This topic is just the gift that keeps on giving. I first introduced the 4S preamp with the volume control on the output almost 12 years ago. And yet there still seems to be a tremendous number of misconceptions about the concept and performance ramifications of volume controls on the output instead of the input. This time the misunderstandings surround an output buffer cathode follower.
Continue readingThese last few days I’ve been working on the driver stage and overall schematic for the new 6L6 SE-UL amplifier. While drawing up the schematic yesterday, I inserted a 250kΩ volume control at the input without much thought. While performing some preliminary analysis, I realized my mistake.
Continue readingSince I first introduced the concept for the “Universal Preamp” over ten years ago on the DIYAudioProjects forum, there has been almost constant discussion of my decision to place the volume control on the output of the preamp. I have been asked questions about it numerous times over the years. I have also had some “spirited discussions” with some who vehemently disagree with that design decision. Well, I thought it was high time to explain that decision once and for all, and to discuss exactly what this configuration means for preamp performance and output impedance.
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