Acoustic guitar made to sound like an electric (900 word post w/ pics)

[James May]

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Background
Most folks who use a magnetic pickup in an acoustic guitar are going for an acoustic sound, trying to get something like the sound of their acoustic guitar, only louder, out of their amplification system.

Not me. I have that base covered with my Ultra Tonic pickup and a ToneDexter. It sounds extremely natural, is feedback resistant, and works perfectly for my acoustic guitar sound needs.

However, I also want this particular guitar, a 2003 Gibson Advanced Jumbo, to sound like an electric guitar. I’m sure this is not a common desire. I do this in the context of my oldies band where for about half the songs, I want to sound like and electric guitarist, and I don’t want to switch guitars to do so.

I have my Ultra Tonic wired to TIP, and a magnetic pickup wired to RING. I use a TRS cable and split into two distinct paths: one for an acoustic sound with a ToneDexter, and one for an electric sound with a distortion pedal, organ simulator, 12-string simulator, and then finally an amp simulator. Both paths terminate in an A/B selector that decides which path gets sent to the effects return of ToneDexter which functions as the DI and feeds the PA mixer.

For the mag pickup, I’ve been using a passive DiMarzio Black Angel for about 6 years now. And while it has worked reasonably well, I’ve not been entirely happy with the sound it gives, and have had to work too hard to EQ it to sound more “electric”. Like all other sound-hole pickups I’m aware of, it is designed to give as much acoustic character as possible. I call that hi fi, with lots of highs and without a strong electric personality.

Recently I got to thinking, why not just put an actual electric guitar pickup on this guitar? Preferably a P90 since that’s the sound I like. So I did. Here’s how, in case you’re interested.

Project Details
• Researched the P90 aftermarket choices and carefully checked the dog ear dimensions. Concluded it would just fit in the sound-hole with clearance for the screws. Lucky me.
• Purchased a Lindy Fralin hum-canceling P90 with extra long wire tail. (They will make it however long you want.)
• Cut some foam pieces with sticky on one side, to act as guards against marring the finish.
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• Scribed the dog ears and holes onto to some Bakelite from an old DIY box I’ve had lying around. Used a hacksaw and file to fabricate the dog ear shape to act as upper dog ears that sandwich the wood with the actual dog ears below the surface.
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• Added some pieces of rubber sheet to take roughly the same thickness as the guitar top.
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• Super glued 4-40 nuts to the bottom of the metal pickup bracket which sits up into the plastic dog ear cover.
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• Put it in place, restrung, and voila, it sounds great. However, there were two problems.

First problem: since I’m using bronze strings, the unwound steel E and B are significantly louder than the wound bronze strings. This is no surprise because they are more magnetic than the bronze (with its small steel core), and thus induce more signal in the coil winding. I raised the 4 pole pieces as much as possible, and lowered the two unwound pole pieces. Still, not quite balanced.

Removed the E and B pole screws. B was perfect, E a little weak. Decided to put the pole screws in from the back so I could get just the height I needed with bottom of the screws (now the top). That worked perfectly. A better looking solution would be to get some steel or chrome or nickel plated hex head #5-32 set screws.
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The other problem: buzz from light dimmers. Even though this is a hum cancelling pickup, I was still getting more hum and buzz than I wanted, and more than I am used to from other electric guitars with P90s. The buzz gets worse when I touch the strings, but is there even when I don’t, though less so. When I touch the strings and touch the guitar cable ground, it all goes away.

Why is this? Well, this gets a bit interesting. The strings by themselves act as antennas to pickup stray RF fields, like hum and buzz. Being in close proximity the pickup coil, which by itself is and antenna, they couple the signal into the pickup. Your body is an even bigger antenna. When you touch the strings, you couple your signal to the string which happily couples it to the pickup coil.

The fix is to ground the strings. That way any RF noise they pick up is shunted to ground and the coil doesn’t see it. Most (if not all) electric guitars ground their strings.

I made a brass plate and glued it in place with a 3-magnet jig. Carefully drilled out the holes and deburred them from below (not shown in pics). All noise gone. (BTW – you do need to have the rest of your wiring well shielded. That is a given. If you don’t, you’ll still have problems even with grounded strings.)
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So how does it sound? A lot more like an electric guitar! Perhaps 80% of the way there, and spades better than the DiMarzio sounded. My EQ settings on my amp simulator are now exactly the same as for my P90-equipped Epiphone Casino.

