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Components in the” signal path”

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  • Components in the” signal path”


    I am gathering strength to take on the next refurbishing project…

    (Apart from this speaker project: )

    ...and that is to make my 2nd amp, a NAD 304, better and to last longer by recapping and re- resistorisize the unit.

    I understand that the high-grade components should be placed in the “signal path” and in other places one can put components of good but lesser quality.

    My question is: Is there a way, in a scheme of a complex amplifier, to determine which components are in the “signal path” and which aren´t?

    Best regards//lasse
    Stockholm, Sweden
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Only parts you need to replace are the electrolytic caps. No need to change resistors. ALL components are in the signal path with maybe the exception of the front panel illumination or a control board. An exception may be a volume control if it has gotten dirty.

    Step one. No signal going in. Power on, volume turned up. With your ear at the speaker, do you hear any hum? If not, there is nothing to fix in the power supply. Up to you if you think replacing the caps in the signal path wil make it sound better.

    "High grade" is marketing. Selection of a cap has multiple considerations. Look at ESR. In many places, you can get lower ESR by going to a higher voltage. Many of the power supply caps were special built and finding better replacements may be hard. Putting it back to original will likely be a big improvement. Do not get sucked into "esoteric, audio grade" caps. Look at the specs. Sometimes tiny improvements can be made by making the input blocking cabs larger. In come cases, you can make them smaller and use good film caps. ( I tent to use a film to implement a 15 Hz HP filter on my inputs rather than a big electro)

    304 was a nice little unit. Worthy of your attention. Do not expect a magical effort will make it better than one at 10 times the cost. That requires circuit changes. You might search for Rotel and Hafler modifications to get an idea what I am talking about. Not seeing the schematic, I do not know if the input current source can be improved, how the feedback was designed etc.


    • #3
      I have used Panasonic FC-caps in the recapping of my Citation 11/12-unit.

      See some of the story here:

      Is Panasonic FC a good "all around" cap in your opinion? (It is readily available in Sweden.....)

      Perry Mason talking to his dentist:

      "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"