["the ALTEC A-340A", "amplifier", "Power amplifiers of the past designed for the 25 to 30 kW power range have at a disadvantage in the choice of target tubes. It has become rather common practice to use small tubes and to adjust the power by a voltage regulator. Very little distortion has been produced, they usually require, at the event of a tube substitution, rather rare adjustments of a nature not reach performed by the amplithe user. The circuit of the A340A amplifier is the Altec Lassing approach to obtaining medium power using the 6550, combined with extreme circuit simplicity. The 6550 tubes draw almost constant plate current regardless of signal level. In this case, so that the regulation of the output current is adequate, this not only eliminates the usual input filterchoke, but more important, it allows the tube to show the average distortion figures for a group of tubes. Over much of the range it can be seen that the residual distor- tion drops to a fraction of the main sum figure indicated.", "The use of 5550 tubes eliminates any necessity of balancing means for either push-pull driver or output stage. 30 db of negative feedback was used to ensure that harmonic content of the output signals would be less than 0.5% for any level below full power. With 20 db of feedback and sufficient cable assistance that would be adequate to eliminate the effects of distortion, the tube would show the average distortion figures for a group of tubes. Over much of the range it can be seen that the residual distor- tion drops to a fraction of the main sum figure indicated.", "Desired carbon resistors of 1% tolerance are used for both push and driver tube loads to allow a long time to equalize between pairs. The tube is mounted on a care of grain oriented plate. Arrangement is such that the ratio of leakage inductance from the primary to the other half is less than 1% by the value of leakage inductance from the faii primary to the secondary. It assures good cancellation of even harmonic distortion in the faii primary range.", "The recent attention by many authors to the loudspeaker damping problem is speedreading a move by many manufacturers to provide amplifiers with which to adjust the damping factor to meet many specific speaker types. Altec Lassing takes no stand on the necessity or uselessness of such controls on speaker type of either manufacture. Altec Lassing speakers invented in recom- mended range exhibit similar characteristics throughout the wide range, hence, controls of this result in no apparent improvement in their performance. Such a control has been incorporated in the A340A amplifier for those who desire this feature; however, it is recommended that the control be set near what has with Altec Lassings features.", "The control is effective for only the 8 &mper; load condition. It is labelled R, and calibrated in emms. Thus, the generator impedance presented to the load can be varied from a negative four to positive four and one half ohms.", "SPECIFICATIONS", "Power, Current and Distortion:", "25 to 30 kW output power at 25 to 30 Hz, 80 to 100 Hz, 100 to 200 Hz, 100 to 300 Hz, 100 to 500 Hz, 100 to 1000 Hz, 100 to 2000 Hz, 100 to 3000 Hz, 100 to 5000 Hz, 100 to 10,000 Hz, 100 to 20,000 Hz, 100 to 30,000 Hz, 100 to 50,000 Hz, 100 to 100,000 Hz, 100 to 200,000 Hz, 100 to 300,000 Hz, 100 to 500,000 Hz, 100 to 100,000 Hz, 100 to 200,0