Derumbleizer — frequently asked questions

Not yet. A version with moving-coil circuitry is in development. The current Basic model is designed for moving-magnet cartridges, which are by far the most common on modern turntables.

Yes. The Derumbleizer includes a high-performance RIAA phono preamp, so it connects directly to an aux or line input, a computer sound card, or a stereo system that has no phono stage.

For the left channel, switch 1 is 50 pF, 2 is 100 pF, 3 is 200 pF and 4 is 400 pF. For the right channel, switches 5–8 are the same as 1–4. All switches add capacitance when pushed down.

Example: to add 250 pF to both channels, set switches 1, 3, 5 and 7 down with 2, 4, 6 and 8 up. You can add 50–750 pF in 50 pF increments.

You can also download a copy of the full instructions (PDF).

Yes. We accept Visa, Mastercard, Discover and American Express, plus eChecks, processed securely through PayPal. Money orders, personal and cashier’s checks, and plain old-fashioned cash are also accepted.

All filters do introduce phase shift — but the phase shift of the Derumbleizer’s low-pass filter is the opposite of the high-pass filter. When the two bands are recombined, the phase shifts cancel out, leaving the original phase of the input. The same is true for the filter amplitudes.

You’re falling for marketing hype. The difference between the resistance of nickel and gold in a circuit with 10,000 ohms impedance is about 0.0000001 dB. Dielectric effects only become important above 500 MHz, and resistance there is in the tens of megohms.

Double-blind A-B-X tests have shown you can’t tell the difference between gold and copper connectors, the most expensive oxygen-free cable and cheap zip cord of the same gauge, or soldered connections versus switches. The same is true of the so-called “skin effect” argument — skin effect only matters at RF frequencies, which is why circuit boards use solid traces even at 100 MHz.

The power supply has a pre-regulator and another regulator circuit operating in tandem, producing a very quiet supply with high ripple rejection. During design, linear regulators, switchers, capacitance multipliers and even batteries were built and measured. The switching supplies were actually the noisiest and the hardest to filter — they are popular with manufacturers mainly because they are cheaper, not because they sound better.

Steel shields against static magnetic fields best, but any conductive metal shields against changing electromagnetic fields like 60 Hz house current or radio signals. Because steel (conductivity 15) is a poorer conductor than aluminum (60), aluminum actually shields better against hum and interference. Only silver, copper and gold conduct better than aluminum.

There was a power jack in the prototype, but if the connector shell contacted the aluminum case it developed a ground loop and hum was heard. Totally insulated power jacks would not fit the available space on the circuit board, so the clean hard-wired design was chosen.

The Derumbleizer consumes minimal current and can be left powered on without concern. Since you wouldn’t usually be able to hear any difference between your records being derumbleized and not — except for the removal of rumble — power and bypass switches were judged unnecessary.

The ICs used are among the quietest chips available. Quieter chips exist, but they are expensive and would require an enclosure two or three times larger. Given that records deliver roughly 60 dB of dynamic range (about 70 dB with CX records), turntables run at around −80 dB, and CDs at −90 dB, the Derumbleizer is far quieter than necessary.

No — we don’t take payment for links on this site. The shop recommends a handful of places we actually use, and the clonewatches.is watch catalog is one of them, because the same anti-markup logic applies: buy the engineering, not the hype. The full list lives on the resources page.