Tubes, caps, and low noise resistors. Or for the same money upgrade to a better unit. The upside of modification is the fun and making the choices. The downside is that the modified unit is likely to be worth less and be more difficult to sell to boot.
To my ear the biggest bang for the buck is to replace the resistors with Vishays, which lower the noise floor allowing you to hear the other mods better. If you want more specifics, I will respond to an email.
To my ear the biggest bang for the buck is to replace the resistors with Vishays, which lower the noise floor allowing you to hear the other mods better. If you want more specifics, I will respond to an email.