Great 3W resistors are the IRC GS3 metal glaze Rs available for $0.45/each from Mouser or Handmade Electronics. Frankly, I find "noisy" carbon comp resistors to be sufficiently-quiet for high-gain stages (phono), just because the current is so low that they can stay cool and behaved.īTW, I would skip the metal oxide. If you are in the 2W territory, try putting two 3W film resistors in parallel for a huge cost savings over wire-wound - this is a fine solution. So, stick with film unless you need to dissipate more than ~2W. Wire-wound is great for high power plate loads on a big driver stage, but if this is on a first stage in a guitar amp, the current is probably fairly low. Metal film is absolutely acceptable as long as you aren't pushing close to the max power rating. But, I wouldn't bother unless you need a premium-grade plate load in a high voltage / high current driver stage. I drove myself nuts trying to install a 1/4W film feedback R the other day when I couldn't find a 1/2W).Ī good choice for audio-grade wire wounds are Mills non-inductive. (just a note, I also like to oversize Rs also for the sake of the fatter leads - a 3W metal film is much easier to work with in a point-to-point circuit, and is no bigger than a 1W carbon comp. just my guide to Rs, I'm sure others will have much to add/disagree with. Same with KOA Speer carbon films, which were recently discovered to be the Kiwame R's true identity Anyways. GS3 (3W) and RN60 parts (1/2W), for example, along with new production carbon comp resistors, are great options. ![]() They are non-magnetic and consistently affordable. ![]() I'm not keen on $$$ resistors - military spec 3W and 1/2W are exceptionally useful, and are available with numeric labels vs. Screen stopper with minimal screen current = Appropriately-sized carbon compĬathode resistor for a power tube = size so it fails at excess current! Grid stop with no grid current = 1W Carbon Comp Grid leak with minimal dissipation <<1/2 W = Premium 1/2W metal film Plate or cathode R dissipating < 1W = Metal film 3Wįeedback R with some dissipation <1W = Premium 3W metal film or bulk foilįeedback R with minimal dissipation <<1/2 W = Premium 1/2W metal film or bulk foil Power supply dropping R 1W = Wire-wound Non-inductive 5W+ Power supply dropping R > 1W = Conventional wire-wound, appropriately sized ![]() If I were to have a simple formula for low-noise and overkill: Carbon comps are great at high voltage AC and pulses, but some film resistors will go "pop" under those conditions. An exception: never overrate cathode Rs in an output stage (they should be metal film and preferably fusible!) - you want them to pop before the output transformer And pay attention to voltage ratings. Better to overrate any resistor that will dissipate power if it can contribute to the noise signal. For example, plate loads on driver stages, cathode resistors in phase inverters, screen resistors that carry current, etc. So, focus on plate resistors, and any other resistors that are dissipating power / carrying current. Arguably best to use the noisy carbon composition resistors there! For grid leak resistors, I typically use standard metal film, as the inductance is benign.įor noise, you want to look for resistors that carry current and dissipate power, since they will be the warmest and thus the noisiest. The grid stoppers rarely carry much current in normal audio applications, so it is better to reduce inductance rather than noise.
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