As some may already know, I’ve been working on a new version of the 6CY7 amplifier. There is a new chassis specifically designed for this amp and some circuit changes to improve performance. But here’s the issue, I can’t seem to get much done. Let me explain.
Continue readingI have made a small change to the website which I hope will be helpful.
Continue readingSo I’ve had the chassis and metal done for the 6CY7 V2 amp since the 4th of July. It has now been a full 13 days and… the paint is not yet fully cured. It is hard for me to remember it ever taking this long for a semi-gloss enamel on metal to cure hard enough to begin assembly work. Obviously the manufacturer has changed the solvent makeup of the paint I use. Time to find another manufacturer. In the mean time, I’ve been working on other things.
Continue readingLike everyone else all over the world, for the last four months I’ve been working from home and limiting my trips out out of the house. But the situation these last four months has not been entirely unwelcome (except of course for people getting sick). For one thing, the view from my home office of trees and mountains is immensely better than the windowless building in which I was working. And for another thing with no commutes and flexible schedules, I have gained several additional hours in my day for doing things I want to do. With all I new found time, I did what any responsible technical person would do in such uncertain times. I’ve been teaching myself some new skills.
Continue readingWell, the new version of the 6CY7 amp is coming together. The wood for the amp has gone from a raw 11″ x 58″ plank of Zebra Wood {Microberlinia brazzavillensis} into a finished amplifier chassis complete with four coats of Tru-Oil finish. I think it looks pretty good.
Continue readingI want to start by rolling the clock all the way back to March 6th of this year. It was Friday and I had just returned from a business trip the night before. That afternoon (Thursday) my employer had decided that everyone was to start working from home immediately. Not wanting to try performing complex engineering tasks with only a laptop screen, I immediately ordered two nice high definition 24″ monitors. But the question was where to put them. The “answer” was, on my office desk where I usually do tube work, including prototyping and assembly. This gave me a good spot to do my job, but with two large monitors and their ample stands, it left little space for power supplies, oscilloscopes, signal generators, and other such trappings of my vacuum tube amplifier work.
Continue readingSo I usually have multiple amp projects going on at any one time. There is a rather large project that I’ve been working on but it’s going rather slowly and I was hungry to make some progress on something. As such, I decided to tackle a smaller project I first prototyped in 2011 and that has been on hold since 2015. I spent the better part of today turning an 11″ x 58″ plank of Zebra Wood {Microberlinia brazzavillensis} into an amp chassis.
Continue readingSo, 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.
Continue readingFor those that are paying particular attention to my amp builds it will come as no surprise that I think the #44 and #47 (0.9 and 0.5 candela respectively) indicator lamps are a little bright to be used on tube amps. I just think that they tend to overpower the look of the amplifier when the room gets dim. However, as these lamps are ubiquitous, it pays to use them in our builds. So, on the 6DJ8 Headphone amp and the 6EM7 vertical amp I included a small adjustment potentiometer to tame these power indicators. And on the Marblewood amp, I chose a fixed 25Ω 1W resistor to dim the indicator.
Continue readingI 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.
Continue readingBeing a proponent of single ended topologies, I am constantly on the lookout for singleton power tubes. Since I’m working on designs with all single ended signal chains, things like matching and bias points as less important to me than tubes which test strong and are reliable. One source containing lots of singleton “New Old Stock” and “Used” power tubes is Ebay. Often I can get a single power tube for far less than buying from one of the more established vacuum tube business on the web. But I have begun to wonder about whether these are really such a great deal after all.
Continue readingEver since I completed the Optimization of the 6V6 SE-UL I have been saying that I was going to do the SE-UL optimization process for more tubes. So yesterday I finally started to make plans.
Continue readingI just got a serious lesson in room acoustics. Please let me explain.
Continue readingI just had a little tussle with with the local blatherskites over at one of the less hospitable internet audio forums. The actual subject of the exchange is unimportant. However it got me to thinking about distortion and how today the concept of distortion has become seriously misunderstood.
Continue readingAnyone who has taken a look around this site should soon realize that I really like my low power amplifiers. What this means is that most of my listening is at lower volume levels. Now the only problem with this is that the sensitivity of the human ear to different frequencies is dependent on volume level. So at low volume levels, the ear has relatively poor sensitivity to both low and high frequencies. And the quieter the music gets, the worse the mismatch becomes. Traditionally the answer to this conundrum was the humble “loudness” control.