A K&K Pickup on a Ukulele Story

[John Maddison]

G’day All

This ‘buyer beware’ scenario relates to the under-performance of a piezo K&K Pickup. A recent commission was for a ukulele with a pickup. The build is a Tiger Myrtle Concert body; 2mm Bearclaw Sitka Spruce top; a tenor-scale neck (i.e. slightly wider fret spacing) and Aquila Low-G concert strings (slightly more tension & brightness) fitted to a WA Jarrah bridge.

I placed an online order for a K&K Twin Spot Internal from Paul Stokes’s sonicwavefactory on eBay. As he was out of stock of the Twin Spots he offered me a substitute K&K Pure Maccaferri for the same price, stating in his email that “the tech specs are the same for both pickups”. In hindsight this hasn’t been the case*. Prior to gluing the pads to the bridge plate I tested each one by plugging them into a small practice amp and tapped each of the metal plates to get an audible signal at mid-volume, so I assumed everything would go according to plan.

Here are a couple of pics of the pickup installation. I used CA Gel as supplied and followed the instructions to ‘apply a liberal amount of the gel’ to ensure a good bond (note the squeeze-out of gel). The bridge patch is a thin slice of rock maple, and the two pads were positioned to lie between the G & C strings, and the E & A strings … i.e. fairly symmetrical under the bridge (see image in instructions for installation on a 6-string acoustic).

KnK Pickup Installed.jpg (215.62 KiB) Viewed 25730 times

Close Up of Pads:

Closeup of Pads.jpg (170 KiB) Viewed 25730 times

When the uke was finished and plugged into the same practice amp – nothing!! Not even the slightest sound with all controls cranked to the max. I tried testing on Pete Young’s guitar amp but still no joy.

Here is the transcript of an email I received from K&K Sound Systems Tech Support via Paul Stokes:

The Pure Maccaferri pickup is of different construction and materials than the Twin Spot Internal. However the Maccaferri pickup should still produce an output signal that is usable. It must be remembered that the acoustic output of most ukuleles is very low and so the pickup produces a small signal. Most practice amps are designed for magnetic pickups and thus have low input impedance which will heavily load the pickup output and reduce the low signal even lower and seriously trim the frequency response. A preamp will probably be necessary to get a good signal level and to isolate the pickup from the amp input load.

As the Pure Maccaferri pads are larger a greater amount of glue is required. If insufficient amounts were used then it is possible to have a bubble or void under the transducers which will dramatically reduce the output level and kill most of the bass response of the pickup. * To correct some information: the diameter listed on the website for the Pure Maccaferri is incorrect; they are not ½” but rather ¾” diameter and the materials are different than the Twin Spot Internal.

I can’t complain about the level of customer service from sonicwavefactory …. in recent days Paul has generously supplied me with a K&K Pure XLR Preamp at a reduced price, PLUS a replacement Twin Spot Internal pickup free of charge (which I’ll use in a replacement build for the client).

The Pure XLR Preamp has improved signal levels just slightly; at least now I have a signal out of the practice amp which is clear and audible, though the gain and volume controls on both the preamp and practice amp have to be wound almost flat out. Not ideal. I tried the uke/preamp combo last night on a mate’s guitar amp with very similar results. At about $300 out-of-pocket I’m chalking this build down to experience; on the up side I’m the proud owner of a new K&K Pure XLR Preamp and the uke itself sounds pretty good unplugged – it’ll be a keeper.

I'm apprehensive about fitting the replacement Twin Spot Internal to this next build just in case I experience the same dramas, raising a few questions:

- Is there a risk in using TOO MUCH of the CA Gel to glue K&K pickup pads?
- Is there an absolutely optimal position to place the Twin Spot pads under a ukulele’s bridge?
- The Twin Spot Internal pickups do not come with CA Gel supplied …. Would I be better off testing the next installation with double-sided tape (supplied) first, before a final fit with CA Gel? Probably yes!
- I’ve bought a tube of Loctite SGX3 Super Glue Xtra Gel for the next build … is this suitable? … Are all CA Gel products pretty much the same?
- Are all guitar leads the same? … i.e. do some have lower loss than others?

Your thoughts and comments are welcomed!

Cheers all

[Tod Gilding]

Hi John, Just looking at your second photo, Is that CA around the area where the wires enter the plastic casing ? and if so,was that put there by you or the manufacturer ?

I only ask because I have been making my own K&K type piezo pups and enclosing the disk in varying density wood,on one occasion I did drop some CA onto the area where the wires exit and ended up with the CA getting into the disk which gave me symptons very similar to what you are describing.

