news from parasound backgrounder photo library parasound.com

 

For immediate release:

Parasound JC 1 Design Elements

by the Parasound JC 1 Design Team

Introduction

Parasound has worked with renowned designer John Curl since 1989. John’s designs are legends dating back to the early 1970s. These include the Mark Levinson JC-2, Denneson JC-80 preamplifier, Vendetta phono preamplifier, electronics for The Grateful Dead, and the master recorders for Wilson Audio and Mobile Fidelity. He has continuously pushed the boundaries of sound reproduction and has pioneered measurement techniques which correlate musical accuracy with the materials used in component parts. We honor John by designating the JC 1’s model number with his initials.

After a decade of working together, John Curl enlisted Bob Crump and Carl Thompson to form CTC Builders in 1999. John creates the electrical designs, Carl engineers the board designs, and Bob chooses the parts, wires and connectors, and voices the final result.

CTC’s products have earned the utmost respect from discerning audiophiles and high end magazine reviewers. Owners of the CTC Blowtorch preamplifier consider it to be without equal.


John Curl on the JC 1 Circuit Design

The JC 1 power amplifier is the culmination of many years of de-sign and modification of Parasound power amplifiers. The JC 1 design is based on a complementary dif-ferential J-FET input stage followed by two stages of selected push-pull MOSFETs, ultimately driving 9 pairs of the most powerful complementary bipolar power transistors that are available today. This gives 400 watts into 8 ohms, 800 watts into 4 ohms, and 1200 watts into 2 ohms, without compromise.

In a sense, the JC 1 design started in 1989 with the original Parasound HCA-2200. This amplifier worked very well, but it was somewhat limited in power output and features. A number of prototypes and modifications over the years then evolved into the HCA-3500. This amp is very powerful, but it lacks some of the JC 1’s refinements, such as much larger heat sinks, twice the power supply, as well as better connectors, wiring, and circuit layout. Also, the JC-1’s class A operating region has been increased to over 25W, so that under normal listening conditions, the amp is operating entirely in the class A region, only extending to the class AB region during very loud musical passages, or ‘special effects’ such as explosions, rocket launches, etc. These refinements are the key to a high end product that is above and beyond a well-engineered power amp design. This makes the JC 1 a world-class amplifier that will compete favorably with any other amplifier presently available at anywhere near its price range and power level. I am very happy with the listening and measured results of this new design.

John Curl

Bob Crump on CTC Builders’ Role in Developing the JC 1

State of the art audio design requires three things to succeed where others have failed: the best electrical de-sign, the best layout, and the best parts. CTC Builders’ skills encompass the best of these three separate worlds and our results have been amazing down through the years.

The JC 1 project arose out of the modifications CTC performed on the Parasound HCA-3500 between 1999 and 2001. Taking things a step at a time, various changes to the circuit design and parts yielded an absolutely wonderful amplifier we called the CTC BBQ. The BBQ was exhibited at the 2001 International Consumer Electronics Show and it turned heads. In 2001 Parasound commissioned CTC to de-velop a no-compromise mono am-plifier comparable to the BBQ and the result is the JC 1.

The JC 1 breaks new ground in parts quality, as there is nothing in high end audio that approaches the quality of parts we chose – reflect-ing many years of our continuing parts research and evaluation.

The JC 1 also breaks new ground for circuit boards which allows such attributes as focus, speed and imme-diacy to shine through due to the highly unusual, very tight layouts Carl designed. Some of the outstanding high performance parts are as follows:

  • Vampire Direct gold-plated OFC RCA jacks
  • Neutrik XLR connectors
  • Reliable RT DC bypass and Zobel capacitors
  • Superior Electric binding posts
  • Vampire continuous cast copper signal and DC wiring
  • Nichicon Great Supply raw DC capacitors (132,000uF in the high current supply)
  • Nichicon Muse DC and local by-pass capacitors
  • Harris hyperfast soft recovery diodes for all bridge rectifiers
  • Sanken output transistors - the most powerful complementary transistors available

The JC 1 delivers 25w in class A allowing most amplification to be contained within the class A mode except for large bass transients. The unit uses separate power supplies for the input/driver section allowing the JC 1 to be totally immune to fluctuations in the AC line voltage. We did the best we could with the electrical design, layout and parts selection/voicing and we’re confident the JC 1 will surpasses virtually every other amplifier on the market regardless of price.

