MY HARLEY BENTON EUB STORY. 

(Last modifications 18-05-2011. Use underlined links to see the typical pictures.)

LISTEN TO THE RESULT AND JUDGE
BEFORE READING ANY FURTHER TO PREVENT DISAPPOINTMENTS!

WHAT TO DO SUMMURIZING:
1. Replace the strings directly with Thomastik 3/4 Bass Orchestra type 3885,OW Light Spiral Core or similar.
2. Remove the present metal tailpiece holder and replace it with a tailgut making the string ends longer
    (about 20-21cm in total between bridge and tailpiece).
3. Remove the present bridge, amplifier, pick-up and black bridge holder and replace a new shaped fixed bridge.
4. Use one self made (or STD1) piëzo film pick-up placed under just one foot under the E string.
5. Add some rubber foil between the foot under the G string and the belly.
6. Use a new low noise self built preamp with 10 Mega ohm input impedance fed either by a battery or a phantom supply.

WHAT WILL IT COST IF YOU DO IT RIGHT THE FIRST TIME:
Harley Benton EUB 500 SB: € 397,= (transport included)
New thomastik strings: € 125,= (ordered with Harley Benton)
New element: € 21,50 (tranport included)
New bridge+tailgut: € 52,10 (tranport included)
New amplifier parts ca: € 24,40
Glew+conductive glue ca: € 30,=
Some work: € 00,=
Total: € 650,=

SIMPLIFIED SOLUTIONS WITHOUT CHANGING THE BRIDGE WITH POSSIBLE A CLOSE GOOD RESULT
(not checked by me):
If you do not want to go through the trouble shaping a new bridge you may keep the present bridge with its holder
in place but just do all other steps. You even can start to use the present used elements, however I should cut it
in half and start with the existing amplifier. Then I should make a new amplifier and then I should by an SDT1 element.

THE WHOLE STORY:

WHY I BOUGHT A HARLEY BENTON EUB IN THE FIRST PLACE ?

I'm not a bass player, but an electronic engineer knowing a lot about audio and sound in general. Since I've at home a very small studio where we play with 3 combo's every week I wanted it to make as easy as possible for my drum and bass players. So drums were already available and since I've got my Harley Benton EUB also a bass is always available in the studio.

I designed and made already the microphones for the flute the sax and the pick-up system for both bass players myself. And everybody seems more then happy with the suberb sound quality. So the EUB was a new challenge. Of course the idea was to spend as little money as possible and get the best result.

So what was the starting point? Looking around at internet, reading and listening. Of course the idea is to get a sound as close as possible to a real double bass. Many tried before and you can buy anything between the € 397,= (Harley Benton delivered at home) and € 2750,= or more. Listening to the Yamaha SLB series and Eminence Bass-E series as a kind of expensive reference at the high end did set a first target but one to reach of course with far less money.

At the low end the Palatino VE-500 seemed to become popular since it delivered relatively good sound for very little money. Then of course I stumbled over the  Harley Benton 500 SB EUB. Was this a renamed original Palatino or was this a copy with lower quality? Nobody seemed to know, some on the internet made what I call stupid remarks based on the fact that they just cannot believe that you can buy the same thing for almost half the price. So I bought the thing.

If you want to hear some YouTube results and remarks about the Palatino VE 500 EUB you can find these here:

http://www.youtube.com/watch?v=VjH5q5FmNwc&feature=related
http://www.youtube.com/watch?v=SWdlqVGa9-4&feature=related
http://www.youtube.com/watch?v=VjH5q5FmNwc&feature=related
http://www.youtube.com/watch?v=jj7tEclxyXc
http://www.youtube.com/watch?v=Gs3g3Vmq56I&feature=related

It seemed that several people were quite happy with this EUB and some started to try make improvements as well. Of course I found the equivalent Harley Benton 500 SB EUB for even considerable less money and sold by a very well known company. So I bought the thing and it was in fact an only renamed Palatino VE 500.