I’m quite pleased, and consider the afternoon it took time well spent.
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[PHJim]

The late Jazz guitarist Gabor Szabo played acoustic looking guitars that sounded like electrics. Early in his career he used a Gibson J-160e and made at least one LP using it.


By the time I saw him in Toronto, he was playing a Martin dreadnought with a DeArmond model #210 pickup.


Neither of these guitars sounded anything like an acoustic guitar.

[PHJim]

Then there's one of Martin's less attractive guitars (looks like it was slapped together), the D-18e.


Tracy Chapman played one of these at the beginning of her career.


For some strange reason, Kurt Cobain used a D-18e, but did not like the sound of the Martin supplied (DeArmond?) pickups, so he used an additional soundhole pickup to play on the inappropriately named MTV Unplugged TV show. I never did see a performer on that show who was not "plugged".

[AeroUSA]

Very cool. Any chance of a demo video?

[jonfields45]

Now that you've got the Ultratonic and a P90 installed (and of course a ToneDexter handy!), it might be fun to try an IR to see if you can get a usable electric tone from the SBT. I realize you can't reproduce the harmonic loss as you play up the neck, but you might find training in the 5th position good enough. Maybe my simple IR generator with no IIR is a good option for this experiment.

I use a compressor to get a more electric tone at gigs out of my SBT. I am not a fan of picking around sound hole pickups so I would not go that route, but maybe I should take my Dean Markley Promag and give it a try at IR generation.

I've got my first post-COVID19 gig Saturday, if the weather is good (outdoors party sponsored by a winery and distillery). I was planning to update my IR for my now only parlor guitar and I'll make a few electric ones to try out. I currently have my HX Stomp programmed to bypass the acoustic IR when the compressor is engaged. It would be simple enough to change IRs instead.

I have used a Platemate, in the past, to ground the strings on an A6 Ultra. The pickup Godin supplied did not need it, but the stacked humbucking Strat-like pickups I tried all did. Maybe side-by-side humbuckers are a better choice for ungrounded strings as the coils are truly symetrical and similarly placed relative to the strings. Does anyone make a side-by-side humcancelling P90?

[jonfields45]

I made two IRs with my script using the passive HFN as the input and an inexpensive Dean Markley Promag Grand soundhole magnetic pickup as the target (in place of a mic on the guitar for a typical acoustic IR).

For the first IR I played in open position only and the second 5th position only.

[Ignorable technical detail: Magnetic pickups not placed adjacent to the bridge, shift their relative position to the vibrating string as you play up the neck. Whether you want to label this non-linear (Larry Fishman), or time variant (me), IRs are fixed and are not going to track where on the neck you are playing.]

For the purpose of making my HFN sound like an electric guitar it sounds GREAT at home. The two unwound strings are fat and electric sounding. It should make my duo's classic rock cover lead solos much better sounding. To cover electric guitar lead solos on acoustic guitar I play as much of them as possible on the high E and B strings.

It does not seem to matter too much which IR I use, open or 5th, for this purpose.

I have a gig Saturday and how it works live is the real test.

[James May]

Originally Posted by jonfields45

I made two IRs with my script using the passive HFN as the input and an inexpensive Dean Markley Promag Grand soundhole magnetic pickup as the target (in place of a mic on the guitar for a typical acoustic IR).

For the first IR I played in open position only and the second 5th position only.

[Ignorable technical detail: Magnetic pickups not placed adjacent to the bridge, shift their relative position to the vibrating string as you play up the neck. Whether you want to label this non-linear (Audio Sprockets & Larry Fishman), or time variant (me), IRs are fixed and are not going to track where on the neck you are playing.]

For the purpose of making my HFN sound like an electric guitar it sounds GREAT at home. The two unwound strings are fat and electric sounding. It should make my duo's classic rock cover lead solos much better sounding. To cover electric guitar lead solos on acoustic guitar I play as much of them as possible on the high E and B strings.

It does not seem to matter too much which IR I use, open or 5th, for this purpose.

I have a gig Saturday and how it works live is the real test.

Jon, this is very cool. I noted your comment a few days ago and am planning a similar experiment with a ToneDexter. I am encouraged by your findings. Stay tuned for more on this from me.

[Rick Jones]

Originally Posted by PHJim

For some strange reason, Kurt Cobain used a D-18e, but did not like the sound of the Martin supplied (DeArmond?) pickups, so he used an additional soundhole pickup to play on the inappropriately named MTV Unplugged TV show. I never did see a performer on that show who was not "plugged".

