Recent content by Retrovert

An L-Pad across the tweeter works as an adjustable voltage divider and allows the right volume to be dialed in. Variable is superior to a fixed resistor because the volume may need adjustment for music type, room dynamics, individual taste, or hearing loss.

Ferrite core is a way to increase inductance using fewer turns than air core; it is a cost- and weight-savings measure which introduces non-linear behavior. Coupling between magnetic fields is the issue. The two coils act like a transformer, with flux inducing currents in the opposite coil...

Turbine oil is a perfectly acceptable, and readily available, substitute for the Anderol bearing lubricant. Likely the same properties. Anything that isn't paraffin sludge dissolved in a solvent. Plus lithium grease for the mechanical surfaces. Works great on turntables.

Prematurely applying B+ destroys tubes, but not for the reasons commonly cited, such as gas, which are dubious as you noted. (Although the residual gas over time can be considerable. Gases diffuse out of metals plus there is the not inconsiderable oxygen baked out of the cathode's oxide...

Capacitors are coils of flat conductor with resistance. Bypassing lowers ESR (Equivalent Series Resistance) because a big resistance in parallel with a small one ends up dropping like a stone, and lowers ESL (Equivalent Series Inductance) in the same way. This is particularly important...

Yes, of course. Thought that was clear. Larger in terms of value, not physical size. Lead length also matters for HiFi, because the Qrr dumped by a diode is at UHF/VHF frequencies. (So is shot noise.) This acts a carrier wave which is then AM modulated by mains frequency so it's buzz all...

Yes, right, of course. I have cathode poisoning on the brain, having been researching B+ issues in output tubes for an amp upgrade. And there it's all about heaters and delayed B+ application. But the point is still that a cold cathode gets deposits on it and you need to get the cathode...

The resistor damps the ringing by converting the noise into heat. This must be a non-inductive, so carbon composite is better than spiral-cut metal film. Resistor size is a tradeoff. The smaller the resistor the more power it routinely passes, but the faster the damping. The bigger the...

The phenomenon of noisy diodes is called "shot noise" and was discovered by Walter Schottky who was researching noise in vacuum-tube diodes, but it applies to solid state. In silicon it has to do with quantized electron migration across the PN junction. Starts in the hundreds of KHz and moves...

This comes down to increased heater voltage to burn the coating off the cathode. As others have noted, you can do this with a tube tester set to a higher than normal heater voltage. Some have built special purpose gadgets for this. Here's what I elsewhere wrote about this: Oxide cathodes...

Looks like a tantalum. They tend to catastrophically fail as shorts. I was once trying to diagnose a circuit and burned myself on one that was a short but had not yet blown up. If the cap is in the audio circuit, i.e. coupling, you should use a better grade of cap. Ceramics are not...

True, but it's far more interesting than this as it reveals some underlying law of the universe. Careful value selection reduces the size of the manufacturing stock, both fabricating and stocking for storage and use. It doesn't matter if it is resistors or balloon ropes or camera lenses or...

Luuuuuke, use the power of the Archive... web.archive.org/web/20120218044424/http://imageevent.com/sidandcoke/sidsposhpowercord

Ummm, not so much. The generally accepted definition can be found here: en.wikipedia.org/wiki/Listener_fatigue Google turns up the same thing. Fatigue caused by repetition in the context of experiments turns up a lot in cognitive testing. I've always heard it called "fatigue" or "burnout"...

Be careful, that is very abrasive and will remove material and reduce the detail. It will also leave deep scratches. Acids will quickly remove the metal oxides, forming soluble metal salts. That's all metal polish is. Really! Typically sulfamic acid plus a mild abrasive and some...