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When you’re suffering the itch to improve your system but can’t find the money, a possible solution is to spend some time fiddling with your turntable. (If you’ve gone CD-only, you’re out of luck here.) Like everything else, the delicate mechanics of turntables are subject to the laws of entropy and will gradually drift out of tune, causing you too perhaps to gradually drift away from listening. Returning every six months or so will restore your faith (if it was flagging) in vinyl and perhaps your system. Read more

I built a 2A3 SE (Single Ended) amp a long time ago. I built it because I wanted to see what all the fuss was about, so I built it using the parts I had. I had received a pair of Chinese 2A3 in return for some help with a phono preamp. I also had some 6SN7s and a Hammond power transformer. But what about the output transformer? I looked through my junk, and found a Beovision 3400 output transformer. The Beovision used a PL84 output tube (EL86 with different heater), so the transformer was the standard 2k4 often used with that tube. Read more

Here’s a 2A3 SE amplifier that I had just finished yesterday. I used a pair of EH’s 2A3 gold grid and a pair of RCA’s 6SN7 for driver stage. The photo shown Chinese 6N8PJ( Chinese Military 6SN7) for testing. I use solid state rectifier and use 2 pcs of 100 ohm paralleled to replace the choke. There’s no hum at all without choke because I’m using 820uF 450V for the supply. The output transformer is 2.5K-8ohm rated 15W, I use paper bobbin and Japanese Z11,EI96 silicon material. Read more

In Brief

Single-Ended Triode (a.k.a SET) amplifier producing 1…1.5W into 8 ohm load. Uses two Russian deflector combo 6f5p tubes wired as triode.

Introduction

6F5P is Russian TV deflection triode/pentode combo tube, somewhat like ECL85/6GV8. If the pentode section is connected in triode mode, the tube provides a great playground for experiments with 2-stage SET designs on a “dime”. It is no joke, however. The plate currves are very linear, reminding 45 or 2A3, input capacitance is low and the plate resistance is < 800 Ohm. Read more

This is such an in depth subject that I will reserve my input to this component to more basic explanations and leave the permeability and make-up of core material, magnetic flux density, shunt capacitance/inductance, electromagnetic theory and the like
to references. Read more

A SE transformer has to do two things in life… carry the unbalanced DC and have enough magnetic oomph to do the AC duties well. PP outputs (largely so) are relieved of the DC duties. As a very general approximation the SE transformer will be four times as large as the PP transformer for equivalent AC power handling capability. Read more

A common-cathode triode stage exibits an harmonic spectrum decreasing (in a monotonic way) with the frequency and the contribution furnished from even harmonics (particularly the second one) is preponderant. A similar pentode stage presents a wider spectrum and therefore a general increment in the THD values and a greater contribution furnished from odd harmonics. These two different behaviours between triodes and pentodes in the common-cathode configuration could be easily justified by observing that the mutual dynamic characteristic (the true entity that characterizes in an unambiguous manner the non linear behaviour of any amplifier stage), is easily referable to 2nd and 3rd geometric curve for triodes and pentodes rispectively as the Fig. 1, extracted from Radiotron Designer’s Handbook, it puts clearly in evidence [2]. Read more

INTRODUCTION

This article is the second part of my examination of the output impedance (Zout) of triode single ended amplifiers using no negative feedback. Here I intent to examine carefully the effects at low frequencies, which I believe can help you understand the sometimes puzzling bass performance of SE amplifiers. With the help of the Thielle/Small theory, I will show how the high output impedance modifies the the system response. Read more

INTRODUCTION

Much has been said about triode SE amplifiers with no negative feedback - how good they sound, how lively they present a musical performance and so on. Two easily measurable characteristics that make this type of amplifiers sound different are the amount of distortion produced with its particular spectrum and the high output impedance. This raises the question of whether they sound so good and musical because of these characteristics or in spite of them. Read more

In the autumn of 2005, just on a whim, I listened to the CSS FR125S (on the right) simply mounted on a board. I was shocked at how much better they sounded than when boxed in, having tried them in several boxes. Then I tried the Visaton B200 (center), which is a driver purposefully designed for an open baffle mounting. Then I tried the Fostex F200a (left); liking this driver with a foam grill to tame the treble. Read more