PICKUP SYSTEMS

There's a lot of talk about pickup systems for doghouse bass. As a webmaster of this site, I got a lot of questions via email. On this page, I'd like to share my personal experiences with you, hope you appreciate it. If you have any additions to this story or have comments / questions, please let me know (doghouse@worldmail.nl)

For the slap bass technique most players prefer two pickups: one pickup to reproduce the bass tone and one pickup to reproduce the slap / fingerboard sound. It is a misunderstanding that this setup is only good for slappin'! If you want to play slappin' bass, you definitely need this setup, but it's also very good for other styles of playing. The fingerboard pickup reproduces the sound that accoutically is there too. This sound is mostly not picked up by the bass pickup! Hope you understand what I mean. For the bass tone pickup, you have several options: a magnetic pickup (pretty similar to the ones used on electric bass guitars), a piezo transducer or an ordinary (condensor) microphone. All pickups have their advantages and disadvantages. For the slap, you mostly use a simple (guitar) piezo pickup or a (small) condensor microphone. First I'll explain a little more about these different types of pickup, then some hints and tips.

Electric pickup:
This pickup is made of one or more (seperate one for each string) magnets and one or more (seperate one for each string) coils. This is how it works: the magnat(s) magnetise the strings (so they become magnets themselves). When you stroke a string, it starts resonating moving towards and away from the pickup coil(s) very quickly. When you move a magnet towards, or away from a coil, a small inductive current starts to flow. Actually, the coil becomes an electric magnet itself: the coil is trying to push the (magnetic!) string away when it is moving towards the coil (making the same magnetic field) and is trying to keep the (magnetic!) string in posistion when it's moving away from the coil (making the opposite magnetic field). The currents in the coil are of course "in sync" with resonance frequency of the string so... there's you're bass tone!

You can buy magnetic pickups that are specially designed for double bass, but some players also use ordinary basguitar (P-style) pickups . Lee Rocker used P-style EMG's for many years. His new pickup system, designed by King Double Bass, is also an electro magnetic system. These type of pickups are mostly mounted at the end of the fingerboard although I know a player that mounted one on the bridge.

Advantage of an electro magnetic pickup is that you (only!) get a big fat bass tone like a bassguitar. It's just reproducing your strings' resonance frequency. For some people this is a disadvantage: although the instrument itself has impact on the resonating of the string (harmonic frequencies), these pickups do not reproduce a true accoustic sound, they literally only pick up the strings' resonance frequency, not (hardly any) body / wood resonance! A big advantage is that these pickups are not sensitive to feedback at all! They pick up magnetic field resonance, no accoustic sound (resonating air). My first pickup was an electro magnetic Schaller pickup. It was not too expensive and did a pretty good job. I did use it in combination with a slap pickup on the backside of the fingerboard.

Before I started playing upright bass I played bassguitar. I guess for that reason, I really liked it very much, itt was the sound I was used to! Later on I wanted a more accoustic sound similar to what I heard on old Bill Haley recordings so I switch to another system. I experienced no problems with feedback, but because the pickup was bolted to the fingerboard and was a bit microphonic, it reproduced a very (too) loud chunky "tock" when I slapped the bass (you can hear this in early live recordings from the Straycats). For some songs, this is great fun, but to me it's a bit over the top. Note that these pickups only work with steel strings so this might be a disadvantage too if you want to use nylon or gut strings.

If you want big booming bass at high volumes, this is the pickup for you . I don't know whether the Schaller pickup is still available but it might be a good option for you. The problem I had with the Schaller was that the mouting braces were not very robust. They could not stand slapping for long period. I made me a pair of more robust braces from aluminum angle profile you can buy that in every do-it-yourself-store, problem solved! Pat (from Fisnhet Stockings) told me that the magnetic poles kept falling out; a simple drop of lock-tight would help I guess. Again: normal P-bass style pickups (2 x 2 poles) will do fine too. It doesn't matter that the space between the pickup poles is a little narrower than the space between your strings as long as the poles are equally far from your strings. Just screw 'm on a piece of plywood and bold this to the fingerboard. Of course you can add passive EQ control (tone, volume), just follow the bass guitar schematics!

