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Acoustic Archtop

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Acoustic Archtop

Postby Ed Lysne » Tue Jul 18, 2017 2:33 pm

I built this guitar for my brother. It's a 16" lower bout and the body is 19.5” long 25” scale. Sitka top...walnut back and sides with a mahogany neck. It's the loudest archtop guitar I've built. The sound just jumps out of it. Has excellent tone... and gorgeous ringing sustain. When I first strung it up… I was thrilled and knew my brother was going to love it (I surprised him with it).

It's a working musician’s guitar... ABS binding with a K&K pickup and an on-board preamp in the side bout. X-Braced with a bolt on neck. I had bent the sides and set them aside during my last build... and the top was just some extra Sitka Spruce I had laying around. It's nothing fancy for sure. I also had cut an extra tailpiece on my CNC when I had the setup loaded... so it's a little of this and that. The Bridge is an adjustable configuration with a bone saddle.

I get a lot of comments about the sound holes…good and bad. It really seems to open up the guitar. My brother is a working musician playing in bars and clubs around the area. He really needed a new axe as his Martin was really starting to show it's age... having years of bar work... summer festivals, airplanes, pickup trucks etc. This archtop was created with that environment in mind. He has been playing it for several weeks... and said feedback has not been an issue and can dial it out with the preamp.

Only issue is the pickup output is a little low (even with the preamp). I really want to find a better solution for an archtop. I love the K&K's... (glued to the underside of the sound board), These pickups are not made specifically for archtops… but they work and have a really great natural sound... but with the bridge setup... and the top... the output is down slightly. I've tried several of the higher output type...glued in around the f-holes (Twinspot)... and while the sound output is good... I find the pickup has way too much ancillary body noise. They also feedback too much. I really want a design under the bridge without all those wires running across the top (the under-bridge design specified for archtops). I’m going to try and contact a few of the manufactures to see if they have any ideas. I really dislike the pickups jammed under the bridge with wires running across the soundboard. As a builder… I just can’t support that look… Something I need to keep working out.
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Re: Acoustic Archtop

Postby Randolph Rhett » Tue Jul 18, 2017 3:53 pm

The archtops I build are most definitely meant as an acoustic instrument. When strung up with nylon strings, the K7K/JJB piezo's are just about the only choice unless I want to go with the RMC madness. However, for players who play mostly steel strings I have had to concede a magnetic pickup. I just cannot get a reasonable sound with the piezo's alone.

For magnetic pickups, I am blown away by the sound and quality of Pete Biltoff's pickups. He will customize for a reasonable price. The Vintage Vibe Charlie Christian is magic. I hate having two jacks on the rim of the guitar, so I've been exploring what to do with the signal chain when I have both the piezo and mag on the guitar. Wiring to a stereo jack and then using a "Y" plug that splits a TRS plug into two TR jacks seems to be the obvious choice. That keeps the guitar clean, but puts the onus on the player to deal with the signal.
The piezo then can be sent to a preamp and the signal recombined at mixing pedal. That't lots of extra gear just for your guitar, but placing all that onboard feels like a step too far.

Of course, the other suggestion is to mic the guitar. Naaah... Way better to use a bunch of single purpose electronics!
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Re: Acoustic Archtop

Postby Beate Ritzert » Tue Jul 18, 2017 5:43 pm

Wow, that's a really beautiful instrument!
I like Archtops with well designed alternatives to the pseudo-classical f-holes.

Regarding the pickup: Your pickup seems to be mounted too far from the strings. The only solution is to find a way to have it closer to the strings.
A commercially available alternative might be the shadow nanomag system, mounted into the edge of the fingerboard.

A custom alternative might be a simple LoZ pickup: 6 Alnico magnets and a small bobbin with just 500 windings of some not too thin wire. This thing will have the output of a microphone, and it requires to be loaded with the low impedance of a microphone preamp. These LoZ magnetic pickups have very linear and wide frequency responses and are able to reproduce a really nice acoustic sound. The treble resonance of the pickup is outside the audible range and needs to be dampened in order to protect the tweeter of the PA. And yes, it can be played passively right away into the Mic socket of a PA.

