General Tech Information Everybody Should Know About

31
danmohr wrote:When you're adding an outlet to an existing circuit in your garage studio, don't double check that the power has been shut off for the circuit by moronically measuring the potential between ground (bare copper) and cold (white). It will be 0V. You will figure it's off because you thought you'd traced the Romex back to the box and killed the breaker. You will unscrew the little yellow cap, grab the white conductor and you will make contact with 120 VAC. It probably won't kill you, but it will scare the shit out of you - at least for a few minutes.


haha! in my limited homeowner/electrical fiascos i've used an uber simple light socket (plastic socket with 2 leads - about .99 at home depot) and lay accross leads to confirm/deny power.

of course it's critical that you test the bulb works when power is known to be on!

i learned that ghetto trick from my old man. resistance schmesistance. light=juice, no light=safe.

doing it the wrong way my whole life.

General Tech Information Everybody Should Know About

33
stackmatic wrote:When trying to loosen a stubborn nut/bolt/pipe fitting with a wrench, slip a length of pipe over the handle of the wrench you are using (thereby extending the length of the handle). The longer the pipe (i.e. the more added leverage) the better. I learned this trick from an old boat mechanic and have used it repeatedly over the years.


yes! leverage!

another i picked up from my grandpa - don't work harder, use a bigger hammer.

(use the most appropriate tool for a given task, even when you have something that CAN get the job done, use the best designed tool)

General Tech Information Everybody Should Know About

34
scott wrote:That would be a great subject for a post, to go into detail about impedance mismatches with tube amps, and what's maybe okay and what's maybe not.

For example, when I talked to Laney's tech support, and asked them what they thought of me hooking up a nominally-6-ohm cab in parallel with the internal 8 ohm speaker, and operating the amp using the 8 ohm tap, they said that they do not recommend a known impedance mismatch of any sort.



My rule of thumb is to NEVER run an amp into a cabinet rated at a lower impedance than the amp's output. Running a 6 ohm cab and an 8 ohm cab in parallel will produce a total impedance of somewhere near 3.4 ohms (don't have a calculator handy and I'm lazy, but that's a ballpark). If your amp wants 8 ohms and you feed it 3.4, it would be too easy to burn through an output trans. If your amp has a 4-ohm output, you'd probably be safe.

No manufacturer is EVER going to tell you that you can mismatch impedance ratings... because if you do that, and it fries your amp, they're liable. The safest way is to just match the impedance all the time. But then again, some car mfg's won't warrantee your car if you use synthetic oil... that doesn't mean it'll blow shit up, it just means they don't want to warrantee it.

I have no trouble plugging a 4 ohm amp into an 8 ohm speaker cabinet. But I'd probably frown on plugging a 4 ohm amp into a 16 ohm cabinet. In this case, your amp needs to work a little harder to overcome the unexpected impedance (layman's terms here) but it won't fry the amp if you're within safe bounds of it's available output. Don't mismatch your amp and cab and then dime the amp. (Hell, I don't dime my amp if the impedance is matched... hard on the ol' tubes).

Somebody else will inevitably be better able to explain this, but that's my $0.02
But then again, life is short and there are too many lies to tell.

General Tech Information Everybody Should Know About

36
skatingbasser wrote:This has been bothering me for awhile. How can you tune a B string on a guitar with harmonics?


using the 12-7 method.

the harmonic on the 12th fret of each string should match the 7th fret of the next one with the sole exception that the 12th fret of the g string should match the 8th fret of the b string.

granted, you're using a harmonic and a regular note for tuning rather than two harmonics, but it works pretty well, and you can still easily hear beat freqs
that damned fly wrote:digital is fine for a couple things. clocks, for example.

and mashups

General Tech Information Everybody Should Know About

37
skatingbasser wrote:This has been bothering me for awhile. How can you tune a B string on a guitar with harmonics?


Tune the 12th fret harmonic on the B string or 5th fret harmonic on the B string (same note, different octaves) to match the 7th fret harmonic on the low E string and/or high E string.

bookofkevin, you can use the 5th fret harmonic on one string to match to the 7th fret harmonic on the next highest string, and they match identically (except between the G and B strings).

Assuming your intonation is set properly, something I recommend checking is that the strings are in tune with each other when you skip a string as well, using unisons, like this:

low E string 10th fret = open D string
A string 10th fret = open G string
D string 9th fret = open B string
G string 9th fret = open high E string

Then there's the skip-string octaves

open low E string = D string 2nd fret
open A string = G string 2nd fret
open D string = B string 3rd fret
open G string = high E string 3rd fret

And the adjacent-string octaves

open low E = A string 7th fret
open A string = D string 7th fret
open D string = G string 7th fret
open G string = B string 8th fret
open B string = high E string 7th fret

and of course the adjacent-string unisons

low E 5th fret = open A string
A string 5th fret = open D string
D string 5th fret = open G string
G string 4th fret = open B string
B string 5th fret = open high E string

using harmonics and fretted notes, I also like to check all of the strings in multiple fashions. I recommend a multiple-approach process like this:

get the D string properly in tune
tune the G string 7th fret harmonic to match the D string 5th fret harmonic
tune the A string 5th fret harmonic to match the D string 7th fret harmonic
tune the low E string 5th fret harmonic to match the A string 7th fret harmonic
tune the high E string 12th fret harmonic to match the low E string 5th fret harmonic
tune the B string 5th fret harmonic to match the high E string 7th fret harmonic
check the B string 12th fret harmonic against the low E string 7th fret harmonic
check that the open B string = the G string 4th fret
check that the open G string matches the B string 8th fret
check that the low E string 10th fret = open D string
check that the A string 10th fret = open G string
check that the D string 9th fret = open B string
check that the G string 9th fret = open high E string

If you make it through all that and everything is in tune, that's great. If it never works out so all of these intervals can be in tune, your intonation is probably messed up.