My conclusion? It might be a better version of the Palatino or at least exactly the same one renamed for the music house thomann.de! Why? Reading several comments from other buyers at thomann.de they seem to deliver very high quality for the money payed and as far as they rename things into Harley Benton (own brand name) there quality control seemed to be way better (German thoroughness) then of the original Chinese products. Secondly the bass was delivered in a package from Palatino where the type number VE-500 was very simply crossed with a black pencil and replaced by 500 SB and the name Palatino was made invisible by a sticker.  Then the total description about the used wood, the weight etc.etc. is exactly the same. The bass looks exactly the same in detail. Everything I've read about the Palatino VE-500 matches except some of the bad points. So YES it is definitely the Palatino itself and certainly nothing less but at worst a very good selection. So that was a relieve. It looks great and is very solid. One thing I noticed later in the experiments is that the laquer does not stick to the wood as one expects. Once you damage the varnish it peals of like it is a complete loose layer. However this is due to my experiments that I did damage the varnish anyway. By the way except for Great Britain the Palatino seems not to be sold in Europe as far as I noticed. And thomann.de does not sell in the USA where the Palatino is beïng sold.  Only in Britain one can buy both the Palatino and the Harley Benton. There is little doubt what one should buy.
 
HOW IT IS CONSTRUCTED ?
Many people may like to know what is inside. It is not a massive piece of wood. The sides are of ca 27 mm Ahorn. The back of ca 13-15 mm Ahorn from top till bottom. The front is ca 19 mm made from Spruce. The fingerboard is of Chinese Ebony, whatever it means it looks and feels nice and has the very correct shape from top till bottom. Which means also the slight bend (hollow bending up at the bottom) over the lenght of the fingerboard, which should be there, is present. There is a bar connecting top plate and bottom plate and positioned at the midline of the bass, which is ca 20 mm wide and starts ca 40 mm above the feet of the bridge and goes down till the and of bottom of the bass. It devides the lower part in two separate hollow spaces. The middle part of the bass is ca 63 mm thick leaving a hollow space of ca 30 mm inside the bass and the lower and upper part are 80 mm thick leaving a hollow space of ca 47 mm. All the dimensions were measured by me via the openings where the amplifier, battery and connector are positioned.

REPLACING THE ENDPIN ?
Replacing the outside endpin assembly by an inside one will conflict with the 20 mm bar which is exactly positioned in the center at the place where an eventually inside endpin should go. This might be the reason why not an inside endpin has been choosen anyhow although I don't understand the necessity of this bar. From a point of view of strenght the bar is completely superfluous in my opinion. From a point of view of sound color I've no idea, but I don't expect it become worse if the bar was beïng removed on the contrary! If you had an endpin of e.g. 14 mm thick (typical endpin thickness) you need to drill a very long hole of say 15 mm diameter over almost the complete lenght of the bar. Apart from finding a drill of that length you will never keep it in the center of the bar over that lenght. So although somebody claimed to have replaced the existing endpin, I don't believe in it unless you completely removed the bar by wobbling the drill. So this idea was exit for me. The only real other possiblity is an ca 20 mm eccentric endpin assembly. The only improvement I made was adding a "super endpin ball" replacing the nylon spike. The nylon spike can easily removed by sawing and drilling. The ball assembly fitted exactly into the existing tube. I only needed to drill one small hole in the tube for a screw which keeps the ball in place. Be warned that the steel endpin tube is made from exceptional hard chrome steel.

FIRST IMPROVEMENTS:
So I started with some for the Palatino VE-500 suggested improvements found on the internet. Putting a rubber foil (suggested is byce-tube, but I used EPDM roof foil) between transducer and holder and between bridge feet and transducer. This was a significant improvement. Secondly stopping the strong resonance between 40 and 80Hz created by the tailpiece by putting a small rubber between tailpiece and top of the bass. Thirdly changing the cheap strings into Thomastik Spirocore Weich. First I didn't even buy the stuff but used an old set from one of the bass player and had it soaked 24 hours into 1 liter 96% alcohol (the stuff you buy at any drugstore) as is suggested to renew old strings. This is an huges improvement. It really starts to sound like an amplified normal DB. So, yes the original strings sound like rubbish but they only sell for € 29,= a set.