Bob Crump


Carl Thompson on the JC 1 Layout

The real challenge in the JC 1 project was to take John’s subtle and elegant circuits, Bob’s well-considered parts selections, and implement everything in an uncompromised, cost-effective manner, without the performance sacrifices usually associated with other than astronomically priced equipment. Circuit functions were divided between four separate, carefully oriented circuit boards (and associated wiring) to minimize un-wanted circuit interactions. Overall, system signal flow was developed in concert with the board layout with special emphasis on overall system grounding. Boards underwent many layout iterations both to optimize manufacturability and performance. The final main board can handle double the very, very substantial current of which the JC 1 is capable. This required very wide matched circuit paths in 2 oz. copper on both sides of the board for critical nodes.

The JC 1 is very difficult to stress so that audible strain due to layout-generated resistance will be vanish-ingly small. Part of the reason for such a beefy layout is the huge power supply that required fitting four very large filter capacitors plus the separate input stage power supply on the main circuit board. The separate dedicated input board is thus more immune to power supply noise and from circuit noise in the separate auto turn on control board. The JC 1 input board mounts directly on the back panel for minimum input and input select wiring length. The layout is absolutely symmetrical with the minimum possible signal path. Here too, there’s an emphasis on minimum resistance to reduce unwanted circuit interactions.

I’ve only occasionally said of the design of very highly refined equipment that it starts to “glow” after a certain point. It’s when you just know that there are virtually no unquestioned design elements and there is a deceptive simplicity and wholeness to the overall package that is apparent to the practiced eye. The JC 1 glows.

Carl Thompson

Parasound JC 1 Design Overview

The Power Supply

The heart of the power supply is a 10 ampere (continuous!) toroid transformer, chosen for its efficiency, low hum field, and high power rating. Encapsulating this massive power transformer in an epoxy-filled steel canister assures ultra-quiet performance.

To create the high voltage B+ and B- supply rails for the output stage, we use high-speed, fast-recovery rectifier diodes and four enormous 33,000 uF Nichicon electrolytic filter capacitors, chosen for their low Equivalent Series Resistance (ESR) and dielectric absorption. In addition, these filter capacitors are bypassed with smaller polypropylene capacitors to reduce AC ripple in the DC supply and to further eliminate noise and interference that is generated in AC power lines from computers and other appliances in the home.

Relay-Bypassed Soft Start Circuit

When the JC 1 is first turned on, there is a significant amount of in-rush current required to charge the enormous power supply capacitors. In order to suppress this in-rush current and to prevent nuisance tripping of circuit breakers, we employ NTC (negative temperature coefficient) resistors. These resistors cut the in-rush current by approximately 50%. Once they heat up, they essentially become a jumper with zero ohms resistance. However, the JC 1 goes one step further for this circuit. After the NTC resistors have done their job of suppressing in-rush current a gold contact relay automatically is activated to jump across the NTC resistors to completely bypass them. This extra step insures that the resistors do not restrict any current whatsoever to the power supply once the JC 1 is in full operation.

Complementary Configuration

Each stage of amplification uses NPN transistors fed by the positive DC power supply and complementary PNP transistors fed by the negative DC power supply. Thus, half the devices amplify the positive half of the musical waveform while the others amplify the negative half. This complementary topology is inher-ently linear, which reduces distortion and improves sonic accuracy.

The Input Stage

The JC 1’s input stage uses matched pairs of discrete JFETs arranged in a differential configuration. JFETs are ideal for the input stage because their inherently high impedance is unaffected by the impedance of source components. Differential configuration provides superior noise reduction. These precision input JFETs are also cascoded to produce the current necessary to drive the MOSFET drivers in the following stage.

The Driver Stage

The driver stage provides critical amplification for which we employ complementary matched pairs of MOSFETs selected for their tube-like sonic qualities. MOSFETs tend to generate less odd-order harmonic distortion than bipolar transistors. This is important because odd-order distortion sounds unnatural and fa-tiguing to the human ear, whereas even-order distortion is less offensive because it is consonant, rather than dissonant. Our MOSFET driver stage prevents the harshness and brittle sound so often found in other amplifiers.

The B+ and B- power for our input and driver stages cannot sag under load because it is supplied by inde-pendent transformer secondary windings with independent rectification, filtering, and voltage regulation. This preserves soundstage width and depth even when the JC 1 output stage is drawing enormous amounts of current.

The Output Stage

The amplifier’s sonic character-istics are established by its input and driver stages. Now, the sole job of its output stage is to deliver the enormous amounts of current and voltage from its power supply to the speakers. Bipolar output transistors are better than MOSFETS in the output stage because of their higher safe operating area (SOA) and inherent ruggedness. The JC 1’s output stage employs nine pairs of high current (15-ampere) bipolar transistors to insure long-term reliability, even with continuous high power operation and challenging speaker loads. Lightning-fast (60 MHz) transistors respond instantly to complex demands in the musical signal, virtually eliminating distortions that occur with slower transistors. Slew rate limiting and Transient Intermodulation Distortion (TIM) are simply not an issue in the JC 1.

