Re:[Harp-L] Modeling vs. Real Amp ++

Well ..... this started as a simple reply ....

If we want authentic ChiBlues sound, the best way to get it is like the originators did, with overdriven tube amps and suitable microphones. Amp modelers are done in software, using digital signal processing (DSP). These can do a pretty good job if carefully adjusted, but even at their very best, they're a compromise. Depending on the sampling rate, they tend to have a dimensionally "flat" sound due to phase shifting at higher frequencies, which is where much psycho-acoustic imaging occurs. Our ears sense direction by measuring time differentials between our two ears. Even so, modelers have their place. They're small, easily portable, pack a lot of variety into a small package,and offer a lot of bang for the buck. They're very common in recording studios. High end recording software (i.e. Pro Tools) make use of DSP for many options, including but not limited to amp modeling.

If we're looking for "that" sound, we just can't beat a real tube amp. Vacuum tubes, sagging power supplies, and loudspeakers driven to their maximum excursion deliver "that" sound, not in spite of, but *because of* inherent "flaws". It's no accident that the best players favor larger sized tube amps. Fortunately, "size doesn't matter", and we can use a combination of tube amp and PA. A small amp (like a Fender Champ) can be mic'd thru the PA. The biggest complaint many have with this setup is that what we hear is now dependent on the sound person. For some unfathomable reason, some sound men bury harp way down in the mix, or EQ it into a thin, trebly, tinny parody of harmonica.

If we only want a louder harmonica, we don't need - or want - an amp modeler. Modelers by definition *change* the original sound. If we're happy with our raw sound, the sound from a particular mic, cupped, uncupped, close, a few inches, or from a greater distance, all we need is the classic audiophile definition of a pre-amp/power amp "straight wire with gain". This idealized amplifier would have but one control, a "loudness" control.

Loudness? Mike, don't you mean "volume control"? Aren't they the same?

No. Volume simply adjusts gain for all frequencies equally. This is nice - but it's not how our ears hear.

Try this experiment when it's REALLY quiet. On your stereo, make sure the LOUDNESS switch is off, set bass and treble to "flat" (zero, straight up, mid-scale), volume to a comfortable, moderately loud listening level, and play a CD, etc., that has a really high fidelity sound and a full range of bass and treble content. Notice the bass, and the shimmering cymbals vocal sibilance (e.g. "S" sounds), or other highs. Note the position of the VOLUME knob, and write it down.

Next, turn the volume WAYYYY down, so you can just *barely* hear it, and replay the same tune. You can hear midrange - voice, guitar,and such. But - where did the BASS go? Where are the cymbals and sibilance? (And why did I have you turn off that Loudness switch?)

Well, let's try turning LOUDNESS back on. Hear the bass and treble change? OK - now turn LOUDNESS off.

Next, adjust bass and treble so the music sounds like it did at the higher volume and you can once again hear the bass and treble content.

Now, turn the volume control back where it was originally. Notice how much LOUDER the bass and treble has become?

And finally, return bass and treble to their flat positions. That's how much louder bass and treble need to be to "sound" the same at lower volume.

Yes, our ear hears differently at different sound levels. At lower sound levels, our ears are more sensitive to midrange. At higher sound levels, our ears become relatively more sensitive to bass and treble. This is known in scientific circles as the "Fletcher-Munsen curve". To keep the SOUND the same, we need to compensate for Fletcher-Munsen, and alter bass and treble as a function of volume. When we do this, our simple volume control becomes a LOUDNESS control.

It's good for musicians to understand loudness. If we need to play at lower volume, the tone settings we use at higher volume won't sound the same.

But - there's more to loudness than Fletcher-Munsen. As volume increases, our ears ability to separate sounds becomes more limited. Muddy Water's bands had constant harmonica - but their volume was not much higher than acoustic. Unamplified double bass, 5 watt harmonica amps, and PAs that required no monitors (in fact, when playing vnues that had sound reinforcement systems with monitors, Muddy had the monitors turned off) allowed the harmonica to be played constantly without interfering with vocals. This model doesn't work at high volume, especially when the vocalist is being obliterated by a blaringly loud guitar ("If you can't hear the vocalist, you're playing too loud").



On Mar 8, 2006, at 1:38 AM, George Leung wrote:

From what I gather on the web, if one want a good approximation of the
Chicago Blues effect, the emulators (ala POD-II, V-Amp) are good enough. However, what if I use amps mainly to boost the volume to the harp? (In fact, do I even need amps if that's all I want, considering I can just feed into a PA system?)

Also, I am deciding between Behringer V-AmpII and X-V-Amp. Which one would be better for the context of playing?


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