Piezo transducers
These pickups actually are microphones. Because of feedback reasons, you need a pickup that is sensitive to the instrument's resonance and insensitive to the "outside world". Piezo microphones are excellent for that. In this microphone there's a (very) small layer of (piezo) crystal. If you'd "squeeze" this material, a small current starts flowing (please don't ask me how/why). If you stick this microphone to an instrument (or anything else), the crystal is "squeezed" by the surface of the object you stuck it to (yes, it's a perfect trigger for electric drums too). Of course the current here is in sync with the resonance of whatever you stick it to, so there's your bass tone again! Note that this pickup is a true microphone so it's picking up all "mechanic resonance", not only bass tones.

A good spot to stick a piezo pickup is the bridge. Some systems require drilling holes in the bridge, but very often one or two piezo pickups are fit into the "wings" of the bridge. The most famous pickup that works like that is the "Underwood". This pickup has two piezo elements, one for each wing. Shadow is cloning this pickup system, it is very resonably priced . Although many bassist use it, I don't like the sound of it very much. It has a bit too less bass and a bit too much ugly mids for me. A disadvantage of the "double" pickups is that you might experience out of phase problems. Therefore many double bass players let one of the pickups just hang loose, mostly they only use the bass side pickup. This gives a bigger and less nosy tone, better to cut through the mix. If you'd know that upfront, you'd better buy yourself a single piezo pickup. The people of K&K (distributed by Bob Gollihur) also noticed this and made a clever pickup, the BassMax. It's a double piezo allright, but in a sandwich construction supposed to go in one wing. No out-of-phase problems and even bigger tone! I'm using it myself and I'm very happy with it! It has a big bass tone and it is very insensitive to feedback compared to other piezo pickups.

Before I had my K&K pickup, I first used a Underwood (piezo on G-side hanging loose) but switched to a simple cheap Bell Cat guitar piezo pickup. When I had this pickup on my guitar, I already noticed it had very good bass characteristics and plenty of output. It fitted exactly into the wing of my bridge and turned out to be a really good pickup for double bass, better than the (original!) Underwood. Bil, afriend of mine, is using it now. I didn't buy the buy the K&K pickup because I was unhappy with my Bell Cat but because I was curious about the complete K&K Slap Special package. If you have the money, buy the K&K pickup! If you don't, experiment with "normal" guitar piezo pickups, you might find a good one for a fair price. If you're planning to use piezo pickups, read the story on preamps because you defenitely need one!

Condensor Microphones
For a true reproduction of you bass' sound a condensor microphone is the best! You have 'm in all sizes, very small clip-on mikes to big Neumann style studio mikes. Major issue with these microphones is feedback! A condensor microphone is picking up everything, not only the sound of your instrument but also from your amp: this original sound from your amp is fed back to the amp again and again (this is feedback). Using a microphone for amplification in an electric band situation is not an option. It is very good for recording though or accoustic perfomances where you need a little extra sound from a PA system or small amp. If you have a drummer in your band, forget it! Lately I'm not completely happy with my slap sound from the piezo transducer. It's only picking up the "nock on wood" and not the real sound I hear. Lay one of your ears on a wooden table, (gentle!) nock on the table and you'll get my point. Be carefull! It's amazingly loud and can damage your ears! Anyway, what you'll hear is just not the same knock as when you hear it accoustically in the room. I'm experimenting with small condensor microphones (bought 10 of them for only $0.50 a piece at an amateur radio market) for the slap signal. I'm not too worried about feedback because I mostly only mix in a little bit of slap and I have seperate EQ for the slap signal on my preamp. When I cut all bass, I'm pretty optimistic about this "tiny project". I will let you know the results and might even publish a schematic on this site!

