Double Bass Building an EUB . . . Sort of . . . .

[BarStarzBass]

Okay, from what I've learned so far by reading these forums and other mega-Googling, I think it will turn out to be more of a "stick" fretless bass guitar that i could probably play upright or horizontally . . . I guess I'm kinda recreating a Zeta Crossover . . . or a Pace with better components . . . .

So the story is, I have laying around the house the following components:

1. G&L L-2000 Fretless Ebony neck
2. Body Blank for a Lap Steel Guitar . . mmm . . . shaped like a n NS Design, but flat-top . . .
3. A [Invalid or Expired Link Removed]
4. A passive control plate wired Volume-Blend-Tone

They're not making any music just sitting around in their boxes . . .. so . . .why not?

Seriously, does anyone see a big "why not" in this setup? Or maybe even a "why bother" . . .

The tone I'm looking for would be in the neighborhood of your basic "woody" fretless tone, but with some acoustic "thwack".

I'm missing a bridge, of course. And I may need to add a magnetic pickup as I honestly have no idea what this setup will sound like - I mean, a pickup meant for an archtop 6-string, on top of a solid hunk of wood? But I figure I'll try that config first, and if it needs more (or needs to go away completely), then I'll just add a mag pup or two and I know what THAT will sound like.

For the bridge, I've done some searching and a Hofner bridge seems to be the best fit for my needs. Though I wish it came in ebony to match the fretboard. Anyone have any better suggestions? Or suggestions for how I can "ebonify" the rosewood?

The other bridge option I found is the Gretsch. But I don't really need the precise intonation, and I'm thinking an all-wood would be more . . ."woody" . . .or would the metal transmit the string vibes better?

Final question - and sorry for the long post - any suggestions for a mag pickup that most closely matches an acoustic tone? I'm leaning toward a Jazz bridge . . . but would a P-bass pickup be closer to the mark for that woody tone? I'd prefer a soapbar shape to the P-bass shape . . .

Any and all advice appreciated!

P.S. I KNOW this is not a true EUB and will not really approach the upright tone . . . .scale too short, can't be bowed, no hollow-body acoustics . . . . that's okay . . .

 

[BarStarzBass]

Whew - 5 days and no response I guess my post WAS too long . . .

Anyway - a quick update. After a little more thought and research, I decided against the floating bridge option. First, I found out the Hofner bridge has a string spacing of only 1 11/16" ! The G&L necks is set up for the semi-standard 2 1/4". If I went the Hofner route, I'd have a limited choice of pickups and the string spacing would just look and feel weird.

Plus . . . given the extra height of the floating bridge, I'd have to carve a sloping neck pocket, something I don't have the skills or tools to do properly.

So I'm going with a standard Fender-style bridge (actually the Hipshot B). I will try fitting the piezo elements between the saddles and the bridge plate. If that sounds awful, I can always upgrade to the Ghost saddles.

 

[scojack]

Hello BarStarzBass dont get despondent, it can be a little slow in here sometimes. You may get more interest in Luthiers Corners section too

My thought...
You may need to look into buying a buffer circuit to match the impedance of your piezo elements with a mag pup.

Good Luck & take some photos

 

[BarStarzBass]

Thanks Scojack. No worries, I was being somewhat tongue-in-cheek with the tears!

Yes that's a good point on the buffer. I'm thinking of doing this incrementally - ie. start with the piezo only, and if it doesn't quite get the sound I want, then add the mag. If I add the mag then from what I understand a buffer is pretty necessary, or the impedance mismatch will make both pups sound sick (and NOT in the good way). I found a a DIY buffer circuit diagram that I may try, or I may spring the $50 bucks for a built one.

The bridge and tuners arrived yesterday so I think I'll start this weekend . . .

 

[BarStarzBass]

Well, my first rough assembly is complete. Still need to route the control cavity, add controls and a jack, and finish the body. And add a stand of some sort. And I may add a mag pup and buffer. But I couldn't wait to string her up and see how she sounds.

She's wearing Rotosound 77 Flatwounds 110-50, and I recorded off the DI of my Walkabout. I also used a Boss Bass Equalizer in lieue of a tone control to cut the highs - from the recording sounds like I should have cut some lows too, but the E string didn't sound that boomy out of my 1x15 cab.

So (apart from my fretless technique which stinks but hopefully will get better), what do you guys think of the tone? Me, I'm pleasantly surprised - didn't know how (or if) the K&K under the saddles was going to work. The string balance is pretty good - the G string is lower volume as expected, but since it's such a brighter tone, to me aurally it hangs in there with the others. And I can't believe the "mwah" I'm getting off flatwounds!

BTW the first pic shows her next to a lap steel - I had two lap-steel blanks so it shows you what the body started out looking like.

Here's the soundclip - nothing fancy, just a little riff - first played up high, then down low.

