Owner's Manual

18
Class A-A/B Operation
Pure class A operation provides the purest sound. However, an amplifier with the output power of the JC
1+ and operating entirely in class A would be enormous, highly inefficient, and generate far too much heat.
Class A/B combines the primary advantage of Class A with the higher efficiency of Class B. This reduces the
heat generated in pure class A operation as well as the higher-order odd harmonic distortions created in class
B. In class AB, the driver and output stages are always partially turned on, which provides a nominal amount
of pure class A operation. At higher power levels, when the musical waveform swings from positive to
negative and vice versa, each bank of transistors is allowed to rest momentarily. This resting, or quiescent
time, makes it possible to deliver high amounts of power without overheating. It also makes possible the use
of passive cooling and avoids fans, whose noise can be heard over the music. The JC 1+ input and driver
stages operate in pure Class A while its output stage operates with greater Class A power than most
amplifiers selling for twice or three times its price. The result is less fatiguing, more natural sound.
Total Protection - DC Servos
Even a miniscule amount of Direct Current (DC) will burn out speakers without any warning. Every power
amplifier must have some way to ensure that DC from its power supply never reaches its + or - speaker
terminals. Most amplifiers simply use adjustable trim controls to reduce their DC offset or capacitors to block
DC. Unfortunately, trim controls can allow DC offset to increase over time, and even the most expensive
capacitors in the audio signal path “veil” sonic clarity and attenuate bass response.
The JC 1+ incorporates fast-acting DC servo circuits which completely eliminates the need for coupling
and blocking capacitors. Thus, the JC 1+ is fully direct (DC) coupled from its input jacks to its speaker
terminals. This advanced protection circuitry never needs adjustment or maintenance. It operates outside the
audio signal path to keep the DC offset at a negligible level. The results are startling clarity, freedom from
listening fatigue, and superior bass response.
Total Protection - Relay
The JC 1+ has a high-current protection relay with gold-plated contacts for long-term reliability. This
relay’s function is to protect the amplifier, the speakers, or both when there is a fault. When the JC 1+ is first
powered on, this relay remains open for approximately three seconds as the positive and negative power
supplies stabilize and reach equilibrium so that no DC offset reaches the speaker terminals. This prevents
annoying popping or other transient noises. Relay protection also prevents damage to your speakers in case
of a catastrophic amplifier failure. Any amplifier that doesn’t use relay protection for its speaker outputs
compromises the safety of the amplifier and your speakers.
Total Protection - Current Overload
Specialized current-sensing transistors are connected to the output stage of the JC 1+ to constantly
monitor the current flow through the output transistors. If the current drawn by this stage exceeds a
predetermined safe level due to a load impedance below 1 ohm or a short circuit at the speaker terminals, the
output relay will open immediately to prevent the output transistors or other parts from failing.
Total Protection - Fuses
In addition to the main fuse on the rear panel the amplifier has two internal fuses for the positive and
negative DC voltage rails of the input stage and four for the output stage. These fuses provide backup
protection in case the over-current protection does not work in time, or if an internal part fails. In the event of a
part failure, these fuses halt operation to minimize damage to additional parts.