Building an acoustic guitar pickup

[Clint Swank]

I recently heard a woman named Natalia Zuckerman (quite good) playing through a Sunrise acoustic guitar pickup. The sound was phenomenal. After some research, I discovered that Sunrise pickups are both very expensive and also produced in very limited numbers. I also note that they are magnetic and require a preamp. I conclude that they are probably low impedance. My pickup building experience is limited to having once rewound a Strat pickup with interesting results-it ended up (unintentionally) low impedance. It sounded quite nice, actually, but it wasn't very loud, natch. I've constructed a bunch of electronic gizmos (compressor, tube preamp, etc.) so now I'm thinking, why not rewind a strat pup or something to low impedance, build a little impedance matching thing and see what it sounds like on my old Martin? Any advice?

[RedHouse]

Boldly go..., report back..., be prepared to dodge flack.

[korinastratkyle]

I've wound a few low impedance humbuckers (planning on production soon) and I tried one with my acoustic and it sounds awesome and is very low noise (especially good since you can't really ground an acoustic bridge easily, although a single coil will pick up hum) and very good at reproducing all the highs, but I might use nickel-steel wound strings on it once I have one actually permanently installed in the guitar because with bronze wound strings it's a little dark sounding and the b and high e strings are much louder. But yeah I'm gonna buy one of those rubber feedback reducers that go in the soundhole and install the pup in there. Anyways, attached is some frequency analysis I performed on my computer of a few pups to give you an idea of how flat of an EQ a low impedance pickup really can be. I'm planning on getting some thinner wire so I can get more winds for more output and hopefully some more bass response. But really, it's current form is very acceptable especially for a bass heavy sound source like a dreadnaught's soundhole.

Also, I'd recommend either running through an external mic preamp (the $30 ART MP Studio actually works quite well) or coming up with an internal preamp if you plan on running into a guitar amp. BUT, if you want to just run into a mixer or an acoustic amp with an XLR input and mic pre you could just go with an XLR out or do what I did and do a 1/4" TRS to XLR deal (had to mod a regular XLR cable to have the male TRS end)

[Possum]

How did you do that frequency analysis?

[korinastratkyle]

Originally Posted by Possum

How did you do that frequency analysis?

I used Adobe Audition to generate a 10 second sine wave that goes from 20-20KHz over the course of it, then I hooked up the pickups one by one into the instrument input on my recording interface (Presonus Firestudio Project) and hooked up a low Z coil (since it's got a flatter EQ and higher fidelity than a high Z coil) with a magnet attached to it to the headphone output, cranked the headphone volume and stuck it to each pickup. Then I played the tone through the coil and recorded the pickup it was attached to. My first analysis was done with my studio headphones but it wasn't as accurate. You could actually hear the sine wave from the pickup coil!

[korinastratkyle]

BTW, if I'm doing something wrong can someone let me know? This was the only logical (and free for me) way to do such a thing that I could think of.

[belwar]

Originally Posted by Clint Swank

I recently heard a woman named Natalia Zuckerman (quite good) playing through a Sunrise acoustic guitar pickup. The sound was phenomenal. After some research, I discovered that Sunrise pickups are both very expensive and also produced in very limited numbers. I also note that they are magnetic and require a preamp. I conclude that they are probably low impedance. My pickup building experience is limited to having once rewound a Strat pickup with interesting results-it ended up (unintentionally) low impedance. It sounded quite nice, actually, but it wasn't very loud, natch. I've constructed a bunch of electronic gizmos (compressor, tube preamp, etc.) so now I'm thinking, why not rewind a strat pup or something to low impedance, build a little impedance matching thing and see what it sounds like on my old Martin? Any advice?

Clint,

As an acoustic guitar maker, i can tell you im sick to death of piezos. There are a few really good magnetic acoustic guiar pickups out there. Take a look at the LR baggs M1 pickup. Dearmond also made acoustic magnetic pickups. Heck thier famous archtop pickup the Rythym chief 1100 is a magnetic pickup. Lane poor had a really ingenous acoustic magnet pickup. I bought one but havent tried it yet. I dont think low impedance is nessesary. The Dearmonds are like 15k DCR, and the LP is in the 6-7 range.

