How Are Passive Soundhole Pups Different from Electric Pups?

[Hoodster]

Whenever I read threads discussing passive acoustic soundhole pickups like the Duncan Woody or the Fishman Neo, people always say you need a preamp or you will have to turn your amplifier up so loud it will feedback, etc.

I’m wondering why the Duncan Woody, for example, would be any different from plugging an electric guitar with a Duncan passive pickup into an amplifier without a preamp?

[pieterh]

Originally Posted by Hoodster

Whenever I read threads discussing passive acoustic soundhole pickups like the Duncan Woody or the Fishman Neo, people always say you need a preamp or you will have to turn your amplifier up so loud it will feedback, etc.

I’m wondering why the Duncan Woody, for example, would be any different from plugging an electric guitar with a Duncan passive pickup into an amplifier without a preamp?

It’s a bit misleading to say that you would have to turn your amp up to compensate…

Many passive pickups have a strong enough signal to not really need a buffer (preamp or line box) in between the guitar and amplifier. In fact an amplifier has a preamp section (input volume, eq section, etc). The important thing is to understand gain structure even if only in the amplifier itself so that signal relative to noise floor is strong enough (signal to noise ratio). A line box to balance the signal will usually improve the signal to noise ratio and help the signal travel longer without degrading (via balanced microphone cable). Making the comparison with an electric guitar with passive pickups is not really fair - the solid or even semi-hollow (such as 335-style) are not as sensitive to feedback-causing resonance whereas an acoustic by definition relies on its own resonance chamber (the guitar body).

A pickup with a preamp built in will often have a stronger signal relative to its noise floor, though even here balancing can be a good idea, depending on the potential cable length and what kind of amp is receiving the signal. What’s more an onboard preamp often adds volume and eq controls and even polarity switch and tuner options.

Having said all this, I almost always use a floor preamp with all my acoustics. In my opinion although you don’t NEED a preamp with passive pickups the additional control you get with an external preamp is hard to beat.

[Doug Young]

Originally Posted by Hoodster

Whenever I read threads discussing passive acoustic soundhole pickups like the Duncan Woody or the Fishman Neo, people always say you need a preamp or you will have to turn your amplifier up so loud it will feedback, etc.

I think this is a misunderstanding somewhere. What matters as far as feedback is how much sound reaches your guitar, and how much it picks that up, triggering feedback. It doesn't matter where the volume comes from - a hotter pickup with the amp gain set low, or a weak pickup with the amp gain set high.

I’m wondering why the Duncan Woody, for example, would be any different from plugging an electric guitar with a Duncan passive pickup into an amplifier without a preamp?

It's not different, the woody is essentially the same as an electric guitar pickup, possibly with some "voicing" to be a tad (but only a tad) more acoustic-sounding. What a preamp does for you is:

1) Impedance matching. Not usually as important for a magnetic pickup, as these tend to be lower impedance than, say, a K&K, which needs to see a high input impedance. But impedance does affect mag pickups, and there are preamp/DIs that provide variable impedance controls specifically for magnetic pickups. Do you need that with a mag? No, but it's a feature that helps sculpt your sound.

2) Buffering and noise reduction. By putting the first amplification stage close to the source, then sending a very low impedance balanced line to a PA, you avoid issues from long cables, like picking up noise, frequency loss of various kinds due to cable capacitance and resistance. Less important if you're just plugging into an amp with a short cable.

3) Useful features. Mute switches, EQ, boost switches. Volume. Routing to both PA and amps. Feedback control (notch filters, etc). All under your control instead of having to ask the sound guy to turn you up or down. If you're not using a PA, but an amp, this may also be less useful, but many preamps have more features than typical amps, better EQ, the feedback controls, etc, so you may still find it helpful.

4) Sort of all of the above, but a preamp gives you a known entity to plug into, so that when you show up to the gig and have no idea what you will be plugging into, you at least have some isolation from whatever junky system they may be providing.

[shufflebeat]

Originally Posted by Doug Young

What matters as far as feedback is how much sound reaches your guitar, and how much it picks that up, triggering feedback...

I'm going to be super-ultra picky here, please forgive, but the term feedback came from the speaker output feeding back into the microphone (pickup in this case).

The sound, which I believe is often referred to in the US as howlaround, has also become known itself as feedback but I think the pedantic differentiation between the cause and the effect is useful in clarifying the subject.

