Through the 1980s Fender, Mesa Boogie, and others often used them as power tube screen resistors. In some positions they can catch fire if something goes wrong. Over time carbon resistors can drift in value, so they need to be replaced for the amp to sound the same or even work correctly. There are even low noise metal film resistors made specifically for audio applications. ![]() Carbon films are a little quieter but not as quiet as metal film resistors. That pan frying sound you hear in old amp is the sound of carbon resistors. What problems do they present?Ĭarbon Comps and Films are noisy and make amps have more hiss, pops, and sizzle. No amp will need more a handful of carbon resistors for this purpose. In some of my amps I will use carbon comps or carbon films in these positions for extra flavor. Certain plate resistors positions in an amp will sound slightly different with carbon comp or carbon film resistors. This only occurs in circuit positions with both high DC voltage with a large, superimposed AC signal. In some positions they can distort the audio signal which is sometimes (not always) desirable. In the vast majority of circuit positions in a tube amp circuit carbon comp and film resistors only add noise. ![]() There are steep trade-offs for using carbon-based resistors: shorter service life, extra noise and the potential for fire. They should only be used if a difference in sound is possible or desired. ![]() None are good reasons to include them in an amp. Boutique makers often use the older carbon comp types to exploit unknowing buyers, out of a lack of education, pure mysticism, or a desire for the inside of their amps to look old timey. Many production amps (lower cost tube amps) have carbon film resistors because they are cheaper than other types saving the builder a few bucks per unit. Many of these older amps used 20% tolerance resistors which meant resistor values were inconsistent which in turn made the amps inconsistent sounding unit to unit. These were a little quieter and more reliable. Marshall and others used often used carbon films. Even after the advent of quieter carbon film resistors Fender and others continued to use them because they were cheaper and consumers at that time expected some noise with their electronics. ![]() Pretty much all electronics had them inside (no TV screens did not look better because of them!). Why do all many vintage amps have Carbon Composition or carbon film, resistors in them?Īt one time (the 1940's to the 1960's) carbon composition resistors and later carbon films were the only types of resistors available for low wattage use and the cheapest. You do need quality parts for good sound but by using the conventional wisdom that better-parts-make-the-amp-sound-great we could make any amp design sound good just by using different parts. Good tone in any amp is achieved by good circuit design and parts selection it is not a result of magic parts. You can find forum posts where a person claims their amp has acquired magical properties from switching over to carbon comp resistors or claiming that they are difference between a good and bad amp. These same people often claim the tone in their amp is partly due to the use of carbon resistors. Sadly many people on the internet and even builders often talk about those little brown carbon based resistors with reverence. Kevin O'Conor of London Power (inventor of power scaling and amp expert) wrote in regards carbon comp resistors : "Old technologies never die-even if they should." I have to agree. The Carbon Composition and Carbon Film Resistor Myth
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |