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Somewhere I saw something along the lines of: “Life hack: Order a ballpoint pen from Amazon, and use the box it comes in to store sheets and blankets.”
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Non-mail day: a shipment with 180 pots and 400 thonkiconns was stolen from the staircase 
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The Behringer Bandit strikes again!
Is there nothing they won’t steal?
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Happy cake day!
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After I dropped the tube I was working on, a friend went around, picked a lot, and sent a selection over.
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Ooh! That’s a friend we wish we all had!
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Any of them usable for audio, like 12AX7 or EL84 etc?
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Frequency scaling is way outside my comfort zone but I would imagine stepping down to audio frequency is possible on most valves.
Time for a deep dive or vague hope someone here knows a good resource.
Oh, there are many sources that write about tubes and their applications.
To name a few:
Or this (note the modest title) (1760+ pages):
With great illustrations like this one:
But this last one has more practical examples maybe:
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Thanks @Jos, that’s quite a list.
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Most of them are odd pentodes and triode/pentodes TV and radio tubes. I find that the typical 12AX/AT/AU used in amplifiers are much less useful in synthesizer circuits, in addition to being 10x more expensive.
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Have you used them in synth circuits, or which would you recommend ? Any examples ?
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Compared to triodes, pentodes have two additional grids that allow modulating the signal without resorting to unconventional arrangements like in Sam’s distorting VCA where a backwards transistor disconnects the cathode from ground. Somehow, I didn’t feel comfortable “abusing” a EUR 20-30 tube in such a way just to get a VCA out of it.
Radio and television pentodes were developed for the purpose of modulating signals and it is no secret that you can get easily a VCA out of them. In addition, you can easily get all those “unwanted” TV and radio tubes for EUR 2-3 each. You get a more elegant and simple VCA for 1/10 of the price. Think of a radio/TV pentode as a CA3080 on steroids, where you get not just one, but possibly, two modulating inputs.
Ken Stone’s simple VCA is a good starting point. By injecting a CV to the second (screen) grid, you get a nice part-VCA part-wavefolder. If you have a pentode where the third (suppressor) grind is available (not tied internally to the cathode), you can also inject a CV to the suppressor grid and get a straightforward VCA as per Eric Barbour’s VCA.
A few points:
- These circuits should work with nearly any pentode. Not just the sub miniature Soviet pentodes that are hyped in boutique modules (and have gone ridiculously up in price). They should also work with heptodes. Just mind the different voltages for the heaters among different tubes which are often higher than the 6.3V found in the usual audio triodes.
- These circuits do not necessarily need high voltages. They should work with 12, 15, or 24V. At these voltages, however, the distortion that you might get will likely negate the purpose of using a good “audio triode”.
- Pentodes can be used in VCFs at the expense of a little more circuit complexity, and, with a little luck, in oscillators.
- Pentodes (and heptodes) typically come in 9 pin arrangements, so you will need a different socket. 9 pin (noval) sockets, however, are cheaper than the 7 pin sockets often used by triodes.
Just look around what’s available on the cheap, consult the datasheets, and pick those that look interesting and useful to play around with.
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this is one " voice " from an old Conn organ . 12AU7 tubes were used .
there were 12 of these in the organ .
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That voice looks massive. Do you have any pictures of other electronic parts of that organ? Or a schematic, dare I ask?
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Looks like they had 12 oscillators for each voice in a divide down kind of arrangement.
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no it was parted out years ago . you may be able to internet something on it was from the Conn organ company .
I made a deal with @stmllr on his offer in the BST thread and today the modues arrived…
we reached an agreement quickly and exchanged modules, no money involved
Allways a pleasure doing buisiness with nice people from this forum
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