Of course you need to keep the tone-control of the Harley Benton always in the maximum low position (maximum anti-clock wise) unless you like a bass guitar sound. I did try to analyze the preamp but seeïng the many and small parts used at the circuitboard (after desoldering the housing) I gave up for the time beïng. To do it properly I had to desolder all the wires as well and the risk that it shouldn't function after resoldering all the stuff was at this moment too high. Since I noticed that also the results of the preamplifier with other transducers was not satisfying I dumped the whole thing later on.

What power amplifiers do I use? Well an Acoustic-Image TEN2 which is great for any bass player. However my studio set up with Mackie300CZ and a separate subwoofer sounds a little bit more natural. But that applies also for the real DB's. Basicly all tone controls are set to straight.

So what do our DB players say. They are flabbergasted. It plays easy, it sounds good, the neck is very smooth (the neck part seemed even to be treated with a special lacquer which differs from lacquer used on the body to make it smooth for your hands), the ebony fingerboard is smooth and plays very well, no torque nothing what I sometimes read on the internet from the Palatino's. The bass player immediatly stopped coming to the studio with there own DB. And one is so happy that he rather likes to play the Harley Benton at coming gig's then his own real DB.

So again either the Harley Benton is a better selected version of the original Palatino or the Palatino must have been improved in general since comments showed up on the internet or the comments were not valid. In any case the smoothness of the neck is as good as you might wish, there was insignificant amplifier hiss with the original preamp and no torque of the fingerboard can be noticed and nothing is needed to be done to improve it, at least according to my two bass players and my own judgement. However at a real gig one of them did prefer his own real DB. The other one choose already for the HB EUB. But of course it did sound still different compared to a real DB. But my goal is to get much more comparable real DB amplified sound, if possible almost the same.

SECOND SUPPLY MODIFICATION USABLE FOR ORIGINAL AND NEW SELF BUILT PREAMP:
So what did I want anymore at that time? I wanted to get rid of the necessity to operate the battery. A battery will always be empty at a wrong moment while the reserve battery cannot be found or is empty as well. Since the Acoustic Image had a phantom-supply I could use that instead of the battery. I modified an XLR to combine it with a jack, which let me get access to the phantom-supply and at the same still use the line input. The microphone input is too sensitive to directly connect to from the element and is not high ohmic. So it is not suited for the bass. Adding some resistors, a zenerdiode and an extra diode did do the trick. The original output jack of the Harley Benton is luckyly enough fitted with a stereo jack, so the not used stereo connection can be used for the supply in case you keep the original preamp. and in case you want to built a self built preamp inside the EUB body. The original EUB preamplifier uses ca 6,6mA. So two resistors from 3k3 each used for the XLR connections and a 10V zener limiting the maximum voltage left sufficient current for the preamplifier operated at ca 9V. Resistor and zener are mounted into the modified XLR-jack connector. A diode in series with this new supply placed in the stereo connector in the EUB prevents the battery beïng short circuited if an mono jack is used with another amplifier and while still using the battery. The supply is connected after the switch which means that the battery could stay switched off if the phantom is used. So normally the battery switch remains in the off position all the time. The red led will light as soon as the phantom-power is on. So this descrption is just for the ones who don't want to implement all my other suggestions, which might get rid of the original preamplifier anyhow.

