Oct 7, 2023 · With 300V to the output stage and 430V to the driver stage, I came up with this: This would be my first build with a shunt feedback output stage. I'm hoping to get a more 'push-pull triode' kind of sound but with a nice 15W max from the pair of EL86s. I'd be very appreciative if anyone cares to give that a look and let me know what they think.

Apr 5, 2023 · For a new project I want to mount the nfb series and shunt resistors directly onto the speaker jack then to run a twisted pair to the relative tube grid and its ground point. The shunt resistor will be 100 ohm or so tied to the speaker jack , then 10-12 inch of twisted wire back to inverter grid and its grounding point.

Jul 26, 2011 · But you can source your NFB from any tap you want. Then design the NFB circuit with the correct voltage division to get any particular, final, NFB voltage. So, if you have a multi-tap OT secondary, you can make NFB switchable by using the SW to select the different OT taps.

Dec 26, 2018 · I don't know how to exactly calculate the resistor value with my amp which is a Marshall 40W combo, push pull 4 x EL84... with a typical long tail pair PI. The amp at the moment just has the tail resistor and AC shunt cap just connected straight to ground.

Oct 11, 2012 · Merlin's triode-pentode morph control is a type of local NFB gain control for pentodes (where the screen is variably AC-tied to the plate).

Schematic of Basic Model of SE mosfet amp with 1 x bjt and 1 x 2SK134. output mosfet with all voltage + current path calculations, more on NFB. Shunt NFB explained, alternative B+, loads, power, psu notes, heatsinks. Notes on SE mosfet designs with choke feed and cap coupling, class A PP alternatives. Picture of inside the amp.

May 18, 2008 · What you're missing is the cap specifically named "NFB-Shunt Cap." Please install it as soon as possible. You need it. That part will help you get up and running, with less chance of destruction. It blocks amplification of DC. You can use any 440uF or larger cap there. The transformer is wired in parallel.

Apr 27, 2022 · Here is the .asc for the Boostrapped Pair 12AU7 with Shunt NFB circuit. It has 2.3X gain, but you can increase the value of R6 to get more gain (but with higher THD of course). This version uses the older Ayumi Nakabayashi model for the 12AU7.

Nov 1, 2022 · From there it could be sent straight to ground like in Vox amps with no NFB but they need something to create a voltage divider for NFB, hence the 4k7 shunt or just the 5k pot...or the 820R (no Presence) in BF Fenders.

Feb 7, 2006 · So, for a 20 watt 6V6 amp with a single 8 Ohm tap, what should the series and shunt resistors be for NFB? If I follow the logic here, my series resistor should be about 9k2 with a 390R shunt. Somehow that doesn't sound right.