Sutherland PhonoBlock phono preamplifier
The PhonoBlock was introduced almost 10 years ago. It performs beautifully and continues to please music lovers all over the world. The circuit remains essentially the same. Improvements focused on providing a better environment to more fully realize its potential. Each PhonoBlock chassis is a self-standing single channel phono preamp. Two are stacked to provide two channels for stereo.
The performance of the PhonoBlock has been refined and improved. Its classic, understated design is still there — even more so.” — Ron Sutherland
In the left shielded compartment…
is one channel of phono preamp circuitry. The front 2/3 is power supply filtering. Audio circuitry is integrated tightly into the back third. Signal path is kept to an absolute minimum.
In the right shielded compartment…
is a well regulated and filtered DC power supply. There are two isolated power suppliers for the two gain stages. Each PhonoBlock chassis is a self-standing single channel phono preamp. Two are stacked to provide two channels for stereo.
The best environment for delicate analog audio signals is LESS environment. A compacted area for the circuit with minimal distance between components is a big advantage. The musical signal will have the tightest, shortest and purest connection from one component to the next. Another performance necessity is a low impedance, low noise power source for the amplifiers. That would be a bank of multiple film and electrolytic capacitors. Ideally, they would be paralleled with very wide copper traces and a very short distance from the amplifiers.
The PhonoBlock refinements are derived from the Argentum design. The much more expensive Argentum is an all–out, hand-wired, silver– signal path version of the classic PhonoBlock. Turns out, the same extremely disciplined short signal path layout could be used to refine the classic PhonoBlock audio board.
Fortunately, there is an alternative to compromise. ONLY signal path components are placed on the top side of the circuit board. With no power supply capacitors on the top side, and a disciplined layout strategy, the signal path is optimally short and direct. A large bank of power supply capacitors is located on the bottom of the circuit board. All of the copper area on the bottom side is dedicated to forming a robust power plane that is located right under the amplifiers.
The tighter signal path gives uncluttered purity and the robust availability to power gives effortless ease to dynamic expression. These improvements bring the listener even closer to the music.
That’s a challenge—how to have a compact layout for the signal path and a large area for multiple power supply capacitors and shortest distance.
The refinement provides an even shorter, simpler pathway.
The individual resistors plug directly into the audio circuit board. Sockets are located even closer and take up even less board area. The signal path is now even shorter and more direct. Add flexibility is another advantage. The most popular gain and loading values are included. However, the user is free to explore those values. Some will want to experiment with different resistor types and/or manufacturers. For those using outboard moving-coil step up transformers, you will have the means of choosing loading resistor values that appropriately reflect through the transformer to the cartridge. The original PhonoBlock used small plug–in circuit boards for setting gain and loading options. They were compact, and provided a short signal path from the plug–in resistor board to the amplifier circuit.
Gain is determined by the resistor value installed in the GAIN resistor socket.
Dale/Vishay RN65-style resistors are included with the following values.
- 121 Ohms for 45 dB gain (1210)
- 75 Ohms for 50 dB gain (75R0)
- 40.2 Ohms for 55 dB gain (40R2)
- 20 Ohms for 60 dB gain (20R0)
- 15 Ohms for 63 dB gain (15R0)
- 10 Ohms for 67 dB gain (10R0)
Cartridge loading is determined by the resistor value installed in the LOADING resistor socket.
Dale/Vishay RN65-style resistors are included with the following values:
- 47.5k Ohms (4752)
- 1000 Ohms (1001)
- 475 Ohms (4750)
- 200 Ohms (2000)
- 100 Ohms (1000)
- 49.9 Ohms (49R9)
- 17” wide
- 17” deep
- 3 1/4″ high
- 21 lbs. each