Remember a few weeks ago in the post When it Rains, It Pours! I said that the Lacewood V2 reservoir capacitor had likely failed? Well, I was wrong.
Continue readingI Spoke Too Soon
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Author Archives: Matt
That Didn’t Go Well!
Have you ever made a mistake? Not a typical everyday little mistake like forgetting to run an errand, but a blunder of such proportions that you’re shocked by your foolishness? One that leaves you thinking you couldn’t have been that naive, that foolish? Well I did. And it left me with significant embarrassment, as well as some smoke coming out of an amplifier.
Continue readingWhen it Rains, It Pours!
Would you believe it? Today while listening to the 6V6 Lacewood V2 I heard a funny little popping sound and a short duration whine. It only lasted a few seconds, then it was gone. But when I walked over to the amp there was a distinct smell of “magic smoke“. Once again, the game’s afoot!
Continue readingSneaky Capacitor Failure
I have witnessed a lot of electrolytic capacitor failures. Most of these failures have occurred from improper wiring polarity or a significant over voltage condition. They generally involve an explosive emptying of the capacitor shell. These failures usually leave a smoking husk of a component and a spray of foil bits, dielectric insulation, and liquid electrolyte spewed across the circuit, chassis, and sometimes, the test technician. But recently I came across a much different failure. One which seemed to be specially concocted to sneak by without notice.
Continue readingAmplifier Voltages
When testing an amplifier, the first thing I generally do is to check voltages. This is what I advise others to do as well. However, the real trick is in determining if the measured voltages are acceptable or not. And herein lies the difficulty.
Continue readingTalking Substitutions
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?
Continue readingA Slight Revision to the 6L6 “Spalted Alder” Amp
Please read the post “That Didn’t Go Well!” before following the power supply change detailed in the later half of this post.
Sometimes a design which seems fine at first can later exhibit some marginal behavior. This exact issue recently reared its head with the design of the 6L6 “Spalted Alder” amplifier.
Continue readingCan We Talk?
I know it’s been a while since my last post. Things have been a little hectic for my family this summer. Hopefully I’ll be able to get back to more regular posting in a few of weeks.
But that’s not what I want to talk about. I want to talk about the major changes currently taking place in the US economy and our supply chains, and some things we as hobbyists can do to help protect ourselves from problems.
Continue readingBack to Work
I guess that some folks have been wondering what I’ve been up to the last month or so. Well, I’ve been trying to take it easy to let a shoulder injury heal. If physical therapy can be considered “taking it easy”. In the last month I’ve learned all about labrum tears. However, today something arrived in the mail and that means it’s time to get back to work.
Continue readingA Small Delay to the EL84 SE-UL Optimization
As I said the other day, “It is my estimation that the EL84 would greatly benefit from a lower percentage UL tap transformer.” Whereas there is much to be learned from the current data set taken with the Edcor GXSE10-5K transformer, I have decided that a different configuration needs to be tested as well.
Continue readingMore Thoughts on the EL84 SE-UL Optimization
So I’ve spent the last week looking at the data from the initial effort. I’ve retaken some data, analyzed the performance and setup, poured over data sheets and characteristics curves, listened to some music at a lot of different operating points, and I’ve drawn some initial conclusions. And I must confess I’ve gotten some interesting surprises.
Continue readingEL84 SE-UL Optimization First Impression
Well, all the data for the aforementioned optimization is collected and in the computer. I’ve been chewing on the data and my notes for the last couple of hours and it’s safe to say, there is a lot more here than first meets the eye.
Continue readingA Quick History Lesson
For anyone who is interested in a little more of the history of feedback development, I have posted an article from the Proceedings of the IEEE from 1999. It’s a relatively quick but informative read about the topic.
Continue readingA Quick Note on Feedback in Audio Amplifiers
This may seem a non-sequitur to some. After all, I don’t post designs on this website that make use of feedback. This is simply because I don’t like the way feedback affects the sound of an audio amplifier. But that doesn’t mean that I don’t understand feedback and make use of it in other applications.
Continue readingMinor Work Stoppage
We’ve had a bit of a cold and rainy snap here which has prevented me from getting to the chassis work for the new 807 amp. But that doesn’t mean I’ve been totally idle.
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