In an acoustic archtop i would attach such a PU to the end of the fingerboard or even integrate it into the latter - but close to the strings!!!! And i would seek for a solution to have a plug at the pickup and leave the soundbox intact. Something like this one (from the 50s) but prettier:

Image
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Re: Acoustic Archtop

Postby Ed Lysne » Tue Jul 18, 2017 6:22 pm

I do the mag pickups on all my jazz guitars... and I have that well under control. This is a piezo system. Mag pickups are great for electrified guitars... I'm really focusing on the pure acoustic sound. I've been thru most of the alternatives... Mag with Mics... Piezos with Mics, mixers etc. Internal mics just don't work well for live settings or bigger venues. I'm really looking for something closer to the sound board where the guitar sound is generated. I've played around with Piezo's under a bone saddle... but the results are predictable... harsh and with quack but big sound. The soundboard mounted K&K type system seems to give the most natural acoustic sound (IMO)... but there are gaps on the mid-range I'm hearing from some of the players using my guitars. On my nylons... Mags are not a choice... and my experience with internal mics has not been great for bigger venues with drums and bass.

I'm also looking at the Fishman Aura® Spectrum DI Preamp. I know James Taylor is using this system now.. with a sound board piezo...and he gets great results in the bigger venues. You can mix the amount of DI into the sound... I haven't tried one but I'm hoping to find a flexible vendor. This is a "Processed" sound... so their are tradeoffs I suspect. No feedback... which works for bigger events. For my Nylons.. I'd have to workout the target sound profile first and use that template to process the sound thru. I've heard mixed results with doing this... and it's takes time to work all this out.

I'm thinking of a one piece bridge with some sort of piezo setup mounted down near the plate... high output with enough of the top plate mixed in to get the sound I want. I'm going to try and engineer something...maybe glue the piezo discs to the side of the bridge with a cover plate... and a wire threaded thru the bridge and down thru the sound board where it's not visible. I want the mount to to be hidden and not detract from the guitar.
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Re: Acoustic Archtop

Postby Beate Ritzert » Tue Jul 18, 2017 8:07 pm

Mhmm, i was talking about low impedance magnetic pickups. These sound REALLY different from what is usually assigned to magnetic pickups. I doubt That Your experience covers this field - it is pretty exotic.

And that has historic reasons: in the late 40s/early 50s it was quite expensive to build high quality microphone inputs and it was a lot more demanding to make HiFi-speakers.
It was a lot easier and cheaper to give magnetic pickups coils with many windings and thus high output. It just saved one triode stage, even a differential one. Giving the pickup coil many windings has a side effect: as a pickup is more or less a 2nd order low pass filter, its corner frequency sank far into the audible range. Not too bad for cheap loudspeakers with their also limited range in the treble. And that made the whole system - guitar plus amplifier affordable for the perfoming musician.
And that's the technology we got used to as electric guitars with magnetic pickups.

What i suggested sounds actually radically different: a magnetic pickup can be really "HiFi" if done "right". And that means linear in the audible range and high pass frequency in the ultrasonic range.

Such a pickup will definitely retain the acoustic sound of the instrument. I tried in a solid body and even there came to a warm "acoustic" sound as far as a solid body can deliver (in this case with a body made of spruce). That's a little less bassy and a lot more sustain than an acoustic. I am using a tele neck pickup (small aperture, i.e. capable to pick all the overtones well) rewound with 500 windings of thick wire which is placed at 10% scale length, i.e. close enough to the bridge in order not too lose too much of the significant overtones.

So i have actually tried what i suggested, and it is really worth trying this. With the exceptions of the Nanomag and the Fishman used by Ken Parker there are no industrial products - You would need either those or have custom designed. Les Paul also used Low impedance pickups, even in his early guitars (afaik, he did not give Gibson the pickup design he was actually using).
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Re: Acoustic Archtop

Postby Barry Daniels » Wed Jul 19, 2017 11:00 am

Here is a link to the Shadow Nanomag: https://shadowelectronics.com/products/micro-sonic-nanomag-pickup-with-volume-control

It looks interesting. In order to mount it into an archtop you could attach the pickup to the end of the fretboard and drill a small hole in the top underneath it where it would be mostly hidden. Also, you would need to install a battery box somewhere in the side of the guitar.

