REDGUM Amplifiers

Why are REDGUM Amplifiers & Audio Equipment so good?

A lot has been written about which sounds better – Vinyl recordings or Compact Disc recordings. The tracking distortion and inherent noise of vinyl players is a permanent and, they think, unacceptable feature. Still, they happen to agree that an excellent vinyl system has an impact that a lot of C.D. systems seem to lack. During the last 30 years they have repaired and serviced over 17,000 HiFi systems and have observed countless exotic (and more mundane) amplifiers working hard (and easy) into complex and simple loads. During this time, the complex interaction and wave-forms saw permanently changed their thinking on what is or is not a good amplifier.

In the last few years, REDGUM has spent much time studying how vinyl players’ bass impact – mainly through exotic valve amplifiers – is a function of the RIAA equalisation curve and the inherent limitations of the output stages of the amplifier. The frequencies they were interested in were all below 50Hz – with particular emphasis on those below 20Hz!

Anyone who has been to a live orchestral performance knows that there is an impact that is felt rather than heard, and just winding up the volume on your HiFi does not create that effect. They finally decided to practice all this information accumulated over the years, with particular emphasis on detail and clarity but not compromising impact in the bass. This was the impetus that led to the REDGUM amplifier.

REDGUM’s overall feeling was to process the sound as little as possible and, to this end, they did some hard thinking about digital recordings. There are some exciting criteria not previously used (to their knowledge). The loudest possible passage recorded on any C.D. is when all 14 bits are “on”, resulting in the maximum registered number 15384. No compact disc can produce a higher recorded level. Thus, the Compact Disc output is predictable. This information was used to consider how much gain/amplification was required to drive any amplifier to its maximum output.

So the next question was whether REDGUM should use valves or transistors. Both have limitations. Valves are inherently noisy and deteriorate from the first moment of use; transistors are quieter but cannot tolerate abusive overloads and are prone to self destruct! They thought that ideal would be a solid-state valve – a MOSFET (Metal-Oxide doped Silicon Field Effect Transistor).

REDGUM worked extensively on High Power MOSFET amplifiers as sole “Official Warranty Service” for several brands of these amplifiers during the 1970s and 1980s, and REDGUM decided to re-evaluate these devices as they have also improved over the years.

Like many designers before them, they eventually settled on the basic circuit from the manufacturer’s handbook on MOSFET amplifier design, but incorporating much faster and ‘stronger’ MOSFETS than the original specification. The circuit incorporates many local and overseas “Go-Fast Modifications”, that are often offered as after-sale upgrades by specialist HiFi shops.