Circuit:
This circuit is inspired by the classic Mullard amplifier design of the 1950's with some 'modern' touches, such as a temperature compensated LM334 CCS (Constant Current Source) and with auto bias using the excellent AB-Qi auto bias module. Bias is pre set by us and from then on will never require adjustment again. The Auto Bias module will compensate for aging tubes as well as the slight difference between each KT88 power tube to keep the bias for each tube at the pre set, optimum operating level for the best sound and longevity of each KT88 output tube.
Once a tube does get to a point, due to wear or a fault, where the auto bias module can no longer hold the pre set bias, the corresponding LED indicator light, which is located on the top plate next to each power tube, will go out which indicates that the tube will need to be replaced.
Power Supply:
Power is supplied by own design power transformer. It is a solid state rectified with a choke input power supply followed by a CRC circuit to arrive at the various levels of the high voltage B+.
To limit inrush current when first powered up, we use an NTC (Negative Temperature Coefficient) thermistor.
Components:
Only high quality components are used in the construction of Elvis MKII. All power supply electrolytic capacitors are name brands such as Nichicon, Panasonic, Illinois Capacitors etc.. Film capacitors are WIMA, and coupling capacitors are Russian PIO (Paper In Oil), hand picked and matched by us from our very own collection. Resistors in the signal paths are Vishay low-noise military spec film resistors. RCA sockets are gold plated, and speaker posts are Rhodium.
The printed circuit boards are designed in house and manufactured to FR4-TG standards. They are double layer with full ground planes to ensure complete screening of the circuits.
The output transformers are the excellent LL1679PP, the power transformer is our own design and custom made for us by Heyboar Transformers.
NOTE: With the Lundahl OPT's, either 4 or 8 ohms speaker impedance is available, not both.
General specs:
Power output with 4x Gold Lion KT88 power tubes: 60Watts/channel from 15Hz to 35KHz at less than 1% THD in ultra linear mode.
IMD: < 0.38% (18Khz and 21Khz) at rated power
Frequency response: 10Hz to 40Khz +/- 0.1dB at 50Watts
Power bandwidth: 16Hz to 39Khz +/- 0.3dB at 50Watts
Sensitivity: 2.5 volt in for 60Watts/channel out
Feedback: 10dB
Damping Factor: 14
Input impedance: 270,000 ohms
Hum & noise: > 90dB below 60Watts output
Power requirement: 120VAC 60Hz or can be wired for 220/240VAC 50Hz
170W
Weight: 42lb
Dimensions: 14.5"W x 13 1/16"D x 8.5"H