Jurassic Electronics: Audio with tubes, and discrete amplifiers

Long time member/lurker, first post on this board.

This may have been broached (many times) before, but are there any audio, pro audio, or instrument amplifier special interest groups that are alive and well at DMS? What about tube electronics? Or something more niche like discrete audio electronics? If not, what’s the level of interest?

I build pro audio and guitar/bass amplifiers, mostly classic designs or variants thereof. I was wondering, for example, if there would be any interest in me bringing up my Hickok 750 tube tester once a month for a testing day for those without a tester. Or a group project to design and build a DIY curve tracer (tubes and/or high power transistors). I can think of a lot of other group oriented projects or classes to suggest, but I have no sense of how many of us are at DMS. I may be the lone freak as far as I know.

Thanks,
Bryan

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I would be interested in this. I have a cache of tubes from the “warehouse” a while back. I’d like to know if they are good tubes. I’d also be interested in your build class.
I’m a novice electronics guy, but I would be interested in any classes regarding amps.

Here’s the warehouse reference thread:
https://talk.dallasmakerspace.org/t/a-treasure-trove-of-maker-goodness-hording-trigger-warning/6288/79

Also from @richmeyer donated a tube tester for electronics lab. New Donation to the Electronics Lab - Vacuum Tube Tester

VECTOR has a tube tester and some tubes since we occasionally work on old tube amps from jukeboxes and antique radios.

We have discussed having a vacuum tube technology 101 class and maybe a class to build something like a tube based headphone amp but the subject matter experts who were talking about putting the classes together have been busy with life and work and had not had time to do so yet.

Personally I want to know more about how they work and how to test and troubleshoot tube based circuits from the level of an amateur self-taught electronics hobbyist. Frequently the tube based stuff I do see is aimed for EE level understanding and not at a level I can pickup much from it.

The first part is simple.

Heat up a metal and it gives off electrons. Position an electrode nearby and it picks up some of them. Apply a negative charge it and it repels the electrons. Apply a positive charge to it and it attracts the electrons. What you now have is a diode; current flows on one direction and not the other.

Position a grid between and by applying a charge to it allows control over the current flow.

For some reason, it says I don’t have access to the “warehouse of tubes” topic when I click the link.

I’d certainly be willing to both help out with testing and sorting the cache of tubes (by intended use and practical use - they don’t always coincide) and with teaching/co-teaching one or more classes on tube electronics. I’m quite busy with work/family, but I could certainly do workshops here and there on it.

And I agree with you Shawn that much of the learning material both online and in books out there go too high or too low for most hobbyist types. I’m confident I could address the DIYer’s needs on a more practical level.

If we have enough interest here, I’ll try to take a pulse on interested folks’ background knowledge level and goals and put together a proposal for a class or two.

Thanks for the feedback so far!

BT

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About a year ago, a guy named Fred, had a warehouse full of all manner of electronics that he needed to be emptied so he donated the whole lot, for the most part, to members of DMS to use any way we saw fit. Of course, much of it DMS couldn’t use so he allowed DMS members to take some of it.

As a result, many people helped him clean out the warehouse by taking stuff home.
I confess to hording some of it myself and that is where these tubes came from. Below are a few pics from the thread and a video of the place.

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Wow. Where was I when that went down! What a score!

BT

Maybe when we meet in your class we can discuss what you need for your classes and or personal projects and I can help you out. There were quite a few folks who helped with the evacuation process. Fred did a lot of contract work for TI, I think, and he had all kinds of tools, parts and components as well as complete systems. It was amazing just touring the place.

Fred’s warehouse opened up around November 2015 and lasted a few months as the 16,000 sqft or so was mostly emptied. Fred kept a bunch of the stuff he wanted, some stuff is at DMS, and a few of us helped give homes to a ton of stuff that otherwise would have ended up in the scrap guys truck or the dumpster. The first time I went it was very packed with narrow walkways wide enough to barely navigate while carrying something. By the end is was mostly cleared.

There was lots of old test gear, semiconductor wafer fab equipment, random parts from thousands of items that had been taken apart over the years and sorted out on a shelf. Just about anything and everything you could possibly think of it was probably there and Fred knew exactly where it was. The business had been a electronics testing lab for many years so they had all kinds of environmental test chambers, lots of unique lab equipment, etc. After that business closed Fred acquired the space and ran his business repairing Genrad test equipment. Fred also would buy surplus stuff from the electronics and semiconductor industry in DFW so there was lots of random stuff that came with the lot that he wanted to get certain items.

I can still find stuff from Fred’s in nearly every corner of DMS. Much of the large and heavy items came over in my truck since I have a liftgate.

I have been slowly sorting through the stuff I picked up from Fred’s warehouse. Most of it is going to be used to outfit my home electronics lab and some of it will likely end up finding new homes with people who can put certain items to use.

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

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.

Thanks, Pearce. Appreciate the perspective.