[John Maddison]

Hi Tod
The CA glue you see in the pics is all from squeeze-out that I applied liberally as per instructions, though I may have gone overboard given this is my first experience with installing transducers. The two pads and associated leads were completely encapsulated in black plastic when they came out of the box (except of course for the brass or copper (?) pads to which I applied CA).

Thanks for thefeedback!
Cheers

[Kim]

I have not fitted K&K's to anything but a 6 string acoustic John and as you know I really like them in that application. I know its probably not much help but it appears the most obvious cause of the problem was the fact that you were supplied with the wrong K&K product. It sounds like Paul Stokes had assumed the K&K maccas were the same specs as the two spot based upon the fact that both kits have only two transducers in the kit. K&K tech support has suggested that you should get 'something' from the macca version and now that you boosted the signal with the preamp that appears to be the case so you know the circuitry is in order. With that I would be looking back at the fact you are using the wrong product for a uke as the core issue rather than getting too concerned about which breed of CA to use.

The two spot iteration has been around a while now and K&K have too much good rep built up from users of their pure and western mini to have it torn down keeping dud products in the line up. If it were me I would use the two spot for the next build as intended, a uke pickup in a uke, and see how you get on. I would reduce the amount of glue your using though, you want enough to makem stick with a tad of squeeze out but that's all you want.

Cheers

Kim

[Kim]

John, I just had a look at the K&K website. The fitting instructions for the two spot internal on a uke appears to show the transducers positioned inline with the outer strings, but well forward of the bridge plate.



http://www.kksound.com/findpickup/ukulele.html

They say to fit them with your fingers through the soundhole using the double sided tape provided. As I said, my own experience with K&K's is restricted to guitar so perhaps there is more to it but I suspect the fact K&K appears to have them position directly to the soundboard in front of the BP could be the reason you have had such grief. Have you checked some of the uke forums to see what others have had to say??


Cheers

Kim

[Bob Connor]

I've fitted a number of twin-spots to mandolins and have had good results placing the pickups under the feet of the bridge.

Regards

[John Maddison]

Kim

You're a bloody genius!!

No, hadn't gotten into other forums to find a solution, but hey thanks for that image and link. The positioning is pretty much spot-on to where Allen Macfarlen placed his transducers on a build featured in the Gallery in recent weeks. Before I glue the top down on the next build I will double-sided tape first and test into the preamp/amp. If all good then remove pads, clear gum residue, then glue down.

All the bestest ... Hope to see you down this way over Summer!!
Cheers

[Trevor Gore]

I've installed lots of K&Ks in both classical and steel string guitars, either the 3 unit mini westerns or the 4 unit mini classics. There's a piece on how I do the installs and some of the (minor) issues you can run into here. The units for the two spot look exactly the same as those used in the mini westerns and mini classics, though I have never used the two spot. I'm inclined to agree with Kim, that you were offered the wrong pick-up. The minis have a huge output and will drive the line level input of a standard hi-fi amp (10k input impedance) quite easily, so with the right pick-ups I find it hard to imagine an install so bad that you would loose nearly all the signal. On guitars, a preamp is really only necessary for impedance matching and EQ, rather than gain and I don't see any reason why you should be short of signal on a uke. So I would suggest getting either the two spot (or the classic with 4 pads and then buy an extra jack socket so you can make 2 two spots, whichever works out cheaper) and installing them in your uke. The install should go fine using the swivel head tool shown in the other thread if you can get the macca ones out reasonably cleanly. I'd be looking at making a custom chisel/mini burger flipper to do the extract (or just leave them in and put the two spots forward of the bridge plate).

[John Maddison]

Cheers Bob
Good to know ... do you use tape or CA Gel? Part of me doesn't trust sticky tape.
All the best to you!

BTW ... Rumor has it the themed instrument for next year's Playmakers in late February will be the Selmer Maccaferri. Yet to see the official program.

[John Maddison]

Thanks Trevor for your sound advice. I had a close look at your original thread when you first posted it, very clever design. I'm not too confident that I'd be able to remove the Pure Maccaferri pads in one piece, given they are WELL stuck, and inside a concert sized Uke body. But your solution is an inspired one!!
Cheers

[J.F. Custom]

G'day John.

I've just installed a twin-spot in a Tenor Ukulele too.

I used the supplied tape on this occasion so as to be able to adjust them more easily should it be required. I also installed them as I have on larger instruments, directly under the saddle. I had not seen the photo Kim posted of the suggested forward position.

Now this brings to mind two questions - Why does their suggested positioning change for a ukulele? I would have thought the best and most direct response would have been under the saddle, but it appears not to be the case? Second, why do they supply only the tape for the twin-spot, not gel glue as with other pickups?

