Vac vintage high power mk2 owners manual
This is the 11 pages manual for vac vintage high power mk2 owners manual.
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Extracted text from vac vintage high power mk2 owners manual (Ocr-read)
Page 1
UnpackingEach tube socket on the amplifier is covered by a small round sticker. The color of this sticker corresponds to the color of the sticker on a tube. Fit each tube into the matching socket, first removing the sticker from the tube and socket. The bias levels for the output tubes have been factory set, but should be checked during the installation procedure. InstallationPhysical requirements: 1)Provide adequate ventilation - allow at least 3 inches above and 1 inch to each side. 2)Do not place in a completely enclosed cabinet. 3)Do not stack other equipment on top of the VAC units. 4)Do not operate on carpet or any other surface that might block air flow. 5)The chassis and power transformers will become hot in normal use. 6)Do not allow the chassis of the VAC components to touch any metal parts, such as the frame of an equipment rack. This might create a parallel ground path that will degrade the sound of your system. Electrical connections: 1)Complete all installation steps before plugging the amplifier into the AC mains supply. 2)Connect signal inputs to the power amplifiers. Single ended interconnect cables equipped with RCA phono plugs provide the input to each channel. 3)Connect loudspeakers between the appropriate pair of binding posts on the back of the power amplifiers. Most popular speaker cables can be accommodated by the output terminal strips. Output impedance matching is available for loads of 2, 4, and 8 ohms. Connect one lead of the speaker cable to the "G" position, and the other to either 2, 4, or 8. The "G" terminal is at ground potential, and the amplifier does not invert phase. 4)Do not connect two amplifier outputs to each other. 5)Connect the AC cord to the power source indicated on the rear panel (100 volts AC, 120 volts AC, 220 volts AC, or 240 volts AC at 50 or 60 Hertz). 6)Follow the BIAS procedure described in this manual to set the idle current. Check the idle current at 1 minute, 30 minutes, 1 hour, and 2 hours. Also, read the section entitled INSTALLING NEW OUTPUT TUBES.
Page 2
OperationContinuous operation is not recommended. If the amplifiers will not be auditioned for a few hours it is best to turn them off. This avoids undue stress to the KT88 output tubes. As with all high fidelity products, the sound characteristics of the VAC amplifiers change somewhat as they warm up. Best sound will be achieved after 15 minutes of operation, with subtle changes occurring for up to one hour. However, we advise against leaving the equipment on at all times because of the attendant acceleration of output tube wear. Life of the output tubes averages between 2,000 and 5,000 hours depending upon brand fitted and random variations within the tubes themselves. Any time that the VAC Power Amplifier has not been used for a few weeks the sound may be different. This is also normal for high resolution audio equipment. Optimum sound should return after a few hours of operation, preferably with an audio signal. Please note that although your VAC amplifiers have been run for 48 hours at the factory, they will continue to "break in" for approximately 150 hours. The break in is most pronounced in the ultra-linear mode. Note that the optional triode mode and ultra-linear mode do not require separate break in periods, and that the ultra-linear mode will improve even if you only operate the amplifiers in the triode mode (this is in most cases the most listenable way to break them in). Also be aware that many components display the need for a new break in period after being transported in unheated cargo aircraft. Bias AdjustmentYour VAC Power Amplifier has been shipped with output tube bias preset. This should be checked when you install your amplifier, and approximately every month thereafter. It must also be set whenever an output tube is changed. Monitoring and adjustment of the output tubes is quite easy, and requires a simple voltmeter. To start, place the black test lead in the center test point (TP5) and the red lead in TP1 (the test probes will "snap" into the test point jacks with moderate pressure). Adjust the associated bias control to obtain the DC voltage reading listed on the top of the chassis. Perform the same operation for TP2, TP3, and TP4. Finally, since the tubes interact slightly, repeat this procedure two or three times until the readings are unchanged. Lower bias readings will not damage the amplifier or tubes, but may affect the sound if more than 1 or 2 volts low. It is most important to have all of the tubes read the same within +/- .5 VDC. When installing new tubes, adjust the bias controls to the centers of their rotations. Check the bias of all tubes as the amplifier warms up - don't wait ten minutes. Recheck after 10 minutes, one hour, and one week. Bias levels should be checked monthly to ensure optimum sound quality. Allow the amplifier to warm up for an hour before checking. It is not unusual for bias current to change with time, particularly when tubes are new. In fact, the greatest amount of drift occurs during the first 200 hours of a tube's life. The drift may change direction periodically, such that the bias control must be increased and then later decreased, or vice versa. Also check bias if the sound seems to be lacking in detail or dynamics.