CHANGING THE TAILGUT:
A next action was trying to use a standard tale nylon rope (49 cm tailgut for a few euro's type:TLB-4434 more sellors)
(see: http://www.mainmusic.nl/nl/product/12731/447/strijkinstrumenten/onderdelen/staartstukken/overige/tailgut_geschikt_voor_double_bass__nylon_490_mm..html  or http://www.stb-music.com/index.php?id=13566 ).
Although I don't advise this solution anymore I still like to describe my experience. The tailgut is fixed around a small round wheel from whatever material you will find in your garage of ca 2-2,5cm diameter and 4,5-8 mm height) mounted at the bottom of the bass and covered with larger 30 mm washer for a 6 mm bold. The wood at the bottom is very thick (> 6 cm) so you can drill a hole (5,5 mm) and mount the stuff with a large 6 mm thread bolt which makes its own thread in the wood. I cutted (by sawing to get flat end) some 14 cm from the 49 cm nylon rope to which will result in ends for the 4 strings which are close to that of a standard bass of ca 21cm. Since both ends of the nylon rope are threaded I bought a 4 mm thread cutter (€ 7,95) and cutted a new thread at the shorted nylon rope, which is an easy job. You need to use a new cutter, not one which already has been used for making steel threads, because the cutter should be as sharp as possible to cut the nylon well enough. I drilled two new holes of 4,2mm (used a for 5 mm threads) into the black tailpiece just in between the center of the E and A string holes and a second one in between the D and G string holes. The holes start at the top side of the tailpiece in the center of the strip (like the old holes from the metal tail piece) and they are drilled under an edge to reach the edge at the other side. You should start with a smaller sizes drill e.g. 2mm. If using the 4.2mm drill the holes larger, drill slow since the wood at the end of the hole will brake out easily. One hole did in my case brake out a little so the best thing is to use some other material to support the place where you expect the hole will to come out. By using edged holes the string holder will stay in a flat position like it was previously forced by the metal construction. Don't use a larger hole then needed. It might allow the threaded nylon to vibrate inside the hole and brake. Two 4mm flat rings are used while the two nuts were filed down with an equivalent edge created by the holes. This new kind of mounting has lots of advantages. The flexibility of the strings with the bridge becomes closer to that of a normal DB. Normal 3/4 strings can be used without the need to remove the silk cover at the end of the strings. Make sure that the threading of the nylon is somewhere in the middle of the hole after mounting.

Above solution did survive just one week! Then the tailgut did brake during overnight, while I was sleeping. I made the mistake to have the thread just sticking out the tailgut 1mm. Due to the vibrations which will bend the tailgut constantly on the cutted thread if it is free, it teared out slowly. So make sure that the tread stays far inside the tailpiece where it will not bend during the vibrations while using your instrument.

Since I didn't even wanted to risk another brake down I now bought a 2 mm diameter stranded steel rustless clothesline in the D.I.Y. shop and used it as tailgut. It is exactly the same stuff if you order an original steel tailgut. I wounded it two times around the bottom wheel and tied it together with one of the screwing clamps wich come with it. I used a heat-shrink black tube around the steel cable to lower the pressure on the nut edge and for a nicer black look.

CHANGING THE BRIDGE:
A next step will be changing the bridge. Why? Because I read and listened to the results of height adjusters in this study here: http://iwk.mdw.ac.at/Forschung/english/dbb/dbb.htm.
The listening results convinced me that in any case the influence of adjusters is a clearly noticeable loss from the original warm DB sound. The aluminium adjusters beïng the worst ones as well. So a fixed bridge is my way to go. I ordered a bridge for a 1/8 DB (€ 30,36 type: B-0318 more sellers), ( see:  http://www.mainmusic.nl/nl/product/5636/446/strijkinstrumenten/onderdelen/kammen/overige/kam_contrabas_18_panpi_model.html or
http://www.stb-music.com/index.php?id=13822  ) which is nearest to the present size.
 
In fact it is the only one which will fit at all measured from the 115 mm feet width. However a 1/8 bridge is still much too high so I had to modify it significantly. First I removed the black bridge holder together with the original piëzo pick-up. The piëzo pick-up is connected inside the base with a small 2.5 mm jack connector, so nothing need to be damaged with this step. Just unscrew the preamp with its controls to get to the connector. The black bridge holder is mounted with two small screws. It is not glued, may be it sticks a little but it loosens easily. So the new bridge will be mounted directly at the bass top.