Class A/AB Operation

Pure class A operation provides the purest sound. However, an amplifier operating entirely in class A opera-tion would be enormous, highly inefficient, and generate far too much heat. Class AB combines some of the advantages of Class A with the efficiency of Class B operation. It is a compromise that reduces the heat generated in pure class A operation and the oddorder harmonic distortion created in class B. In class AB, the driver and out-put stages are always 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 it possible to use passive cooling and avoid fans, whose noise can be heard over the music. The JC 1 input and driver stages are 100% pure Class A while its output stage provides up to 25 watts of pure Class A -- more than amplifiers selling for three or four times its price. The result is less fatiguing, more natural sound at a refreshing price.

Total Protection

DC Servo

Direct Current (DC) burns out speakers. Therefore, every power amplifier must have some way to insure that DC from its power supply never reaches its + or - speaker terminals. Most amplifiers simply use 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 will “veil” sonic clarity and attenuate bass response.

Parasound power amplifiers incorporate ingenious and fast-acting DC servo circuits, completely eliminating the need for coupling and blocking capacitors. The JC 1 is direct-coupled from its input jack to its speaker terminals. This advanced circuitry never needs adjustment or maintenance. It operates outside the audio signal path to keep the DC offset at the output of the JC 1 at a constant 0.00 Vdc. The results are startling clarity, freedom from listening fatigue, and formidable bass response.

Relay Protection

The JC 1 has a high-quality protection relay with gold-plated contacts for long-term reliability. This relay functions to protect either the amplifier, the speaker, or both. When the JC 1 is first powered on, the relay remains open for three seconds as the positive and negative power supplies stabilize and reach equilibrium. This prevents annoying popping or other transient noises. Relay protection also prevents speaker damage in case of a catastrophic amplifier failure. Any amplifier that doesn’t use relay protection for its speaker outputs compromises the safety of the am-plifier and your speakers.

Over-Current Protection

Specialized current-sensing transis-tors 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.

Fuse Protection

The JC 1 has a separate fuse for its positive and negative DC voltage rails. 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.

Chassis

The JC 1 chassis is heavy gauge aluminum. Aluminum is non-magnetic and cannot be energized by high voltage and current flow, thereby removing a potential cause of “smearing” or other audible in-trusion.



Parasound JC 1 Specifications


RMS Power, 20 Hz - 20 kHz
400 watts continuous, 8 Ohm
800 watts continuous, 4 Ohm
1200 watts short term, 2 Ohm
Class A Power, 20 Hz - 20 kHz
25 watts, bias set to high, 8 Ohm
10 watts, bias set to low, 8 Ohm
Current Capacity
135 amperes peak
Slew Rate
> 130 V/µsecond
Frequency Response
2 Hz - 120 kHz, +0/-3 dB
Total Harmonic Distortion
< 0.15 % at full power
< 0.018 % typical levels
IM Distortion
< 0.03 %
TIM
Unmeasureable
Dynamic Headroom
> 1.8 dB
Input Impedance
Balanced - 100 k Ohms
Unbalanced - 50 k Ohms

Input Sensitivity
Balanced - 1 V for 28.28 V output into 8 Ohms
Unbalanced - 1 V per leg for 28.28 V output into 8 Ohms
Signal to Noise Ratio
> 122 dB, IHF A-weighted, bias set to low
> 120 dB, IHF A-weighted, bias set to high
> 113 dB, Unweighted, bias set to low
> 111 dB, Unweighted, bias set to high
Damping Factor
> 1200 at 20 Hz
DC Trigger Requirements
+9 Vdc to +12 Vdc, 2 mA
Audio Trigger Requirements
50-250 mV AC
DC Trigger Output Capacity
+12 Vdc, 150 mA
Dimensions
Total Width: 17-3/4” (451 mm)
Panel Height: 7” (178 mm)
Total Height with feet: 7-5/8” (194 mm)
Depth: 20 “ (508 mm)
Power Requirement
Idle: 250 Watts
Full Power into 4 Ohms: 1280 Watts
Net Weight
64 lb. (29.1 kg)
Shipping Weight
79 lb. (35.9 kg)

Features and specifications subject to change without notice.
 

 

 

 

 

Press Contact:

Gordon Sell   

908 788-0700

e-mail:
gordon@gspr.com

Gordon Sell
Public Relations

www.gspr.com




Parasound Products, Inc.
2250
McKinnon Ave.
San Francisco CA   94124

(415) 397-7100

Gordon Sell Public Relations
63 Main Street
Flemington, NJ 08822

(908) 788-0700