I've been thinking about trying to make one, but my fear is that acoustic strings and electric strings are so much different. The material of the strings could really have an impact on a magnet pickups.

[Clint Swank]

Okay, so I go to the guitar shop and rummage through the dead pup drawer. (They let me do stuff like that--I teach there.) I find this old Gretsch single coil--adjustable sprung pole pieces--nice. Then I go to Radio Shack and buy a reel of AWG 30 (yeah, I know, but that was the all they had), I go home, rip out the guts of the Gretsch, rewind it, about 180 turns (all I could get on there). I connect it to an XLR and plug it into my mixer, bang it with a screwdriver--boom, boom. I go to the craft store and buy a couple of 5" or so square slices of mystery wood, take 'em home, carve pickup size holes, glue together a sandwich with shims (looks sort of like a Dean Markley made in shop class). I stick it on the Martin and...it sounds amazing. Louder than my electric lined into the same channel, no noise, clearer, more natural and much louder than the junky piezo I got in there. I can't believe it. Now, about a preamp/transformer....

[korinastratkyle]

Originally Posted by Clint Swank

Okay, so I go to the guitar shop and rummage through the dead pup drawer. (They let me do stuff like that--I teach there.) I find this old Gretsch single coil--adjustable sprung pole pieces--nice. Then I go to Radio Shack and buy a reel of AWG 30 (yeah, I know, but that was the all they had), I go home, rip out the guts of the Gretsch, rewind it, about 180 turns (all I could get on there). I connect it to an XLR and plug it into my mixer, bang it with a screwdriver--boom, boom. I go to the craft store and buy a couple of 5" or so square slices of mystery wood, take 'em home, carve pickup size holes, glue together a sandwich with shims (looks sort of like a Dean Markley made in shop class). I stick it on the Martin and...it sounds amazing. Louder than my electric lined into the same channel, no noise, clearer, more natural and much louder than the junky piezo I got in there. I can't believe it. Now, about a preamp/transformer....

Yeah I just used 250 winds of 32 AWG for each coil on my standard sized humbuckers. Might try like 33 or 34 for more winds though so I don't have to boost it so much.

[Clint Swank]

I'm on my way right now to this place that has thirty four. We'll see what happens. This is the most fun I've had in at least a day or two. Les Paul was right!

[DMW]

Welcome! | Wendler electroCoustic

Dave Wendler is a guy worth speaking with about acoustic pickup designs. He has a MagPi system which uses magnetic and piezo pickups. Dave used to be the production manager for Peavey's guitar factory and he's had his own product line for a number of years. There is another magnetic design that he has for which I can't seem to find the review at Harmony-Central as I once could, but it uses a coil suspended below the bridge of an acoustic guitar.

His current company is Wendler Instruments, and his guitar design is the electroCoustic. Audio clips are at his web site.

By the way, the DW is a coincidence. I am NOT Dave Wendler.

[Clint Swank]

Ok, so I've wound this pickup twice, once with 180 turns of 30 AWG, once with 400 turns of AWG 34. As you would expect, the 400 is a lot hotter, but with an (easily gatable) slight hum. The volume is significantly louder than my Seymour Duncan humbuckers in my electric, in fact, so I have some room here.The pickup sounds wonderful, but I'm interested in making it even slicker (dare I say perfect?). So... how much difference would 50 fewer turns make, or 100? Enough to justify pulling it out of the guitar, taking it apart, yadda yadda? The housing is glued together, which makes dismantling it tantamount to destroying it, not that I'd mind rebuilding it, but only if it's worth it.

[David Schwab]

Originally Posted by Clint Swank

The volume is significantly louder than my Seymour Duncan humbuckers in my electric, in fact, so I have some room here.

That's surprising. What are you plugging it into?

[bbsailor]

Originally Posted by Clint Swank

Ok, so I've wound this pickup twice, once with 180 turns of 30 AWG, once with 400 turns of AWG 34. As you would expect, the 400 is a lot hotter, but with an (easily gatable) slight hum. The volume is significantly louder than my Seymour Duncan humbuckers in my electric, in fact, so I have some room here.The pickup sounds wonderful, but I'm interested in making it even slicker (dare I say perfect?). So... how much difference would 50 fewer turns make, or 100? Enough to justify pulling it out of the guitar, taking it apart, yadda yadda? The housing is glued together, which makes dismantling it tantamount to destroying it, not that I'd mind rebuilding it, but only if it's worth it.

