errors in The Ultimate Tone by K. O'Connor

[Dave H]

WHy adopt nano farads if I don't also adopt millifarads. Anyone ever write 1mf in place of 1000uf? I sure don't.

I've seen 1000u written as 1m0 but I haven't used it myself. We would write uf as uF but normally only one letter is used so it would be 100p, 100n or 100u Resistor values lower than 1 ohm are written as 0R22, 0R33

[Enzo]

If I see 10m, I have to stop and think about it. I don't immediately visualize a large can cap in a power supply. I will write 10,000uf the rest of my days.

[mozz]

Many old schematics used m on resistors also, meaning k ohms. 10m, 220m or 100m meant 10k, 220k 100k. I saw some review on Premier guitar once where he got all the values wrong saying "you don't see 100meg resistors much these days". I saw the original post and took it as "u" just written in cursive.

[bob p]

s

Many old schematics used m on resistors also, meaning k ohms. 10m, 220m or 100m meant 10k, 220k 100k. I saw some review on Premier guitar once where he got all the values wrong saying "you don't see 100meg resistors much these days"...

Many of the really old schematics do use "M" on resistors to mean k ohms. Gibson amps from the 1930s are famous for that. The schematics were actually so inconsistently drawn in that era that the schematics for the same amp would use both "M" and "K" to mean kilo-ohms.

The practice of using "M" is derived from the Roman Numeral for 1000, which is a capital M.

https://en.wikipedia.org/wiki/Roman_numerals

I think that those schematics that used "m" to mean kilo-ohms were drawn by somebody who made a mistake in writing the Roman Numeral for 1000 as "m" instead of "M". Roman Numerals are exclusively capitalized, so drawing "m" for 1000 would amount to someone using the old system making a transcriptional error.

Here is a Gibson schematic from the 1930s that demonstrates some of the ambiguity inherent in the old system:

EH-150 Amp.pdf

Interestingly, these are two schematics from Gibson for the original EH-150 and the successor EH-150. In the original schematic Gibson used "M" to mean 1000 ohms, and in the later schematic it used a capital K to mean 1000 ohms... two different conventions were used for two amps with the same model number!

These old abbrevations only add to the confusion. They pre-date the official SI abbreviations developed by IUPAP in 1948; the implementation of SI was designed to specifically disambiguate the different abbreviations that were commonly in use at the time, so that "M" would be universally recognized as "Mega", "m" as "milli", "k" as Kilo and "K" as Kelvin.

If you're aware of the history then it would be clear to you as a reader that on an old schematic like the Gibson EH-150 (see attachment) that 100K means 100 kilo-ohms not 100* Kelvin, and that 500M means 500 kilo-ohms, not 500 Meg-ohms. But if you're not familiar with the history it could cause a lot of confusion. It's frustrating when two different schematics for the "same" amp contain such confusing and inconsistent abbreviations. Chances are that they were drawn by two different engineers.

I agree with Enzo's point that it's important to read the legend notations on a schematic. Modern professionally drawn schematics are thoughtfully drawn and go out of their way to prevent mistakes from being made in reading the figures. They commonly tell you what the implied non-standard abbreviations are, whether test point voltages are AC or DC depending upon how they're drawn with a circle or a box, how controls should be set when taking test measurements, etc. Modern schematics with detailed legends help a lot to make things clear and unambiguous. Hand drawn schematics remain a challenge because many of the conventions get violated in the interest of brevity. Because there are still a lot of them floating around we have to learn all of these idiosyncrasies if we're to make sense of things.

[Gnobuddy]

I was familiar with the symbol, I just wasn't recognizing it in it's sloppy form. Even now that I understand what is going on, it still looks more like an N to me.

It might help to remember that the SI prefix "n" is lower case (for nano). You can see that O'Connor has used that properly where he writes "22n".

To me that hand-writen "mu" is very clearly a "mu". It would be a horribly distorted "N", if it were an "N". However, I have seen a lot of teen-aged and early twenties vocational electronics students mistake hand-written "mu" symbols for uppercase N's. The younger generations have lost the ability to read or write cursive - it is neither taught nor required in many school systems now, up to and including college. I suspect many also have never encountered the Greek letters, which we older people encountered in algebra and trigonometry and science classes.

The loss of the ability to read and write cursive is a great pity, because it turns out to be excellent brain-exercise: https://www.nytimes.com/2014/06/03/s...ing-fades.html

(I first learned about research studies showing the beneficial effects of cursive writing in the excellent book "The Brain That Teaches Itself", but the NY Times article is easily available online.)

