Tag Archives: Amplifier

Improving Testing with Modern Technology

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There are lots of practices in the DIY world that are more than a little out dated. I’m obviously not talking about using vacuum tubes but rather the methods used in building and testing the circuits we build with them. Many of these test methods came about for very good reasons; perfectly applicable at the time. But as technology has advanced the reasons for many of these practices are no longer valid. And there is really no better example of this than the practice of testing audio amplifiers with square wave (or various sawtooth or triangle wave) signals.

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Talking Substitutions

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This topic comes up a lot! Someone will email me with, “I want to build {insert project here} from your web site. But…”. Sometimes it’s just that part availability varies. Sometimes people want to use parts on hand which are slightly different. Sometimes people want to substitute tubes, transformers, or whole assemblies. And sometimes people want to actually change the topology! So at what point is the amp being built no longer the design on my website?

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That “Other” Project

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I have been working on the new SET chassis design but that’s not all I’ve been doing. This morning I got a little surprise when I checked on my sump pump under the house. It’s starting the rainy season here and I wanted to make sure everything was ready to go. Unfortunately, I found myself replacing a GFCI outlet and the sump pump that had failed and taken the outlet with it. Since the morning was shot, I decided to finish up a couple of other little projects this afternoon. Last week I mentioned another project, the portable class D amp. We’ll, I took a little time this afternoon to finish off that one.

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Revisiting Past Endeavors

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So, I was sitting here on this rainy Sunday morning going through some amplifier designs and looking through my stash of tubes and various amplifier building supplies. While standing there looking at the shelves of vacuum tubes, transformers, and various piece-parts, my eyes drifted up to an amplifier sitting on the top shelf. It was my 6AS5 µ-power UL amplifier documented here. But why was the little amp sitting on a shelf collecting dust? Then I remembered.

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Grounding Philosophy

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I keep getting questions about amp grounding so I thought I would consolidate some of my previous notes on the subject. The first is a reprint of a forum post I made back in 2013 on the DIYAudioProjects Forum.

Warning: It has been brought to my attention that some people reading this post mistakenly believe that I am advocating the override, disconnection, or elimination of the safety ground (or bonding) connection in some pieces of equipment. This is not correct! The safety ground or bonding requirement for every piece of equipment is a firm requirement. At no time should any signal cable or independent wire be expected to fulfill the safety ground requirement for any piece of equipment. The process of “ground lift” is simply to provide a different signal ground reference in a piece of equipment.

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