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Private Projects from before RMS Acoustics & Mechatronics

The following two projects cover the extremes in the range of audio related design activities that I worked on during my regular career at Philips, ASML and the TU Delft. They acted as learning vehicle to better understand both the technology behinds audio systems and to develop listening skills "ears!" to be able to judge the musical properties op hi-end audio equipment.

The MFB loudspeaker has served for many years and is still in working order and according to ,many people who heard them they typically clearly show the control of the lowest frequencies combined with a very pleasant spectral response.

The tubeamp is, though technically well conceived, less successful due to power supply related issues. The project as described is the present status and sometime in the future I will improve it based on the advice of Menno vd Veen and Guido Tent.

Although I am willing to reply on mails regarding these subjects, they are purely private matter and not intended for production or other activities inside RMS Acoustics & Mechatronics.

I hope you enjoy reading it!

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The first project that is described is a large MFB loudspeaker with active 4th order Linkwitz-Riley filters and many active protections, like a maximum excursion limiter of the woofer. The project is not directly suitable for "DIY", as several components are from many years ago which means that they have to be replaced by more recent units. A possible address for a useable accelerometer is for instance available with Piratelogic. Anyway I hope that it will inspire you.



This second project is based on the wish to design a tubeamplifier using the recent knowledge on control of transistor amplifiers and active mechatronic systems. Because I have built many tube amplifiers in my highschool time, sometimes over a weekend, I thought that I could manage it now also in a few weeks. Due to the regular job and the wish to make it perfect it took me however 3 years before it was at the present state. Key features are a fully balanced design. Ring-core output transformers from Amplimo, designed by Menno vd Veen, Instrumentation input circuits with MOSFET input Op-Amps and two active control circuits, one to set the bias current and one to balance the DC value of the anode voltages over the driver tubes. The input triodes ECC83 and the professional driver triodes E88CC are original vintage Philips tubes and the power tubes KT88 are from Svetlana.



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