I removed several mm from the feet untill at the outer ends were 2,5 mm thickness was left resulting in about 4,5 mm thickness at the inner sides of the feet. Also the legs were shortened considerable to reduce the height. To do that I sawed the (lowered) feets at ca 14,5 mm from the bottom of the feet. Then the legs were sawed at 28 mm below the top of the two wings. Then I glued back the two feet with UHU hart for model building. Of course before you do so make all surfaces very flat and sand them till they fit as good as possible without any slits and with keeping the feet on a flat surface. Also a considerable part has been removed from the top of the bridge by sawing and filing till quite near to the heart. For the D string the top was 11,7 mm from the top of the heart shaped whole. For the A string it was 12,3 mm. The curve of the top was copied from the curve of the previous bridge. The curve of the inner side of the bridge was filed down till only the name Panpi was still readable (keeping the name had no meaning, it's just mentioned as a reference), I can't remember how much it was a few mm's. Then I had to reduce the thickness of the top till 4 mm in the middle. See the photo and measure from the photo. See also the drawing. I cutted the top thinner by means of a scraping machine which is quite easy. To do this use flat wooden surface (old piece of large wood) to lay down the bridge. Then use a number of small nails to lock all side of the bridge on the flat surface. Make sure that the nails do not stick out more then 3 mm from the surface. Then use your scraping machine to make the bridge thinner from the bottom up till the top. Keep the thickness at the bottom of the feet original. Use a sanding machine to finish the job. To give it even more professional look I scraped some of the edges a little bit with a sharp knife. Then we end up with a completely modified Panpi bridge.

TOTAL BRIDGE HEIGHT:
The total height of the bridge will also depend on the height of the strings you prefer. So before shortening the legs like I described you should try to make up your mind about the string height you prefer. Although a new adjustable bridge (or the old one with some added wood) is still a solution you may prefer, I tried to go for the more optimum sound and then an adjustable bridge was no optium to me. I shoot for spaces between strings and end of the fingerboard as follows: G=5mm D=6mm A=7mm en E=8mm.

CHANGING THE pick-up:
I also had ordered some new piëzofilm pick-ups, which are cheap and nothing less then the famous ones from "The Realist", I used one already at one DB bass with suberb result. The piëzo can be double folded to creates its own screening. The contact ends need still to be screened by some extra cupper foil. The screening need to be 100% otherwise you will be stuck with hum. The piëzo foil which is perfectly doïng the job is ordered here:
http://windworld.com/products-page/electronic-hardware/piezo-films/ and costs $ 16.50 + $ 14.00 transport for Europe. In practice it is delivered in 1 week, no conformations of orders are send, just pay and wait, total price ca € 21,50. I use always the 3/4" x 6" large foil and modify it for my own purpose. The element has two wires which should be cut of till some 5 mm wire is still present. These are used to solder on the screened coaxial wire you need. Do only heat the wires while soldering because the contacting will very easily be damaged if soldering directly onto the crimp contacts. The very thin micro millimeter silver coating of the piëzo will just vapourize if you heat the crimp contacts after which you can throw away the element. It is virtually impossible to make contacts onto the piëzo yourself. You can shorten the element with a sharp scissors. The lenght you need (of the completely with silver covered part) is twice the lenght of the foot + say 1 mm to stick out at both sides. So is the lenght of the foot 33 mm keep 2x35 = ca 70 mm piëzo element lenght (excluding the contacts). I always check if no short circuit will happen after cutting. The two silver coatings of the piëzo may due to the cutting make a short circuit although it never me happened untill now but you never know. Then fold over the element exactly in half and use cyanacrylate glue for synthetic materials like polypropylene to stick the layers together. This glue is mostly delivered with an extra primer to be used before glueïng. After glueing you may check the element for short circuit and if it is ok you preferable coat the cutted end with a thin layer of extra glue to prevent short circuit if applying other conductive elements (cupper or silver coating against hum).
I used for all glueïng "Secondelijm Uni-rapide for plastics from Pattex. Make it a neat job so the inner layers are exactly covering each other. If you don't do that you will be stuck with needless hum. So prefold it very precise before glueïng to create a sharp folding edge on forehand, since you cannot reposition the foil after glueïng. At the fold edge the element may become a little thicker, but try to prevent this as much as possible by pressing hard on the fold edge while glueing. So let this edge ca 1mm free from the foot when mounting. At the contact side you are left with 20-25 contact strips and wiring. This should be wrapped into cupper foil, which is soldered via a separate wire to the screening of the coaxial wire. Since still a small amount of hum may be pick-upped by the unscreened sides of the element I painted those with conductive paint which normally is used to repair car window heating conductors. It is expensive stuff but it did completely make the element hum free. Make sure that the paint makes contact with the negative contact of the piëzo element. Make also sure that you don't paint the cutted edge of piëzo element since this will create a short circuit (which happened to me once).  Also the jack connector should be completely screened with cupper foil including the coaxial connections. Failing to do this will undoubtedly create too much hum.
See also the whole story about building you own piëzo pick-upon at the homepage.

