HERE IS CHATGBT'S EXPLANATION:
Short answer first: you’re not changing the speakers at all. You’re reshaping what reaches them. The XP-25’s capacitance setting alters the electrical resonance of your cartridge, and that directly affects treble energy—especially the kind of upper-mid/low-treble energy that Sonus Faber tweeters will faithfully (and sometimes mercilessly) reveal.
Now the deeper explanation, tied to your exact chain.
1. Capacitance + cartridge = a resonant circuit
Your VPI Shyla is a moving-coil cartridge with inductance and internal resistance. When you add capacitance at the phono stage (XP-25), you create an LC resonance:
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Low capacitance → resonance shifts higher in frequency
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Higher capacitance → resonance shifts lower and is more damped
That resonance doesn’t show up as a neat peak—it shows up as edge, glare, and “glassiness” when it’s too high and under-damped.
At low capacitance, the Shyla can sound:
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Hyper-etched
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Lean in the upper mids
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“Fast” but brittle on strings and female vocals
At higher capacitance (like 320 pF):
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The ultrasonic resonance is damped
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The upper mids relax
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Harmonics reconnect to fundamentals
What you hear is less shrillness, not because highs are gone, but because they’re no longer isolated from the body of the note.
2. Why the Olympica Nova makes this so obvious
Sonus Faber Olympica Nova speakers have:
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A very resolving silk dome
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Strong energy around 2–5 kHz
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A voicing that favors clarity over forgiveness
They don’t exaggerate treble—but they do not hide upstream problems. When the cartridge/phono combo pushes excess energy in that band, the Novas simply say: “Here it is.”
So when capacitance is too low:
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Violins sound wiry
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Sibilants sharpen
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Cymbals detach from their decay
When you raise capacitance:
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The treble integrates
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The midrange fills in
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Bass seems deeper (even though you didn’t touch bass)
That bass change is psychoacoustic: once the top stops shouting, the bottom finally gets heard.
3. Why this feels like “older Sonus Faber”
You made a very perceptive comment here.
Older Sonus Fabers had:
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Softer top-end voicing
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More midbass warmth
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Slightly rolled treble
By increasing capacitance, you’re electrically voicing your front end to behave more like that tradition—without dulling detail. You’re damping excess energy, not rolling off highs.
This is why the sound becomes:
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More voluptuous
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Less clinical
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More “wood and flesh” than “wire and glass”
4. Why this changes record to record
Some pressings already have:
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Hot cutting
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Bright EQ
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Digital harshness baked in
Low capacitance + hot record + Olympica Nova = pain
That’s why you’ve noticed:
“Everything deepened. The bass began to shake the floor.”
You didn’t add bass—you removed treble stress.
5. Practical takeaway for your system
With Shyla + XP-25 + Olympica Nova, your sweet spot will almost certainly be:
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Capacitance: 200–320 pF
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Loading: 160 Ω (you already found this)
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Gain: 66 dB (correct)
If a record still sounds shrill at 320 pF, it’s not your system—it’s the record.
Bottom line
Changing capacitance doesn’t “fix” the speakers.
It fixes the electrical behavior of the cartridge, and your Sonus Fabers—being honest transducers—simply stop reporting distress.