Trillbee & CapacitorX
CapacitorX
Trillbee, I’ve been working on a low‑noise bias network for a preamp, but the power supply ripple keeps messing with the hiss. Any tricks to tame those spikes without messing with the tone?
Trillbee
Hey, try adding a little low‑pass filter on the supply – a couple of low‑ESR caps in series with a tiny ferrite bead can choke the ripple, and put a bulk electrolytic right next to the amp for that steady supply. A small π‑filter (C‑L‑C) before the bias network will tame the spikes without shifting the tone. Keep the values modest so you don’t alter the bias; just enough to smooth out the hiss. Also make sure the ground is clean and the cables are twisted – a good shielded line keeps the noise out. Give it a spin, and the hiss should drop while the vibe stays crisp.
CapacitorX
Got it, I’ll rack the ferrite bead and 0.33 µF low‑ESR caps in series, then add 10 µF bulk electrolytic right next to the preamp. The π‑filter will be 0.1 µF, 22 nH, 0.1 µF. I’ll double‑check the ESR values with a meter, log the voltage before and after, and monitor the bias point with a scope. The ground plane will be a solid copper layer, all cables twisted, and I’ll add a 1 Ω series resistor to the bias line to clamp any transient spikes. Logging every reading for a 5‑minute window before and after the filter. Once the ripple is below 10 mVpp, I’ll consider it stable. Keep the bias constant, no drifting. That’s the plan.
Trillbee
That’s a solid play‑book! Love the mix of a ferrite bead, those tight‑tuned caps, and the π‑filter—should cut the hiss without touching the tone. Keep an eye on the ESR, and that 1 Ω clamp will keep any nasty spikes from messing up the bias. Logging 5 minutes each side is smart; you’ll see the ripple drop in real time. Once it’s under 10 mVpp, you’re in the sweet spot. You’re all set—just hit that test and let the preamp breathe cleanly. Good luck!
CapacitorX
Thanks. I’ll log the data, run the test, and tweak if anything’s off. The preamp should finally breathe.