Preamp (impedance match!)
What is very important when using piezo pickups is a preamp! Piezo pickups have a very high impedance. This means that it produces a reletively high Voltage at a relatively (very) low current. High impedance devices are very sensitive to electrical influences by other electrical components like capacitors. The cable to your amp is a capacitor (!!) and the length determines it's capacity. This can have major impact on your sound because you're actually making a resonance circuit that acts like a tone pass or block filter! Now you don't want that do you?! If you connect this pickup directly to a bass amp, you'll also run into trouble because many "normal" bass amps expect to see a much lower impedance. If you mismatch the impedance, your signal is not used efficiently by the amp. It's only picking up the tiny current and more or less ignoring the big Voltage (I know this is not how it works, just trying to explain the problem in an easy way).

Although a piezo has relatively high output, the output seems very low when connecting it to a normal amp. A piezo is very sensitive microphone, but nevertheless you'll have to turn up the amp all the way to get some sound due to the inefficient match. Very sensitive pickup + amp turned up all the way often results in feedback, even at pretty low volumes. Mismatching also does things to the characteristics of your signal. I've seen spectrum charts of guitar pickups that were mismatched on purpose dramatically and I couldn't believe my eyes. I don't want to go into details, but take it from me: the more the mismatch, the worse the signal characteristics, mostly losing bass and highs and getting very strange peaks in (mostly ugly) mids.

So, if you use piezo pickups, use a preamp! Many preamps use typical OpAmp IC's that have high impedance input and low impedance output. This is ideal for piezo microphones! Don't think that you don't need a preamp because you already have big bass amp. You need a preamp to amplify the signal, but to match it's impedance to the input impedance of your bass amp. Extra amplification and EQ controls are nice of course, but that's not what all the fuzz is about! I use a K&K 2-channel preamp that comes with the K&K Rockabilly Slap Special system. My friend Bil (now using my Bell Cat piezo) uses a El' Cheapo 4-channel microphone mixer. Before he did this, he used to play on my bass because the feedback with his bass were just not acceptable. The bass sound was OK but not great though. When he started using this basic $20 mixer, his feedback problems disappeared and the sound became much bigger! For best results: mount the preamp close to the pickups (on the bass or clip it to your belt). We never realised my K&K preamp was so good until Bil's preamp got broke. We hooked up his piezo's to my preamp and were very astouned to hear that it sounded MUCH better!! Pretty much the same as my bass with the K&K pickups. The tone controls inside my K&K preamp are not set very drastically but probably help: a little extra bass and less highs for the tone pickup and the opposite for the slap pickup. This settings were excellent for Bil's pickups too. Big fat round bass tone and clear slap. Excellent product!

Hints & Tips:
Find a piezo pickup that fits in the bass side of your bridge wing. If it doesn't fit, you can use a thin piece of plywood or a folded piece of paper. Make sure it's fitted snug, but not too snug! Listen to it with a short cable connected directly to your amp. If the sound is thin, even a preamp with EQ will not get you a good sound. Many piezo's are "full range" so there's a good chance you might yourself a good bass pickup for little money. For the fingerboard, I honestly think that it doesn't make too much difference. Note that changing the position of the piezo only 1 mm (in wing as well as on fingerboard) can result in completely different sound!

Basis pickup system is two piezo pickups wired in parallel connected directly to your amp. I did this with my Underwood + for years, not great, but fair enough. Maybe you can find yourself a 2-channel bass amp (Peavey made these in the 80's and are pretty good for double bass), have two cables running into the two channels. Remember: two piezo's in parallel with only a single channel preamp is better than no preamp at all, even if you have a two channel bas amp. You can think of many combinations, if you only have one preamp, only use it for the bass pickup. You can experiment with the normal accoustic guitar preamps (check Michel van Son's page, he's using two $10 guitar preamps!) or El' Cheapo microphone mixers. If the preamp doesn't have tone controls, don't worry about that too much. You can think of using some simple tone mods like a capacitor to ground for the bass pickup (short circuit highs) or a capacitor in series with slap pickup signal to block bass and mids. I will publish some more details on this soon!