Parts Selection for Best Sound Quality and Reliability in the Restoration of Vintage Equipment

In the days of yesteryear, the parts commonly used were limited to only a few variations of readily available and cost effective types. Typically used were carbon composition or carbon film resistors, and paper or polyester dielectric (insulation) capacitors. These types were usually not intermixed as they are sometimes today to provide a particular sound the manufacturer is trying to archive in his product. 

Examples of differing sound qualities in these parts are as follows:  Carbon composition resistors have a slightly thicker sound than carbon film types, which have better detail and less noise. Metal film resistors have a very detailed and slightly hard sound with the lowest noise. To preserve the tonal characteristics of a vintage piece, resistors that need replacing, should be replaced with the same type. If you desire to change the tone in a slightly different direction, resistor types could be selected to accomplish this.

      Capacitors made today come in many varying types and from a wide range of manufacturers, and they all

      sound different !  Commonly seen are polyester and polyproplyene types from a wide variety of companies.

      When replacing paper capacitors in vintage gear, certain brands of polyester types sound very close to these

      in tone. Paper, as you might surmise is not the best insulator but it was extensively used in equipment made

      prior to about 1965 because suitable quality plastic film was not being made. Polypropylene capacitors are

      superior to polyester with excellent definition and smoothness, and I have used these in some vintage amp

      restorations with many customers remarking how much more they like the tone. Polyester, though is a better

      choice for a more authentic sound, with the 150M brand (formerly Mallory) usually being the best choice, Sprague

      225P is also very good. For polypropylene, Xicon is exceptionally good, and Spague 715/716P is very good, but

      can impart a little too much thickness to the sound.
 

      As for filter capacitors used in the power supply section, there is no significant difference in sound among the various

      brands, however, the quality of construction does vary, and most modern types are quite good and reliable.

      Prefered types are the excellent Spague Atoms for most US made gear, and for British and European gear, the

      German made F&T brand is a top quality choice. Illinois brand capacitors are also very good and cost slightly less.
      

      As you can see there are a lot of choices to be made to provide the sound that you want and some of this can get

      a little too complex, if you just want your amp fixed that can be simply done, but if you want to go beyond that,

      this can give you a little insight into the possibilities.