Onboard Preamp

[KennyE]

Thought I'd post this here in the builder's forum rather than general discussions. Simply because it has to do with modding an existing mandolin. Which brings me right to the first question: Have any of you installed a preamp in your mandolins or someone else's, ala the type used in guitars? I know guitar pre-amps are way too large for a mandolin. But what about smaller ones, not necessarily designed for guitars?

I'm versed in pre-amps on the floor, just don't like them. And I feel one could have better control over the sound of an amplified mandolin with controls you could get to more easily - such as those side mounted.

I found a small ukulele pre-amp that seems like it might fit. I have a new Eastman octave and I'd like to put that pre-amp in the mandolin. But ... I'm not sure what I would be cutting into as I've not seen the inside of a mandolin. The cutout would be 1.3" * 1.4" * 1.2 (deep)". The overall dimensions are 2" * 1.6". The overall depth of the side on the octave is shown as 1.875". Seems ... tight.

I asked one shop about installation - they quoted $300. Just to mount the pre-amp. I know that's cutting and fitting. But ... $300? Or is that reasonable?
Hope that isn't too rambling of a post.

[rockies]

Kenny, I've used tha Artec ME-2 preamp made for mandolins with the K&K internal pickup in about 20 or so mandolins when I had my shop. I use it in my own mandolin in the band I play in. I just did another of my mandolins a couple of months ago but had a terrible time getting one. The USA dealer stocks the Artec guitar preamps but wouldn't even answer emails about the mando preamp. They sell for about $25 USD and work great.
Dave

[KennyE]

Dave, that's encouraging. I looked briefly at the Artec a couple of weeks ago. Ended up with an Ammoon. Did you use a standard output jack with your units? I may look at the ME-2 again, since you've had success with it. Thanks!

[rockies]

Kenny yes I used the a standard 1/4" phone jack that came with the K&K internal pickup. I would drill out the tailpiece and the body to 1/2" for the jack and then modify the little mini plug to the input of the ME-2. I actually installed the K&K's after cutting the hole in the side to install the pickup as it gave me access to the inside of the mando. Good luck getting the ME-2 from the dealer .. I actually contacted Artec in Asia and whined enough that they gave in and sold me one direct, they usually have a minimum order of 20 units. Try the dealer and maybe he'll start stocking them again. Good luck.
Dave

[Nevin]

I don't know what labor rates are where you are but in expensive NYC $300 sounds reasonable. The work involves some pretty big changes that should be done very cleanly while working on curved uneven surfaces and then wiring in pretty small space. It is detail oriented fussy kind of work where a lot can go wrong easily. I would pay $300 to know it was being done right.

[Ray(T)]

Isn't the main problem of installing a preamp in a mandolin where to put the battery?

I started a thread a couple of years ago when I had a problem with an acoustic bass which seemed to be picking up hum in the house making it largely unplayable. I thought I might improve things by fitting a preamp as close to the pickup as possible but, as it has a solid mahogany body, there was nowhere to easily fit a battery. I recently ended up fitting a Mi-Si Crystal preamp - http://mi-si.com/products/

They don't need a battery; you simply charge them up with a wall wart through the jack socket. I thought they might be useful on mandolins.

[Tavy]

+1 on the endpin pre-amp - a quick search will show up all kind of models, but as Ray says, finding somewhere to mount the battery is an issue. The neck block on an oval hole mando would just about be doable, but is no good for an f-hole model

You could fit a standard allparts battery holder, but this has the same issue as fitting a side-mounted preamp: you'll be cutting into some very thin mandolin sides, and greatly weakening the structure of the mandolin. Ideally the cut out area should be properly reinforced, otherwise not only will the screws pull out in short order, but if you ever ding the instrument on the weakened area, will likely turn into a mass of splinters - in fact I know more than one person who's basically wrecked a nice instrument doing exactly that!

[pops1]

Years ago I had Misi make a preamp for a fishman bridge pickup for a mandolin. I didn't like their setup as you would have to shim whenever you moved the bridge up or down. I sent them the fishman and he used the capacitance in the fishman for the storange of the charge. A piezo is like a capacitor and that is what stores the charge, it's pretty ingenious actually. You could do the same thing with a K&K and install it inside, the only difference is that they would have to build the preamp on an endpin that you could put into your mandolin instead of a long female jack that they use in the carpenter. They were nice folks and very accommodating. If something like this interests you I would contact them.

Another drawback is you would not have a volume on the mandolin, but since you are coming out of a preamp already you could use any volume pedal without a problem.

