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| General Questions about Conrad-Johnson Components: Q. How do I know if my conrad-johnson component is phase inverting? A. Phase information on conrad-johnson products is in all but the earliest conrad-johnson owner’s manuals (PV1,PV2, PV3, MV45 and MV75). Early conrad-johnson preamplifiers were phase correct (with the exceptions of the PV3 and the PV4 which inverted phase of line-level inputs). From the PV7 and the Premier 7 on, all conrad-johnson brand preamplifiers (both tube and solid-state) have been phase inverting in the line-stage. All three pre-preamplifiers (HV1, HV2 and Premier Six) were phase inverting. All conrad-johnson power amplifiers, tube and solid-state, are phase correct except the Premier 350. Q. How do I correct for a phase inverting component? A. The total number of phase inversions in the system should be either 0 or an even number. If you have an odd number of inversions (typically 1), compensate by inverting phase at the speaker terminals. Be sure to reverse the polarity on BOTH speaker terminal. In other words connect the amplifier positive (+ or red) connector to your speakers negative ("-" or black) connector for both sets of speaker wires. Q. Why is my conrad-johnson component phase inverting? A. Each active voltage gain stage in a circuit inverts phase once. In pursuit of ultimate purity in music reproduction, recent conrad-johnson preamplifiers have been designed for the absolute minimum number of gain stages – one. One stage, one inversion, hence these components invert phase. By the nature of its design, the Premier 350, which also has a single voltage gain stage, is phase inverting. Q. What type of interconnect or speaker wire is best suited for my conrad-johnson component? A. The choice of wires depends on the specific components in your system and, to an extent, on your personal preferences. Please consult your authorized conrad-johnson dealer for the best choice of interconnects and speaker wire for your system. Q. Should I leave my preamp/amp on all of the time? A. To obtain maximum tube life, vacuum-tube products should be switched off when not in use. A good general rule for is that if you will not be listening for more than an hour, turn any tube component off. Conrad-Johnson solid-state preamps (including Sonographe and Motif), on the other hand, are designed to be left on at all times. We recommend switching power amps off when unattended and over night. Q. Should I use a line conditioner with my preamp and/or amp? A. Try it. If you hear a sonic improvement leave it in the system. Results will vary depending on your system and on the quality of your ac power line. Q. What is the input impedance value of my conrad-johnson component? A. For preamplifiers, this varies from model to model. Check your owner’s manual. The line level inputs are designed to be used with most high-level devices such as CD players, DVD players, VHS players, tape decks, and tuners without any impedance problems. The input impedance of conrad-johnson power amplifiers (including Motif and Sonographe) is 100 kOhms. Questions about Conrad-Johnson Vacuum-Tube Components: Q. Can I replace a tube with a different tube type? A. No. You should only use the tube type that is specified by conrad-johnson or an exact substitute. Using a different tube type can be expected to degrade performance and may damage the product. Q. Can I substitute a 12AX7 for a 5751? A. It is not recommended that you do this. While it may technically "work" there are subtle differences in these tubes. You will notice a degradation of deep bass and a reduction of dynamics. Please contact either your local dealer or conrad johnson to order the 5751 replacement tube. Q. Why are identical numbered tube types (i.e. 12AU7) slightly different in sizes, shapes, and colors? A. There are several manufacturers of vacuum tubes and each manufacturer may chose a slightly different exterior. What is important is that the inside of each tube meet the proper electrical specifications. Q. Why do different brands of tubes of the same type sound different? A. Each manufacturer may use slightly different internal materials when constructing the tube. This is because there is no industry standard for internal materials. The only standards apply to fairly broad electrical specifications. At conrad-johnson we spend countless hours evaluating various vacuum tubes for each product. The tubes are selected based on sound quality and reliability. We know of no currently available tubes that are reliable and will improve the sound quality of your conrad-johnson component. All tubes that we supply are then tested in circuit for performance to our specifications. For consistent results, we recommend that you purchase tubes supplied by conrad-johnson. Q. Why do some tubes of the same brand and type glow at different brightness levels? A. Some variation in brightness is normal – having to do with the amount and positioning of the internal silvering on the glass. You need not be concerned if one tube glows brighter than another. Q. How long do tubes last? A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time. Q. What is the silver material on the inside of the glass of a vacuum tube? A. It is called "getter-compound" The getter-compound is used when the final sealing of tube is done. Some tubes have more of this than others but that will not affect the quality of the sound. Q. On