A year ago, when I set out to bring myself up-to-date with Class-D amplifier designs, this DIYaudio forum was a great help. It has been 35 years since I last researched and published Class D and Class E output circuit designs, and the new audio power amp chips were exactly what I needed for a new system I am building, based around a MiniDSP and my bi-amped "ground effect omnidirectional" speaker design.
But one thing which was lacking here was detailed information on available output filter technologies and components. It seems as though much of the technology produced in the '70s has disappeared into the mists of time. So I decided to document my deliberations, and make the design available for all DIYaudio members.
I couldn't buy any 'reference' TDA7498 circuit boards, so I bought a few SURE Electronics boards from Ebay, ripped out the key components, optimized them, soldered in the latest surface-mount TDA7498 chips from Mouser, and started working on today's design issues.
The previous threads I have started here have gotten quite messy in the handling of images, so I decided to put up the complete 'tutorial' on my personal website, and duplicate any key material here. I would also be happy to answer the technical questions that members may have.
I started by reducing the SURE board's distortion at high frequencies by ten times. From 3% to 0.3%. By changing just two components on the board. But you can see on the photo below the full set of changes I made to the SURE assemblies before I was happy with them
The result has been to make my SURE TDA7498 assemblies into top-notch (IMO), clean, powerful audio amplifiers. More than adequate for the compact HiFi speakers they are intended to match.
The leftmost attachment is the (final) modded board (without the heatsink) with the measured 8 ohm THD vs frequency curve next to it, followed by the distortion vs power-out curve. Note that I have separated the second, third, fourth and fifth harmonic distortions on the power-out curve to make it easier to see the interplay between even and odd harmonics.
The complete tutorial is on my website at Trevor Marshall - Class D Audio Amplifier Design - TDA7498 Output filters
This output filter topology will work equally well with most of the new >50W bridged amp chips now in the market.
Happy New Year to one and all....
.
But one thing which was lacking here was detailed information on available output filter technologies and components. It seems as though much of the technology produced in the '70s has disappeared into the mists of time. So I decided to document my deliberations, and make the design available for all DIYaudio members.
I couldn't buy any 'reference' TDA7498 circuit boards, so I bought a few SURE Electronics boards from Ebay, ripped out the key components, optimized them, soldered in the latest surface-mount TDA7498 chips from Mouser, and started working on today's design issues.
The previous threads I have started here have gotten quite messy in the handling of images, so I decided to put up the complete 'tutorial' on my personal website, and duplicate any key material here. I would also be happy to answer the technical questions that members may have.
I started by reducing the SURE board's distortion at high frequencies by ten times. From 3% to 0.3%. By changing just two components on the board. But you can see on the photo below the full set of changes I made to the SURE assemblies before I was happy with them
The result has been to make my SURE TDA7498 assemblies into top-notch (IMO), clean, powerful audio amplifiers. More than adequate for the compact HiFi speakers they are intended to match.
The leftmost attachment is the (final) modded board (without the heatsink) with the measured 8 ohm THD vs frequency curve next to it, followed by the distortion vs power-out curve. Note that I have separated the second, third, fourth and fifth harmonic distortions on the power-out curve to make it easier to see the interplay between even and odd harmonics.
The complete tutorial is on my website at Trevor Marshall - Class D Audio Amplifier Design - TDA7498 Output filters
This output filter topology will work equally well with most of the new >50W bridged amp chips now in the market.
Happy New Year to one and all....
.