Coach_Kaarlo
Active Member
There was a Harmon / Kardon amp, commissioned around 1980, which is by far the best I have experience with - so far.......
The owner has asked me not to mention it's model, as he is seriously hunting for another, to add to the 2 he already owns (for spares and for investment).
It had the following (taken from the company blurb);
Slew rate = 200V/us
Rise time = 1.5 us
250W into 8 ohm
440W into 4 ohm
200 amps continuous current
14,000W into 0.35 ohm load
42kg (92.5 lbs)
Design philosophies chosen for the ultimate amplifier :
1. Previous amplifiers were substandard.
2. No problem is incurable.
3. Audio is not a fashion.
4. The simpler the solution to a problem, the better .
5. The dynamic (music) state's importance over the steady (test tone) state .
6. Evaluate results with human ears, not just test equipment.
[Edit - I love these philosophies but question their modern interpretations in the Audio industry - seems many products come up well short on #5 and #6 - IMO]
But it was SOME GUYS Fifth philosophy which led to many of the discoveries and innovations incorporated in the final design. This was SOME GUYS concept of dynamic design and measurement versus the steady state. SOME GUY determined that an amplifier's performance while handling music (dynamic state) differs drastically from its performance while utilizing sine wave test tones (steady state) . The dynamic state is especially difficult to design for, because most standard and commonly understood test methods are of a steady state nature. Therefore, complex evaluation techniques and performance criteria were first created in order to test the dynamic (music) state of a given circuit design. SOME GUYS design, to achieve his ultimate goal, had to perform exceptionally well in the dynamic state.
Four Design Parameters That Make The Difference
1. High Current Capability (HCC)
The concept of the dynamic state plays an important role in the design of an amplifier's power capability. When an amplifier's power characteristics are measured by conventional test signals (steady state), it means only half the story is told. The Standard technique for measuring power output utilizes a static 8 ohm resistor to simulate a speaker system. But speaker impedances actually vary greatly according to the content of the input signal. The impedance characteristic of a loudspeaker is measured by feeding it a sine wave test tone that slowly changes in frequency. From this raw data, a "nominal" value is determined. This nominal value is the specified or rated impedance.
But, under dynamic conditions, the nominal steady state impedance rating has little relevance. The speaker system may require a huge amount of power for a very short period of time, such as a few ten-thousandths of a second. During this short period, the speaker system (2) may require the same amount of current as a 1-2 ohm resistor. It is critical that an amplifier provide the current required to give loudspeakers accurate dynamic range and transient response. This is why BLANK is designed with 200 amperes of instantaneous current capability, enabling the amplifier to react to constant impedance variations caused by the dynamic characteristics of the music signal.
BLANK delivers 14,000 watts per channel into a 0.35 ohm load under transient conditions. This dynamic power output is exclusive to BLANK!! HCC enables the amplifier to accurately control speaker cone movement by delivering the energy necessary to force the speaker cone to precisely react to transients. This performance has significant importance in high fidelity reproduction.
2. Phase Intermodulation Distortion (PIM)
Phase intermodulation distortion can be an unwanted by-product of negative feedback. Negative feedback, which is used in every amplifier, routes part of the output signal back to the input, 180 degrees out-of-phase with the original signal. The combination of these two signals, out-of-phase with each other, creates an error - correction signal that greatly reduces the steady state harmonic distortion inherent in the amplifier. However, a high amount of negative feedback creates a high (and very audible) amount of Phase Intermodulation distortion (PIM) in place of the harmonic distortion it eliminates. This was proven by SOME GUY and presented to the Audio Engineering Society in 1980 at a convention in Hamburg. Since negative feedback merely transforms one type of distortion to another, the BLANK is designed to have minimal inherent distortion. The result is very low PIM and THD.
