errors in The Ultimate Tone by K. O'Connor

[rjb]

Tera is a base-10 unit, hence the introduction of the more accurate Tebi (and similar for other units) to describe base-2 magnitudes.

Thanks for that. I just learned the difference between kB, KB, and KiB.
https://en.wikipedia.org/wiki/Kilobyte

[mooreamps]

here . here ......

[R.G.]

Welcome back, Gary.

[Gingertube]

There are 10 types of people in the world - those who understand binary arithmatic and those who don't.

On the metric System:
As a design eng of 30+ years I note that we Engineer types stick to powers of 3, that is: pico, nano, micro, milli, kilo, mega, giga etc., but then blow our cred. by using capital letters for just the mega(M) and giga(G) - surely the kilo should therefore have been "K" not "k".
As for the SI Units themselves, lower case first letter for all except for those (well most actually) where the unit is a persons name such as Ohm, Volt, Ampere.

Scientist types tend to be all over the shop.

Gets difficult when trying to talk with Scientists.
As one example:
The Laser System I design in the day job is used worldwide including in the US, so it has to comply with both International Standards and US Standards. The US standard does use metric BUT all laser exposure limits are given in milli-Joules per centimeter squared. Converting that to Joules per metre squared to check agaisnt the International Standard is a pain. That tells me that the US Standard was drafted by Science Types with no reference to Engineer types who have to make it work (not an un-common practice).

OZ converted to metric in 1978 - The attached "Electronics and the metric system" from the Metric Conversion Board was published in Electronics Australia at that time. I have had it in my file of "mostly useless information" since 1978 and it has been handy quite a few times over the years..

Cheers,
Ian

[SoulFetish]

an EL84 is minus ten Hoovers?

-Gnobuddy

How DARE you, sir?!

[J M Fahey]

The US standard does use metric BUT all laser exposure limits are given in milli-Joules per centimeter squared. Converting that to Joules per metre squared to check agaisnt the International Standard is a pain.

Just multiply by 10 or move the decimal point one place to the right, whichever causes less pain

[Gnobuddy]

How DARE you, sir?!

I'm actually surprised it took this long for someone to chew me out over that little jibe.

Just kidding in the spirit of this thread - my own ears have never loved any amp with EL84s, but of course I know they're one of the most popular guitar amp valves on the planet!

-Gnobuddy

[Justin Thomas]

(Looks around for a Mr. Potatohead with a hidden camera) "Oh, good, he's not here... Anyway, what is popular is not always right..."

Justin

[Gnobuddy]

Anyway, what is popular is not always right...

Heh. Fanning the flames, are we?

Tubelab George on the DIY Audio forum said it best, I think: "...6V6's were made to sing the blues but EL84's rock!" (Frequency Response of Output Tubes - diyAudio, see post #5)

Me, I like small, bluesy (or even less) amounts of distortion, so that you can still play, say, a minor seventh chord, and not have it sound awful, and single note guitar solos still sound like a guitar. People who think the proper number of notes in a "chord" is two, root and fifth, and single note solos should sound like an angry power tool, will probably like EL84s better.

It's not just about 6V6s and EL84s. It seems that true pentodes (like the EL84) intrinsically have a tendency to generate more third harmonic distortion, and less second harmonic distortion, than a beam tetrode (like a 6V6). In fact excessive 2nd harmonic distortion was considered a weakness of the original 6L6 beam tetrode design, and the design whitepaper reassures readers that this will cancel out when used in push-pull topology!

Anyway, to my ears, more third harmonic typically seems to sound a little growlier or edgier or more like rock, while more second harmonic tends to sound smoother and more vocal and more like traditional bluesy tones. The EL84's high transconductance also makes it easy to overdrive the heck out of the things, at which point they are "crunchy" to some ears, but "harsh" to mine.

It's fun experimenting with small-signal beam tetrodes (rather than pentodes) in guitar preamps - to my ears, you can get some very nice singing timbres out of them, and they don't sound exactly like those vintage pentode EF86 preamps. Some of the unloved later-generation "TV tubes" on the dollar menu are really beam tetrodes even when the datasheet says "pentode", which you can verify easily enough by taking a magnifying glass and counting how many support rods you can see holding grids inside the glass envelope. Only four support rods? There are only two grids, ergo, it's a beam tetrode, and not a pentode.

-Gnobuddy

[Justin Thomas]

I was just trying to get Chuck's attention, as the foremost proponent of EL84s in these parts that I can think of... But I know he kills them, too. Data sheet, my ass.

I actually made 2 EL84 amps. I liked both of em.

Justin

[Chuck H]

I push my el84's a little at 360ish Vp and 330ish screens, 470R screen grid resistors and biased hot at idle too, but the bias rise at the cathode R is fixed by a zener to get a fixed AB bias when clipping hard. I've taken to using the Rusky 6p14p-k tubes because they're more rugged. IMHE the regular offerings WILL take excessive voltage and current just fine, but jingle like Santa in short order. So I'm trying something new.

I also use efficient speakers. I get 17ish watts from a pair and the combination of pushing the tubes and the efficient speaker make this design useful for MOST small to medium size rooms. But one thing I will admit...

As small bottles go, if I were going to gig a medium sized room and I had to pick (sound unheard) between anyone else's el84 amp (of unknown performance) or their 6v6 amp (of unknown performance), I'd pick the 6v6 amp because there's a greater likelihood it will be loud enough. I got bit by a pipsqueak 2xel84 amp on stage once at a jam night.

[Justin Thomas]

I'd pick the 6v6 amp because there's a greater likelihood it will be loud enough. I got bit by a pipsqueak 2xel84 amp on stage once at a jam night.

Because everyone is afraid they'll blow up their EL84s. Myself, I follow my tech's advice when I asked how far I could push them: "tubes are cheap."

Justin

[Chuck H]

My amps are equipped with an OT driven line out. I "suggest" a mic in front, but as anyone who gigs knows there isn't always an extra input on the board. Speaker efficiency is paramount. Interestingly, the Vox AC30 is notorious for it's audibility in the mix. I wouldn't say that the amp is "cutting" though it IS bright. But it's also smooth. There's a reason it's popular. My customer with the 4xel84 version of my amp might be the only one that plays out a lot and he hasn't had a complaint. I'm considering making 4xel84's the standard. The 2xel84 thing CAN be made to "work" but it might be passé. In the end... There's nothing "wrong" with el84's except that they just don't put out that much power and volume. I still love that tube and I still love the 2x design. It's just the right amount of volume to get things humping acoustically WRT feedback in a closed room (studio, bedroom, etc.) Without pushing it to 17W (most "18 watt" amps are putting out 13W to 15W) and using an efficient speaker the 2x design is a little short of stage work without a mic or line out bump. Especially if you want to play any clean tones. Truth.