The power supply is one of the
most important parts of an amplifier.
It is also one of the most common places to cut costs.
At the core of the Jones PA-M300 is a 1000 VA low-noise
toroidal transformer that is electrically and magnetically shielded.
This transformer delivers abundant, clean power regardless of line conditions.
Not only can it run the amplifier at full tilt without breaking a sweat, but it has plenty of extra power - above its RMS rating - for transients. This combined with a large bank of reservoir capacitors gives the amplifier unmatched authority and dynamics.
Just about any amplifier can sound "loud". But realistic reproductions of orchestras, rock bands and movie explosions take more than just "loud". It takes explosive power AND exemplary control.
The amplifier circuit in the PA-M300 can harness all of the power from the power supply and deliver it to your speakers with precision, low distortion and reliability.
Noise
Much of what makes music engaging rather than simply pleasant comes from low level details. These details can be the ambience of a concert hall, the harmonic signature of a famed instrument or the tone of a legendary guitar player.
To avoid squashing these subtle cues, an amplifier must be quiet. That is why we are so excited about the ability of the PA-M300 to reject noise. Looking over the measurements of power amplifiers in published reviews since 2005, we found none quieter than our PA-M300. In fact the vast majority had noise levels three times or more higher.
Distortion has been the subject of much debate, confusion and frustration. The sound of an amplifier cannot be made as simple as one number, such as total harmonic distortion or intermodulation distortion. Some amplifiers can test well on one or both of these parameters and still sound poor. Much of this is related to the way an amplifier handles high frequencies and musical transients.
What you can't hear
affects what you can hear!
Reproducing the higher frequencies of a musical signal is difficult for the output devices used in most amplifiers. These large bipolar transistors are slow to turn off because of the capacitance of their semiconductor junctions. When this happens, the transistors quite literally cannot keep time with the music. Not only does this muddy up the treble, but it pushes distortion artifacts down into lower frequencies. This means that even if the initial distortion involves a frequency above the audible band, it can have significant effects at a lower frequency that is audible.
Below is a visual representation of this phenomenon. In this example, the pictures represent music being sent to your amplifier. The top portion of each photo in our example represents the high-frequency portion of the music.
The far left image represents the entire uncompressed performance, including frequencies above what your speakers can produce and what you can hear. The middle picture and the far right picture represent two amplifiers with the same reported frequency response and the same reported distortion for audible frequencies.
These amplifiers should sound the same right? They have the same specifications after all. They may actually sound very similar playing audible frequencies. But when asked to play frequencies above the audible range, there is a clear difference. The middle amplifier cleanly slices off the inaudible range. The far right amplifier, due to its slower output devices as we mentioned above, will smear them into the audible range. We see this in the picture on the far right. What you can't hear, effects what you can hear.
MOSFET output stages are immune to this type of high frequency distortion. That is one of the main reasons we use MOSFET output devices in the PA-M300. This gives you the silky highs of a tube amp, without losing the depth, realism and detail found in the most accurate solid-state amplifiers. MOSFET’s cost a few times more than the alternatives and present some design challenges, but we are not looking for easy or cheap, just excellence.
Are you getting the performance that you paid for? From time to time manufacturers are sent bad parts – maybe a resistor or a capacitor that is out of tolerance. These bad parts will make their way into products and cause problems. If the problem is severe enough, the amplifier will fail and be caught by even the most relaxed quality control program. More often, however, the problem is more subtle. The amplifier may be able to play music and satisfy safety concerns, but its performance is greatly diminished.
Even if all of the parts are as they should be, some amplifiers are very susceptible to bias current shift. Precise adjustment of the bias current minimizes crossover distortion. Our amplifier design features a very stable bias generator. This means that your Jones Amplifier should perform as well in 10 years as it did the day you bought it, giving you years of pleasure and protecting your investment.
Occasionally you will see where a manufacturer has sent an out-of-tolerance product, or a product whose bias current has shifted, to an audio magazine for a public review. You will never have to worry about the performance of your Jones amplifier. Every Jones product is tested and certified to meet its promised level of performance before it leaves the factory.
The only time you will hear distortion from a Jones amp is when clipped. Clipping can be a big problem in solid-state amplifiers. Much of the dislike for solid-state sound is related to clipping behavior. Many claim that tube amplifiers sound louder or more powerful than solid-state amplifiers. Obviously they are not actually more powerful. However, tube amps naturally clip in a "soft" pattern. Our perception of this is related to the harmonic content of the clipped waveform. This soft-clipping is so much more pleasant than typical solid-state hard clipping that some actually like the sound.
That is why we have designed the PA-M300 to soft-clip, just like a tube amp. While actual clipping will be infrequent in an amplifier with the power of the PA-M300, it is unlikely you will notice if it does happen.
With the power, clarity, openness and resolution of a solid-state amplifier and the clipping behavior of a tube amp, you have the best of both worlds.
Our amplifiers are constructed by hand in the USA. Meticulous care is given to the construction process and part selection. We use solid copper busbars for the central ground point for all the amplifier circuitry. We use relays and output devices that are generously overspecified. When parts aren't operating at extremes, they behave better and last longer. This gives Jones owners many years of excellent performance.