MA-70 - 70-Watt Magnetic Amplifiers


If there is one thing that can be said about the MA-70 for certain, it's that it's unique amongst amplifiers. It has a wonderful inner clarity and realism like no other amplifier we know of, at any price.

Operation type:
70 watt 8 ohm, 90 watt 4 ohm Class A/B Current injection construction - a purely current driven amplifier
Single stage equivalent amplifier

Specifications:
Gain: 60db in current mode
Speed: Slewing rate 400 V/µs
Input impedance: 5k
Frequency resonance 1Hz-2MHz
Signal to noise ratio: 120db
Total Harmonic Distortion (THD): 70 watts - less than 0.0001%
Intermodulation Distortion (IMD): Measured with 19 & 20Khz intermixed equally - 0.0005%
Total square wave distortion: Less than 0.001% musical signal under load
Damping Factor: 1000
Channel separation: Infinite
Musical Fast Fourier transform distortion: Less than 0.01% under load

With the creation of this new circuit came a demand for new testing parameters. In the world of audio, amplifiers are most often tested without music signal or load, and therefore the testing is not in a real world environment, which means little to the end user.

Therefore, two brand new tests have been added to the specifications of the amplifier: Total Square Wave Distortion and Musical Fast Fourier Transform distortion.

These new specifications teach us what the amplifier does in the real world with music and under load. Operating under load in a real signal flow environment is the most difficult part for any amplifier. The challenge for any amp is to actually reproduce music accurately.

So these new tests are critical in understanding the potential of this circuit to deliver reproduced music like never before. These tests are preformed to allow the user to know what will happen to the music signal when the amplifier is actually in use playing music. This is a surprisingly new concept we have not seen before - something we hope eventually becomes commonplace.

These are measurements that make an amplifier truly unique and truly in a class by itself.

Here's a brief description of both of these new tests:

Musical Fast Fourier transform distortion: Real world test using a music sample of 1/10 of a second intervals. By breaking down the music sample into 1/10 of a second or keeping the bits limited they are reasonable enough in number to fully analyze the data. This measures the input to output data of the amplifier's performance, allowing listeners to know the total sum of all distortion that will actually be added to the music.

Total Square wave distortion: Although it's not uncommon to see square wave distortion testing on an amp, it is quite uncommon to see it as important. It is also uncommon to see square waves accurately reproduced by audio amplifiers. A square wave is the most demanding of signals. We feel it is critical for an amplifier to be able to reproduce square waves without distortion. The amp, if required, could reproduce any signal virtually without distortion.

This new amplifier design only amplifies current. It is a current amplifier only, as transistors can only amplify current and are only linear when operated in a current mode.

Current injection is unique. All the transistors inject current into one common line that then drives the speaker. Each transistor is connected to the input instead of to the stage before it, effectively creating a one-stage amplifier.

Magna-drive Transistor treatment is unique to Luminance MA-70 amplifiers. It comes from the technology of Magnetic condition from High Fidelity Cables and Magnetic Innovations. Magna-drive uses a powerful magnetic field across the transistor to apply powerful lines of flux through the transistor. This helps to guide electrons at the quantum state, and give them a more calculated pathway through the transistor. The result is lower noise, better resolution, and greater dynamics.

Magnetic conduction technology wave-guides are used to help deliver signal accurately and cleanly. The equivalent of two Pro Series power cables are used. One to filter the AC power from the secondary of the transformer, and the second to filter the DC power side after rectification. These are used to magnetically and mechanically reduce noise within the amplifier. In all, this helps to make MA-70 one of the most natural and musical amps on the market today.

Mechanically grounded Chassis: The chassis uses a technology known as mechanical grounding. It is designed to eliminate unwanted vibrations and noise. The solid brass base plate and back are designed with complementary footers to quickly eliminate unwanted vibrations for the various parts within the amps. The circuit board and all other components are mounted either directly to these bass plates or via brass connecting rods. The entire amp becomes a sink, to rid the internal components of unwanted vibrations and guide them out to the floor beneath.

Premium audiophile-grade parts: Premium quality hand picked parts like Texas Instruments Naked Vishay resistors go into each and every amplifier.

Overall, this new amp design is a revelation in thinking. It is truly a new concept and it comes from one of the great designers Steve Keiser. Steve has been an analog circuit designer dating all the way back to early B&K. His circuits of been a revelation in the past and are certainly proving to be once again in our more modern era.

Contact us for more details and pricing.






Other amps:

MA-1
MA-70
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