Here is some of my findings from this upgrade I uploaded on YouTube
My Research:
This mod uses Local Negative Feedback (LNFB) to shape the feel and response of your amp’s second gain stage. By feeding a small portion of the tube’s output signal (plate) back to its input (grid) through a resistor and capacitor, we reduce distortion, smooth out the transition into clipping, and increase clarity and touch sensitivity — all without changing the amp’s core tone.
The lower the resistance, the stronger the feedback effect.
🎵 13 Amazing Benefits
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Tames early clipping and lets you push the amp harder before distortion kicks in.
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Reduces Stage Gain Safely
LNFB offers a cleaner way to reduce gain without changing cathode or plate resistor values — maintaining original voicing.
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Smooths Out Distortion
Makes overdrive more even and round, with less buzzy or harsh harmonics.
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Improves Clarity
Notes retain more definition
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Reduces amplified noise floor (less hiss/hum etc..)
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Widens out the sweet spot
More of the gain stage becomes usable — smooth breakup and great tone across a wider dynamic range. Edge of break up easier
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Reduces higher-order (odd) harmonics that are often unpleasant — makes the output more spectrally balanced.
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Reduces Mud
Helps tighten up the low mids, making the amp feel less boomy or congested.
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Useful in Cascaded Gain Stages
In multi-stage designs (like Dumble, Soldano, etc.), it pre-conditions the gain to behave more musically further down the chain.
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Adds “Glassiness” Without Harshness
Preserves treble detail in a sweet, musical way, not brittle or ice-picky.
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Compresses Naturally
Introduces a subtle compression that can make the amp feel more -polished.
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Makes Gain More Usable
You can run more gain without losing articulation — great for stacking or cascaded gain stages.
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Works Well with Other Mods
Plays nicely alongside mid boost switches, cathode bypass cap mods, and relay switching — non-invasive and modular.
🎧 Why it’s not the same as turning the gain down
✅ 1. It Changes the Shape of the Overdrive, Not Just the Level
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Turning down gain reduces the input signal hitting the tube → less clipping.
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LNFB alters the tube’s nonlinearity by feeding back an out-of-phase signal, which reshapes how the tube distorts.
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It creates a smoother, more gradual onset of clipping, more like the feel of a big clean amp being pushed.
✅ 2. It Tames Odd-Order Harmonics
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Tubes naturally produce odd-order distortion. LNFB tends to cancel or soften the harsher odd-order content, leaving the tone rounder and less harsh — something a gain knob won’t do.
✅ 3. Dynamic Response Becomes More Controlled
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LNFB acts like a “soft limiter” — loud peaks get gently reined in after amplification, not before.
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This leads to that “touch-sensitive” feel where the amp reacts more to your playing, not just signal strength.
✅ 4. It Affects Compression and Bloom
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With LNFB, there’s often a subtle increase in clarity and articulation, especially during chord decay or string muting.
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You don’t get that with a gain knob — turning down gain often just makes things lifeless or weak.
🎛️ "LNFB is like installing a smart limiter that reacts musically" — Explained
✅ Limiter
In studio gear, a limiter gently keeps the signal from going over a certain threshold.
LNFB does something similar:
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It feeds a small portion of the inverted output (plate signal) back into the input (grid),
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This opposes the incoming signal just enough to flatten the peaks.
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But it doesn’t clamp or squash it like a compressor — it still breathes.
✅ Smart
It’s "smart" because:
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It only acts when the gain stage starts to clip or become nonlinear.
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At lower levels, it mostly stays out of the way.
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The more you push it, the more LNFB gently pushes back, keeping the signal from spiralling into harsh clipping.
✅ Musically
This is where it shines for players:
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It doesn’t choke the amp — it makes it feel smoother and more controlled.
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Your pick attack, dynamics, and guitar volume still shine through.
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Notes bloom instead of splattering — and chords stay articulate.
