Crown D-150 Power Amplifier
Today were highlighting the vintage Crown D-150 Power Amplifier. The D-150 is an extremely well regarded power amplifier, an under-the-radar machines used in many high-end mono and stereo setups for their known performance standards one would not expect from Crown. Often times we will see these amplifiers dedicated as tri/quad amp lo pass dedicated machines. The D-150 was available in two formats, industrial and home use with a faceplate and a few later models D-150A & (MKii). Sold during 1971-1974 the D-150 was compared to the larger DC-300 model which is DC coupled unlike the D-150. Uniquely the D-150 uses a pair of unbalance 1/4 mono jacks (25K)
The power supply stage consists of a simple full wave bridge rectifier at a total 18,000MFD filtering stage for the developed rails. These originals were replaced with modern Mallory can capacitors in this rebuild and new bypass films across the diode bridge (1MFD/1KV ECW Polypropylenes)
The driver stage, considered to be realistically a Class B (A+B) amplifier with a fixed Bias, adjustable by emitter resistor pass. The front-end differential stage utilizes a Fairchild (U)A739C OPAMP. The 739C is a high gain Dual IC with a 3-stage Class A PNP output stage. All of the electrolytic’s were replaced with VP and high temp (105C) Nichicon capacitors with an increase in operating voltages. The Bias was attenuated with new (10W) KOA resistors and a new 739C was sourced and install onto a chipset versus direct. New UF400# Ultra-Fast diodes and modern 4148 type installed as well.
(Next to the Yamaha M-2..this is one of the best performing amplifiers of this period Ive tested yet!)