Once the signal feeds back into the mic/pickup beyond a certain threshold it will reproduce itself at whatever frequencies the circuit/system is resonant between the speaker and the mic/pickup.

As Doug says, an insensitive mic can be boosted to the level of a sensitive one with no more tendency to feed back.

Signal to noise ratio is a different matter as applying high levels of gain to a weak signal also boosts any noise inherent in the preamp, which is why insensitive mics such as the Beyer m201 or Shure sm7 need low noise/high gain preamps (or super-loud sound sources).

As far as the original question goes - the difference between "electric" and "acoustic" magnetic pickups is a cultural one.

Originally electric guitars of the Charlie Christian era were criticised for not sounding like acoustic guitars (much like today) but over time artist and public taste evolved to embrace the "deficiencies" of magnetic pickups + valve amp and make something once removed from the sound of wood.

As public taste has further evolved back towards "realist" then the design brief for new products harnessing existing technology has changed. It's an old conversation, revived.

[Hoodster]

Thanks, guys. So, if my interest in a soundhole pickup is mainly in order to amplify slide playing for my own enjoyment at home, plugging a passive pup straight into a guitar amplifier should work, correct?

[pieterh]

Originally Posted by Hoodster

Thanks, guys. So, if my interest in a soundhole pickup is mainly in order to amplify slide playing for my own enjoyment at home, plugging a passive pup straight into a guitar amplifier should work, correct?

Definitely worth trying anyway - just be aware of your position with the guitar in relation to the amp. Enjoy!

[Rudy4]

Originally Posted by Hoodster

Thanks, guys. So, if my interest in a soundhole pickup is mainly in order to amplify slide playing for my own enjoyment at home, plugging a passive pup straight into a guitar amplifier should work, correct?

Actually, in many cases there IS a difference between magnetic soundhole pickup types sold to install in acoustic guitars.

Check the specifications of any magnetic sound hole pickup made for acoustic guitar before purchase. Several of these magnetic pickups are built to have a certain level of "microphonics" incorporated into their design. This simply means that the coil or other parts of the mechanical structure are designed to respond to the vibrating top. This is what makes a magnetic pickup microphonic, and also what makes it prone to feedback at higher volume levels.

When a manufacturer designs a magnetic pickup for acoustic guitar to respond to the top movement it may well contribute to a more acoustic tone, but it also makes it more prone to feedback.

For your use any of them will work and you do not need a preamp.

[Doug Young]

Originally Posted by Rudy4

Actually, in many cases there IS a difference between magnetic soundhole pickup types sold to install in acoustic guitars.

Check the specifications of any magnetic sound hole pickup made for acoustic guitar before purchase. Several of these magnetic pickups are built to have a certain level of "microphonics" incorporated into their design. This simply means that the coil or other parts of the mechanical structure are designed to respond to the vibrating top. This is what makes a magnetic pickup microphonic, and also what makes it prone to feedback at higher volume levels.

When a manufacturer designs a magnetic pickup for acoustic guitar to respond to the top movement it may well contribute to a more acoustic tone, but it also makes it more prone to feedback.

For your use any of them will work and you do not need a preamp.

That's true in a few cases, mostly the Baggs M1 and M80, which are basically mag+SBT in their behavior. There may be some others that do this, but I'm not remembering any. It was sort of a Baggs breakthru feature. Some others, like the mojotone simply claim mic-like EQ curves, but not microphonic behavior if I recall. And of course some mag pickups have mics built-in, like the Rare Earth or Duncan MagMic, which will therefore have different feedback behavior.

But the Duncan Woody is very similar to the Sunrise, and is just a plain old humbucker, very much like typical electric pickups. There is still some sensing of the top motion, in the sense that when the top moves, the mag moves relative to the strings, and that's going to happen a lot more with an acoustic than with a Les Paul or even an archtop, but that's a difference in the guitar, not the pickup. And even with the Baggs pickups, this aspect doesn't affect what you plug into.

[douglasfan1]

Originally Posted by Doug Young

That's true in a few cases, mostly the Baggs M1 and M80, which are basically mag+SBT in their behavior. There may be some others that do this, but I'm not remembering any. It was sort of a Baggs breakthru feature. Some others, like the mojotone simply claim mic-like EQ curves, but not microphonic behavior if I recall. And of course some mag pickups have mics built-in, like the Rare Earth or Duncan MagMic, which will therefore have different feedback behavior.

