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Before you call or email, see if your questions are answered in the FAQs below...

Contact info

By appointment only. Please email or call to receive directions.

info at precision dash ar dot com


Frequently Asked Questions

Why don't you use gold/teflon connectors, which sound better?
You're falling for snake oil marketing bilge. The difference between the resistance of nickel and gold in a circuit with 10,000 ohms impedance is 0.0000001db. The dielectric constant of the insulation material only becomes important above 500MHz, and the resistance is in the dozens of megohms, again, a very small fracion of a decibel. Any effects are inaudible and almost unmeasurable. Besides, our supplier does not supply gold connectors in that configuration.
Double-blind A-B-X tests (where neither the operator or the subject know what they're listening to) have proved that 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), and soldered connections and switches.
Another fallacy is "skin effect" with regard to solid versus stranded conductors at audio frequencies. Totally bogus. Skin effect only happens at high RF frequencies. That's why your FM tuner doesn't have stranded wires on the PC board inside, solid traces are just fine. So if solid wires are fine for 100MHz, why do some say that it happens at 20kHz? Don't fall for it.
Sorry for going on for so long, but there's a lot of junk science going around in the audiophile world.
Look at Douglas Self's article on Science and Subjectivism.

I took your unit apart, and there's no quiet switching power supply, just a simple linear regulator. What's up?
The power supply has a pre-regulator and another regulator circuit operating in tandem. This makes a very quiet power supply with high ripple rejection. During the design phase of the Derumbleizer, numerous power supplies were tested to see which were the quietest, and which had the most ripple rejection. Linear regulators, switchers, and capacitance multipliers were built and measured, as well as combinations of regulators and pre-regulators. Even batteries were tried. The power supply in the unit is one of the quietest. There were one or two power supply designs only slightly quieter, but the differences were almost unmeasurable. In fact, the switching power supplies were the noisiest, and the noise was hard to filter out. Switching power supplies are popular with manufacturers because they are cheaper to build than linear power supplies.

You use ICs in the unit, why not discrete transistors or (insert IC number), which is quieter than yours?
The ICs used are some of the quietest chips available. There are quieter chips out there, but they're expensive, and the box would have to be two or three times bigger to fit the circuit inside, so it would also have to be more expensive.
Besides, the dynamic range of records is around 60db, (70db at the most with CX records) and with turntables having noise levels at around -80db, and CDs at -90db, the noise level of the Derumbleizer is more than quiet enough.

How come there's no power switch or bypass switch?
The Derumbleizer consumes minimal current, and can be left powered without concern, and since you probably wouldn't be able to hear any difference between your records being derumbleized and not (except for rumble), power and bypass switches were determined to be unnecessary.

How come your enclosure is aluminum, not steel? Doesn't steel shield against magnetic fields better?
Steel shields against STATIC magnetic fields, like from magnets, better than anything except mu-metals, but ANY conductive metal will shield against electromagnetic fields, like 60Hz house current or radio signals. That's why many electronic devices have boxes made from aluminum, steel, or metalized plastic.

A changing electromagnetic field encountering a conductor will be converted into electricity, and if that conductor is a box around something, the box will "short out" the EM field and prevent it from getting inside. According to conductivity charts, steel (at 15) is a poorer conductor than aluminum (at 60), therefore, aluminum shields better than steel. Only boxes made from silver (106), copper (90-100), and gold (65) would perform better than aluminum.

Why is the power supply hard wired into the unit, instead of having a connector?
There was a power jack in the prototype, but if the shell of the connector contacted the aluminum case, it developed a ground loop, and hum was heard. Totally insulated power jacks would not fit available real estate on the PC board.

I have a moving coil phono cartridge, will the Derumbleizer work with it?
Not yet. A version with moving coil circuitry is being developed. Stay tuned...

I lost my instructions, how do I set the capacitance switches?
For the left channel, switch 1 is 50pf, 2 is 100pf, 3 is 200pf, and 4 is 400pf. For the right channel, switches 5-8 are the same as 1-4. All switches add the capacitance when pushed down. So to add 250pf to both channels, set switches 1, 3, 5 and 7 down, and 2, 4, 6 and 8 up. You can add 50-750pf capacitance in 50pf increments.
Or you can download a copy of the instructions in .pdf format.

Do you accept credit cards?
We accept Money orders, personal and cashier's checks, plain old fashioned cash, eChecks and yes, credit cards. Credit cards accepted are Visa, Mastercard, Discover and American Express. eChecks and credit cards are processed by Paypal, using their secure online connections, and you don't even need a Paypal account, but if you do, you can pay that way too.

How can you claim there's no phase shift? All high pass and low pass filters introduce phase shift!
All filters do introduce phase shift. But the phase shift of the Derumbleizer's low pass filter is the opposite of the high pass, so when you recombine the two, the phase shifts cancel out and you're left with the original phase of the input. The same is true for the amplitudes of the filters. When you recombine the outputs, you get the input.

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Back to Precision Audio Restoration

Mailing address:
Precision Audio Restoration
14419 Greenwood Ave. N., Suite A, Box 321
Seattle, WA 98133
Call 206-387-5662 or email to receive directions
to purchase a Derumbleizer personally.
By appointment only.

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