I would be interested in a simple “build a tube amp” class. It’s been something that I have always wanted to build for a home office setup
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Great story. That’s the kind of windfall electronics geeks dream of! Would have been cool just to see his space in all its glory.
Thanks Pearce. Got you on the tally sheet for “interest in a tube amp class”.
I missed the target on your question. I know there are a few audio nerds around here. I’ve always been fascinated by audio tech myself but feel like I can’t actually hear the difference. (What’s worse than a tin ear?)
I think you could easily make a special interest group under the electronics committee, and people would show up to your meetings or workdays.
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Thanks, Pearce. Appreciate the perspective.
Some thoughts on “wave one” of possible classes I could put together:
- Practical Introduction to Tube Electronics and Working Safely with High Voltages
- Build a Single-Ended Tube Guitar Amplifier
- Troubleshooting Tube Electronics Safely
- Build a JFET Guitar Amplifier
- Introduction to Jurassic Audio Electronics: Tubes and Discrete Solid State Amplifiers
I can think of a bunch. Let me know if any interest you and if you have other suggestions.
thanks,
BT
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If you want to use a hybrid module, I have 2 listed on Makertrade for free.
How about adding Vacuum Tube Testing to the list.
I have several different types of Vacuum Tube Testers, everything from a; generic filament tester, Emission Tester, Mutual Dynamic Conductance Tester, even the Military TV-7 which is the best one. Plus I have 100+ various tubes and many inline socket adapters that be used. The inline socket adapters allows one to measure the various pins with a Scope or Meter while under operation.
Raymond: yes, I’m interested in the modules. Don’t see those much anymore.
Rich, great idea. I think you walked by one day when I had my Hickok 750 up there to loan to another member. We joked around about it looking like the Project Mercury control room or something like that. Seems like between you and me, we could do a testing class and discuss the different types of testers (including the low-cost, newer curve tracers like the U-tracer and older ones like the classic Tektronics 576 ), how to pick the right kind, cautions (will it test the tubes you’re interested in? are the roll charts still available, etc). Hopefully there’s interest. I think there is.
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So it sounds like there’s enough interest to give a couple of classes a shot and see how much interest there is in the broader community. I’ll work on submitting two classes for the August/September time frame. Thanks to all who commented.
I’m leaning towards:
- Intro to vacuum tube electronics. Fundamentals and safety
- Choosing and using a tube tester for tube electronics projects (hopefully Rich can help out, or at least bring some of his testers up).
For the first class, I think it’d be a good idea to make that one mandatory for anyone new to tube electronics due to the high voltages involved. It would cover how tubes work, different types and uses, equipment needed, new manufacture vs old stock, basic tube circuits as used in audio applications, common topologies/architectures, and an overview of several good starter projects of varying difficulties. The safety portion would cover proper measurement techniques, using isolation transformers/importance of floating units under test/build, variacs vs isolation transformers, overview of the “death capacitor” and old, dangerous grounding techniques, adding a ground prong to old units, etc. There’s enough there that it might be a good idea to make the safety portion a class of its own.
For the testing class, I have three working testers, a Hickok 750, a Jackson 637 and a little Realistic emissions tester. I’m about to start work on a modern USB connected curve tracer based on a board/software from France. So I can basically cover true Gm testers, dynamic mutual conductance, cathode emissions testers and PC-connected curve tracers. It would be nice to fill in the gaps/show other examples from your collection, Rich. Happy to work with you as much as you’re willing to develop/teach the class.
Thanks again all.
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thats a great name for a tube company “jurassic electronics”
The newer Curve Tracer that was mentioned, the U-Tracer, is an unusual instrument. Instead of using true DC voltages it uses Pulse Width Modulated (PCM) DC for all the tube operating parameters. This process makes for smaller adjustable filament supply circuitry without the use of a heavy isolation transformer. The resulting sweep waveforms look okay. But, the older tubes filaments were never designed for PWM. The original response curve is therefore much different. That’s why the U-Tracer does not give a pass/fail indication like a tube tester does, it just displays a response curve. The operator still has to decide if the response curve is good or bad. Transconductance is based on a sine wave impossed on the grid, not a PWM signal. The U-Tracer is a great kit but it does have it’s limitations when testing vacuum tubes.
