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Thread: Amplification Basics for Uke: Pickups, Mics, Preamps, Amps, Feedback

  1. #1
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    Default Amplification Basics for Uke: Pickups, Mics, Preamps, Amps, Feedback

    There are several ways to amplify acoustic instruments. Amongst the most common are:

    * Piezo transducer pickup
    * External microphone
    * Internal microphone pickup


    The most popular are the transducers of which there are two main types:

    * Under-saddle transducer
    This is a thin strip element which is placed in the bridge slot underneath the saddle insert. A thin cable goes through a small hole drilled down through the end of the slot and into the body cavity. This is the kind of pickup found in most electro-acoustic instruments.

    * Surface-mounted "bug"
    The bug type is a small stick-on transducer. They are usually mounted inside the instrument just beneath the bridge, or sometimes externally, often behind the bridge.

    Both of these types generally use a piezo element - a piece of material that generates a small electric charge when bent, squeezed or subjected to vibration.

    Active and Passive Pickups, Preamps

    If a pickup element is wired directly to an output jack, then it is a passive pickup. Passive pickups generally produce a fairly weak and thin signal which will benefit from boosting before going to an amplifier.

    Boosting, and sometimes tone modification, are done by a preamp, which is a kind of mini amplifier designed to add gain and sometimes some EQ modification. You may have seen electro-acoustic instruments which feature a little control panel with volume and tone controls and a battery compartment - that is usually a preamp.

    An active pickup is a pickup system which includes some kind of preamp.

    Onboard preamps usually have to include a battery. For this reason they add weight to the instrument, and require some wiring inside.

    Many players prefer to minimise weight and clutter by having a passive pickup, which needs no battery. A passive pickup will often be used with an external or outboard preamp such as a Fishman ProEQ II, Fishman ProEQ Platinum or LR Baggs Para Acoustic DI.

    Here are a couple of earlier threads discussing pickups and preamps:
    http://www.ukuleleunderground.com/fo...ad.php?t=17485
    http://www.ukuleleunderground.com/fo...ad.php?t=18172


    Microphone Pickups

    Another kind of pickup is the mini condenser mic. These mount onto an endpin jack as in the case of the Washburn ROMP, or onto an onboard preamp. Mini condenser pickups are tiny microphones and they are sometimes used in combination with piezo pickups, like those described above, in order to give versatility of tone. The Fishman Blend systems feature this mixture of piezo and mini condenser mic.

    External Mics

    External mics used to amplify acoustic instruments are usually condenser mics. The two main kinds are the large diaphragm type, such as the Behringer C1, and the small diaphragm kind such as the Shure PG81. Condenser mics, unlike dynamic vocal mics, need a bit of extra power which may be supplied by a battery or, more often, by what is called phantom power. Phantom power comes from specially equipped amplifiers through a cable fitted with 3-pin mic connectors called XLR.


    Pros and Cons:

    Under-saddle
    Pro: Comparitively good resistance to feedback; not much handling noise; usually reliable; allows freedom of movement on stage
    Con: Not a faithful reproduction of the instrument's acoustic tone

    Stick-on bug
    Pro: Easy to fit; inexpensive; usually reliable; allows freedom of movement
    Con: Not a faithful reproduction of the instrument's acoustic tone; prone to feedback problems; often suffers significantly from handling noise; can suffer from a percussive "thump" as fingers/pick strike strings

    Internal mic
    Pro: More natural sound than piezo pickups
    Con: Prone to feedback and handling noise

    External mic
    Pro: Very good sound reproduction; doesn't amplify handling noise
    Con: can have feedback problems; limits the performer's freedom of movement on stage as the player usually needs to play right into the mic.


    Amplifiers

    Ukuleles will work fine with guitar amplifiers or they can be plugged into a PA.

    If one uses a guitar amplifier the main choice is whether to use a standard guitar amp or a purpose-designed acoustic amp.

    A ukulele pickup will work with either amplifier. The difference is that a standard guitar amp is made to work with magnetic pickups. An acoustic amp will usually be designed to also work well with piezo pickups and mics. Players who seek a natural acoustic tone will often select an acoustic amplifier.

    Here's an extensive earlier thread on the subject of amplifiers:
    http://www.ukuleleunderground.com/fo...ad.php?t=12784

    And another thread with info on pickups, preamps, DI boxes and amplifiers:
    http://www.ukuleleunderground.com/fo...ight=behringer


    Feedback

    Feedback is a problem for amplified acoustic instruments more than for solid bodied instruments.

    There are several ways to tackle feedback. The player may need to employ a combination of these measures. The physical approaches are:

    * Positioning
    * String/body damping
    * Soundhole blocking

    Electronic measures are:

    * Phase switching
    * EQ and frequency filtering

    Positioning

    Positioning the player and his instrument away from speakers can do a lot to eliminate feedback. If the player is playing into an external mic then it is wise to ensure that speakers and monitors do not point in those directions that the mic is designed to monitor. You don't want the amplified sound coming from behind the player and going into the mic.

    String/body damping

    In some marginal situations the feedback occurs when the instrument is idle. In this case it is often enough to simply place a hand across the strings, or across the strings and soundhole. This stops sympathetic vibration and reduces the tendency to feed back.

    It is also often possible to stuff cloth or foam inside the body of the instrument, although this can damage wiring if not done carefully, and can affect tone. I have not found it to be a very convenient solution.

