User manual SUMMIT EQP-200B

[. . . ] Low Frequency Boost : This potentiometer controls the amount of boost engaged for the 20, 30, 60, 100, 180 Hz frequencies. Low Frequency Cut : This potentiometer controls the amount of cut engaged for the 20, 30, 60, 100, 180 Hz frequencies. Low Frequency Select : This five-position rotary switch selects between frequencies of 20, 30, 60, 100, and 180 Hz for which the low frequency boost and cut controls have effect. Mid-High Frequency Select : This eight-position rotary switch selects between frequencies of 1. 5k, 3k, 5k, 8k, 10k, 12k, and 16k Hz for which the mid-high frequency boost control has effect. [. . . ] This type of equalizer is made of resistors, capacitors and inductors. The equalizer has approximately a 20dB gain loss which must be overcome. The equalizer circuit feeds the first stage of the tube amplifier and the second stage of the amplifier has a cathode follower for low output impedance. A Word About Tubes The tubes that are used in the EQP-200B are selected to give the best possible performance in the position that they are in on the printed circuit board. Switching them to different positions will cause performance deterioration on the audio path. Replacing them with "gold" or high end tube types may not be desirable. In cases that we have measured, these tubes have shown higher distortion and noise as compared to the tubes we have selected. In some cases, the so called "gold" or high end tubes have made the unit unusable. The reason for this is some of the "gold type" tubes are selected for high distortion in guitar amplifiers. All of these so called "Brand X" types are selected with 6. 3 volts AC on the heaters, whereas Summit Audio uses 5 volts DC on the heaters for longer tube life and lower noise. The reduced gain can raise the noise floor, increase distortion, and reduce headroom. For proper performance from a tube, the replacements must be selected using 5 volts DC on the filaments. The tubes we use are selected in the circuits that they are used in to ensure proper operation, long life, and low distortion and noise. In at least 50% of the cases we have tested, gear that has been used for several years actually have lower noise and distortion levels than when new. If a tube turns micro-phonic, the distortion will be obvious and the tube must be replaced. However, tube life will most likely be greater than 10, 000 hours of operation. Tubes are generally very reliable; don't replace them just because they are old. In the EQP-200B there are gain adjustments that will need to be checked when the tubes are replaced, or else the metering could become inaccurate and the noise floor could change. Replacement should be done on the bench with a distortion analyzer attached to ensure that the distortion levels are proper and it is comprised of second order harmonics. Before replacing the tubes in your EQP-200B, please talk to your dealer, call Summit Audio, or find a technician who has experience working with tubes and high end audio equipment. Electrical Connections: (This EQP-200B is wired as a pin 2 hot device. [. . . ] "A" weighted, dB (B), dB C weighted, etc. ), the measurement devices are basically EQed or filtered before the measurement is taken. This filtering was developed so that sound pressure level (SPL) measurements can more nearly match human's non-linear hearing characteristics. However, when used in noise, frequency response, and distortion measurements, weighting will alter the results. Completely flat frequency measurements are key to giving accurate specifications. [. . . ]