Kurt is using a Bartolini soundhole pickup there... I used to have one and much to my dismay I can't find it, but if you ever come across one (they are no longer made) snap that bad boy up (if you like warm, somewhere between a strat neck pickup and a hollow-body sound).

They have a really, really nice dynamic response that I have never heard from another pickup. Kurt's playing – as iconic as it is – doesn't really show it.

I used to run a magnetic along with a soundboard transducer and undersaddle (twin outputs) and run my magnetic into a Fender Twin, for years.

I love the idea of putting a P90 in a Gibson... I bet it would be amazing for slide!

[James May]

I just tried an interesting experiment, suggested by Jon Fields, to see if I could make my Ultra Tonic SBT sound like the P90 mag pickup in this same guitar.

I used ToneDexter with the SBT feeding the pickup input (source), and the P90 feeding the mic input (target). I used a DC blocking cap to keep the phantom power out of the P90.

The results were not very satisfying. While it did sound much closer to the P90 in terms of tonal balance, it was still not very convincing. There were more highs present (surprisingly), and it lacked juiciness (not very scientific I know).

I tried training at 1st position only, 5th position only, and all along the neck. None of that seemed to make a noticeable difference.

I suspect the issue is related to what I believe is non-linear behavior from the mag pickup. I make a distinction between non linear and time variant.

Time variant would encompass position variations as well, and would take into account differences in the mag pickup response while playing at different locations along the neck. That does not seem to be a big factor in this particular case.

By non-linear I mean differences in the harmonic content that mag pickup transduces, relative to the harmonic content the SBT transduces.

We know that piezo transducers are linear, but of course the guitar's physical construction is anything but. However, we can count on a piezo to give a linear (i.e., 1:1) relationship in electrical output relative to the forces acting on it. I'm not sure that is true of a magnetic pickup, and to further muddy the waters, I'm pretty sure the string vibrations don't act the same way on the top as they do flailing about in free air as they disturb the magnetic field in front of the pickup.

To get a glimpse of this difference, I plugged the SBT into channel 1 of a spectrum analyzer, and the mag pickup into channel 2, with the spectra laid on top of each other. I set it up to trigger and hold as I played notes.

Playing unwound B and E strings, the spectra were quite similar, but never identical. Playing the wound strings however showed significant differences. The 2nd harmonic was always way down in the mag, and there were other significant variations in the upper harmonics as well.

That's as far as I took it for now. I don't pretend to understand this topic thoroughly, but I feel safe in saying that a mag pickup will give you something that you can't get with a piezo or with a piezo plus an IR.

[Brent Hahn]

James -- really interesting. RE the string-balance issue, the pole-piece solution is the same one that Baggs uses. Their magnetics ship with the B pole gone and the E pole screwed all the way down.

As for strings with my magnetics, I've found the best compromise between acoustic tone that works for me and electric balance to be Martin Marquis. They're also nickel-free (I'm allergic) and relatively cheap.

Looking forward to you posting some sound clips. Always nice to get a peek at the artist side of you designer folks.

[jonfields45]

Originally Posted by James May

I just tried an interesting experiment, suggested by Jon Fields, to see if I could make my Ultra Tonic SBT sound like the P90 mag pickup in this same guitar.

I used ToneDexter with the SBT feeding the pickup input (source), and the P90 feeding the mic input (target). I used a DC blocking cap to keep the phantom power out of the P90.

The results were not very satisfying. While it did sound much closer to the P90 in terms of tonal balance, it was still not very convincing. There were more highs present (surprisingly), and it lacked juiciness (not very scientific I know).

I tried training at 1st position only, 5th position only, and all along the neck. None of that seemed to make a noticeable difference.

I suspect the issue is related to what I believe is non-linear behavior from the mag pickup. I make a distinction between non linear and time variant. The 2.9 update went untested by me because of the lack of gigs during the PA lockdown.

Time variant would encompass position variations as well, and would take into account differences in the mag pickup response while playing at different locations along the neck. That does not seem to be a big factor in this particular case.

By non-linear I mean differences in the harmonic content that mag pickup transduces, relative to the harmonic content the SBT transduces.

