Practical Considerations on Designing and Measering LCR RIAA Filters

I’ve already mentioned that my great passion is analogue music playback and records in particular. If you take a closer look, you will realise that the signal has to be filtered before it can be cut into a master lath. Low frequencies are attenuated and high frequencies are boosted in order to achieve roughly equal levels. This is usually referred to as an inverse RIAA filter. During playback, a corresponding reciprocal RIAA filter is applied in order to achieve a straight frequency response. The following article was written back in 2018, when Sowter helped me build an LCR-RIAA filter with twice the impedance of the usual 600 Ohm modules. At that time, Sowter still offered a custom design service.

The development process, theoretical principles and practical tips were summarized in a white paper and Brian Sowter published the white paper on his web site:

https://www.sowter.co.uk/pdf/LCR-RIAA%20Ahlswede.pdf

I didn’t have my own website back then. I would therefore like to publish the topic again in this article.

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DrBA Analogue Test Bench: The Turntable

Let me start this article with one of my favorite motivational sayings:

Everyone said it couldn’t be done! But then someone came along who didn’t know that —and just did it.

But we’ll get to that later. I would like to extend my blog writing about analogue music sources. This applies to both equipment and outstanding recordings. Vinyl records have been my great passion for decades. I think that many people strive for optimizing their own HiFi equipment over the years. The most important component in this context is of course the record player or many say simply turntable. This involves three essential components: the turntable itself (just spinning the records with constant speed), the tonearm and the cartridge. There are only a few manufacturers who produce these three components themselves and then also offer a complete product that can play at the highest level. Therefore, this hobby is often about putting together the best components yourself. This may also be a reason why it never gets boring, because combining different setups can produce very different sound results. For people who have nothing to do with this hobby, it may seem strange that there are a variety of turntables available for purchase, and the only features is to rotate the record at a constant speed and to provide the option of mounting different tonearms. I know three different drive methods to spin the platter: belt drive, rim drive, direct drive. For decades I have always used belt drives units. The belt provides a very good isolation to motor noise but it’s own flexibility is a problem when it comes to speed stability and dynamics and the belt needs to be replaced regularly. So already a while ago I decided to replace my belt drive turntable with a direct drive. I had also decided that it would be my “last” turntable. I know what some people are thinking now and I have to admit that they might be right. You tell this yourself as justification and in the end things turn out differently…

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