3. Interface Intermodulation Distortion (IIM)
Interface Intermodulation Distortion , or IIM in abbreviated form, occurs in the speaker/amplifier interface. The moving cone and coil structure in the speaker generates its own voltage which returns to the output stage of the amplifier. This voltage is called the Back Electromotive Force (Back EMF). Once this voltage passes the output stage, it travels through the negative feedback circuit and returns to the input stage where it combines with the input signal. This mixing of the legitimate musical input signal and the Back EMF speaker generated signal results in increased dynamic distortion. This creates excessive IIM which results in an obscured lower mid-range, which makes the sound appear vague and lacking in definition. The minimization of IIM in BLANK is carried out by reducing the negative feedback, and by decreasing the internal resistance of the output stage. The result is that BLANK has clear mid and low frequency reproduction, which is pure and well balanced.
4. Transient Intermodulation Distortion (TIM)
Transient Intermodulation Distortion or TIM, as it is referred to, occurs when fast transients - such as in dynamic music passages - pass through an amplification stage prior to the return of the output signal via the negative feedback. These transients then overload the first stage sufficiently to cause internal clipping - hence, TIM.
The BLANK counters the negative aspects of TIM with three special design parameters:
A. The BLANK utilizes a super-low distortion driver stage which exhibits localized feedback (feedback within each stage versus feedback around the entire circuit).
B. The introduction of transistors with extremely quick response speed, excellent linearity, and a large, safe operating area.
C. The incorporation of a dual power supply system with high and low voltage sources. The high voltage source, dedicated to the driver , has the ability to supply the proper voltage under any condition .
Controlling negative feedback and utilization of circuitry not dependent on negative feedback enables the BLANK to virtually eliminate TIM.
[Edit - some interesting facts about the boards]
(A) Normally , the circuit boards in an amplifier's audio signal path are made either of phenolic or fiberglass material. When the amplifier heats up, it causes these circuit boards to expand and "flex " which degrades the mechanical integrity and can increase distortion.
(B) BLANK hybrid circuit boards are made of ground sapphire, which like diamond, is extremely rigid, and does not expand or flex when heated. This eliminates mechanical stress on the circuitry which ensures long-term reliability.
(C) The metal-film resistors in BLANK circuitry are made of silver palladium , a rare earth metal which never corrodes thereby keeping resistor values perfect forever.
The owner has asked me not to mention it's model, as he is seriously hunting for another, to add to the 2 he already owns (for spares and for investment).
It had the following (taken from the company blurb);
Slew rate = 200V/us
Rise time = 1.5 us
250W into 8 ohm
440W into 4 ohm
200 amps continuous current
14,000W into 0.35 ohm load
42kg (92.5 lbs)
Design philosophies chosen for the ultimate amplifier :
1. Previous amplifiers were substandard.
2. No problem is incurable.
3. Audio is not a fashion.
4. The simpler the solution to a problem, the better .
5. The dynamic (music) state's importance over the steady (test tone) state .
6. Evaluate results with human ears, not just test equipment.
[Edit - I love these philosophies but question their modern interpretations in the Audio industry - seems many products come up well short on #5 and #6 - IMO]
But it was SOME GUYS Fifth philosophy which led to many of the discoveries and innovations incorporated in the final design. This was SOME GUYS concept of dynamic design and measurement versus the steady state. SOME GUY determined that an amplifier's performance while handling music (dynamic state) differs drastically from its performance while utilizing sine wave test tones (steady state) . The dynamic state is especially difficult to design for, because most standard and commonly understood test methods are of a steady state nature. Therefore, complex evaluation techniques and performance criteria were first created in order to test the dynamic (music) state of a given circuit design. SOME GUYS design, to achieve his ultimate goal, had to perform exceptionally well in the dynamic state.
Four Design Parameters That Make The Difference
1. High Current Capability (HCC)
The concept of the dynamic state plays an important role in the design of an amplifier's power capability. When an amplifier's power characteristics are measured by conventional test signals (steady state), it means only half the story is told. The Standard technique for measuring power output utilizes a static 8 ohm resistor to simulate a speaker system. But speaker impedances actually vary greatly according to the content of the input signal. The impedance characteristic of a loudspeaker is measured by feeding it a sine wave test tone that slowly changes in frequency. From this raw data, a "nominal" value is determined. This nominal value is the specified or rated impedance.
