Wire Wrapping: Discrete Components

[Dr Jefyll]

Fun stuff indeed! It's interesting that moderate temperature changes would be that significant. It's also interesting that, "the active noise reduction will really only be effective in the low frequencies (which works out ok, because it's the lows that don't get sealed out well by the earcup and ear cushion)."

GARTHWILSON wrote:

In car stereos, they've gone for 4Ω and apparently even 2Ω speakers, plus bridged outputs, because the power supply voltage is so limited.

Yeah, those are two approaches that've been used: lower-impedance loudspeakers, and/or two amplifiers per loudspeaker.

Another approach I've seen doesn't use the car's 12 Volts directly. Instead, the power amplifier chassis also incorporates an inverter -- a switch-mode power oscillator and a toroidal step-up transformer, followed by rectifiers and filter cap's. Of course this arrangement can supply DC to the power amp's at pretty well any voltage you choose; you're no longer stuck with 12 volts.

I don't do a lot of mucking about with this sort of gear, so I'm not sure how widely adopted this approach is. But I've heard some ridiculously loud car stereos, and I expect that, at such high power levels, the inverter approach becomes the only reasonable option.

Cheers,
Jeff

[barrym95838]

Dr Jefyll wrote:

... [snip] ...
I don't do a lot of mucking about with this sort of gear, so I'm not sure how widely adopted this approach is. But I've heard some ridiculously loud car stereos, and I expect that, at such high power levels, the inverter approach becomes the only reasonable option.

Ridiculous doesn't even adequately express the levels that have been reached. There are car audio competitions producing SPLs that are easily and immediately LETHAL to any human sitting in the vehicle. Instrumentation measures the levels, while judges and bystanders keep a safe distance.

Mike

[ElEctric_EyE]

Personally, this is exactly why I don't care about this kind of noise pollution.
10%+ IMD&THD is acceptable to these kinds of folks.

[Dr Jefyll]

barrym95838 wrote:

Ridiculous doesn't even adequately express the levels that have been reached.

You'd almost wonder whether these systems could tax the (comparatively vast) power of the car's internal combustion engine! Hmmm, maybe not. One horsepower translates to about 750 watts...

One thing for sure: a heavy-duty alternator will be required if you want this sort of gear to perform to its potential. Another necessity (getting remotely back on topic here! ) is short, fat cables terminated with absolutely pristine connections. After all, you'll be carrying scores or even hundreds of amperes of 12V power to the amplifier assembly. At those current levels, it doesn't take many milliohms of resistance to seriously degrade performance -- and/or start a fire.

[GARTHWILSON]

Fortunately that's illegal in California, but unfortunately it doesn't seem to be enforced much.  Perhaps 20 or 25 years ago, they made it law that if your car stereo can be heard more than 50 feet from the car, you can be cited.  A policeman friend said they primarily use it as an excuse to stop cars they suspect of having drugs in them.

Quote:

After all, you'll be carrying scores or even hundreds of amperes of 12V power to the amplifier assembly.

The big boom boxes sometimes use huge banks of capacitors next to the amplifier to keep the power flowing during demand on the peaks.  Those, and the huge speakers, take a lot of room.  This is not normal car stereo territory.  A big switching power supply would take a lot of room too.  A shop three miles away that installed boom boxes went out of business recently, and I suspect they were forced out because they were installing equipment that is only used to break the law.

Quote:

Personally, this is exactly why I don't care about this kind of noise pollution.
10%+ IMD&THD is acceptable to these kinds of folks.

In one of the Brüel & Kjær [*] seminars I've been to, the presenter showed how bad typical speaker distortion numbers are compared to typical amplifier distortion numbers.  He had a smallish but high-quality speaker there that sounded relatively good, but the analyzer said the distortion was 5%.  He had another one there with a scrape that was also at 5%, but it sounded absolutely horrible.  The two had nearly the same number, but the distortion products were distributed differently, and the results were night-and-day.  The idiots with the boom boxes however seem to have every kind.  To get the pounding on your body adequate for re-starting a stopped heart, they turn the base way up, but of course no matter what you do, there's the area below the bass resonance where you just can't get anything out, so there's this huge single-frequency peak down there, plus the rattling of the license plate frame and probably the dashboard crashpad and absolutely everything else on that car that could possibly rattle, going like crazy.  To call it "mud city" is only the beginning of it.

[*] Brüel & Kjær is a manufacturer of high-end laboratory instrumentation for the measurement and analysis of sound and vibration.

[BigDumbDinosaur]

GARTHWILSON wrote:

Fortunately that's illegal in California, but unfortunately it doesn't seem to be enforced much. Perhaps 20 or 25 years ago, they made it law that if your car stereo can be heard more than 50 feet from the car, you can be cited.

Similar law in Illinois, except it's 75 feet instead of 50. It's not well-enforced state-wide, but here in our little burg, the gendarmes do enforce it and it's a 100 dollar fine if you get cited. Needless to say, there aren't many thumping car stereos around here.

[enso]

Sorry I'll be on topic for a while.

I often find myself breaking off two pins from a pin header, and wedging 0805 or 0603 surface-mount parts between the pins at one end. A tiny bit of solder will hold them in place. The pins can be then inserted into the board and wrapped.

[Johnny Starr]

I noticed this video today https://www.youtube.com/watch?v=l5RV6IfVOGY

What type of method is this where the headers are wrapped from the top? Is this conventional?
Also, I imagine he had to solder the pins at the bottom?

[GARTHWILSON]

Johnny Starr wrote:

I noticed this video today https://www.youtube.com/watch?v=l5RV6IfVOGY

What type of method is this where the headers are wrapped from the top? Is this conventional?
Also, I imagine he had to solder the pins at the bottom?

It looks like he's using something like these which as you can see on the page are rather expensive.  Why not just use wire-wrap sockets, put them closer together for better high-frequency behavior, and wire the bottom.

What kind of ROM gives the 17ns access time he was talking about?