[rockies]

The Artec preamp ME-2 shown in photo comes with a battery box which I mount in the lower treble bout. It has a door that opens for replacement. I use my main mandolin in the band about 12 hours a month and replace battery yearly, just because..as it's never gone dead. The ME-2 has volume, bass and treble controls and installs easily in the mando rim as in photo. All of the ones I installed (about 20) were retro fits (cut openings, install pickups, jacks etc) other than the one I use in the band. It had preamp, pickups installed before the back went on.
Dave
Dave

[KennyE]

I've attached a pic of the one I currently have. Not necessarily the one I'll end up with. Not too worried about the preamp. But that end pin box could be problematic, since it does require a bigger hole in the bottom side, not in the end pin.

I had thought about reinforcing the holes with some furring strips of some sort. Glued to the inside of the rim. That way the screws would have something more to hang on to.

I've spent the morning trying to locate a preamp with EQ and Tuner small enough to fit the rim AND with an endpin jack. Nada so far. The MiSi look cool. But not exactly what I'm after. If I'm going to cut into this thing I figure I might as well get what I want. And, it's not like I'm cutting into a $7k hand made OM. It's a $700 mando. Not chump change, but not what I spent on my MD615 or the Heritage H40 for that matter.

Appreciate all the good advice.

[KennyE]

The Artec preamp ME-2 shown in photo comes with a battery box which I mount in the lower treble bout. It has a door that opens for replacement. I use my main mandolin in the band about 12 hours a month and replace battery yearly, just because..as it's never gone dead. The ME-2 has volume, bass and treble controls and installs easily in the mando rim as in photo. All of the ones I installed (about 20) were retro fits (cut openings, install pickups, jacks etc) other than the one I use in the band. It had preamp, pickups installed before the back went on.
Dave
Dave

Dave, Artec has a newer eq with tuner that looks interesting. It's the UTN3 <-- link. Seems Artec's American dealer is now only selling on the 'bay. With no real way to contact them. I'd need that thing and the end pin jack. The battery is in the preamp box. No need for internal mounts. What do you think?

[Ray(T)]

Pops - Not so sure about the piezo being a capacitor but the Mi-Si I linked to has what appears to be a large capacitor on a small board attached to an end-pin jack. In some ways, it might be easier mounting one inside a mandolin than with the bass; i.e. Its no worse than fitting an endpin jack.

[rockies]

I meant to mention that on my installs, after cutting the openings for the preamp and battery holder I did reinforce the rim where the mounting screws went with a 1/16" strip of maple. Rim thickness is on the order of .100" and when the metal plate is screwed to the rim it actually takes the place of the removed rim material. Over the 12 or so years I did these installs I have never had one come back with a problem other than a couple where the output jack came loose and needed yhe nuts to be tightened. Now mind you I never installed these in really expensive mandos even though I was asked, I suggested they purchase used decent quality ones if they were needing band amplification. I found the ones I liked best (tone wise) were installs in Kentucky and a couple Eastmans. The best to my ears was my own build but I may be prejudiced.
Dave

[rockies]

Kenny that's what I found so I cried to Artec Company on their website contact to get one. If you use the K&K internal pickup which I recommend (no matter what preamp) it comes with the output jack you will need.
Dave

[KennyE]

Kenny that's what I found so I cried to Artec Company on their website contact to get one. If you use the K&K internal pickup which I recommend (no matter what preamp) it comes with the output jack you will need.
Dave

Dave, I just fired off an email to them, right before seeing your post. Great minds and all. How often did you have to bug them before getting a reply? Will look at the K&K, again. I have some JJB's sitting around. Ones I work with them on when Jesse did the violin/mandolin set (that's my fiddle on their website). But, they do not have endpin jacks.

Good deal on the maple reinforcement. Will def do that.

[pops1]

Pops - Not so sure about the piezo being a capacitor but the Mi-Si I linked to has what appears to be a large capacitor on a small board attached to an end-pin jack. In some ways, it might be easier mounting one inside a mandolin than with the bass; i.e. Its no worse than fitting an endpin jack.

Ray, yes there is an electrolytic cap on the preamp, but they told me at Misi that they had to match the capacitance of the pickup with the preamp, so I thought it was part of the charging along with the electrolytic. A cap is a nonconductor between two conductors and that is what a piezo is also.

[Ray(T)]

The installation guide says that its designed specifically for passive piezo pickups - http://mi-si.com/wp-content/uploads/...tal_manual.pdf and advises you to ask if you wish to use anything else. My bass has a Baggs.

[kkmm]

I have installed one similar preamp (with in the bridge transducer) on 3 mandolins, one violin and one viola.
The preamp which is easy to remove so one can replace battery. Here are the photo on a Kentucky pancacke mandolin. (2" thick).