Clint,

The hum comes from the strings not being grounded.
Go to Stewart McDonald and get a "PlateMate". Get the model that matches your pin hole spacing. Solder a wire to the metal plate and connect it to the pickup ground wire. The ball end of the strings will make a good contact with this matal plate and make a good acoustic guitar string ground.

Most microphone macthing transformers (Shure 95 series) are rated about 500 ohms to 50,000 ohms. It typically has a 1 to 10 turns ratio. Your AWG 34, 400 turn coil is approximately equivalent to a 4000 turn pickup coil of much thinner wire after taking into account of the turns ratio boost.

Another thing you can try is obtain from Jameco or Mouser Electronics a few CSE187L, low frequency current transformers and a few magnets from allelectronics.com (CAT# MAG-138). Wrap with a single loop of AWG 12 household solid wire around the magnet. Use thin copper tubing to connect the AWG 12 wire to the transformer primary. The CSE187L has a 1 to 500 turns ratio so that it will match very well to a mic input of a mixer or a matching transformer. Just ground the low impedance loop to the metal transformer case and the output ground. This makes a very quiet wide bandwidth pickup. See some of my other posts for more details about making low impedance pickups.

Joseph Rogowski

[Clint Swank]

Well, the pickup goes out on a TRS, which terminates in an XLR, so I use that to plug into my mixer. Otherwise, I just plug the XLR into a Radio Shack line transformer, and go into my guitar amp or my effects pedal. I'm a little surprised at how loud it is myself, but the freak out peaks on my DAW don't lie, and my electric never does that. I set the input levels on two adjacent channels identically and there it is. Why isn't everybody into low impedance? I'm totally hooked--the touch sensitivity, clarity and dynamics of this thing just amaze me. Not to mention the fact that hand winding 400 turns took me all of 15 minutes.

[David Schwab]

Originally Posted by Clint Swank

Well, the pickup goes out on a TRS, which terminates in an XLR, so I use that to plug into my mixer. Otherwise, I just plug the XLR into a Radio Shack line transformer, and go into my guitar amp or my effects pedal. I'm a little surprised at how loud it is myself, but the freak out peaks on my DAW don't lie, and my electric never does that. I set the input levels on two adjacent channels identically and there it is. Why isn't everybody into low impedance? I'm totally hooked--the touch sensitivity, clarity and dynamics of this thing just amaze me. Not to mention the fact that hand winding 400 turns took me all of 15 minutes.

OK, the pickup is louder than the Duncan, because you are plugging into a mixer. It's a low Z pickup. The mixer will load down the Duncan, so it wont be so loud, and it will be dull sounding. Same thing if you plug it right into a sound card. They aren't made for high z guitar pickups.

Try that pickup in a regular guitar amp without the transformer, and you will see it's not that loud.

I only asked because I've made a lot of low Z pickups, and they all required a preamp to use with a regular amp, but worked just fine into a mixer. As you noticed, you get a very clear uncolored tone from a low Z pickup.

[Clint Swank]

Well, ok, you're right. I plugged the LoZ (with the line transformer) straight into my Fender and, yes, the Duncan is slightly louder. However, my next question is: Does a line transformer qualify as a preamp? Because the output of my LoZ , with the transformer, is certainly usable as is, though I will, actually, be running it through my pedal board. (Which does qualify as a preamp.)

But in terms of fidelity, there's just no comparison. My LoZ pickup sounds more like my Martin sounds, acoustically, than anything I've ever tried, and I've tried everything. Plus, it's way, way louder than the piezo it's replacing.

Which makes me wonder why LoZ isn't more universally adopted. It reminds me of the situation with independent suspension in American cars. American manufacturers were loath to abandon solid axles for many, many years because they were cheaper, and they assumed (perhaps correctly) that American drivers were morons who didn't care about handling.

I haven't seen a HiZ microphone in a professional situation since I was a teenager (ages ago). So why is HiZ still the sine qua non in guitar pickups? Is it just output? And why does that matter anymore, given the ubiquity of gain sources?