And of course, never get a string in tune by detuning it (tuning it lower). Always do it heading *up* to hit the note. If the string you're tuning is a little sharp, rather than tuning it down a little, tune it down a bunch, like 2 or 3 frets worth, and tune up to get to the proper note.

Unless your guitar's nut is frictionless (which doesn't exist), you're better off not detuning. Or if you insist on detuning, either tug vigorously on all of the strings before you declare yourself done tuning. Or play the shit out of each/all strings for a few seconds and then check again.

Detuning to hit a note without following up with tugging or wailing is a good way to get your guitar in tune (all the notes check out) and then about 10 seconds after you're playing it nice and hard, you've got strings that have gone out of tune. Only being in tune for 10 seconds or less is pretty pointless. Don't detune!!!
"The bastards have landed"

www.myspace.com/thechromerobes - now has a couple songs from the new album

General Tech Information Everybody Should Know About

38
scott wrote:This thread is intended as a place where you can share pieces of information that you are really glad you learned, and you think everybody in the world of music/tech would benefit from knowing about...

I will start it off with something horsewhip brought up in another thread, something that everybody should know, and it's awesome to not have to learn it the hard way...

NEVER TAKE YOUR TUBE (VALVE) AMP HEAD OUT OF STANDBY WITH NO SPEAKERS HOOKED UP!

With tube amps, the output transformer is looking for there to be a very specific load attached to it (an impedance, measured in Ohms, as in "4 Ohms" or "8 Ohms" or "2 Ohms minimum") and if that very specific load is not there, the amp can get seriously fucked up to the tune of $100+ worth of damage.

You do not want to fry your output transformer! Do not take your tube amp out of standby without a proper speaker load hooked up to it!


TMH is correct. There's no point in being pedantic about this. What is stated above is true and the advice should be followed for using tube / valve amps - ie. they always need to be connected to the correct specified load.

There seems to be some misunderstanding from others who are confusing the load requirements of solid-state amplifiers. These amplifiers can generally operate with any load which is above the minimum stated impedance. This includes open circuit (infinity ohms) - ie. no speaker connected. Simple!

General Tech Information Everybody Should Know About

39
scott wrote:
skatingbasser wrote:This has been bothering me for awhile. How can you tune a B string on a guitar with harmonics?


Tune the 12th fret harmonic on the B string or 5th fret harmonic on the B string (same note, different octaves) to match the 7th fret harmonic on the low E string and/or high E string.


I don't know about you, but I usually tune low E first, then A, and then so forth. Going in that direction leaves you kindof fucked when you use the traditional harmonic tuning method (kindly described below). Unless of course you tune your hi-E to the low E based on the octave and then go down to your B and make sure they're all lined up that way, but that's way more complex and ear intensive.

scott wrote:bookofkevin, you can use the 5th fret harmonic on one string to match to the 7th fret harmonic on the next highest string, and they match identically
No shit.
scott wrote: (except between the G and B strings).

That's precisely what skatingbasser was asking about. A method that will allow you to bypass or at least say "fuck you" to the "except between the G and B strings"

The method I proposed (if you understood it right, if I explained it decently) involves using one harmonic and one note. It will allow you to hear beat frequencies better than using the 4th fret G / open B method and also enable you to use at least one harmonic in tuning the B string to the G
that damned fly wrote:digital is fine for a couple things. clocks, for example.

and mashups

General Tech Information Everybody Should Know About

40
A couple of notes to add-
1. The above warnings about tube amp voltage hold doubly true, even if the amp is disconnected from AC. Keeping one hand in your pocket doesn't always help, though. My first real amplifier was a Laney ProTube 50. It had been unplugged for about 6 hours, and was still unplugged when I opened it up and immediately shorted out one of the AC filter caps with my hand. Kicked me across the room...I actually saw white for a couple of seconds. The muscles on my arms and chest ached for quite some time from the instantaneous hyperflexion. Stupid.
2. The aforementioned XLR layout isn't always true...sometimes European equipment reverses the polarity on the positive and negative sides. I found this out the hard way when we sold NASA some sound gear that included a Harmond Kardon parametric EQ. RTFM.
3. You can use speaker cable as instrument cable, if you absolutely need to. It might add a bit of noise to your signal, but it won't hurt anything.
4. Cocaigne and potentiometers do not mix.
5. You can build perfectly serviceable guitar straps out of duct tape.

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