one of my tubes the glass appears white? Why? A. It is damaged! Turn your unit off and contact your local dealer of conrad johnson and replace that tube with a factory approved tube immediately. Continued operation can cause damage to the component. Q. Should I clean the tube pins and tubes sockets? A. Tube pins and sockets can be cleaned by turning off the system, disconnecting the component from the ac power line, and then removing each tube and replacing it in the socket once or twice. If the tubes are replaced every two to three years, this should normally be clean the sockets sufficiently. Q. Should I use tube dampers on my tubes? A. Many of the newer CJ preamps and power amplifiers come with circular rubber tube dampers as standard. We recommend the use of these on all preamplifier tubes and on amplifier input tubes. Avoid using the very soft Sorbothane tube dampers that have been commercially marketed. These melt from the heat of the tubes and can foul the tube sockets. Do not use any kind of damper on amplifier power output tubes. Conrad Johnson Vacuum Tube Power Amplifiers: Q. How do I bias my power output tubes? A. Conrad-Johnson tube amplifiers feature a unique, easy to use bias circuit. Biasing is done with NO signal going to the amplifier (turn the preamp off, or all the way down). Let the amplifier warm up for about half an hour (if biasing a new set of tubes for the first time, do this first after about 3-4 minutes, then repeat once after a half an hour). Adjacent to each output tube you will see an adjustment screw and an indicator light. After the amplifier has warmed up, turn the screw clockwise until the red light comes on. Then slowly back off (counter-clockwise) that adjustment until the red LED just goes off and stays off. You will need to do this for each tube. Some of the LED’s may come back on while you are adjusting other tubes. Just re-adjust so that all of the LED’s are off after all adjustments are completed. After the biasing procedure is completed, you may find the indicator lights coming on from time to time when no music is playing. This can happen as power line voltages vary over time, and as the amplifier conditions change a bit with use. There is no need to re-bias unless all leds come on and stay on for several minutes. Q. Why do the LED’s flash when I am playing music? A. That is normal. These indicators are showing the amount of current flowing through each output tube. As you play music the current through the output tube will rise and fall with the music. If you listen at relatively high levels, the LEDs may glow steadily while the music is playing. After the music is finished and the amplifier has had a few minutes to rest, the LED’s should all go off. Q. How often should I bias my power tubes? A. There is no need to obsess over the output stage biasing. Unless the amplifier appears to be in a fixed state of over-bias (all LEDs stay lit for an extended period of time), there is no need to rebias more than every six months or so. Q. Why is there no sound or very low level, highly distorted sound from one channel even though all of the tubes are glowing? A. The output stage of your amplifier is protected by fuses in the plate circuit of the output tubes. There is one "plate" fuse per channel. These are in the large fuse holders located on the back or top deck of the amplifier. Most likely there is a blown "plate" fuse in the channel in question. Check to see if the LED associated with one of the fuses is glowing red. If so, that plate fuse is blown and will need to be replaced. Be sure to turn the power amplifier off before replacing the plate fuse, as these fuses operate at a very high voltage. A blown plate fuse indicates a possible problem with the associated power tube. It may have occurred because of a voltage spike but it may also have occurred because the power tube may need to be replaced. If the unit continues to blow plate fuses then you need to either replace the tube or contact conrad johnson for repair. DO NOT SUBSTITUTE OTHER FUSES OR VALUES AS THIS CAN CAUSE DAMAGE TO YOUR AMPLIFIER! Q. Why is the LED on beside the large fuse holder? A. The plate fuse is blown and needs to be replaced. Please review the answer listed above for possible reasons. Q. Where can I buy plate fuses for my tube amp? A. These special, high-voltage rated fuses can be hard to find. They are available from conrad johnson or through your local authorized conrad johnson dealer. DO NOT SUBSTITUTE OTHER FUSES OR VALUES AS THIS CAN CAUSE DAMAGE TO YOUR AMPLIFIER! Conrad Johnson Solid-State Power Amplifiers: Q. Why is there no sound or very low level, highly distorted sound from one channel even though the amplifier power indicator is lit? A. The output stage of your amplifier is protected by fuses in the positive and negative power supply circuits. There are two of these "rail" fuses per channel. These fuses will blow if the output stage is short circuited (even for a moment) or if the amplifier is called on to play at very high levels into very low impedance speakers. These fuses are located in fuse holders on the back of the amplifier, or in fuse clips on the printed circuit board. Turn the amplifier off, then check for one or more blown fuses. Replace as needed with the same type and value of fuse. |
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conrad-johnson design, inc. 2733 Merrilee Drive Fairfax, VA 22031 phone: 703-698-8581, fax: 703-560-5360 |