ot coolest places

I lived in Berlin for some years in a delightful Kietz very similar to number 1 on this list: antiquarian booksellers on every street. Some really fascinating titles got published pre-1900; stuff that would never see the light of day now.

I modestly note that my little niche is #35 on the list. My little lab is a two minute walk from GPS, which is an authentic old dive bar.

I asked the bar lady "Do you have any good rum, like Ron Zacapa?" and she said "This ain't that kind of joint, honey."

The Glen Park library is were they busted the Silk Road guy. A few blocks away is (or emphatically was) the first dynamite factory in the USA.

I've heard this term 'dive bar' before in popular songs. What exactly is that? I'm guessing some seedy joint where felonious types play pool?

Classic Americana. :-D

Oh dear! Go *bang* did it? Very quiet here today. Not even any of the regular trolls around.

It's an old neighborhood bar that smells like an old neighborhood bar, partonized by locals and worker-guys. It might have a pool table or a fireplace. It has a few good but not fancy beers on tap.

The pizza place close by makes deliveries to your table at GPS. People hate to let eating interfere with their drinking.

Yes. It lasted almost two years. They rebuilt it a couple miles to the west, and that lasted two more.

Not much electronics here lately.

I need a small circuit to make +20 volts into -20 at maybe 400 mA. There are lots of ways to do that.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I need to make 250VDC @ 150mA from 240VAC Gotta be low noise. Any suggestions?

Looks like the photo of Plateau-Mont-Royal, Montréal managed to find the one English sign in the neighborhood on a temporary tent.

Quebec has their own "Great French Replacement" theory, so whenever there's a wave of French nationalism in response to the fear that the province's French culture is being replaced the one thing the locals seem to be able to agree on is "We need more signage in French."

Montréal in particular has a love of putting up French street signs, like in a US city where there'd be one "Do Not Enter" sign at an intersection in Montréal it seems like there are at least six "Entrée interdite."

Something funny's going on with that picture too, it's been foreshortened or something, the Olympic stadium doesn't look nearly as impressive from that vantage point in reality.

There's not much in the way of commercial supplies in that range, and nothing affordable.

A transformer+rectifier+filter should be OK.

What's the load going to be?

I got one of these

It's weird, in that the actual output voltage is very close to the setpoint voltage, but it always displays 5 volts high.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I'd have thought *someone* must have such a supply, but as you say, not much around.

What - you mean an isolation transformer or something with more secodary turns?

Plate voltages for 4x ECC83 toobs. They will run at above and below

Something like that.

So you don't need regulation, and you can RC filter for the supply to early single-ended stages.

Sounds like a classic toob amp. Do what they did.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

That is exactly what I'm not going to do, John. This may shock you, but for the first time in 30 years on this group, I've decided to actually *design* something! There's a first time for everything, they say, and God knows I've been told enough times over the years to go design something for a change. Well that time has finally come. I've been spending 99% of my time fixing up old vintage test equipment and I fancy a change. And let's be honest: it's well overdue. Wish me luck! :-)

Tubes are wildly variant. The data sheets are just sorta approximations, so I wouldn't sweat a few volts.

Tubes vary so much that people used to sell matched pairs. That was before negative feedback was invented.

Ack! That's unprecidented here.

Yes. Let me know if I can help. We have a lot of parts in stock, but no tubes or octal sockets or cloth-covered wire or like that.

I started designing with tubes when I was a kid. They were free and a CK722 germanium transistor cost $7.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

BJTs are notorious for that, too. And people also selected matched pairs of those for the same reason.

Certainly is in my case! :-)

I have the tubes. The sockets: some I have, some I'll need to order. I was planning to make it all-tube, but difficulty in finding decent quality output transformers of the right spec put paid to that. So now it's to be a hybrid: tube front end going into BJTs for the current amplification side of things.

Same here. But over the decades I'd forgotten much about them. I couldn't even recall whether grids had to be above or below cathode potential! I just want to do something a bit different. Been messing around with semis for far too long; time to get back to my roots.

Or mosfets.

Tubes are usually run in depletion mode, but nasty class-C RF ones are sometimes run with serious positive grid swing. You can see the grids glowing.

Tubes are awful.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

If the cathode glows but the grid doesn't, you have got it the right way around.

Well, I'm aware Mosfets are used for certain exotic amplifier modes (can't recall exactly which but might be class D or G or something) but I'm going full traditional here with class A or AB perhaps. And you can't use Mosfets for that AFAICS. But sure, if you're going to chop up the signal and mess around with it, Mosfets are ideal.

Bit of a sweeping generalization there, John!

If the cathodes are glowing I'd have done something wrong!

If they aren't, you've forgotten to switch it on.

You seem to be thinking of the heaters making it appear that the cathodes are glowing.

....

My father had a copy of this. I found it very interesting as soon as I could read.