ALTERNATIVE READY pick-up SOLUTION:
One can also order a completely screened and connected device with a coax called SDT1 at windworld.com. ($ 32 without connector and $39 with connector)
The spec of that element can be found here: http://www.disensors.com/downloads/products/SDT Series_174.pdf .The overall width of the SDT1 is 16 mm and the lenght 30 mm. The foot print is 33x20 mm. Although a little less it seems to fit rather good for this bridge foot. So it might be a good idea to use this solution preventing the risks of glueïng, scissoring, screening and connecting the element. Since I didn't try it I cannot judge the quality but it very likely is a very simple approach with probably a lot of advantages for a little extra money. The thickness of the device is specified in the document to be only 75 micro meter which cannot be true. Probably it should have been 750 micro meter (0,75mm), which is about equally to my double folded element.

POOR MEN's pick-up SOLUTION:
A third poor men's option is to use half of the original pick-up element of the HB EUB itself. It did cover both feets. The elements exist of two 12 mm squared piëzo pieces 0,8 mm thick. In the picture we see left the intact half with coax still connected. Right you see the cutted half of the circuit board covered with the black rubber isolation and the squared hole for the piëzo (white squared ceramics). In front the cutted copper screening wich came off.
Capacitance of each piëzo is ca 4640 pF each. Totally 9280 pF. They are pressed between two conducting cupperfaces and the total is beïng wrapped into screening aluminium foil. The whole is covered by the isolation foil (2 heatshrink's). Contacts are ensured by the high pressure of the feet. Cutting of one side at say 8 mm from the centered connection does not harm anything. Just peel of the left over few mm isolation and fold back the aluminium foil. Then cut another 2 or 3 mm off from the total piézo and fold the little alumunium foil, which you had back folded, to screen the end. So now you have one pick-up which can be used underneath one foot (under the E string). This whole pick-up however is 2 mm thick. So you might want to compensate for the string height by taking of another 2 mm from the bridge somewhere. Probably at the top. If you intended already to do this before shaping the bridge you can anticipate for it in the bridge legs length. I did not investigate the influence on the sound quality although I expect little differences compared to the previous mentioned solutions. The layers of cupper foil, aluminium foil, 1 mm circuitboard together with a rubber sheet around the connector and heatshrink isolation will undoubtedly have some influence on the sound, but I still expect it to be not significant for the pick-up sound, but again I didn't investigate it.

The original preamplifier does mess up the sound to my opinion especially in the lower part. For testing the preamplifier I used my own built element. I did a rough test but it clearly did hiss a lot more then any other of my own preamplifiers. So some of the on internet mentioned Palatino hiss seemed to be definetely true although if using the complete original set up it is hardly noticeable. The signal amplitude of the 12 mm squared piëzo used in this HB EUB is significant higher then of the piëzo film which made the preamplifier hiss relatively insignificant. Anyhow the built in preamplifier is no real option since there is still a huges difference in sound quality. It suffers some loss in low and may be an additional frequency dip seem to be implemented.