-Gnobuddy

[Gnobuddy]

If I see 10m, I have to stop and think about it. I don't immediately visualize a large can cap in a power supply. I will write 10,000uf the rest of my days.

Years ago, I noticed that there is a peculiar oddity in the way SI prefixes are used in America: schematics drawn here rarely or never use two of the SI prefixes, nano and milli, for capacitance values. So you'll find "0.047uF" where the rest of the world uses "47 nF", and you'll find "4700 uF" instead of "4.7mF".

Both "0.047 uF" and "4700 uF" actually violate the rule for properly using SI prefixes. The rule is that the numerical part in front of the prefix should have a magnitude between 1 and 1000. You have to choose the correct SI prefix to make this happen.

So "0.047 uF" and "47000 pF" are both improper use of SI prefixes, because 0.047 is less than 1, and 47000 is more than 1000. Instead, you write "47 nF" - this is correct, because 47 is between 1 and 1000.

The same goes for 10,000 uF. Since 10,000 is bigger than 1000, proper usage is to pick the next bigger SI prefix after "mu", which is "m". Ergo, 10,000 uF is properly written "10 mF".

Fascinatingly, the American prejudice against "nano" and "milli" only seems to exist when it comes to capacitors. The same prefixes are used freely in America when it comes to other physical quantities - resistance, say, or length, or mass, or voltage, or current.

If anyone knows how this odd neglect of nano farads and milli farads in America came to be, I would love to know!

-Gnobuddy

[MarkusBass]

I'm not sure about capacitance symbols and the SI system in general but here is a funny video about the Metric System not being used in the US:

[Enzo]

I grew up on uuf, then at some point pf took over. But the use of nano came much later. To me it is relatively recent. The names were developed long long ago, but now immediately adopted. In the USA, we have not officially adopted those units. In typical American fashion we look upon the metric system, and by association SI units this way, "Them people think they can dictate to us? We ain't laying down out soveraignty for damn foreigners." Decades ago we passed legislation to assist changing to metric, but folks objected to even having metric on signs with imperial. SO we have "Detroit 60mi" signs as signs saying "Detroit 100km/60mi" were too much for us to handle.

0.047uf is perfectly clear to us techs, so there is no particular incentive for us to change that to 47nf. Also, if I use only pf and uf, then IO only have two units to work with. If I add in the mf and nf, I now have four units. I freely admit it is whatever you are used to, and what will happen is as the generations progress, what you were taught will become what you use.

One obstacle for me is reading it. I can see 1k5 and know instantly what it means, but when I discuss things, I can't imagine myself saying "You need to check your one kay five resistor."

Resistors? We do say kilo and mega, but how often would giga ohms even come up? I am sure in physics that micro, nano, and pico ohms exist, but hardly are useful in electronics. At least in our sort of electronics. SO the range of resistance limits the number of units we will apply to it. Our use of caps spreads across more orders of magnitude. But I will say that millifarads don't come up all that often, relatively speaking. Mostly large power supply filters. So to write 10mf instead of 10,000uf, to me would be applying a conscious effort to do it "on purpose".

I forget when it happened, but I recall being put off by Hertz. We had used the perfectly descriptive "cps" ever since AC was invented. Now they wanted us to start calling it an arbitrary name. Nothing against Mr Hertz. Plus a nit for me was it was never plural. 60 Hertzes? No, One Hertz or 100 Hertz. Maybe it is like sheep. Volts and Ohms etc are all plural when more than one is present.

Remember in the USA, no one is two meters tall, or 200cm. We are feet and inches, god love us. Same with weight. We weigh 220 pounds, not 100 kilos. And the store is a mile away, not...um... some number of meters.

Wouldn't that 4700uf cap be 4m7? Like 1.5k ohms versus 1k5? No system is perfect, 4m7 suggests that 4m7 and 4n7 look very similar and are easily mistaken, about as easily as overlooked decimal points.

One thing I have noticed is context. If a lot of caps are in the pico range in a circuit, I might expect and even prefer to see 1000pf on a part rather than 1uf. Likewise on those schematics where "all caps are in microfarads unless noted" we lose that simplicity when we add the extra units.

Wait until someone decides we should start using deci-ohms and centi-ohms.

We can discuss cursive elsewhere. All write?

[Jazz P Bass]

I'm not sure about capacitance symbols and the SI system in general but here is a funny video about the Metric System not being used in the US:

Wanda Sykes.
Thankyou!

