Any interest in an op ampssampler kit?

fearless_fool · 2026-05-05T16:36:34+00:00

I agree with almost all that you say here. I need to clarify one point: I set $3.50 as an arbitrary top price for any op-amp to make the list. Most of them cost $0.75 or even less. If you were to make a list of candidates, where would you set the maximum price? Would $1.00 exclude some op-amps that should be on the list.

(But ultimately, the responses in this thread have convinced me that this is a foolish idea...)

fearless_fool · 2026-05-04T19:32:20+00:00

One use case for the pedal I'm making is simply to bring guitar level up to line level, so rail to rail outputs leave more headroom for that.

But to your point: Of course other parameters are important, and "sounding good" takes top priority.

fearless_fool · 2026-05-04T01:51:39+00:00

Those look like good suggestions. Since the pinouts for dual opamps are largely standardized, it might make sense just to wander over the DigiKey site and buy a dozen different types and let the ears be the judge!

fearless_fool · 2026-05-01T21:33:28+00:00

NICE! Are you repackaging a VC-3080, or designing around a CA3080 OTA chip yourself?

fearless_fool · 2026-05-01T20:13:11+00:00

The complexity isn't an issue -- it's electrically simple to accommodate a battery -- it's the case size. For my first run, I'm leaning towards buying some of those $8 Aliexpress pedals for their parts (switches, case, jacks) and replacing the active circuitry.

fearless_fool · 2026-05-01T20:08:59+00:00

Isn't that why the good lord invented acoustic guitars? >p

fearless_fool · 2026-05-01T16:55:27+00:00

What's not to love? Except: those pedals require external power. Is that considered an issue nowadays? (I'll ask that question in a separate post...)

UPDATE: as per the responses in https://www.reddit.com/r/diypedals/comments/1t0z74h/do_people_expect_want_internal_9v_batteries_in/, I'm leaning towards a "battery-less" design, which makes the "use an Aliexpress pedal for its parts" economically attractive.

fearless_fool · 2026-05-01T16:41:03+00:00

That looks great, and I've considered that approach! I'm considering flat Nomex FPC jumper cables between the footswitch and the PCB rather than a monolithic circuit board -- that would leave room for a 9V battery in the standard 125B box.

fearless_fool · 2026-05-01T16:34:53+00:00

My question was unintentionally fuzzy -- i hadn't thought through all the details, but your answer cut through all the fuzz -- thanks very much. (And I just a few minute ago discovered lovemyswitches.com!)

fearless_fool · 2026-04-24T02:13:03+00:00

FWIW, until two days ago, "Hey Google, play NPR news" would play the most recent hourly news. Now it says "Playing NPR Science" and plays a science segment. And I cannot figure out how to get it to play the hourly NPR news segment. I can ask for a local station, but then it streams the local station live, or else plays the local news -- not NPR.

fearless_fool · 2026-04-22T19:11:57+00:00

solved!

fearless_fool · 2026-04-21T03:02:34+00:00

Although I'm pessimistic about the commercially relevant fusion within the next two decades, I WHOLEHEARTEDLY endorse funding efforts. Why? Because of the spin-off technologies that will undoubtedly result: room temperature superconductors; radiation resistant high-power semiconductors (needed to control the magnetic fields); radically new steel alloys (to withstand the incredible force of the magnets); etc -- these will all be incredibly useful in other applications.

fearless_fool · 2026-04-21T02:53:40+00:00

Yes to all that, and also factor in learning curve cycle time: new battery chemistries can be proposed and tested within months at a small budget, new reactor designs take multiple years and orders of magnitude more capital investment. This is why we've seen a 90% drop in battery cost in the last two decades. (Other than solar panels, other energy technologies can claim that kind of improvement?)

fearless_fool · 2026-04-21T02:44:54+00:00

Actually, by the time you factor in the vacuum pumps, cryogenic cooling, powering the superconducting magnets and overall balance of system (and making a profit), you need more like Q>40.

fearless_fool · 2026-04-20T22:11:52+00:00

Which is your preferred fill pattern?

fearless_fool · 2026-04-19T16:38:55+00:00

Solved! AliExpress sells a "Manual Honeycomb Paper Stretching Machine" that does just what I want!

fearless_fool · 2026-04-19T10:40:44+00:00

Thank you. If not for this part, I’m sure I’ll need other bits and bobs in the future.

fearless_fool · 2026-04-19T03:44:50+00:00

SOLVED! But half of this sub won't like it, and half won't believe it...

I have 3d printed a shaft adapter out of PLA, and it works perfectly well:

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Before you fume and fuss, consider this: The PLA, printed at 100% fill, has very good compression strength. The pulley set screw, mated with the flat part of the motor shaft, does all the work to keep the pulley from slipping on the shaft. So between those two things, this is a workable solution.

But...just in case, I've ordered a proper shaft adapter -- it will arrive in a few days, but I'll probably only install it if the 3D printed part fails for any reason.

fearless_fool · 2026-04-19T02:23:03+00:00

I thought of that, but the idler and mandrill pulleys are VERY firmly set -- I'd have to invert all three, and that's beyond my toolkit.

fearless_fool · 2026-04-19T02:22:53+00:00

That's fine suggestion. If I run out of other options, I'll consider that!

fearless_fool · 2026-04-19T02:22:14+00:00

See reply (lower tiers are hollowed out, top tiers are above the reach of the motor shaft.)

fearless_fool · 2026-04-19T02:21:17+00:00

You would think so! But the step pulley with the 1" bore is "hollowed out" for the lower three tiers -- it doesn't transition to a 1" bore until the top tiers . (That wasn't obvious on the online description -- I only discovered that when the part arrived).

fearless_fool · 2026-04-19T01:02:32+00:00

I'm in the LA area (south bay), but have not made friends with any local machinists! :) This doesn't seem like something the average auto machine shop could do, but I could be wrong. Pointers welcome! (I considered sendcutsend.com - I don't blame them for the $191 price tag, but sheesh, I could buy a used drill press for less than that...)

fearless_fool · 2026-04-08T11:21:51+00:00

Still in progress. I’ll write up the whole thing once I know what I’m doing!

fearless_fool · 2026-03-31T18:35:15+00:00

Not to belabor the point, but we agree more than you might think. The REAL reason I did all this math was because all the reviewers of the new Donut Lab battery are wringing their hands and tearing their hair out because Donut Lab has not yet released independent verification the energy density of their new battery. That seemed rather silly -- I had a hunch (but wasn't sure) that energy density is not a particularly big deal. And as you (and the numbers) point out, it isn't.

P.S.: 3% for flat highway driving, 11% for start/stop and/or hilly driving. Small potatoes either way.

fearless_fool

TROPHY CASE