CF in SE?

[Tobyk]

Has anyone tried a cathode follower in a single ended amp? SE’s overdriven often are a bit harsh/ragged compared to a push pull, so maybe a CF with dampen that with a bit of added compression?

[bepone]

trafo must have low impedance ( cca 800 Ohms maybe), this is first what is coming to my mind..

you can read if Broskie wrote something smart about that subject, and imagine about overload.
https://www.tubecad.com/2012/05/blog0230.htm

[Tobyk]

Sorry, I’m talking about preamp, not output..

[bepone]

what you want to do with the preamp? and where in preamp is "SE" output stage in your application?

[Tobyk]

CF in preamp, normal Single ended 6V6 output..

[roberto]

It is plenty of MArshall 2203 kind of preamp into a simple SE power amp.
A bit of nfb around the output tube could help with the fizzness.

[Stevem]

Harshness more often then not is caused by driving a down stream gain stage ( preamp or output ) too hard, this makes for a lot of unrelated upper harmonics being made that are unrelated to the root note, and that condition can be further aggravated by the up stream stage running on a lot of voltage ( V+ ) which only serves to widen the frequency response of the tube.

I don’t see any usage in a CF stage helping that condition.

There are plenty of ways to change things, lower plate voltage, lesser gain by means of cathode and plate resistors and then of course in the tone stack.

Don’t forget, a CF stage will always have a tad less then unity gain.

If your play any amp up loud enough to where it’s starting to clipping hard and then play just two notes , a root and a fifth and those two notes start to sound out of tune to each other, when they are in tune to each other when played clean, then that is a clear cut case of clipping harmonics added up and pushing each note off pitch.

[Tobyk]

It is plenty of MArshall 2203 kind of preamp into a simple SE power amp.
A bit of nfb around the output tube could help with the fizzness.

I’ve never seen any schematics on how to do this kind of feedback. Is it just a wire with a resistor of say 100K? between anode and grid (connected before grid resistor) on the output tube? And a mixing resistor of say 100K? before that?

[thetragichero]

A bit of nfb around the output tube could help with the fizzness.

I’ve never seen any schematics on how to do this kind of feedback. Is it just a wire with a resistor of say 100K? between anode and grid (connected before grid resistor) on the output tube? And a mixing resistor of say 100K? before that?

it's been done a lot, for a long time: https://cdn.shopify.com/s/files/1/2325/ ... 0715640943

[Tobyk]

A bit of nfb around the output tube could help with the fizzness.

I’ve never seen any schematics on how to do this kind of feedback. Is it just a wire with a resistor of say 100K? between anode and grid (connected before grid resistor) on the output tube? And a mixing resistor of say 100K? before that?

it's been done a lot, for a long time: https://cdn.shopify.com/s/files/1/2325/ ... 0715640943

I ment feedback just around the power tube (anode to cathode). Not like the Champ..

[thetragichero]

you'd want the signal decoupled so that you wouldn't be effecting the dc bias of the cathode (all we're looking to do is feed back ac signal) so you'd need to use a capacitor. blackface vibrochamp uses a cap from grid to cathode. could also do anode to cathode. cap value would require doing some math, or using an rc filter calculator

[Tobyk]

Sorry, I ment anode to grid LFB of a 6V6..
Do you know of any examples of that?

[sluckey]

Not a SE amp but the Bassman AB165 has LNFB from plate to grid.

I assume the same principle would work for a SE amp.

[10thTx]

Has anyone tried a cathode follower in a single ended amp?

Yes, I have. https://soundclick.com/r/s86rcl


With respect, 10thtx

[Tobyk]

Not a SE amp but the Bassman AB165 has LNFB from plate to grid.

I assume the same principle would work for a SE amp.

Great, finally a schematic – thanks!