We know that piezo transducers are linear, but of course the guitar's physical construction is anything but. However, we can count on a piezo to give a linear (i.e., 1:1) relationship in electrical output relative to the forces acting on it. I'm not sure that is true of a magnetic pickup, and to further muddy the waters, I'm pretty sure the string vibrations don't act the same way on the top as they do flailing about in free air as they disturb the magnetic field in front of the pickup.

To get a glimpse of this difference, I plugged the SBT into channel 1 of a spectrum analyzer, and the mag pickup into channel 2, with the spectra laid on top of each other. I set it up to trigger and hold as I played notes.

Playing unwound B and E strings, the spectra were quite similar, but never identical. Playing the wound strings however showed significant differences. The 2nd harmonic was always way down in the mag, and there were other significant variations in the upper harmonics as well.

That's as far as I took it for now. I don't pretend to understand this topic thoroughly, but I feel safe in saying that a mag pickup will give you something that you can't get with a piezo or with a piezo plus an IR.

There are so many electric guitar options that so many players love to the exclusion of most others, it seems like an IR on a SBT to sound like an acceptable magnetic is a long shot. Maybe my bar is too low. I'm just trying to get enough electric guitar fatness to make single note solos have the right hand feel and sound. Tomorrow's gig will tell if it has any merit for me, but I will still have the compressor option handy on my HX Stomp.

Roland used to sell a hexaphonic IR based guitar system (similar to Variax), in addition to their midi adapters, that ran off a magnetic pickup placed next to the bridge. Fender sold a Mexican Strat with that system stock. It was not a great product IMO.

And not really related, the 2.9 firmware upgrade just short of bricked my HX Stomp. The pedal would only react to the USB interface to my PC which allowed me to load 2.92. I loaded 2.9 when it came out and never tested it due to the lack of gigs during the PA Covid-19 lockdown.

I also forgot to comment earlier on the really nice looking mechanical design of your P90 conversion!

[James May]

Originally Posted by jonfields45

There are so many electric guitar options that so many players love to the exclusion of most others, it seems like an IR on a SBT to sound like an acceptable magnetic is a long shot. ...

I also forgot to comment earlier on the really nice looking mechanical design of your P90 conversion!

Yeah, I thought is was a long shot too, but was curious to see if I could learn a bit more, which I did.

Thanks.

[jonfields45]

Here is a quick sample of the HFN to Dean Markley Grand 1st position training IR (bypass to IR, chords, then single note riff, 50/50 IR/bypass when on). It really sounded very much like the Dean Markley to me when I still had the Dean Markley in the guitar to set my expectations... Still might be useful tomorrow. Maybe I got carried away.

https://drive.google.com/file/d/1Naa...ew?usp=sharing

EDIT: I did some high volume testing: No IR w/compressor (my standard technique), Mag IR, Mag IR w/compressor. Mag IR w/compression is a clear winner for electric guitar style single note riffs.

[jdubdub]

Just wondering what Curtis Novak did with his pickups.
https://acousticguitar.com/gear-revi...dhole-pickups/

Would different unwound strings change it? Leo Kottke, "I use stainless steel to accommodate the magnetic pickup. To the ear, it has about half the magnetic zap of regular strings."

[SpruceTop]

Originally Posted by Snorse

Kurt is using a Bartolini soundhole pickup there... I used to have one and much to my dismay I can't find it, but if you ever come across one (they are no longer made) snap that bad boy up (if you like warm, somewhere between a strat neck pickup and a hollow-body sound).

They have a really, really nice dynamic response that I have never heard from another pickup. Kurt's playing – as iconic as it is – doesn't really show it.

I used to run a magnetic along with a soundboard transducer and undersaddle (twin outputs) and run my magnetic into a Fender Twin, for years.

I love the idea of putting a P90 in a Gibson... I bet it would be amazing for slide!

Early on, circa 1977, I used a Bartolini magnetic soundhole pickup (plexiglass mounting) along with a Barcus-Berry stick-on external bridge-mounted piezo (the wooden-encased model) in my new Martin 000-28. I blended the two separate outputs at the mixer and got a decent-sounding blend of tone. Any tonal deficiencies were likely due to the Barcus-Berry's putty installation which never could transmit good vibrational characteristics via this installation. If I pushed down on the Barcus-Berry with my finger while hitting the strings my pick, the amplified tone was immediately transformed into a really nice-sounding tone. Obviously, I couldn't play a song with one finger pushing on that pickup. This was just before my discovery internal mounting of piezos with superglue.