WHERE TO PLACE THE pick-up:
The piëzo is beïng placed between one foot and the bass belly below the E string. At the G string side some EPDM rubber foil was placed between bridge foot and belly. This latter will probably give in particular the G string the nice extra dark sound you need. The common mistake made is using two elements in parallel below each foot of the bridge. Mostly this leads to a less warm sound. However this is done in this original design. This will always create an also a more unnatural sound. The reason is that both feet are passing energy of all strings and so producing similar signals in both pick-ups. The frequency spectra at both feets however are similar in containing all frequencys, but may differ in amplitude and differ in phase from completely in phase till completely out of phase, which is all completely unpredictable. Adding two such signals will fundamentally create a "comb filter effect", which means that some frequencies in the spectrum are doubled in amplitude and some are completely removed. "Comb filter effects" are known by specialist to be immediately recognised as unnatural. The end result of all above mentioned modifications is phenominal. The modified EUB sounds almost equivalent to the result  of an original DB.

PRE-AMPLIFIER:
A STD1 element source capacitance is 2780pF (spec.). Since the lowest frequency which need to be amplified is 41Hz (E string) and a low drop and phase should be realized a roll of starting at below 20Hz is needed (-3dB). The minimum input impedance can be calculated from that beïng: 1/(20 x pi x 2,78 10power-9) = 5,72 Mega ohm. So choose 10 Mega ohm. This can be done with a simple low noise TL082 JFET Opamp. The piëzo film is relatively insensitive compared to thicker piëzo's and need a good low noise preamp. I feed the preamp by means of a phantom supply, but a 9V battery is also possible. My self made element has a capacitance of 4700pF and half the original Palatino element is 4640pF as well. So 10 Mega ohm input impedance is more then sufficient for these solutions as well.If your bass amp has already 10Mega ohm input impedance, a low noise preamp and enough gain you don't need a preamp.

SUPPORT BAR:
The support bar from the original EUB is too thin and so uncomfortable. By using some 3cm heatpipe isolation tube surrounded with black wide tape you can easily solve this problem. I bought even some tape which is used for tennis racquet grips which adds another few soft mm material and gives a nicer look. Further before doïng this I bended (difficult job very stiff tube) the support bar tube a little more at the bottom side and a little back at the top side to bring it parallel again with the bottom end. This will match the side curve of an original 3/4 double bass somewhat better. Compare the two photo's at the top of this page.

PHYLOSOPHY:
The soundwaves passed on from strings via the bridge activating the pickup(s) will be basicaly the same in this EUB as in a real DB. Seen from the strings and bridge we could try to simulate the impedance of the top from the EUB to be nearly the same as from a real DB. Which means one can try to reach the same flexibility and the same absorption by adding materials like byce-tube rubber or anything else like coark between bridge feet and belly. The top of the EUB is 18 mm thick and so compared to the belly of a real DB very stiff.

Measurements and experiments are usefull to create strings and bridge to get an equivalent flexibility and attenuation to that from a real double bass resulting in similar sustain characteristics. However the sound which is reflected back from the body of a real double bass cannot be simulated. In fact this can be seen as frequency dependent impedance components which are very difficult to simulate by adding other materials. These reflected and picked up sounds will add of course extra sound which may create  a more typical real DB sound which is additionally generated by its body. However since the mass of the strings is low, the contribution of the body sound will be less then one think and becomes even more negligable when a pick-up is positioned nearer to the strings. So a pick-up positioned under the bridge feet will contribute more body sound and less string sound. Keeping these facts in mind I even dare to predict that using e.g. a Bass Master Pro (K&K) with 4 pick-ups directly mounted beneath the 4 strings on this  Harley Benton EUB and comparing the results with any other whatever quality real DB does not need to sound any different at all. Playing it is another issue. Keep in mind that the sound experience of the player is a lot different from the sound experience of the listner to the amplified bass.

An final action might be a change from the body which may have a significant impact is sawing slits into the sides of the body. This quite destructive act may cause the belly to become more flexible with the result to add more colorfull vibrations which will be reflected in the sound from the pick-up if they are placed under the bridge feet. But it is might be an unexpected destructive step, so not for the time beïng.

For now I'm very, very satisfied with the present sound.