to anode 12ax7

** Please see in the attach

My questions : What is it purpose?

Thank for comment.

You can use this online calculator to see the Effects on frequencies :

https://www.ampbooks.com/mobile/amplifi ... capacitor/


Fred.

[martin manning]

In the schematic the capacitor is bypassing 0.05% of the load. I can’t imagine it is doing much of anything.

[Reeltarded]

Dave's tiny suppressors never impress Martin. lol

I think at some point they had a few amps squealing and they snub all amps a little so no tweaking individuals. Production hammer. I also think that people copying the circuits would just copy the circuit and make the origin instantly identifiable.. it's a little bit psyche war in a couple ways.

There are many ironies in amp design..

[chief mushroom cloud]

for a smoother shave
it's an old Norelco circuit

[Reeltarded]

for a smoother shave
it's an old Norelco circuit

Santa rides a razor edge.

[Ten Over]

R2 is 100K, not 100.

[KrishnaphatM]

Thank for the clarification

[Reeltarded]

A third of the plate load is bypassed. 500p over the 100k in a 300k split load basically sounds frequency wise like a 220 unbypassed plate but is still hotter.. right.

[martin manning]

Well that makes a lot more sense. Ra at 300k produces very high stage gain. Bypassing a third of it may be aimed at reduced gain at higher frequencies, preventing oscillation, or both.

[roberto]

330k to 470k it’s quite typical in that kind of design. Partial snubbers too to focus the gain of the amp.

[gingertube]

Yep
effective load at high frequencies is 200K The cap effectively bypasses the 100K. gain is reduced to 2/3.
effective load at low frequencies is 200K + 100K = 300K

The half gain change frequency (when Capacitive Impedance = 100K) is at 3183 Hz.

Cheers,
Ian