But the Duncan Woody is very similar to the Sunrise, and is just a plain old humbucker, very much like typical electric pickups. There is still some sensing of the top motion, in the sense that when the top moves, the mag moves relative to the strings, and that's going to happen a lot more with an acoustic than with a Les Paul or even an archtop, but that's a difference in the guitar, not the pickup. And even with the Baggs pickups, this aspect doesn't affect what you plug into.

I would like to ask a question further:
Since magnetic pickup of acoustic guitar and electric guitar are basically the same, could I plug the signal from sunrise pickup into an electric tube amp to get a electric guitar tone?

[pieterh]

Originally Posted by douglasfan1

I would like to ask a question further:
Since magnetic pickup of acoustic guitar and electric guitar are basically the same, could I plug the signal from sunrise pickup into an electric tube amp to get a electric guitar tone?

To a certain extent yes; though acoustic magnetic pickups are voiced for acoustic strings and electric amps are voiced for electric guitars!

In other words, you will get an acoustic magnetic pickup sound from a Woody for example but this will be “tamed” (for want of a better description) by the electric amp which won’t reproduce the higher frequencies (full range speaker, no tweeter overtones) nor is it supposed to.

It’s been something like 25 years since I last used a Woody but my Dad still uses one together with a UST. Personally I don’t want my acoustics sounding more like electrics (I have electrics for that) but it’s certainly a sound worth pursuing for its own sake.

[Pnewsom]

I play with a fellow who uses a Gibson mini-humbucker(electric guitar pu) rigged as a sound hole pup on a small body guitar. Sounds fatter and juicier than my Baggs M1 does. He also plugs straight into a Fender BF Pro Reverb. Great top end, warm and fat for delta blues with slide and finger style.

There was another guy I played with in the past who used a strat pu in his acoustics with good results.

A lot of the high frequency sounds and textures that people prize when amplifying acoustic guitars gets lost on the bandstand. Sometimes you just need a good solid guitar sound getting out there.

[Rudy4]

Originally Posted by douglasfan1

I would like to ask a question further:
Since magnetic pickup of acoustic guitar and electric guitar are basically the same, could I plug the signal from sunrise pickup into an electric tube amp to get a electric guitar tone?

The simple answer is no.

The strings of an acoustic guitar are physically coupled to the top, and the top movement that is created by string energy is in turn coupled back to the string. You'll end up hearing that induced top sound through the magnetic pickup, and that's the reason a magnetic soundhole pickup won't sound the same as a guitar that's designed for magnetic pickups to begin with.

There are other small contributory factors that determine what sound can be obtained by using a magnetic soundhole pickup, but mechanical coupling of the top's vibrations is the prime influence.

Anyone doubting the physics of how this all works can speak loudly directly to the top and hear your voice as it is picked up by the magnetic pickup and converted to electrical energy that is then amplified.

This is also the reason why an acoustic guitar fitted with a magnetic pickup can feed back at higher volumes easily. It's a matter of simple physics.

[shufflebeat]

Originally Posted by douglasfan1

Since magnetic pickup of acoustic guitar and electric guitar are basically the same, could I plug the signal from sunrise pickup into an electric tube amp to get a electric guitar tone?

See Nirvana "unplugged".

[Doug Young]

Originally Posted by douglasfan1

I would like to ask a question further:
Since magnetic pickup of acoustic guitar and electric guitar are basically the same, could I plug the signal from sunrise pickup into an electric tube amp to get a electric guitar tone?

There's no harm in plugging anything into anything, give it a try and see if you like it. It won't sound like a Les Paul, because the guitars are different, and also different pickups are voiced differently. Even among pickups meant for electric guitars, different magnetic pickups sound different, but it will make a sound, so see if you like it.

People like Monte Montgomery use overdrive and distortion with an acoustic (not sure if he uses a mag or not off the top my head). The Fishman BlackStack is another pickup that mimics the Sunrise, and they marketted it as a "roadhouse blues" sound for acoustic guitar, so it was supposed to sound a bit electric (as do nearly all magnetic pickups).

[Hoodster]

I answered my own questions about the Woody here: