Resistor types in non-signal areas and effects on tone.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by scottosan, Jan 13, 2006.

  1. scottosan

    scottosan Supporting Member

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    I'm sure we all can agree the difference in tone between resistor types. I'm completly on board with this but only for resistors in series with the signal path, and not so much with cathode and power resistors. I believe that the sonic differences in componenents used in cathode positions are less distinguishable if using the same tolerance of cathode resistors and cathode bypass caps.

    Care to discuss?
     
  2. scottl

    scottl Member

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  3. loverocker

    loverocker Member

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    "I'm sure we all can agree the difference in tone between resistor types."

    I'm sure you're wrong - there's no agreement even on that bit. :)
     
  4. donnyjaguar

    donnyjaguar Member

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    I have to disagree with this. :) Signal (input) on the cathode has just as much affect on sound as that on the control grid. Its the variance in voltage between these two that determines the current flow from the plate to the cathode. If this were not the case, a paraphase invertor as used in most every guitar amplifier wouldn't work. The cathode resistor handles just as much current as the plate resistor, and moreso than most every place in the signal chain, so if its defective it will show up here sooner and most definintely be heard through the speaker.

    As for resistors used in the power supply section. Any effect these may have is largely filtered out by the electrolytic capacitors so I'm in agreement here. Some people seem to find it necessary to put lower value, and presumably lower ESR, capacitors across the electrolytics to filter out high-frequency (presumably hash) noise. YMMV.

    There is one resistor in your ampliifer that is more important than any other. See if you can guess which it is. Hint: In some older amplifiers its absent.

    DJ
     
  5. John Phillips

    John Phillips Member

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    +1.

    Power supply B+ chain resistors, screen grid resistors and power-stage cathode resistor types have no effect on the tone that I can tell. I like to use high-power ceramic-cased wirewounds for all these positions for the simple reason that they are the most durable especially under overload (eg tube failure) conditions.

    I'm not 100% sure about preamp cathode resistors, particularly if they're unbypassed and high value, but that's from an "I think there could be a difference so I won't rule it out" perspective, I've never actually noticed any :).
     

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