 

[scojack]

Cant hear the soundclip at the mo' im afraid (cyber defences at my work wont let it through).

Very interesting setup though...
How have you mounted the K&K in the end, is it a two paddle job (its hard to see on the website)?

IanM

 

[delta7fred]

BarStarzBass

I'm very interested in your little project, something I have been thinking about for a while.

I think the tone sounds pretty good but I have zero EUB or DB experience so I wouldn't take too much notice of me.

Looking at the K&K site it says you can use the pickup without a preamp but I would think that a long cable would kill a bit of treble (if that worries you) due to the inherently high output impedance of piezo devices.

I suspect fitting a magnetic pickup would only make it sound more like a standard EB.

What I have done in the past for quick tests on pickups is to make an aluminium 'top hat' mounting for them so the pickup is above the strings rather than having to route the body. I attach the feet of the bracket to the body using Blue Tack. It does not harm the finish and saves unwanted routes.

 

[BarStarzBass]

Cant hear the soundclip at the mo' im afraid (cyber defences at my work wont let it through).

Very interesting setup though...
How have you mounted the K&K in the end, is it a two paddle job (its hard to see on the website)?

IanM

Hi Ian - yes sorry for the crappy cell-phone pic but the battery in my real camera just gave up the ghost. The K&K does have two paddles - I made a little metal bar the same width as the paddles and the length of the bridge so it could spread the load from the four saddles (actually 8 points of contact since each has those two height-adjustment screws) - this sandwich adds 1/16" to the bridge height so I compensated by routing the neck pocket 1/16 less than usual. I'll take a closeup pic.

 

[BarStarzBass]

Hi Delta7. Good idea on the mag pickup frame - seems a good way to find the sweet-spot too!

Still not sure I'm going to add the mag - I'm going to set up the control cavity so there's room for a blend pot and a buffer - but I'm going to play it a while and see if I think there's anything missing in the sound.

As to loss of treble - well the setup I recorded with included a pair of one-foot long alligator clip jumpers, a 15' cord into the EQ pedal and another 5-footer into the amp - not to mention the 15' XLR from the DI to my sound card - and I had to put a BIG frowny face on the right side of the EQ to tame the sizzling high end! It was bright to the point of being metallic - and this is with heavy gauge flatwounds.

 

[scojack]

It does sound pretty bright.

 

[BarStarzBass]

Yup - pretty bright - maybe too much so. I can shave off a little more with the EQ - and I'm sure the tone knob will tame it a little once I get around to adding the control cavity this weekend. And the Rotosounds are brand new so I'm sure they'll mellow out a little too.

But for now I'm kind-of digging the brightness - I'm mainly looking at this fretless as a bit of a "solo bass"/lead instrument for some pseudo-ambient stuff that's in my head right now, so I want it to stand out in the mix more than my other basses which are used for the traditional support role.

I'm going to record a little test ditty with some percussion, acoustic and electric guitar as SUPPORT instruments (Ha! take THAT, guitards!) and see if the brightness is just right or still too much.

 

[delta7fred]

I was working from memory with the treble cut thing and my memory is getting a bit hazy of late.

It's along time since I had dealings with piezo devices, I remember they are very high impedance and that we used to feed them into charge amplifiers but whether that was to cut high frequency response or boost it escapes me now. I will phone an old EE friend and see what he says, he had more to do with that side than I had.

 

[delta7fred]

After a fairly lengthy phone conversation and much long distance head scratching we have come to the conclusion that feeding a piezo pickup into a normal preamp will result in the bass being greatly reduced.

This is because the pickup can be viewed as an ideal AC voltage source in series with a fairly low value capacitor. The upshot of this will be that the impedance of this internal capacitance will be fall as the frequency rises so the higher the frequency the more signal 'gets through'.

Feeding it into a proper piezo preamp (charge amplifier) will bring the frequency response curve to something approaching what we are used to hearing from a pickup and the EQ and tone controls can be returned to their normal positions.

I have seen somewhere on the net a simple piezo preamp. I will see if I can find it again.

But if you prefer the way it sounds now then go with that.

 

[BarStarzBass]

Thanks Delta7 - that's good information. I must admit to being pretty much a noob when it comes to piezo's (I didn't even know it's pronounced pee-eh-zo until a week ago - I thought it was pie-zo!).

I know piezo's usually need a special pre-amp, however this particular K&K says it works fine without a pre. It sounds fine to me - it's pretty bright, but that low-E shook my walls when I recorded that little piece and played it back on a system with a subwoofer - and not a very big one. I can't imagine wanting MORE low-end.

Is a piezo "buffer" the same as a "pre-amp"? I'm not sure I know the difference between the two - I think they might be interchangeable in this context. I know I need a buffer to match the impedance of a mag pickup if I decide to add one - so based on your description that would also take care of any impedance issues going into the preamp?

