Volume still doubles when you dial it from 1 to 1.0001.Things that remain unchanged includes: large filter cap, output transformer, C2 preamp caps, tone stack.ĭespite the improvements in IV, there are still problems that exist.Bias is still fixed with the factory resistors being 33k for R51 (unchanged) and 27k for R52 (increased from 22k).C8 preamp caps is upgraded from 0.0022uF to 0.022uF.Speakers: IV uses the Celestion A-Type while III uses the “lighting bolt” speakerįor the more technical incline, here are some additional differences in terms of actual component change from III to IV:.Cabinet: Suppose to be lighter but can’t really tell.

This an effort to make the amp more versatile to keep up with the times.

Pedals: The IV has made using pedals even more easy.

Sound Brightness: III is well known for having a brighter sound and it is still valid, even against IV.

When you compare the two side by side, the IV sounds fuller

Gain: IV has stronger and even louder gain.

Reverb: IV has rearranged the reverb in a different part of the circuit, resulting in a more warn sounding reverb as III is a bit wash out.

Fender has clearly made this change to answer critics who wasn’t happy with III’s bass handling.

This is the main difference that is obvious on the first hearing. Bass: IV has a stronger, rounder and clearer bass, especially when you used distortion.These differences are listed below for more specific descriptions: It also differs in the quality of the speakers and the cabinet built quality. The Fender Blues jr IV exhibit a stronger bass and a more responsive reverb than the III. The main difference between Fender Blues Junior iv vs iii is the significant jump in sound quality. Is the Fender Blues Jr IV worth an upgrades over the III? I would say probably not but if you were deciding between the two, the IV is definitely the winner.

Fender blues jr iii schematic