I’d be interested! I’m an audio engineer (FOH and A2 sound guy) and system designer/integrator by trade. Would love to learn more about the tube amps I use a lot as well as maybe build a small, tube amp. Maybe a headphone amp?
30 year restorer of tube radios here. ~20 years TV, 25 years jukeboxes. EE degree but all the tube stuff is self-taught with the help of a few retired TV/radio repair guys. I’d be game for helping teach a course or two. I’d approached VECTOR about doing it a few months ago but life had other ideas. PM me.
Mike
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Matt A, noted. Would be cool to get a FOH guy’s perspective in the class. You guys deal with all kinds of challenging, real world problems. Glad you’re interested.
Mike, that’s great to hear! I think collaborating on course content and co-teaching would make for a much better class. I’ve got quite a busy schedule for the next few weeks, but I could meet up at DMS one day for a couple of hours to talk about class content and maybe divvy up some pre-work (projects to bring/demonstrate, slides, etc). Thanks for offering.
I’ll PM you if the above sounds good and we can find a time. If you have better ideas, I’m all ears, too.
Josh, that’s what I use for the custom studio gear I build. One offs only (not a boutique operation), but the logo has a brontosaurus silhouette with “Jurassic Pro Audio” beneath it.
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Rich,
Spot on, Rich. While not a testing instrument in the vein of traditional gm/dynamic transconductance/emissions testers, I mentioned the U-tracer as I think there are likely a fair number of folks whose main interest might lie in tube instrument amplifiers or hi-fi, where tube matching for PP output stages, balanced input stages, or compressor/limiter circuits would be a common need. While there are cheaper methods of matching tubes, I think it’d be worthwhile to spend a few minutes on options like the U-tracer, among others. I’m sure you know the Tektronics 576 and its ilk performed a similar function, but powered the tube and injected a signal using traditional methods. Those have made a nice comeback with many old units restored to former glory as awareness has grown of them. I think spending some time talking about those would also be worthwhile.
But as you say, not really testers in the sense of good/bad, weak/strong testing.
These great instruments are still around. Many of them have a bad or weak CRT. The CRT is the hardest repair part to find.
For a lot of FOH applications, the newest emulators on the market (slate, etc), actually do a pretty great job! In a live environment, it can be incredibly difficult to tell the difference between a tube amp (most of which aren’t mic’d correctly anyway) and a good (expensive) emulator, at least in rock shows. In the studio, however, tubes make massive sonic differences. You may not hear the difference on its own, but you’ll gain clarity in your mix that can be hard to obtain otherwise.
Excited to see what you guys come up with!
Any new thoughts on the tube topic? Plans for a class? I have a Tandberg reel to reel sitting in my garage I would love to get working again. Class would need to have some piece on high voltage power supplies. Most times the power supplies seem to die while the tubes are fine.
Glad to hear there’s more interest! I’ve been working on and off for the last couple of weeks on this - drafting an agenda, building/digging up/stealing power point slides, digging out example components/projects/teaching aides, etc.
Before I submit the class and proposed dates, I’d like to post the final draft of the agenda here to get everyone’s feedback.
It’s pretty clear at this point that to do this right, we’ll have to make it at least a two part class. Hate to do that, because it’s harder for people to get the time to attend multiple classes just to get through a particular subject, but I don’t think people will want to sit through 5 or so hours of class in one sitting. I may be wrong, but that’s my impression at present. Would like folks’ feedback on that.
And you’re absolutely right about needing a section or two on power supplies. Other than faulty/dried out caps (I’ll include PS filter caps here), power supply issues are the number one root cause of problems with tube gear (I could say the same about vintage solid state gear as well). I already have a lot of the material on that topic pulled together, in fact.
At present, I’m thinking a mid-September date/dates are what we’ll have to shoot for.
Any thoughts on this are welcomed.
Thanks,
BT