But back to my original question: How much difference will small changes in the number of turns make in the sound, output level, and the amount of noise ? You've obviously made a lot more pickups than I have, David, so, since there's a drastic difference in the number of turns (and the wire gauge) between Hi and LoZ, are we looking at a sort of fractal scale situation here? i.e: Do very small changes on the LoZ scale equal large changes on the HiZ scale?

[Clint Swank]

Yeah, even when I had a piezo I was wondering how to do a string ground. The piezo had such a low output that I had to jack the gain astronomically, and the hum was almost equally loud--unless I held onto the output jack. Makes playing a little dificult.
So I'll order one of those puppies, though the hum is really pretty quiet, and my pedalboard gates it right away.

[David Schwab]

Originally Posted by Clint Swank

Well, ok, you're right. I plugged the LoZ (with the line transformer) straight into my Fender and, yes, the Duncan is slightly louder. However, my next question is: Does a line transformer qualify as a preamp? Because the output of my LoZ , with the transformer, is certainly usable as is, though I will, actually, be running it through my pedal board. (Which does qualify as a preamp.)

Try the pickup without the transformer into the Fender. That's the real output!

Yes, the transformer is boosting the signal. I discovered that back in the 70's when I ran my Rickenbacker 4001 bridge pickup through a mic transformer from a Bogan PA. I was shocked how much louder it was.

The Lace Alumitone and Transsensor pickups are low Z and use integrated step up transformers.

But in terms of fidelity, there's just no comparison. My LoZ pickup sounds more like my Martin sounds, acoustically, than anything I've ever tried, and I've tried everything. Plus, it's way, way louder than the piezo it's replacing.

Yes, it's a very wide and flat response. Hi-z pickups impart their own tone on the instrument.

Which makes me wonder why LoZ isn't more universally adopted. It reminds me of the situation with independent suspension in American cars. American manufacturers were loath to abandon solid axles for many, many years because they were cheaper, and they assumed (perhaps correctly) that American drivers were morons who didn't care about handling.

Les Paul has said this time and time again. But most of the early electric guitars and amps were high z, so that became the norm.

Also, a lot of people don't care for Les' tone... too bright and thin and hi-fi. Guitarists have gotten used to the tone of high Z pickups. The old Gibson Les Paul Recording, Personal, Signature, and Professional models had low Z pickups, as well as the Triumph and Signature basses.

Here's a web pages about them: Gibson Les Paul Recording guitar page

Alembic uses low Z pickups. The Epiphone Jack Casady bass (which is a reissue of the Les Paul Signature bass) has a low Z pickup, and a built in stepup transformer with different taps.

Low Z pickups need a transformer or preamp, and I guess some people don't want to be bothered.

I haven't seen a HiZ microphone in a professional situation since I was a teenager (ages ago). So why is HiZ still the sine qua non in guitar pickups? Is it just output? And why does that matter anymore, given the ubiquity of gain sources?

You can't run a long length of cable with hi-z mics.

But back to my original question: How much difference will small changes in the number of turns make in the sound, output level, and the amount of noise ? You've obviously made a lot more pickups than I have, David, so, since there's a drastic difference in the number of turns (and the wire gauge) between Hi and LoZ, are we looking at a sort of fractal scale situation here? i.e: Do very small changes on the LoZ scale equal large changes on the HiZ scale?

A small number of turns more might not alter the tone much. The more turns, the more output. I noticed the tone started to get fuller sounding with more turns. But I found a formula I liked and then stuck with that.

You can also experiment with different wire gauges. As the wire gets thinner, you get more pronounced mids and a tighter tone. This is true in high Z pickups as well.

bbsailor here posted a few really informative threads on low Z pickups.

[Clint Swank]

Latest version is a stacked humbucker. I was getting a bit of noise with the original single coil (especially apparent when recording), but I really loved the original junk pile single coil bobbin, so I built a second bobbin out of plywood. The magnets on the original bobbin are very long rods adjustable with even longer spring-suspended screws (which go right through the bottom of the lower bobbin.)
Ca. 375 turns of AWG 34, bobbins just taped together--voila. Impedance is around 600 ohms.

It sounds even better than the original and it's dead quiet.