They claim the gel glue to be far superior in vibration transfer, than the tape on the pure mini literature. Yet on the twin spot, they suggest the tape is completely transparent of any influence on signal... ?? They can't both be correct.

In any case, this instrument is incomplete. I have installed the pickup, but the instrument is about to undergo it's finishing regime. I'll be able to move mine if I am unhappy with the performance upon completion. On the other hand, if I'm happy with the signal where they are, I probably won't remove them to use glue instead.

Finally, as the glue supplied with say, their pure mini, is "KRAZY" super glue in gel form, I'd say any gel cyanoacrylate will work just as effectively! Hardly 'top of the range' super glue that...

Good luck.

Jeremy.

[vandenboom]

I'm surprised that you got such little change following use of the pre-amp. Just checking that you got inside the preamp and adjusted the 'hotness' of the input, as I am assuming that this feature exists on this unit.
Frank

[Kim]

John, the only impact of the macca version where they sit now is all negative so there is no point leaving them there swinging from the bridge patch. I would suggest removing them and you can do that pretty quick easily with a big fucking hammer.......

Just kidding..but you can get K&Ks out without doing any damage to the uke...probably won't do the K&Ks much chop though. When fixing other peoples bad installs (true I promise, mine have all gone quite well however the first was just a bit soft on the bass because of poor alignment) I have used a mirror and a cotton wool swab soaked in acetone, (you could use a bit of cotton wool wound onto a sprig of stiff wire) to drench the buds to dissolve the CA and clean up the BP.

I've only done this twice...First time it destroyed, i.e. melted the K&K's, well one of the buds anyhow, and the next time I got them all off clean so the set was reusable. More importantly no harm was done to either instrument.. By the way I am not suggesting I had learnt something from the first attempt which improved the outcome on the second because I am wise enough to know that when it comes to removing K&Ks this way, complete success lay solely at the whim of the great spirit Footah..

Cheers

Kim

[Bob Connor]

Hi John

I've always used CA and recently K&K haven't supplied the CA gel so I've used whatever I've had on hand.

Regards

[Kim]

G'day John.

Now this brings to mind two questions - Why does their suggested positioning change for a ukulele? I would have thought the best and most direct response would have been under the saddle, but it appears not to be the case? Second, why do they supply only the tape for the twin-spot, not gel glue as with other pickups?

Jeremy.

Jeremy, just my speculation but searching around to help John out I came across other installs of the twin spot, I think a mando and an oud which had the buds fitted directly to the soundboard. Maybe a guitar has the punch to drive three buds from the BP, but perhaps instruments with less drive work better with just 2 buds direct to the board and whilst K&K do suggest that CA is superior to tape when fixing to the BP, perhaps it would make things too hot and brash when fixing the buds directly to the soundboard so the preference becomes tape in order to take the edge off them?

As I say its just speculation but I do know that quite a few people over the years have had problems with their guitars sounding brash and boomey when they had assumed the K&K pure and western standards, which have large transducers, would work better than the pure and western minis, its a mistake they only make once because these things are quite sensitive and little changes can make a huge difference.

Cheers

Kim

[charangohabsburg]

Now this brings to mind two questions - Why does their suggested positioning change for a ukulele?

To me it looks as they are talking (or thinking) of fitting the pickups to a finished instrument. They write:

You can reach these spots with your fingers through the soundhole.

In a ukulele I can not reach with my fingers through the soundhole down to the bridge position.

[John Maddison]

Gentlemen

I thank you for your collective wisdom re this post.

Frank - I'm gobsmacked too and more than a little disappointed after forking out $190 that adding a K&K Preamp did not result in much improvement. There does not appear to be an on-board pot which allow the user to adjust the 'hotness' of the preamp; the only conventional controls are a smaller pot labelled Gain and the larger knob to adjust Volume ... see image here with the cover off:

XLR 2.JPG (309.81 KiB) Viewed 25642 times

Kim - I think you've summed up very well a response to Jeremy's well-thought out questions; would be keen to see links to the sites relating to an install of the Twin Spots on Mandos and/or Ouds. Rather than getting in there and trying to remove the Maccaferri pads I'm inclined to just leave them alone for posterity and keep this uke for acoustic playing, and also trust that given they are well super-glued on they will stay put. Good tip though regarding the use of acetone to soften CA - a tip I wasn't aware of till now. An interesting comment too about uke soundboards having less 'drive' that a steel string acoustic. Makes sense!

Interesting point too, Bob, that K&K pickups are no longer supplied with CA gel. I STILL have a lingering doubt about fastening the pads with double sided tape - a friend recently showed me a uke with pickup that had a loose pad which had been installed using tape.