If I get one, it will probably be this one:

[Invalid or Expired Link Removed]

 

[scojack]

TB'er .....Fdeck sells a VERY VERY highly rated pre-amp for this kind of thing......

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You could try an sit the paddles under the bridge itself see if this makes any difference or even go for a floating wooden bridge arrangement (see my last build) just takes a small bit of hardwood and a few holes to anchor the strings.

As i understand it ....

You need a buffer for the piezos if your mixing with mags.
You can then add a pre-amp to handle both signals.
Bartolini makes a unit that does both and allows you to blend both signals.

A pre-amp does work as a buffer and matches the impedance of your piezos with your amp.
If you have an amp with a high impedance input ...you theoretically dont need a pre-amp.

Having said all that .....i get a perfectly good output from my transducer without a preamp.

Ian

 

[delta7fred]

I know piezo's usually need a special pre-amp, however this particular K&K says it works fine without a pre. It sounds fine to me - it's pretty bright, but that low-E shook my walls when I recorded that little piece and played it back on a system with a subwoofer - and not a very big one. I can't imagine wanting MORE low-end.

Is a piezo "buffer" the same as a "pre-amp"? I'm not sure I know the difference between the two - I think they might be interchangeable in this context. I know I need a buffer to match the impedance of a mag pickup if I decide to add one - so based on your description that would also take care of any impedance issues going into the preamp?

If I get one, it will probably be this one:

[Invalid or Expired Link Removed]

K&K say it works ok without a special pre and they should know, and from your experience it does so it you like the sound leave it as it is.

A normal preamp is a voltage amplifier. A piezo buffer is called a charge amplifier*, not wanting to get too technical but they are completely different.

*Charge amplifier is actually the wrong description, it is really a charge to voltage converter but they have been called charge amplifiers as long as I have known so that is probably how they will stay.

I am pretty sure the buffer circuit in your link is a charge amplifier. I certainly is not a standard preamp or buffer.

 

[delta7fred]

As i understand it ....

You need a buffer for the piezos if your mixing with mags.

A pre-amp does work as a buffer and matches the impedance of your piezos with your amp.
If you have an amp with a high impedance input ...you theoretically dont need a pre-amp.

Having said all that .....i get a perfectly good output from my transducer without a preamp.

Ian

You are absolutely correct, you definitely need a piezo buffer if mixing piezo and mag pups.

A piezo pup is not like a mag pickup where you just need to match impedances. To be theoretically correct you need a proper piezo buffer (charge amplifier). But they do work straight into a preamp or amp input. I would be very interested to hear the differences in sound between that and using a piezo buffer. No doubt it would tame the highs quite a bit.

 

[BarStarzBass]

Ian and Delta7 - first of all, thanks again for all your input - I'm learning a lot here, and this is what Talkbass is all about.

Well, I've decided I'm going to go the full whack and install a pre/buffer/charge amp and a mag pickup. My semi-logical rationale is:

- As much as I'm enjoying the tone, I'm always gonna wonder if it could be that much sweeter with a buffer

- I've already got about $500 invested in this project, so what's another $100-$150 for (possibly) better tone out of the piezo and the added tonal palette of a mag pup?

- I'm REALLY impressed by the HPF-pre (thanks for that link!) - especially the high-pass-filter portion as, reading Fdeck's docs, I think what I reported earlier as "excessive low end" that was rattling my subwoofer is really the subharmonic "thump" that Fdeck describes. This makes sense, as the thump just isn't there through my bass amp or when I play back the clip on a system without a subwoofer - but I do need to get that under control if this instrument is going to be useful in a variety of PA/playback setups.

I'm going to contact Fdeck to see if somehow I can get an "unboxed" version from him so I can mount it onboard.

Now, I'm a have-your-cake-and-eat-it-too kind of guy when I'm designing a project - so I'm going to also install an SPDT switch so I can bypass the pre and retain the tone I have now (though I won't be able to mix with the mag in that condition) - thus answering the a/b comparison question with the piezo.

 

[BarStarzBass]

Well, the control and jack cavities are done, and the volume, tone and blend controls are mounted. My single neck Jazz pickup arrived today, and Francis Deck is going to build me a "naked" version of his HPF Pre that I can mount on-board - it's really coming together!

Here's that clip with accompaniment I promised. Recorded the acoustic guitar, electric guitar and percussion straight into my iPad's mike using the Everyday Looper app, and loaded them to Ableton where I then played the solo bass part, with a touch (okay, more than a touch - but I like that saturated sound) of chorus and reverb.

 

[delta7fred]

I am just wondering where you found room to mount all the controls on such a compact body.

I love the sound of it with the chorus and reverb on, although I have never been a pedals sort of person*.

Like you, I am wondering what it would sound like with a preamp.

*Probably because when I started playing nobody used them, if you could afford a half decent bass, a head and a couple of 4X12s (and knock out a 12 bar) you were set up. It is only since joining TB that I realised everyone is now using them but me.