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Dirty-South Blues Harp forum: wail on! >
Acoustic amps, whats the difference?
Acoustic amps, whats the difference?
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Oisin
812 posts
Jun 05, 2011
6:49 AM
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What is the difference between Acoustic amps and "normal" amps. I know they will be used for amplifying acoustic instruments but why are they different to guitar amps, i.e components, valves etc
Can they be used for harp?
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Oisin
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5F6H
709 posts
Jun 05, 2011
7:50 AM
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"Can they be used for harp?" amps just see a signal voltage, they don't know what kind of instrument is producing that voltage. Problems may occur if the signal voltage is so large that it distorts the input stage (often the case with guitar amps used for harp, which can make whole volts at the input, compared to say, 0.05VAC for some acoustic pick ups). By "distorts", I mean adds any artefacts/harmonics/compression/fuzz etc., that were not there prior to the input. Regular guitar amps are not really designed to do this, they are designed to "colour the sound in a flattering (to the manufacturer's ear) manner.
An amp designed for an acoustic instrument will usually be designed to pick up a signal from an electro-acoustic guitar's piezo or electret condenser pick up...so not really "acoustic" in the truest sense (to capture the full acoustic nuances of a guitar you would often put a sensitive mic, or two, in front of the instrument, but on stage this isn't always practical), but the point is that they are designed to let the (theoretically) uncoloured sound of the instrument shine through.
Some acoustic amps agitate a solid board, instead of a speaker cone, I'd avoid these unless you do an A/B test as I have no idea how well they work for harp.
There is no specific topology or type of amp/valve/component that would suit one better than the other...apart from perhaps an extended hi frequency capability on the "acoustic" amp (most guitar speakers only reproduce up to 6-7kHz - more for the same speaker in a multi speaker array), you might want well over 12kHz to give the impression of a clean pure sound for acoustic), which may have hi frequency "tweeters".
Probably best for those who seek a brighter, less coloured tone...this doesn't describe the vast majority of harp players that I see or hear. But really suitability comes down to the specific amp in question, rather than it's perceived use...like a 70W UL Pro Reverb will probably make a better "acoustic" guitar amp than many 15-30W acoustic amps. So don't rule them out, just be sure to compare them to a known good datum. Don't be hoodwinked by sales blurb/specs.
A regular valve guitar amp can usually be modified relatively easily to improve its performance with an acoustic instrument.
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swampboy
45 posts
Jun 05, 2011
8:29 AM
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I've used an acoustic guitar amp for harp a few times, mainly in an acoutic duo where I was also playing guitar and there wasn't much room for multiple amps.
The tone is broadly similar to a playing straight into the PA tone (depending how you set it up).
As 56FH says, you need to check that the input signal is not clipping too much, most acoustic amps have some sort of indication for this....anyway you would be much better off using a low impedance vocal mic with this set up, and a lot of these amps also have a dedicated mic input.
Why not just go through the PA? Well you have better control over your sound/ monitoring and can tweak as you play.
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Baker
124 posts
Jun 06, 2011
5:29 AM
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Hi Oisin. I don't know anything about the technical side of things, however I do use a Marshall Acoustic amp [http://www.marshallamps.com/product.asp?productCode=AS50D] as my main amp.
I use an SM57 plugged into the dedicated mic (XLR) input. This set up has a really lovely warm tone and a bit of bite. The amp also has a built in reverb.
However it doesn't produce the kind of over driven Chicago blues sound very well. I have tried it with a Harp Attack pedal and a bullet mic with an old CM element in and it sounds terrible.
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colynjames
14 posts
Jun 06, 2011
5:55 AM
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Most acoustic amps are designed with a "clean" sound in mind. Some amps have a really "treble" clean sound, which can be harsh unless your instrument or sound calls for a more biting tone. In general, however, most acoustic amps strive to have a "warm" clean, clear sound that isn't harsh, but is very representative of the instrument played through it. For harp, if the mic you use doesn't "dirty" up the sound or otherwise color it, your harp with sound pretty much like you are playing through the PA, as stated above, and it's going to be extremely hard to "play dirty" through that sort of rig normally.
If you play harp "acoustically," it may serve you in some capacity to have an acoustic amp, but most acoustic players I've seen are just playing through a PA and don't really need a practice amp or even their own mic, although some people don't like you to moisten their mics for them, so it doesn't hurt.
So the short answer would have been...acoustic amps suck for what is known as "amplified harp" today.
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Oisin
816 posts
Jun 07, 2011
10:15 PM
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Chaps,
thanks very much for this info. I looking at a Carlsboro Shearwood Acoustic amp which was going cheap on ebay here in the UK but I don't think it's what I'm after. I do like the overdriven, dirty sound so I don't think it's for me.
Hey Baker...it's good to hear from you again.Hope you are well.
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Oisin
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