    Soundhole blocking

    Guitarists put black rubber or plastic plugs in the soundholes of their guitars. These "feedback busters" can greatly lessen feedback, sometimes eliminating it altogether. They are available in several sizes, although they can be hard to find in uke sizes. However, it is easy to improvise plugs for most uke soundholes using various plastic stoppers and plugs. E.g., a mailing tube end plug can be adapted to fit a Makala soprano, and the plastic lid from a gravy granule container will fit a Kala tenor.

    These plugs do have a noticeable effect on the tone of the instrument, so some players try to balance maximum feedback reduction with a minimal effect on tone by having small holes in the plug.

    Electronic measures

    Phase switching

    A phase switch is a two-position switch on a preamp or amplifier. If feedback occurs with the phase switch in one position, flipping it to the other position often reduces the problem.

    The Fishman ProEQ II, Fishman ProEQ Platinum and LR Baggs Para Acoustic DI Preamps all feature phase switches, as do the Marshall AS series acoustic amplifiers and many other acoustic amps.

    EQ

    The simplest EQ-based anti-feedback measure to use is the notch filter. A notch filter is one of the most effective measures to be found on most acoustic amplifiers. It is simply a knob which, when switched on, suppresses a narrow band of EQ frequencies. When feedback occurs one simply switches on the notch filter and then turns the knob until reaching the point where feedback is eliminated or minimised. In my opinion, this is one of the most useful features to look for on an acoustic amplifier.

    The Marshall AS acoustic amplifier series models feature notch filters. The Fishman ProEQ Platinum and LR Baggs Para Acoustic DI preamps both feature notch filters.

    If your preamp or amplifier do not have a notch filter facility, a guitar multi-band EQ can help. It is sometimes possible to locate the frequency band within which the feedback is occurring, and to cut it by reducing the level of the slider/knob controlling that band.

    Guitar multi-band EQ pedals are available from Boss and, more affordably, from Behringer.


    NB 1: No financial interest in any products linked. Examples are simply chosen because they are products with which I am familiar and of which, in most cases, I have first hand experience.

    NB 2: I'll expand and tidy up this article as time allows. Corrections and suggestions are most welcome, thanks.


    Last edited by buddhuu; 07-08-2010 at 03:40 AM. Reason: update

  2. #2
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    Thanks, buddhu!! This should be a sticky for this forum....mods?

    People here have been needing something just like this....
    Things get better with age. I'm approaching magnificent....

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    "And if you don't know where you're going, any road will take you there..." - George Harrison

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  3. #3
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    Thanks so much for this helpful post!!
    Somebody definitely oughta sticky this.
    Those are my principles, and if you don't like them... well, I have others.--Groucho Marx

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    awesome buddhu thanks

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    Wow, tons of great info. FB friend request sent.

  6. #6
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    I don't see a specific category for types of PA systems for the performers here. This amp basics seems to be the closest. I wanted to know from the performers here what systems they use to perform with and any additional instrumentation they use to enhance their performances. I use a Bose L1 Compact PA. It's very light (35 lbs) and very portable - sets up in under 5 minutes. I also use a Porchboard Floor Bass to add some bottom percussion. I also use a Digitech Vocalist 4 pedal that give me harmony when I sing.
    My News is Blues!
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  7. #7
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    I did plan to add a section about PA, but I'm afraid the original post in this thread is right at its length limit.

    I may do a separate thread giving an overview of PA equipment, then everyone could chime in on that thread with their own experiences and recommendations for PA gear. Just a matter of finding the time.
    And whether the blood be highland, lowland or no,
    And whether the skin be black or white as the snow,
    Of kith and of kin we are one, be it right, be it wrong,
    As long as our hearts beat true to the lilt of a song.

  8. #8
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    Hi All,

    i am getting a custom made soprano with built in amp with volume and tone control.

    Is it ok for a soprano to have this built in? Cause i usually see concerts and tenors with built in

    Thanks

  9. #9
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    It's fine to have whatever you like, but a few things you may want to consider.

    A preamp with controls is generally a slightly bulky and weighty affair - largely due to the battery and its housing. On a soprano this extra weight is likely to be more noticeable than on the larger uke sizes.

    Depending upon the quality of the ukulele and the acuteness of your hearing, there is also a chance that the presence of a large preamp could affect the unplugged sound - partly due to the mass of the unit, and partly because it occupies volume inside the body's air chamber. A very finely tuned and crafted instrument could be affected slightly. There are critical ratios observed by some builders regarding things such as area of sound hole to air chamber volume etc etc. Whether the difference would be audible to an average listener I have no idea.

    If you are planning to play mostly amplified then the only real issue is if the extra weight annoys you.

    Options to consider that may lessen the extra weight/bulk:

    • Pickup only - keep all controls and preamp external
    • A passive vol/tone control with external preamp - no battery on-board, so smaller and lighter
    • MiSi pickup. Uses a rechargeable capacitor instead of a battery. Smaller/lighter and very popular with UU members.
    And whether the blood be highland, lowland or no,
    And whether the skin be black or white as the snow,
    Of kith and of kin we are one, be it right, be it wrong,
    As long as our hearts beat true to the lilt of a song.

  10. #10
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    Hi BuddhUU,

    Thanks so much for your reply..

    I usually play the uke at home. Just thought i will get the built in just in case i need it.

    But will def think about it after reading ur comments

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