[Justin Thomas]

Personally, I find much easier to convert in either Standard or very limited metric. Standard measures, I only have a few to worry about - inches, yard, miles. Those three units pretty much cover anything I will use. Also, in metric specifically caps, I find it easier to work with microfarads and picofarads. Even though technically incorrect, trying to convert between about ten different potential prefixes to choose from gets a little mushy. I am slowly learning to convert .047uF into 47 nF, but if we all got into milli, centi, deci, deca, etc. for caps, I'd go bonkers.

I find that for the most part, what I am using to build and repair amps only needs a rather limited number of quantities to be concerned with. Now, if we're talking data storage or going to the moon, I might expect to have to know a lot more...

Justin

[Gnobuddy]

But I will say that millifarads don't come up all that often, relatively speaking. Mostly large power supply filters.

I used to see big caps of that size a lot more when I was a teenager, and every solid-state power amp had to use a big electrolytic cap to keep DC off the speaker. I even had the values memorized - 1000 uF (or 1 mF!) for a 20 Hz corner frequency with an 8 ohm speaker, 2200 uF (nearest standard value) if you were using a 4 ohm speaker.

At some point after that power amps started to morph into bigger versions of op-amps, with dual supply rails, and DC-coupled outputs. The big output capacitors went away.

I forget when it happened, but I recall being put off by Hertz.

It probably didn't help that "Hertz" usually means "car rental company" in the USA. A car rental company that had the misfortune to pick O.J. Simpson as the public face of the company, at that!

Remember in the USA, no one is two meters tall, or 200cm. We are feet and inches, god love us. Same with weight. We weigh 220 pounds, not 100 kilos. And the store is a mile away, not...um... some number of meters.

I lived in the USA for over twenty years, and have now been in Canada for a little while. In popular use, units are not that different here. Road signs and car speedometers have kilometers on them, sure, but at the gas station, the air pump for my tyres (sorry, tires!) is still labelled in pounds per square inch. Go to Home Depot, and all the lumber is sized in inches, the screws have inch lengths and the usual utterly confusing multiple systems for thickness (fractional inches, or just a number).

The industrial past of North America (both Canada and the USA) was heavily based on Imperial units, with a good lot of utterly crazy random units thrown in (drill bit sizes grumble grumble), and much of it seems unlikely to change.

One thing I have noticed is context.

In college I had friends who were astrophysicists. Their preferred unit of mass is the weight of the sun; if a star has a weight of 2.3, that means 2.3 solar masses. Similarly, their preferred units of length were parsecs and light-years.

I found those choices incredibly confusing (eg. what's the speed of light when you measure distance in light years? One light-year per year? Or is it 0.000000031709791983765 light years per second? And should we worry about leap years?)

But those guys worked with those weird units day in and day out, so they became second nature eventually.

We can discuss cursive elsewhere. All write?

Groan!

-Gnobuddy

[Gnobuddy]

Now, if we're talking data storage or going to the moon, I might expect to have to know a lot more...
Justin

Scientists and engineers have actually had to create new SI prefixes several times over the decades, as our science and technology keeps expanding downwards into ever-smaller sizes, and upwards into ever-bigger ones.

Thirty years ago only scientists knew what Tera stood for, though it has been an official SI prefix since 1960. It was such a huge unit that nobody would ever encounter it in ordinary life. Nowadays, we all know about terabyte hard drives, and there is nothing even remotely exotic about one. Amazing!

-Gnobuddy

[Jazz P Bass]

The 'original' definition of the meter was one 10 millionth of the distance from the equator to the North Pole.

I guess they had to start somewhere.

[Thoriated Tungsten]

Stop complaining y'all, or I will force the lot you to go back to using cm instead of Farad as the unit of measure for capacitance. One pF is about - yet not quite - 0.9 cm. (Or maybe it was the other way round...? )

Europe: You come across a nice WW-II era German military radio transmitter, yet you discover that one of the panel meters is missing a small screw. Eyeballing the size you grab an M3 screw from the parts bin, screw it in and continue on your way.

US: You come across a nice WW-II era US military radio transmitter, yet you discover that one of the panel meters is missing a small screw. You are now ready to kill yourself...

[nosaj]

Stop complaining y'all, or I will force the lot you to go back to using cm instead of Farad as the unit of measure for capacitance. One pF is about - yet not quite - 0.9 cm. (Or maybe it was the other way round...? )

Europe: You come across a nice WW-II era German military radio transmitter, yet you discover that one of the panel meters is missing a small screw. Eyeballing the size you grab an M3 screw from the parts bin, screw it in and continue on your way.

US: You come across a nice WW-II era US military radio transmitter, yet you discover that one of the panel meters is missing a small screw. You are now ready to kill yourself...

Actually I'd just retap it and go on. Of course though when I brek down equip i no longer have a use for I do have a been for modern and older screws.
nosaj