metal-film vs carbon resistors

Discuss Yocto construction and related issues
  • as always in electronics, one is cheaper than the other, and you always try to be as cheap as possible while still beeing as accurate as possible, so for example the logic part with all the leds, dont require stable resistors you can choose cheap here, in other parts like the t networks for sound porpuse, you maybe want the be very accurate or you aim for a certain sound so you have to have certain passive elements with certain characteristics.

    So if you wanna live easy always buy the most expensive most accurate stuff, that will always work, but comes with a prize.
  • or if you want to be oldsql and close to the original that used carbon or metal, use the same.
  • Metal-film resistors are less noisy than carbon ones. Hence in theory, the built device will have less background noise.
    From an audiophile point of view, that would be better. Otherwise for our purpose, carbons and metal-films are the same.
    Original 808 and 909 were built with carbon resistors. So if you want to have the most faithful reproduction, it's carbon, not metal-film.

    However, the "master section" basically just amplifies the final result of the whole 808, the "magic" (sound generation) doesn't happen here.
    So it may be interesting to substitute metal films to have the less noise possible at the end.

    In my opinion, the only benefit is that Mouser always has in stock all metal-film values. That's not necessarly the case for carbon resistors
  • Go ask this question at a tube guitar amp forum and see what happens! :lol:
  • So thanks very much for the replies. I'll then go for metal film resistors since they are cheaper and the avaibility is better.
    Since every 808 sounds slightly different anyway this shouldn't be a problem at all. ;)
  • Metal-film resistors are less noisy than carbon ones
    You got any source for that statement?

    I am of the opinion, noise in resistors is only happening due to therman noise, so called johnson noise.

    And its only dependend on the resistor value, so if you have high value you get bigger noise, no matter carbon or metal.

    But feel free to teach me otherwise :)
  • mex wrote:
    Metal-film resistors are less noisy than carbon ones
    You got any source for that statement?

    I am of the opinion, noise in resistors is only happening due to therman noise, so called johnson noise.

    And its only dependend on the resistor value, so if you have high value you get bigger noise, no matter carbon or metal.

    But feel free to teach me otherwise :)
    Thermal noise is in all types of resistors. It is dependent on resistor value and temperature.

    Carbon resistors suffer from a couple of problems that metal film resistors don't. For example, they can drift in value over time and with temperature. Even just soldering a carbon resistor into a board may change its value by more than 5%. As far as noise goes, carbon resistors exhibit significantly more flicker noise (1/f) than metal film resistors do. This is a good topic to research online, but be wary of documents without graphs.
  • mex wrote:
    Metal-film resistors are less noisy than carbon ones
    You got any source for that statement?

    I am of the opinion, noise in resistors is only happening due to therman noise, so called johnson noise.

    And its only dependend on the resistor value, so if you have high value you get bigger noise, no matter carbon or metal.

    But feel free to teach me otherwise :)
    http://www.vishay.com/docs/28771/basics.pdf
    Take a look at table page 5.
    I absolutely agree with your remark regarding noise increasing with resistor value.
    However, for the same (big) value, let's say 2M2, metal will be less noisy compared with carbon.

    As I already said, in our case, this is irrelevant, the original 808 was built with the most common, if not the cheapest, components available. This is not hi-fi or a scientific instrument.