[John Maddison]

Excellent points Markus ... I had the same thought this evening that K&K are selling these Twin Spot Internals with a view to the client retrofitting a ukulele, rather than installing the pads during a build prior to gluing down the top.
Cheers

[Kim]

would be keen to see links to the sites relating to an install of the Twin Spots on Mandos and/or Ouds.

With a quick scan though chromes visited links I managed to dig up the mando reference John, but there is at least one or two more images out there of other instruments I came across this arvo that show the same thing, buds attached direct to the soundboard.




http://artisanguitars.com/k-k-mandolin- ... nal-pickup

Cheers

Kim

[John Maddison]

Good stuff, Kim.
Notice that site refers to the word 'retrofit' and the use of tape to fix to soundboard.
I dropped a line to K&K Tech Support tonight regarding some of the points raised here. Given the time difference I await their reply soon. Will post here any advice they offer.
Chiz

[Kim]

It certainly looks like the twin spot is a product designed to cater for the reto fit market. The fact it can be fitted directly to the soundboard offers a solution for those instruments with limited access, such as archies, mandos and ukes etc but it will be interesting to know if it is not recommended to fit then to the BP...we wait and see..

Cheers

Kim

[jeffhigh]

Despite what K and K have told you about "different construction" I am surprised that you are not getting usable volume.
Perhaps a fault in the soldering at the jack or an internal fault within the jack?

Kim, when you melted a K&K removing it, did you find anything other than a piezo disc and a plastic cover?
I suspect a lot of the differentiation between the models offered is just Disc size selection, cable length, and output jack type.

[Tod Gilding]

Despite what K and K have told you about "different construction" I am surprised that you are not getting usable volume.
Perhaps a fault in the soldering at the jack or an internal fault within the jack?

Kim, when you melted a K&K removing it, did you find anything other than a piezo disc and a plastic cover?
I suspect a lot of the differentiation between the models offered is just Disc size selection, cable length, and output jack type.

+1 Yes it would be hard to not get a useable volume regardless of where the piezo was placed
I would also be interested in knowing what's inside Jeff, maybe K&K has devolped a Piezo magic dust

[John Maddison]

Gents, an update!

These are the questions I posed to K&K Tech Support in an email Wednesday night.


Hi Jack

Can you confirm whether your help page on installing a twin spot internal pickup to a ukulele (http://www.kksound.com/findpickup/ukulele.html) relates only to retrofitting an EXISTING ukulele.

I am a ukulele maker and would like to install this model pickup in its 'optimal' position which I would imagine is on the bridge patch itself,
prior to gluing the top to the body. If this is the case would you install the pads directly underneath the G and A outside strings, or install them
directly below the gaps between the G & C, and E & A strings, or is there no difference likely?

Also, is CA Gel a better alternative than using double sided tape supplied with the unit, or is there very little difference in output
performance/frequency range either way?

With thanks

John Maddison
Albany Western Australia



Lo & behold by first thing Thursday morning here is the reply. Jack Baley is the tech guy who sent me the original email re preamps (above) via Paul at sonicwavefactory …

John,

You are correct in your assessment of the installation instructions for ukulele; they are for fitting to a completed instrument. The position shown
is a compromise due to the extreme difficulty in getting the transducers of the pickup very far inside the instrument because of the limited access.

In the case of installation before the back is on the instrument the best location is directly under the saddle centered below the two outside strings. This results in the best balance of signals.

The tape method is used for the same reasons, difficulty in access. When installing the pickup during construction the gel superglue will result in a superior mechanical contact and therefore an increase in both volume and tonal range.

If I can be of any further assistance please do not hesitate to contact us.

Best regards,

Jack Baley
K&K Sound Systems
Technical Support


So there we go ... and Jack's now my new guru! Must say I'm feeling a lot more confident about the next build .
Cheers

[J.F. Custom]

Ah. Now that makes sense, as Markus guessed above. I could not fathom why that position would have been "better".

Well, I've placed my sensors directly beneath the saddle, but between the 1st and 2nd, 3rd and 4th strings. Will see how I go with this.

So the tape is completely acoustically transparent, but the gel works better? Hmmm. Still, it makes sense the cyanoacrylate would work best and I had assumed as much, despite their claim on the tape. I just wanted them to be easier to move if it became required in this case, being the first installation in a uke. My comment about removing them to glue instead, or not, is based on whether the risk of damage during removal - even with tape, outweighs the benefits to be gained by glue. Obviously this remains to be heard. If the output and balance is good, I don't think the risk would be justified.

Future ukes however I would glue, knowing the position is correct.

Jeremy.