Can anyone recommend any sources on this subject? More specifically, I'd like to know what the amplified setup (i.e. tube amp + mic + cupping) actually does to the sound, tonal range and the harmonics of the harmonica. WHY does it sound like a totally different instrument?
How much of it can be compared to electric guitar's distortion? Does the harp have aural characteristics that are unique in this sense?
I don't know if this has been discussed here 10 times before, but if anyone can share sources, explain this briefly or link a thread from this forum, I'd appreciate it.
Phew! How about a hard, complicated question next time? ;-)
There's no legitimate "science" per se, more observed behaviour, empirical testing & deduction...comparisons with other instruments are impractical.
Cupping is the critical aspect, if you play uncupped into an amp you will hear more of the natural instrument if your amp is set clean & if the speakers will handle the full range (guitar/harp amp speakers typically shelve around 8kHz, but this can be extended by multi speaker set ups). A PA system is an "amp", a clean amp typically, with full range speakers...nobody who plays to large audiences does so purely acoustically, as if 2 or 3 people started talking, they would then go unheard!
When you cup up you damp/shut down a lot of the higher frequencies that would be heard if playing the harp in free air, this is exacerbated by the mic's diaphragm also no longer working in a free air environment & it's characteristics subsequently changing.
Really, none of it can be compared to an electric guitar, solid body guitars have very limited (but still some) acoustic attributes, semi-acoustics have more but are predominantly still heard via the magnetic pick ups (harps don't have magnetic pick ups, closest thing is Jim Antaki's optical pick up ELX harp?). The equivalent of what we do with a harp would be to take a solely acoustic guitar, have someone tightly cup a mic over the sound hole (somehow without fouling the strings?)...it is entirely impractical and would take 2 people to amplify one guitar...badly.
Additionally, hi-z mics (& low-z mics fitted with matching transformers) with harp produce very large signal voltages (in excess of a volt AC typically), which affects the following amplifier differently to a low level signal derived from a magnetic pick up (~100-800mVAC).
Those are the facts, sorry about the lack of "science"...you can imagine I am wearing a white lab coat & making notes on a clipboard if it makes you happier? :-) Remember science is often the tool we use to explain & quantify how/why things that are already happening & have been happening for millennia in some cases...long before humans & before they coined the term.
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Last Edited by on Sep 05, 2012 12:00 PM
Thanks. The reason I mentioned guitar is that I heard once that some distortion effects create a kind of harmonic interval of effect. It sounds crazy and I don't know what it's about, but at the same time it sounds somehow reasonable as many heavy metal distortions make electric guitar sound like there's more than 1 note playing. It doesn't apply to the harmonica as such I'm sure...
A HARMONIC is a sound which is a multiple or fraction of the fundamental sound, where the multiplier or divider is a power of two.
For example, say F = the fundamental frequency, any frequency, but lets use 440 cycles per second which makes the note called A in the middle of the piano.
So F = 440.
The powers of two are 1, 2, 4, 8, 16, 32... each number twice the one before.
As multipliers we get 1F, 2F, 4F... etc. = 440, 880, 1760, 3520... etc. cycles per second. All of these are also the note A but in successively higher octaves.
As fractions we get F/1, F/2, F/4... etc. = 440, 220, 110... etc. cycles per second. All of these are also the note A but in successively lower octaves.
When a tube is overdriven (the input voltage from the mic is greater than the 'clean' range of the tube, the extra energy is lost or pressed back down which changes the shape of the cycles from sine waves (or complex mixtures of multiple sine waves of different frequencies) to waves flattened and shoved sideways near the top of the waves - all that is 'distortion' and it sounds different from the original signal - sometimes better, sometimes worse, according to your own preference.
These distortions usually sound like they've been generated on top of the fundamental sound, added to it at lower volumes, making a more interesting, or perhaps distressing, sound. This might sound like more than one simultaneous note being played, but generally it sounds like 'fizz' or 'crunch', or one of many such subjective terms, otherwise categorized as noise.
Last Edited by on Sep 07, 2012 8:12 AM
5F6H's answer is as close to science as you can get. Note that it isn't just the amp that makes harmonics. Any time you combine two notes, you get not just the fundamental frequencies, but harmonics that come from the addition and subtraction as the two fundamental sine waves get into and out of phase with each other. And because the sound a harp makes isn't a pure sine wave, even single notes have these. The amplifier amplifies these - which may otherwise be inaudible. The best example is that if you play a chord, a bass note is produced - it is hard to hear acoustically because it is a much lower frequency at much lower volume. But with an amp, you usually CAN hear it. As you draw a 2-3 chord, for example, harder and harder, one of the reeds will bend slightly and the bass note can be heard to "sag" - it starts out in tune and goes out of tune creating BIG distortion.
@ Bluemoose - Ha ha, not going there, it's of too much a potential minefield... especially with the language issues, what with "pants" & "suspenders" having very different meanings depending on which side of the pond you live..:-) ---------- www.myspace.com/markburness
Great video on wave forms , harmonics and intervals Greg. Thanks for sharing that. It filled in and solidified what I already knew. I just recently started using an oscilloscope on my amp bench. At some point it would be interesting to study and learn to 'read' distortion trace what parts of the mic/ preamp/ amp circuit generate the types of crunch we like. ----------
Last Edited by on Sep 07, 2012 5:52 PM
I've looked at the signal from the input all the way through a Kalamazoo on an oscilloscope, using a harp mic and harmonica for input. It is so distorted at the beginning, there's no hope of seeing much useful past that. I think the only way to see what's going on in the amp is to use a signal generator and begin by feeding it very clean signal. ---------- /Greg
Interesting, thanks. I don't have a dedicated signal generator yet, except as computer and iPhone apps- which I suppose I could set up to use. ----------
if you dampin a note on guitar and release you get overtones jump out in your ear so i guess that hard cup on harp is a dampin and brings out some overtones that usualy stay back,anyway fat tone is overtones ringing out with the main note... and thats with any instrument and voice....and a master player can manipulate overtones and make them sing !