To put the transducer inside the bridge, I cut the bridge in two (parallel to the sound board), insert a transducer which is cut to fit lengthwise, then use epoxy to glue the two pieces of the bridge together. This works on both flat top and curve top mandolin.
I bought these preamps from eBay for 15$/each. The output it standard 1/4", exactly the same as on guitar.

[kkmm]

Here is the photo showing the preamp removed to expose the coin type battery.,
Attachment 162067
It's very easy to remove the preamp and insert it back.

By the way, I had to drill a tiny hole (2mm diameter) on the top sound board , under the bridge where the transducer cable sticks out so it goes inside the body. Since the hole is under the bridge, it is not visible.

For violin, I use the flat type transducer that lays under the bridge and enter the body via the F hole, no hole drilling is needed on the top sound board. I can't hardly tell whether the acoustic sound is any different with or without this transducer. Amplified sound is of course depends on electronics.

[KennyE]

I have installed one similar preamp (with in the bridge transducer) on 3 mandolins, one violin and one viola.
The preamp which is easy to remove so one can replace battery. Here are the photo on a Kentucky pancacke mandolin. (2" thick).


To put the transducer inside the bridge, I cut the bridge in two (parallel to the sound board), insert a transducer which is cut to fit lengthwise, then use epoxy to glue the two pieces of the bridge together. This works on both flat top and curve top mandolin.
I bought these preamps from eBay for 15$/each. The output it standard 1/4", exactly the same as on guitar.

Interesting take on the adding the piezo. Altho' I'm not so sure I'm up to cutting a bridge in half. I currently have the piezo rod that came with the unit stuck between the base and the top on the bridge. I shimmed it just a bit with some old picks cut in strips. Sounds pretty darned good. And is just ... almost ... the right height. This is all temporary as I'm trying out the preamp, first. I've got some 2.5mm plugs coming that I'm going to wire my old JJBs into and see how it reacts to that preamp. All before I cut into it. Or order newer piezo discs.

Did you drill a hole thru your bridge for the connecting wire? And how did you run it to the jack?

[almeriastrings]

It is worth noting that the EQ circuits (especially), and in virtually all cases except for a few 'high end' types, the front end (impedance matching) sections are not even remotely close in quality and technical performance to what is typical in the better external piezo preamps. The EQ is 'rough' and imprecise, and the front end noisy and with very restricted headroom. This is even more the case in those that run off the 1.5v 'coin' cells. Given that you can get some extremely small, but very high quality and versatile external boxes that vastly outperform any of these cheap units, and you also avoid chopping holes in your instrument, I'd think long and hard before taking this route. The little Headway EDM (on the left here) is one example of a very small pro-grade external pre that works just great with almost any piezo install. It even has a belt clip and stand mount for easy access. You also get a fully balanced (via TRS) DI output from this and it can run from phantom power too...

[KennyE]

For me it's one less pedal. This will not be my main instrument on stage. Rather, one of 5. Anything to cut down on the clutter.

I'd read in another post about the lack of headroom with the coin batteries. In my rigged up setup I haven't noticed that ... yet. Taking it all for a spin with the loud prog band today. That should have some definitive results.

[almeriastrings]

I'd read in another post about the lack of headroom with the coin batteries. In my rigged up setup I haven't noticed that ... yet. Taking it all for a spin with the loud prog band today. That should have some definitive results.

The 'headroom' issue manifests when the transducers produce large peak-to-peak voltages when driven hard, effectively exceeding the capability of the front-end of the preamp to cope with it. This can even be a problem with circuits powered by 9v batteries - with 1.5v it is exceedingly difficult to overcome. Even with some of the top-rated piezo DI's/preamps, they generally perform better when powered by +48v than they do from batteries for this very reason.

[Mandobart]

I'm with almeriastrings regarding chopping into small instruments. I've used the K&K Pure preamp quite a bit. Good sound, inexpensive, volume and eq pots close at hand. Belt clip mount so its not another floor pedal. Another good similar option is Baggs' Gigpro. No major mando surgery required.

[rudy44]

Ditto on hacking holes in an instrument. I'm an advocate of the K&K transducers; run them to a floor device with a high quality low capacitance 1/4" cable, preferably no longer than 10 feet in length. Using a preamp is much more about impediance matching than actual EQ, although it's nice to have the ability to boost for solos, etc.

I used a good multieffects pedal when I gigged with a lot of instruments and had presets for mandolin, lap steel, fiddle, Telecaster, and acoustic guitar. I programmed in a MUTE patch so switching instruments was quick as well as silent. My total rig was a Digitech pedal and a D.I. box, so "stage clutter" wasn't an issue.