Here’s the layout plan (for everything except from the OT secondary to the outputs, which are trivial to do):
It’s easier to read when printed, but the different sections of wiring are on different layers, so on-screen I can choose layer colors that emphasize the section I’m working on. I’ll post the LibreCAD file when I have time to work around WordPress (it won’t upload .DXF files).
I make a point of getting out in nature for a stroll at least a few times a week, but this &^%$ pandemic and my chemo vacation have given me the time & mental energy to finally get serious about the Beamer layout.
I’ve “finished” a chassis drilling drawing (maybe 2 more holes…) to give to my son & his milling machine, and I’ve been making progress on the electrical layout and one part is done. Knowing that maximizing the IN-13 performance would require some experimentation, I wanted to lay out the circuit on a small prototyping board (and use trim pots in a couple of extra places). This Adafruit board is only 2 x 1.7 inches and looks like it will do the trick nicely:
Note that the B+IN13 supply rail goes directly to the tube. Did you spot the change from the schematic?
The full chassis layout looks a little different, but uses similar shorthand. Components are just sketched in with rough sizes & only enough detail to identify the part; parts overlap without any indication of final 3-dimensional status. The emphasis is on connections while ensuring enough space.
I’m getting pretty good at LibreCAD, btw…
First: I give up — The Beamer is gonna be the name.
Second: In addition to the Nasty/Nice channel switch & LED, the new schematics include circuitry for this IN-13 linear indicator tube I’ve always wanted to use:
The active length (between the two red lines) is 4 inches, so it should look great if I can come up with a good way to mount it (horizontally). The schematic currently has it getting the signal after the Master volume, but I’m thinking it’ll probably end up tapping the signal just before that pot, so it’s not boring at low volumes.
https://www.youtube.com/watch?v=wG2OKaJdsFU shows 10 of them used on a spectrum analyzer.
The spec for the IN-13 has me thinking a standby switch is probabaly the simplest way to (mostly) adhere to the startup recommendations, so that’s back in.
I haven’t done any detailed layout yet, but I have decided that – for both electrical layout and control clarity reasons – it will be best to place the input jack between the Nasty & Nice volume controls. I’m also planning on using different/larger knobs for the Nasty, Nice and Master volumes:
Drive Tone NASTY jack NICE Bass Treble MASTER lamp
The red LED will go above the Nasty knob, and the channel switch will go above the input jack.
Schematics on the Beamer page…
Tuesday (6/17/2020) I spent the afternoon by the bay, recording this wind sculpture by Dave Ayer. He was hoping for high wind speeds and I wanted to test my fuzzy blimp windscreen on my shotgun mic.
There was wind, probably even up to 15 mph, but most of the time it was probably only 5 mph or so. It meant some long stretches of soundless sculpture, but sometimes I’d also catch several minutes of reasonably frequent and varied excitation.
Here are a few excerpts:
The shotgun picked up the sounds of the sculpture well enough, but was disappointingly non-directional. Those crackling noises are very dry leaves blowing along the path.
[I still need a better name!]
While avoiding the layout of the next version of the prototype, it ocurred to me that I haven’t even shared that schematic yet.
So I’ve started a Beamer page [<– over there] with PDFs of the three pages of the current schematic. This is essentially the current prototype as it will be built into a fresh box, with something close to a final layout. Be aure to read the notes…
Then I’ll play with a few Rs and Cs to perfect the sound!
Re-entering amp design mode has meant having to generate schematics, which has never been something I could do well in freehand. When I was still at Logitech, I could use my OrCAD license for tube projects as long as I could provide the vacuum tube (valve) library, but those days are gone and I’ve had to look for an alternative.
A little searching led me to KiCad — a totally free EDA tool suite (from folks at CERN!) that even has library parts for a few common tubes/valves. It’s easy to use, and has library parts for most anything you’d need in a tube amp. The weakest library (for tube stuff) is the transformers, but there are reasonable ways to get around that (see my next Beamer schematic).
Now I’m trying to make myself plan a proper layout, but since I don’t use PCBs that’ll be in a 2D mechanical CAD program. I’ve just started to get serious about it, but LibreCAD looks promising…
Here’s that schematic I referred to.
(Looks like WordPress makes *some* things more complicated…)
I’m not crazy about “Beamer” as an amp name (derived from the push-pull 6BM8 design), but that’s all I’ve got. Suggestions are welcome!
The more I look through my schematics & notes from 15 years ago, the more I realize that my Beamer project really wants to be a stripped-down Verberator II: no reverb or tremolo (we have boxes & software for that these days), just a wide tonal range, from clean to dirty.
Today I dug out my old Verberator II prototype (grrrr: link not working) chassis and immediately realized that I’d already done much of the work toward a Beamer. I suspect I gave up on it (and amp building) because the tremolo was more than I could master. With all the crazy shit you can do with software these days, it makes sense to leave that to post-production and concentrate on the core function (TONE) with electric guitars. So we’re talking about a gain pot, a foot-switchable ‘boost’ stage, and a master volume, with one or two tone stacks (or single-pot controls).
The rest is left as an exercise for the builder…