The MIMF blending preamp with three watch batteries under the pickguard is a more elegant solution. As far as I know, I made the only one in existence (the archtop version that is).
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Re: Acoustic Archtop

Postby Mike Conner » Wed Jul 19, 2017 11:12 am

Ed,
I'm getting output equivalent to a magnetic pickup using JJB 220 piezo's (essentially the same as K&K) mounted in my X-braced 16" archtop and 14.5" octave mandolins as shown:
B042 - Pickup Elements installed.jpg


The JJB is encapsulated somehow and gives a nice warm tone glued directly to the top plate using gel superglue (without the K&K recommended 3M tape). The treble transducer is just in front of the treble bridge post, and the bass tranducer is about 3/4" ahead of the bass bridge post.

For dual magnetic/acoustic builds I am using either a Vintage Vibe neck mounted humbucker or a full size top mounted humbucker wired to the tip stereo endpin connection, and the JJB to the ring connection. A 1/4" stereo cable to a Radial Tonebone allows for buffering and blending. The volume settings I am using are essentially identical, so the pickup outputs are likely identical also.

The location of the piezo transducers have a big effect on the output and tone. The usual installation through the f-holes on a completed instrument tends to be just inside the f-holes, which yields a "tubbier" sound and significantly less volume.

Can you share more information on the preamp package, and how you addressed the 9V battery location?
//mike
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Re: Acoustic Archtop

Postby Ed Lysne » Wed Jul 19, 2017 2:40 pm

I have an email into Barbera transducers. The prices have me floored a bit... but I my customers will pay for it if we can get the right blend. He makes them custom for the saddle size you request. There are some youtube videos if you do a search. This may be the answer I'm looking for.. but we'll have to see.
http://www.barberatransducers.com/
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Re: Acoustic Archtop

Postby Steven Wheeler » Wed Jul 19, 2017 10:50 pm

Greetings Ed,
Long time. The new guitar looks great, I'm sure your brother is quite pleased.
As I was reading through the thread I was thinking Barbera the whole time but you found your way there on your own. I've no experience with them but knew there was an alternative to what you have tried. I do have a twin JJB in a drawer if you want to give it a try.

Steve
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Re: Acoustic Archtop

Postby Mark Swanson » Thu Jul 20, 2017 1:15 pm

You could use a regular undersaddle type piezo or a Fishman type bridge with the pickup built into it if you don't mind drilling a hole under the bridge. I know it sounds scary drilling a hole under the bridge location but it will be covered by the bridge all the time. I do it on my mandolins, it has never been a problem. I do glue a small spruce disc on the underside of the top at the holes' location for a little extra reinforcement.
    Mark Swanson, guitarist, MIMForum Staff
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Re: Acoustic Archtop

Postby Ed Lysne » Thu Jul 20, 2017 3:06 pm

Steve--> thanks... yes it's been awhile... we should connect sometime. I've used the JJB's...and they are about the same as the K&K's in my opinion. They work for sure.. but some of the frequencies are cut short compared to pure acoustic sound on an Archtop.

Mark... yes, thanks... I'm thinking along the same path... small hole thru the soundboard with bridge mounted piezo/transducer. I figure I can get the setup all worked out and then drill the hole where it can't be seen...with a small cavity under the bridge for wire to sit and not get pinched... which would also allow for slight adjustments to dial back in pitch for differing string gauges. I've always struggled with the piezo quack... and when I hear some older installations I cringe a bit. The technology has really evolved in the last 5 years for sure...and now I think it's about finding the right solution using an under-saddle solution.

This is really all about my Nylon Sting Archtops... which I really love building now. I have a few customers who really like the sound... and attack... but are frustrated by the amplified sound. I also want to solve the steel string issue... and I'd like to do it with high quality discreet components.

I wish I knew more about this whole subject... I'm just not a gearhead when it comes to amplification... I should have paid more attention when I was around the experts. The technicalities of pre-amps... low-high impedance and the differences between amplifiers and PA systems are not something I have a full grasp. I've gone out to hear players using my guitars in various situations... and the differences between sounds systems can really drive you nuts. Several pro players I work with regularly travel for gigs... and don't always haul an Amp with them... so the guitar needs to work in this environment too. I good sound engineer can usually quickly work this out... but that's not always the case at a festival for example. I'm learning... and trying not to spend a kings ransom along the way.
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