Vacuum Tube Amplifier Theory
Of course, no lover of tubes should be without the original masterpiece, Russel O. Hamm’s Tubes vs. Transistors.
Henry Pasternack (who will always have my respect for being a solid engineer) wrote some good posts to rec.audio.tech and rec.audio.tubes over the years. Here are three series on: tube amp power supplies, vacuum tube fundamentals, and electromagnetics.
I typed out this short but hopefully sweet primer on compensation and negative feedback.
A small description of grid current.
Here is an article on an inductively coupled concertina phase splitter, which provides better performance than a more traditional resistance loaded design.
Here’s how to design a low noise input stage.
An email I wrote about the cascode connection.
A quick note on operating points by Paul Joppa.
Here’s a couple of emails between myself and Steve Bench regarding slew rate limiting. Here is a detailed description of slew rate, and how to avoid slew rate limiting (a work in progress). Also, here are a few posts from the Audio Asylum between Lynn Olson and myself on the same subject, and an old couple of posts from R.A.T.
Here’s another email from Steve on paralleling electrolytic capacitors.
Scott Frankland provides some wisdom on regulating pentode g2 supplies.
Bill Perkins of PEARL gives some thoughts on triode connecting multi grid tubes.
Sometimes I would blow a mains fuse on powering up the BAGA, and sometimes I wouldn’t. Steve tells me what the deal is here.
I go off on a little ramble about designing guitar amp circuits in this email.
Ever wonder why triodes are so damned linear? They can be thought of as pentodes with negative feedback applied. For more info, click here.
Henry Pasternack and I discuss back-EMF.
Filamentary triodes sound different with AC vs. DC heater current. Here Steve Bench talks about why.
Sometimes a cap input filter actually has better regulation that a choke input filter. Find out here.
Ever wonder about snubber circuits? Click here and here for more info.
Remco Stoutjesdijk offers a primer on digital encoding.
Paul Joppa offers some ballpark numbers for parallel feed fidelity.
Lynn Olson offers some sage words on the effects of different rectifiers.
Some words on Mumetal and shielding.
How to wind and use your own toroidal transformers.
Emulation of Amplifier Overdrive Through the Use of the Nonlinear Output Response of Diodes By Dustin Lindley, and Nishant Parulekar
SE Class A notes by Nelson Pass of PassLabs.
Erno Borbely talks about JFETS.
I recently installed a CCS plate load for the input stage of my guitar preamp. Here’s a small discussion.
Here’s a few words on the pole-zero pair that is found in the bypassed cathode (or source, or emitter) resistor.
How do long-tailed pairs split phase, even with one input? Find out!
A short discussion on the ramifications of paralleled output tubes.
Here’s an article on the effects of fixed vs. cathode bias on output stages (thanks to Sound Practices).
Ivan Johnson goes into detail about the cancellation of distortion which occurs when two stages are cascaded (thanks to Sound Practices). Also Guido Tent uses some heavy math to calculate the effects of two non-linear stages in cascade.
Push-pull theory got you down? Here’s an article that goes into more detail. Ever wonder why class A push-pull amps work into a load of Raa/2 instead of Raa/4 as the turns ratio would suggest? Wonder no longer! (Thanks to Dave Slagle for scanning it from Eastman, “Fundamentals of Vacuum Tubes.”)
Here’s an article by Yuziro Kusunoze entitled “Calculation of Characteristics and the Design of Triodes,” which appeared in the October, 1929 Proc. IRE.
Wonder about cathodes and contact potentials? Go here for a discussion.
Here you can find a rant of mine on guitar amp tone. I also go off for a while about playing music at very high SPLs.
You’ve probably heard that the Ampeg SVT is capable of class AB2 operation. I don’t agree!
“Introduction to the Low Noise, High Bandwidth, Zero Rumble, Vacuum Tube Modification Manual,” by Ike Eisenson, Audio Dimensions, Inc.
All About Capacitors (quick reference guide).
Here are some chapters from Norman Crowhurst’s “Trouble Tracing Guide,” 1951: Chapter 1; Chapters 2-5, Chapters 6-8, Chapters 9-10.
An Electrolytic Capacitor Application Guide from RIFA.
Here are some pictures and formulas regarding NFB.
Ever wonder how a high voltage electrolytic cap’s voltage limit is determined? This article from RIFA explains it.
Sonic Frontiers wrote this primer on the Taste of Tubes.
Hi kg,
I’m a lurker from the ole ampage days. Thanks for hosting this site…I do use it and learn from it (have for years). I had saved a few old Ampage posts that you had made (I call it the ‘kg on …’ series lol) and sometimes I reference them. But when I’m posting in a thread I don’t want to plagiarize you…nor post your words without your consent…and if I paraphrase it still feels ‘dirty’ plus I might screw it up (unless I pretty much plagiarize you). Any suggestions on how I should handle this? Should I post your words and give you credit…paraphrase as best I can? Thanks and take care.
Matt
PS - the most recent one was a ‘kg on grid current’ post where you said (and explained) how grid stoppers actually harden the clipping due to +ve grid current. It seems that many people think it’s just the opposite.
hey matt, i remember you from way back when… )
personally what i would do (and have done before) is cut n paste if you have the original source, and just put a reference.
then if you then want to try to explain it yourself from another angle or using your own words/interpretation/whatever, it’s clear that it’s a different speaker.
if during some kind of discussion you fired off an email or whatever and gave me the heads up so that i could explain my point of view (or even revise it–hell i’ve been wrong plenty too!) that’d be fine, but that’s up to you… certainly don’t have to do that.
i still enjoy tube stuff and electronics very much, but i haven’t had the time to play with them as i used to. when you’re not messing with stuff, there isn’t much to say, you know?
i’ve really got do to an substantial overhaul of my guitar preamp though and just have to make time to do it.
Hello Ken, I didn’t know you have a web site. I’ve been enjoying some of the articles. I found your site whilst looking up specs on some 6 banana boxes full of tubes that I decided to pull down from the attic. They’re mostly from old TV service centers so they’re predominantly TV and Radio tubes. However, I find the variation in designs and specs to be rather fascinating.
Anyway, I’m writing to make you an offer since I have so frikken many of them, I’m willing to give some away to a few people that might make good use of them. Lemme know if you ever want any such animals.
BTW, hopefully by the end of this year, I’ll have a sound clip of my current amp design project, an ultra-fi SS guitar amp that sounds pretty amazing. For me, the ultra-fi was the last piece of the puzzle in my quest to design an SS amp that can rival tube amps.
I had in the past designed some pretty amazing SS circuits that could do warm tubelike OD, but the clean aspect (depth and dimension) of my SS amps were noticeably lacking when A-B’d with a good well tweaked tube amp. This latest incarnation A-B’s pretty well and it isn’t even totally evolved to the point where it fully exploits the theory upon which it is based. If all goes well, I hope to have it evolved to that point by years end.
Highest Regards
Dave Moore