SuperFilter

[richbass939]

That's a pretty interesting design.  It definitely would be easier to transport.  I see the soundhole under the tailpiece.  Are those small soundholes that I see near the upper bee stings?
Rich

[dfung60]

Orbit -  
 
OK, between the description and picture, I see that the Baggs pickup is a passive piezo pickup.  It doesn't pick up up hum, but you really do need the buffer amp that Edwin mentions to get good sound from most amps. Without it, the output from the instrument will seriously lack bass.
 
Impedance is sort of the AC equivalent of DC resistance.  Resistance is simple to calculate and characterize; impedance is really complicated, as it varies with frequency and amplitude.  From a setup standpoint, if you want to deliver a full-range signal to your amplifier, the input impedance of the amp must be much higher than the output impedance of the pickup.  For magnetic pickups, amp input impedance of 40-100K ohms will work great.  
 
The output impedance of a piezo pickup is much higher than a magnetic and requires an input impedance of something like a megohm or more to get a flat response signal.  It's no problem to build a solid state/op-amp preamp to provide the proper loading.  A preamp which has very high input impedance and doesn't boost the signal level (unity gain) is called a buffer amp.  It's a necessary part of the signal chain, but people don't want to cut up acoustic instruments, so the buffer is often outboard.
 
The thin single wire is actually a coaxial cable - the signal passes through a center wire which is surrounded by insulation and the other conductor which acts as a shield.  
 
If the output jack is not a factory-made connection, this is probably where the ground problem is - it's hard to make coax connections cleanly, so I'd definitely check the output jack connections.  You probably will need grounded shielding around the area where the output jack is located.  If you don't have that, the tiny unshielded stretch of the coax center conductor can be the source of the hum.
 
If you have a 1/4 jack mounted on the instrument and room for a battery, then there are many internal buffer amps that you can use including systems from Baggs or EMG.  There are also a lot of external system including Fishman, Countryman and others over a wide range of prices.  
 
David Fung

[orbit]

sigh...this is pretty well over my head david...i dont know how i would check the output jack connection? the output jack has the baggs logo and ultrabass logo on it so its not a custom jack its a factory made jack.
 
ive no idea how to tell if its ground shielded. the creator of the bass bought the pickup and installed it to specifications.
 
Rich, yeah there are small soundholes and they are designed to look like eyes in conjuction to the soundhole mouth its pretty clever IMO...the bee stings are actually free floating or whatever so there is free-er vibration...thats what the creator was telling me.
 
its surprisingly loud for such low body mass compared to a normal standup...and yeah its SO nice transporting it, i drive a mitsu mirage TWO DOOR and i just recline the front seat and put it on its side and it fits perfect, a HUUUUGE perk for me, i could not own a normal upright for this purpose....
 
now if i can only get this thing sounding good through my amp!
 
David...i think i would be better off taking the bass to my local hoffman music store and seeing if they will let me put another pickup on it (one that isnt permanently/semi permanently attached like mine) and seeing if another pickup sounds much better and then if it does i will just replace the whole pickup and get one of those buffer amps.
 
does that sound like a good plan of attack?

[orbit]

also david, can you help me find a buffer amp? this seems to be a very specific type of gear and i cant find anything that seems specific to using it with an upright or anything?

[dfung60]

Orbit -  
 
Thanks for the good description.  I wasn't familiar with the Baggs pickup which is why I keep making mistakes about its specifics (it's passive, etc.).  Each followup prompts me to do a little more research...
 
First off, you don't need to try to debug the output jack connection.  When I looked up a picture of the Ultrabass pickup, I realize what that round thing in your picture was.  The coax cable from the pickup element is going into the Ultrabass jack assembly and this was assembled at the factory.  
 
The white wire you see is a coax cable.  There's a thin conductor running down the center of the wire which carries the signal from your instrument.  It's surrounded by insulation and that's wrapped with a foil or braided metal shield, then there's another insulating cover around the shield which is the external appearance of the wire.  To avoid hum, that center conductor must be surrounded by a grounded shield over it's entire length to the output jack and continued over your guitar cable to the amp.  The shield blocks electromagnetic fields in the air - if there's any gap, the EM field will leak into the signal and cause hum.
 
So, this whole grounding discussion had to so with whether the full length of the cable was shielded, particularly where it connects to the output jack.  It's easy to make a mistake there when you're wiring up a regular output jack like a Strat or Les Paul.  In your case, Baggs built the output jack area inside a metal housing, so you don't have to do anything special.
 
The bad news is that it's starting to look like there's a damaged conductor or shield in the pickup assembly or ourput jack and that may be hard to fix.  
 
The best test for this kind of problem is to substitute a known-good pickup for the questionable one and see if the problem goes away, which is what you suggested at the end of your post.  If they have a unit out, you can just hold it against the bridge and see if there are buzz or output level problem.  That's cheaper and faster than any test you can do on the Baggs.
 
I've never used an external buffer, but what you're looking for is an external preamp that has at least 1 megohm input impedance and hopefully 10 megohm.  On the low end, you can get a Fishman BII (around $50).  There's probably no limit to how much you could spend on a buffer, but devices like the D-TAR Solstice (this has two channels and EQ) would be around $325.  Baggs has a product called the MixPro which would also work (this one looks like it's $160).  
 
If you're changing pickups, then you might look for a system that includes a pickup plus external buffer amp.
 
David Fung

[edwin]

I'd like to second the D-TAR Solstice. I've played with a ton of acoustic musicians who have used everything out there and this is the most musical sounding preamp of its type I've heard. It's also incredibly versatile and has every patching and routing option you could want. I had one for a while and sold it to our guitarist, Vince Herman, but sadly it grew legs after a gig in Charlotte. He keeps talking about getting another and we're all waiting as it gave him the best sound for his acoustic and mandolin that we've heard. It's got patch points for a more sophisticated EQ should you need it.
 
Edwin

[orbit]

edwin...that looks like a nice preamp, but 24db of gain on the 1/4 in, that sounds like it is not going to be NEARLY enough for my bass? or is the fact that its a 10megohm input going to fix my problem?
 
it almost seems like the hum issue i have is simply because i have to give so much gain to have a loud enough output...and by so much gain im talking about 85-100 db of gain