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THE AP TESTING GRAPHICS AND COMMENTS
I'd like to make several comments about the testing of the amplifier system based on the
LM3886 devices. In particular, the THD numbers (Click for the AP testing Graphic)
achieved in your system are substantially better than what I've seen obtained in previous
implementations.
I'd like to make several comments about the testing of the amplifier system based on the
LM3886 devices. In particular, the THD numbers (Click for the AP testing Graphic)
achieved in your system are substantially better than what I've seen obtained in previous
implementations.
These distortion numbers were so low that I
spent an extra amount of time checking the test
setup to see if something was being
overlooked. By triple checking with different
pieces of test gear. I am confident that what I
am seeing is correct and repeatable. Your
engineers have obviously made some correct
design decisions in partitioning the circuitry and
laying it out. The chassis and PCB layout are
very organized and clean. If a channel ever
needed to be replaced it could be done in just a
few minutes. It is obvious from inspecting the
channel assemblies that extra attention was
placed in the high quality components that were
selected.
spent an extra amount of time checking the test
setup to see if something was being
overlooked. By triple checking with different
pieces of test gear. I am confident that what I
am seeing is correct and repeatable. Your
engineers have obviously made some correct
design decisions in partitioning the circuitry and
laying it out. The chassis and PCB layout are
very organized and clean. If a channel ever
needed to be replaced it could be done in just a
few minutes. It is obvious from inspecting the
channel assemblies that extra attention was
placed in the high quality components that were
selected.
There was another thing that caught my attention. The amplifier system was very well behaved
when subjected to some very abusive input conditions that occurred as I came up to speed
with using a new analyzer system. The amplifier never complained or blew a fuse.
Occasionally the muting relays would politely click, but that was the extent of it.
During the frequency response (Click for the AP testing Graphic) testing I was caught off
guard that the response at full power was nearly identical in shape to the 1 Watt response
curve. This shows that slew rate limiting is not occurring at high output levels. It confirms that
proper bandwidth limiting was employed.
If I were to make any criticism, it is that the spacing of the 5 way binding posts is wider than a
standard dual bananas. But this is something that is only an inconvenience on the test bench.
The end user will welcome the added room for heavy gauge loudspeaker termination.
Regards - Alan Martin
Field Applications Engineer
National Semiconductor
when subjected to some very abusive input conditions that occurred as I came up to speed
with using a new analyzer system. The amplifier never complained or blew a fuse.
Occasionally the muting relays would politely click, but that was the extent of it.
During the frequency response (Click for the AP testing Graphic) testing I was caught off
guard that the response at full power was nearly identical in shape to the 1 Watt response
curve. This shows that slew rate limiting is not occurring at high output levels. It confirms that
proper bandwidth limiting was employed.
If I were to make any criticism, it is that the spacing of the 5 way binding posts is wider than a
standard dual bananas. But this is something that is only an inconvenience on the test bench.
The end user will welcome the added room for heavy gauge loudspeaker termination.
Regards - Alan Martin
Field Applications Engineer
National Semiconductor
I think the choice to use a parallel combination of filter capacitor rather than just a single
monstrous capacitor per supply rail is also of benefit. This allows you to select newer
chemistry low ESR / ESL types that are targeted for switching supply applications. This will
provide a sonic benefit as these will maintain desirable characteristics across the audio range
much better than the typical "computer grade" types that have traditionally been used. The use
of multiple smaller units not only places the ESRs and ESLs in parallel to improve supply
performance but has an added benefit that the capacitor surface area is increased which will
lengthen their operating life.
monstrous capacitor per supply rail is also of benefit. This allows you to select newer
chemistry low ESR / ESL types that are targeted for switching supply applications. This will
provide a sonic benefit as these will maintain desirable characteristics across the audio range
much better than the typical "computer grade" types that have traditionally been used. The use
of multiple smaller units not only places the ESRs and ESLs in parallel to improve supply
performance but has an added benefit that the capacitor surface area is increased which will
lengthen their operating life.
AP2140A/5140A, Jaton Operetta Power Amplifiers User's Feedback
Introduction Specification Review Dealer's Comments
Introduction Specification Review Dealer's Comments