Ask Ron Sutherland about beauty and his mind travels to the tall grass prairie in the flint hills of Kansas. In those flowing waves of tall grass, Ron appreciates the elegant patterns of life. The purity of simplicity and the essence of design.
Ron grew up on a small farm in Missouri, attended Drury College in Springfield, MO where he attained a degree in Physics and then attended the University of Kansas. For his Masters project, Sutherland designed and built a stereo preamplifier that used digital logic to automatically control its functions, including automatic input selection. The volume controls were touch plates, with a digital volume display. His innovative approach to audio design was a sign of things to come. One afternoon Ron bicycled out to Kief’s Stereo Store where his appetite for high-end audio was kindled. A deal was struck with store manager Gayle Sanders. In exchange for gear, Ron would help Gayle build an electrostatic speaker. Soon, almost all evenings were split between Gayle’s basement shop and Ron’s access to a machine shop. Using their middle names (Gayle Martin Sanders and Ronald Logan Sutherland) they began Martin-Logan Ltd. After years of struggle, Martin-Logan was built into a very successful global company. Ron then started Sutherland Engineering with his brother John. They began doing contract manufacturing for clients who wanted high quality workmanship (including Martin-Logan) and Ron began to explore amplifier design concepts. After a few years, he created the first Sutherland Engineering audio product, the C-1000 which instantly became one of the most desired amplifiers in the Asian market. Ron is inspired by nature, especially the sublime beauty of the connection and relationship between all things in the natural world. This beauty and connectivity is expressed through his phono preamplifier designs. There is a clarity of vision and an elegance in the execution of his designs, an efficient simplicity which translates to sonics which are being celebrated all over the world for their musicality, flow and emotional communication. |
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what is transimpedance?
To understand the concept of a transimpedance amplifier, a great starting point is to have clarity about the difference between current and voltage. In the application of physics and engineering, the units of voltage and current are precisely defined as follows:
1 Volt = 1 joule/coulomb. A Joule is a unit of energy. A Coulomb is a unit of charge. Referred to as ‘voltage’.
1 Ampere = A flow of 1 coulomb/second. Referred to as ‘current’.
To make things easier to understand, we often use the analogy of a fluid circuit when thinking about electrical circuits. In such comparisons, voltage (the energy available to push for charge flow) is analogous to water PRESSURE and current (the rate of charge flow) is analogous to water FLOW.
So let’s think of the cartridge as our water pump. It is ‘cranked’ by the moving stylus. If its flow path is blocked, there will be pressure changes that reflect stylus movement. That PRESSURE is energy for charge flow, but there is no charge flow. That’s analogous to a voltage output and no current flow (a voltage signal that can be amplified). If the flow path is completely unobstructed, the water will FLOW in a way reflecting stylus movement. That is analogous to a current output, but no voltage potential difference.
Ordinarily, we operate our cartridges with some loading. There will be some current flowing from the cartridge. But what we use as the signal is the voltage across the two coil terminals. The input VOLTAGE is amplified by a voltage amplifier, i.e. a small input voltage becomes a larger output voltage. Voltage gain is expressed in dB (60 dB of voltage gain means the output is 1,000 times larger than the input).
When we want to use current as the input parameter, the cartridge coil terminals are shorted together (that is the unobstructed path for coil current flow). In a transimpedance amplifier, we need to measure that flow. We do so, by ‘breaking’ the shorted path and connecting the coils terminals to the transimpedance input terminals. The amplifier uses active feedback to drive those two terminals to the SAME voltage (a virtual short).
If there is no voltage difference between two points is looks and acts like a short. So the transimpedance amplifier has constructed a signal that forces the input terminals to a virtual short. That constructed signal will be used as the amplifier’s output voltage (signal input is current, signal output is volts). In this instance, gain cannot be expressed in dB. There is no input voltage. Any inclinations for a voltage at the input have been ‘corrected’ to make a virtual short. Transimpedance gain is expressed in units of Ohms.
1 Volt = 1 joule/coulomb. A Joule is a unit of energy. A Coulomb is a unit of charge. Referred to as ‘voltage’.
1 Ampere = A flow of 1 coulomb/second. Referred to as ‘current’.
To make things easier to understand, we often use the analogy of a fluid circuit when thinking about electrical circuits. In such comparisons, voltage (the energy available to push for charge flow) is analogous to water PRESSURE and current (the rate of charge flow) is analogous to water FLOW.
So let’s think of the cartridge as our water pump. It is ‘cranked’ by the moving stylus. If its flow path is blocked, there will be pressure changes that reflect stylus movement. That PRESSURE is energy for charge flow, but there is no charge flow. That’s analogous to a voltage output and no current flow (a voltage signal that can be amplified). If the flow path is completely unobstructed, the water will FLOW in a way reflecting stylus movement. That is analogous to a current output, but no voltage potential difference.
Ordinarily, we operate our cartridges with some loading. There will be some current flowing from the cartridge. But what we use as the signal is the voltage across the two coil terminals. The input VOLTAGE is amplified by a voltage amplifier, i.e. a small input voltage becomes a larger output voltage. Voltage gain is expressed in dB (60 dB of voltage gain means the output is 1,000 times larger than the input).
When we want to use current as the input parameter, the cartridge coil terminals are shorted together (that is the unobstructed path for coil current flow). In a transimpedance amplifier, we need to measure that flow. We do so, by ‘breaking’ the shorted path and connecting the coils terminals to the transimpedance input terminals. The amplifier uses active feedback to drive those two terminals to the SAME voltage (a virtual short).
If there is no voltage difference between two points is looks and acts like a short. So the transimpedance amplifier has constructed a signal that forces the input terminals to a virtual short. That constructed signal will be used as the amplifier’s output voltage (signal input is current, signal output is volts). In this instance, gain cannot be expressed in dB. There is no input voltage. Any inclinations for a voltage at the input have been ‘corrected’ to make a virtual short. Transimpedance gain is expressed in units of Ohms.
Approach to the craft
There is an almost irresistible urge to add complexity to any endeavour. The result is a tangled knot of disparate good ideas. Because there is always more that could be added, there is never an opportunity for long-term satisfaction. Never enough.
Sutherland offers a different vision – it may be more closely aligned with your values. It is a very disciplined approach that refines design to the essential elements – and then executes the design to perfection. There is no allowance for superfluous clutter. Nothing extra will be allowed between you and the music.
Sutherland Engineering Design Values:
Sutherland offers a different vision – it may be more closely aligned with your values. It is a very disciplined approach that refines design to the essential elements – and then executes the design to perfection. There is no allowance for superfluous clutter. Nothing extra will be allowed between you and the music.
Sutherland Engineering Design Values:
- Avoid electronic colourations by keeping signal path uncluttered and straightforward.
- Refine the circuitry and layout for one audio channel. Then build it twice for stereo.
- Keep the clutter of options out of the signal path and off the circuit board.
- Keep contaminating AC power line noise out.
- Use the best components in a conservative manner, for long life and effortless performance.
- Design and build with a sense of instrument grade craftsmanship.
