Power Supply Filter Caps Signal Path Caps: Coupling & Blocking


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Call 'em condensors, cans, caps, or capacitors -- they're all the same. Caps are designed to do one thing -- store electrical charges.

Caps like exercise! They tend to degrade with age (and non-use) and their failure can wipe out expensive tubes and transformers. Re-capping is an important part of restoring safe and reliable operation of your vintage H.H. Scott tube gear.

Caps are composed of two electrical conductors separated by an insulator called a dielectric; and they can be constructed using a variety of materials: Foil and film, metal and air, silver and mica, mylar, metalized polystyrene, polypropylene, etc.

They come in endless sizes and shapes and the unit of capacitance is the Farad. Your vintage H. H. Scott unit will have two basic types of capacitors: electrolytic (larger) and non-polarized (typically smaller).

Electrolytics are the big cylindrical guys in the power supply (typically found above the chassis) designed to remove or filter the AC "ripple" from the power supply AC-to-DC rectifier. Basically, the electrolytic is polarized: only letting current flow in one direction. These large caps act as reservoirs, filling up with rippled current and letting out a "smoothed" current. 'Lytics can do their job so well they can store a lethal charge for days or even weeks, so use caution! Caution: 'lytics were generally not designed to last more than about ten years, so it is highly recommended you or a qualified technician replace them.

Non-polarized caps are relatively small. They come in a variety of shapes and sizes and can look a little like candy (orange) drops, rolled paper tubes, little discs. They can radically affect the tone or sound characteristics of circuit. Some of the more modern (expensive), so-called premium or "super" caps, can sound "dry" and "harsh" when used in vintage H.H. Scott tube gear. It may be more art than science, but experiment with good foil and film type non-polarized caps to retain that warm, vintage, original H.H. Scott tube sound. Replacing your tired and worn-out signal-path coupling caps is inexpensive and generally will result in a noticeable sonic improvement.


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