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A Unity Coupled KT88 Amp with Plitron Transformers
I was always fascinated by the Unity Coupled output stage in old McIntosh tube amps. In many ways it is an incredibly elegant solution to many design problems in output transformers. Ever since I first...
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A Push-Pull Amplifier with Simple Plate-Grid Voltage Feedback Driven by a...
For this post, I want to go back to some stuff I did in December 2013. Some time before that I read O. H. Schade's paper Beam Power Tubes and was fascinated by the characteristics shown in that paper...
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A Test Amplifier for Tube Circuits
Have you ever just needed to test a driver-type tube stage but your sound card output can't put out enough voltage drive to get it where it needs to go? Well I have, and here is how I solved my...
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P-Channel Shunt Feedback KT88 Amp Revisited
This is Part 2 of a series on an amp I designed and built. Click here for Part 1.It has been a couple of years since I built and delivered an amplifier to my brother. I thought it was a pretty novel,...
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How to Make a Pentode Voltage Amplifier That is More Linear Than Any Triode
It is generally accepted that pentodes are on average a good bit less linear as voltage amplifiers than triodes. Today I'm going to show how to take a pentode and make it more linear than any triode,...
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Unity-Coupled Plitron Amp Revisited
I decided to re-work my Unity-Coupled amplifier that I wrote up here. One thing that always bothered me was that I used a split-rail supply (-300V/+500V) to get 800V total supply voltage for the 841...
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If UNSET and the RCA50W Had a Baby
What's UNSET? See here. It's a clever way of wrapping series-applied voltage feedback around an output stage and sharing some of the idle dissipation in the output stage between a mosfet follower and...
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Idea for Ultra-Low Distortion Unity-Coupled Amp
I had some great results in experiments with an SE amp design. In that amp, I took feedback from the output tube plate and applied it to a high-gain pentode/p-channel FET input stage. This gave...
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An Ultra-Low Distortion 826 SE Amp
And when I claim ultra-low distortion, I'm getting 0.027% THD at 1W. As of the time of writing this, I'm unaware of any other series-feed SE tube amp that does better.It's currently a breadboard amp...
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My 6384 SE Experiments
In this post I'd like to detail a series of experiments that led to the design of the 826 amp that I wrote about in my last post. I investigated several circuits using a 6384 output tube, with the...
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