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Double Bass What kind of volume potentiometer?

D

davidilag

Jul 26, 2008
7
0
#1
Hi everybody.

I have the SHADOW SH 950 (or something that looks like it) on my double bass. I just ordered the FISHMAN PRO-EQ PLATINUM BASS preamp.

What I now want is to install some kind of volume knob between the pickup and the preamp. I am planing to to attach the volume knob under the tailpiece or better still, on the bridge itself if it's not ugly and big.

Why the volume knob? Well, so I don't have to bend all the way down to the floor, or where ever I have my preamp, to turn the volume down (or up)! Why don't I just use a volume pedal you may ask you self! Because I want to keep it simple and clean (clean = the sound) without spending a lot of time setting up pedals and wires every time I'm playing.

I'm thinking of a simple, passive volume potentiomenter. What specs in terms of Ohm ec. should I be looking for? I was planning to build the thing myself, but if you know of at product that meets my need, please let me know :hyper:

Thanks in advance.

-Dávid
 
#3
I probably will mount the preamp on the back of the tailpiece, but I don't think that it will allow me easy access to the volume control!

What do you mean by "that will defeat the purpose of the preamp"? Will the impedance change? Maybe it's better to place the volume pot. between the preamp and the amp!
 
#4
You will need a simple FET buffer in front of the volume pot. Search on "FET buffer" in this forum (Amps, Mics & Pickups [DB]) and you should find plenty of info to build your own.

Here's an example circuit:

attachment.jpg


To add a volume control, the 100K resistor would be replaced by an audio taper pot.
 
#5
davidilag said:
I probably will mount the preamp on the back of the tailpiece, but I don't think that it will allow me easy access to the volume control!

What do you mean by "that will defeat the purpose of the preamp"? Will the impedance change? Maybe it's better to place the volume pot. between the preamp and the amp!
Click to expand...

Get a volume pedal, velcro mount it in line on a small pedalboard *after* your pre amp. Visual Sound and Ernie Ball manufacture quality volume pedals. You will only need to make two cable connections that way. 1.) pu to preamp/volume pedal 2.) volume pedal to amp.

Some volume pedals have a tuner out as well. That can be handy.
 
#6
@robgrow:
Thanks for the schematic. I was hoping for something simpler, much simpler. Any advice?

@MR PC:
My goal is to have no pedal board. I mean lets face it; when one has to drag a double bass cross city it is much easier not having to deal with a pedal board. But then again, I do use a tuner, not only to tune my bass, but to ensure that I play in tune at all times.

My current setup is this: pickup - tuner - mutepedal - preamp - amp. The PA gets the signal from my preamp. As I said I was hoping to get rid of the pedals (if that's even possible!).
 
#7
I probably didn't make it clear that just hanging a volume pot off of a pickup probably won't work very well (I've tried it). Most double bass pickups need to see a very high impedance, so a buffer is needed between the pickup and volume control pot. Same things go for passive volume pedals.

There's nothing complicated about a simple buffer, and they're pretty easy and cheap to build. There are also ready-made buffers available. For example, Invalid Link Removed with a built-in volume control would probably work well for your application and could be mounted on the tailpiece.
 
#10
OK, as a test, maybe you could just try wiring your pickup to a pot, say 1megaohm, and find out how it sounds. There will be radio freq noise issues unless you fully shield the wiring.

Or borrow a volume pedal to check out how it sounds, that would be even simpler as a test. I'm surprised you haven't tried this yet.

Do you realize, that beyond the resistance you are putting in the signal path with the pot, you will also lose even more fidelity as you turn the pot down?

Do you have any idea of the effect hanging the Fishman Pre on the tailpiece will effect the sound of your bass? That's kind of a big and heavy piece in terms of tailpiece real estate. You might want to give that a trial run as well.
 
#11
I'd go back to the post-pre pot idea. You could fashion a pre-to-amp cable which has a second cable (going to the pot) coming out of one end, and mount the pot on your tailpiece or even tape it under the fingerboard. One more wire on your bass, but none of the other disadvantages. You can purchase pots with extra deep mounting threads and conceivably mount it in one of the string holes in the tailpiece. I prefer a volume pedal myself. Another thing to schlepp, but then I can adjust anytime, even during lots of eighth notes:hyper:
 
#12
davidilag said:
Hi everybody.

I I just ordered the FISHMAN PRO-EQ PLATINUM BASS preamp.

What I now want is to install some kind of volume knob between the pickup and the preamp. I am planing to to attach the volume knob under the tailpiece or better still, on the bridge itself if it's not ugly and big.
Click to expand...