But, under dynamic conditions, the nominal steady state impedance rating has little relevance. The speaker system may require a huge amount of power for a very short period of time, such as a few ten-thousandths of a second. During this short period, the speaker system (2) may require the same amount of current as a 1-2 ohm resistor. It is critical that an amplifier provide the current required to give loudspeakers accurate dynamic range and transient response. This is why BLANK is designed with 200 amperes of instantaneous current capability, enabling the amplifier to react to constant impedance variations caused by the dynamic characteristics of the music signal.
BLANK delivers 14,000 watts per channel into a 0.35 ohm load under transient conditions. This dynamic power output is exclusive to BLANK!! HCC enables the amplifier to accurately control speaker cone movement by delivering the energy necessary to force the speaker cone to precisely react to transients. This performance has significant importance in high fidelity reproduction.
2. Phase Intermodulation Distortion (PIM)
Phase intermodulation distortion can be an unwanted by-product of negative feedback. Negative feedback, which is used in every amplifier, routes part of the output signal back to the input, 180 degrees out-of-phase with the original signal. The combination of these two signals, out-of-phase with each other, creates an error - correction signal that greatly reduces the steady state harmonic distortion inherent in the amplifier. However, a high amount of negative feedback creates a high (and very audible) amount of Phase Intermodulation distortion (PIM) in place of the harmonic distortion it eliminates. This was proven by SOME GUY and presented to the Audio Engineering Society in 1980 at a convention in Hamburg. Since negative feedback merely transforms one type of distortion to another, the BLANK is designed to have minimal inherent distortion. The result is very low PIM and THD.
3. Interface Intermodulation Distortion (IIM)
Interface Intermodulation Distortion , or IIM in abbreviated form, occurs in the speaker/amplifier interface. The moving cone and coil structure in the speaker generates its own voltage which returns to the output stage of the amplifier. This voltage is called the Back Electromotive Force (Back EMF). Once this voltage passes the output stage, it travels through the negative feedback circuit and returns to the input stage where it combines with the input signal. This mixing of the legitimate musical input signal and the Back EMF speaker generated signal results in increased dynamic distortion. This creates excessive IIM which results in an obscured lower mid-range, which makes the sound appear vague and lacking in definition. The minimization of IIM in BLANK is carried out by reducing the negative feedback, and by decreasing the internal resistance of the output stage. The result is that BLANK has clear mid and low frequency reproduction, which is pure and well balanced.
4. Transient Intermodulation Distortion (TIM)
Transient Intermodulation Distortion or TIM, as it is referred to, occurs when fast transients - such as in dynamic music passages - pass through an amplification stage prior to the return of the output signal via the negative feedback. These transients then overload the first stage sufficiently to cause internal clipping - hence, TIM.
The BLANK counters the negative aspects of TIM with three special design parameters:
A. The BLANK utilizes a super-low distortion driver stage which exhibits localized feedback (feedback within each stage versus feedback around the entire circuit).
B. The introduction of transistors with extremely quick response speed, excellent linearity, and a large, safe operating area.
C. The incorporation of a dual power supply system with high and low voltage sources. The high voltage source, dedicated to the driver , has the ability to supply the proper voltage under any condition .
Controlling negative feedback and utilization of circuitry not dependent on negative feedback enables the BLANK to virtually eliminate TIM.
[Edit - some interesting facts about the boards]
(A) Normally , the circuit boards in an amplifier's audio signal path are made either of phenolic or fiberglass material. When the amplifier heats up, it causes these circuit boards to expand and "flex " which degrades the mechanical integrity and can increase distortion.
(B) BLANK hybrid circuit boards are made of ground sapphire, which like diamond, is extremely rigid, and does not expand or flex when heated. This eliminates mechanical stress on the circuitry which ensures long-term reliability.
(C) The metal-film resistors in BLANK circuitry are made of silver palladium , a rare earth metal which never corrodes thereby keeping resistor values perfect forever.