David,
1. The Pro-Platinum already has a volume control. Yes?
2. I wouldn't recommend hanging anything of the tailpiece because it's a vibrating surface.

davidilag said:
Why the volume knob? Well, so I don't have to bend all the way down to the floor, or where ever I have my preamp, to turn the volume down (or up)!
Click to expand...

I don't know how tech savvy you are but I have enough trouble remembering where I set the Volume on the pre amp for the Ehrlund and the Volume on the amp. Having three volume controls is fraught with peril for some one like me.

A simple solution would be to attach the Pro Platinum to a mic stand so it's easy to reach.

P.S. That's why I like this pre amp, It's setup to be mounted on a mic stand.

[Invalid or Expired Link Removed]
 
#14
Thanks for all the all the great ideas.

My DB is rather big, almost a size 7/8. The tailpiece is also larger than on a "normal" DB.
I just ordered the Fishman PLATINUM on the internet and have'nt received it yet. Will let you all know how it fits on the tailpiece on my DB and how it affects the sound.

The reason for me wanting a easy access volume pot. (I try to stay clear of pedals, just makes the setup easier) is that first of all I want to be able to turn down the volume while I'm playing. My band plays very dynamic music, it can get loud and and quiet in the same song, and in the quiet part I want to turn the volume down so I can play with a regular attack on the strings (hope it makes sense!). Secondly I can use the volume pot. as a mute function.

@robgrow
I will defently have a closer look on the HPF-Pre unit. Looks like at quality product.

@MR PC
I think I will try out a 1 Mohm pot. and see how that works. It might affect the quality of the sound in a way that it is no good.

@rotobass
I like the idea of mounting the pot. in one of the string holes in the tailpiece, discreet and good looking. It might just work...

@Ric Vice
I did'nt know that the Fishman PLATINUM can be mounted on at mic stand! That could come in handy some day: I play all the time, electric and DB, and the setup is always different so you never know.
 
#15
Y'all hurt my head with all this gear talk. If you are willing to do all that extra wiring, putting **** on mic stands, clipping **** on you belt or tailpiece, why balk at a volume pedal idea. I use one when I have to do big rocks gigs with my BassMax because the group I play with I go between pizz and arco. It is a snap and solid factory built stuff has less chance of failure plus what's more hands free than working your volume with your foot. That's just me.
 
#16
MR PC said:
Get a volume pedal, velcro mount it in line on a small pedalboard *after* your pre amp.
Click to expand...

I'm interested in learning more about this. When I use a volume pedal I am often using a Plat Pro too. I usually put the volume pedal first in the signal chain. bass-->volume pedal-->plat pro-->amp. I'm stupid about electronical type stuff though. Should I switch the signal chain?
 
#17
If you put the Platinum first, you are taking advantage of the input impedance which is designed to make your pu more dynamic and sound better. I don't know what kind of volume pedal you are using, but mine is a *passive* one with a 1 meg volume pot attached to a string (Ernie Ball). If i plug my bass into the volume pedal first, the fidelity suffers, because you are putting a passive resistor in the signal path. The more you turn the pedal down, the more the fidelity changes.

If I plug it in to the preamp first, it sounds mo bettah. Just try it at home, and on a gig and you will hear for yourself if switching it makes a difference to you.

OTH, Steve Rodby built a volume pedal with a rotary switch that let him choose a bunch of different resistors to mess with the tone of the pu. I wanna guess that he was plugging into some kind of preamp first though.
 
#18
MR PC said:
OTH, Steve Rodby built a volume pedal with a rotary switch that let him choose a bunch of different resistors to mess with the tone of the pu. I wanna guess that he was plugging into some kind of preamp first though.
Click to expand...
Probably not. (just a shot in the dark)
Changing the load resistance to a piezo pickup (input impedance) will change the tone, and that's what he wants.
Changing the load *after* the preamp won't change anything. (or the volume, at worst)
 
#19
Francis:

Yes , maybe so, I suppose he could have plugged into the his pedal first. I remember that the old Polytone and some Barcus Berry pu's had resistors wired in the cables, it was a way to refine the relatively poor performance of those pickups of the era, 30-40 years ago now.

Isn't a potentiometer a just resistor that can be adjusted? If I measure the resistance of a 1 meg audio pot on my test meter, the measurement changes and becomes smaller as I turn the pot down. AS the resistance goes down in this scenario, doesn't it change the sound?

It shouldn't make any difference if the signal passing through the pot is passive or active, the effect of the resistance is pretty much the same on the signal it's reading, right?

Isn't it more advantageous to buffer a piezo pick up without any added passive load resistance of an audio pot on the pickup, taking advantage of the audio headroom the buffer provides?

:)
 

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