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Old 7th April 2008, 08:41 PM   #1
jenks is offline jenks  United Kingdom
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Default electric bass guitar impedance and level

I'm undergoing my first electronics project atm and I've just started breadboarding a bit of an overdrive. I wanted it to be a bit of a overdrive, pre-amp and D.I project. just realised though that I'm not sure what impedance or signal level my bass is pushing out with which to design/build a D.I etc

I have an active bass (ibanez SR500) does anybody have any idea what impedance and signal level i'm pushing out??

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Old 8th April 2008, 11:52 AM   #2
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An active bass is more of a line signal than anything else, 50K should be fine for an input impedance - with 500K and up for a passive bass.

Signal level varies depending how you play, but you could easily hit over 1V RMS.
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Old 8th April 2008, 12:03 PM   #3
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Default Re: electric bass guitar impedance and level

Quote:
Originally posted by jenks
I have an active bass (ibanez SR500) does anybody have any idea what impedance and signal level i'm pushing out??

Cheers.
Measure it. I have three dozen basses, active and passive, of all different levels. The one thing you can be assured of is: there is no standard.
Quote:
Originally posted by Nigel Goodwin
An active bass is more of a line signal than anything else, 50K should be fine for an input impedance - with 500K and up for a passive bass.
No. Some are no different in level (EQ flat) from the passive equivalent.
There are good reasons why this might be so.
Quote:
Originally posted by Nigel Goodwin
Signal level varies depending how you play, but you could easily hit over 1V RMS.
You need to measure again. Some of my basses hit 12dB or better than that on peaks with slapping or plectrum work.
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Old 8th April 2008, 12:16 PM   #4
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if you're just looking to boost the signal, a simple preamp using a TL062/72/82 and a max gain of 10 would suffice.

in the circuit below, the second half of the op amp splits the 9V battery and provides an active ground. the other half is a noninverting preamp with a gain of 0-11. using a TL062 will give a nice clean signal and low current draw from the battery. and the whole thing fits on a pc board smaller than the battery.

you may want to add a couple of 220uf caps between the supply rails and ground.
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Old 8th April 2008, 06:53 PM   #5
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At the moment I'm building a device which has a TS-9 circuit inside which I've just breadboarded and I'm gonna test it soon.

But, I wanted two outputs: one with the impedance and level modified for input to a desk, so that's pretty much a D.I. and the other just line-level jack to put the device in line with rest of my pedals.

So it looks like I should measure the impedance and the average level that my bass outputs before building the D.I then...
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Old 8th April 2008, 10:19 PM   #6
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Previous post is correct. You can simply measure the resistance of the bass output and consider that the characteristic impedence of the pickups since the paralllel capacitance and series inductance of the PUs is nominal. Seymour D has detailed specs in his catalogue. Just remember that everything changes when you play with the volume pot and tone control. Now for the controversial IMHO part. A bass with good single coil pickup wants to look into a valve stage. They don't like transistors, and will lose all of there character (Balls, Timbre, ability to sing). So if I want overdrive, I'd get one of those Mesa foot pedal boxes with a 12ax7, or put a switch in the cathode section of the first stage of the Amp, so I can change the gain of the first stage,which will overdrive the second stage. I once had a dual channel Alembic preamp that I would cascade, that is daisy chain the A and B channel. Very sweet.
Test my tube vs x-sistor theory for youself. Plug something like a '62 jazz bass into your favorite tube head (SVT, Mesa Boogie 400, Sunn Model T, whatever). Notice the grinding growl when you crank it up. And yet it sings like a Stratavarius when you back off. Now plug it into whatever transistor head you want (GK, Trace Elliot, New Fender). Now everything is compressed and tone has flown the coup. Every thing sounds like it's been processed by a computer chip (Line-6 ?). Flea cries out "But my GK has all this PUNCH!" Well so does Mike Tyson, but that doesn't get him the job as first cellist with the Chicago Symphony does it?
Well I've tried my best to start a flame war. Don't let me down!
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Old 9th April 2008, 07:40 AM   #7
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Quote:
Originally posted by makinson1
Previous post is correct. You can simply measure the resistance of the bass output and consider that the characteristic impedence of the pickups since the paralllel capacitance and series inductance of the PUs is nominal.
Typically bass pups have between 4 and 16H of L Capacitance is between 200 and 300pF. At least the ones I measured.

Quote:
Originally posted by makinson1
Just remember that everything changes when you play with the volume pot and tone control.
Best dats, but still not much.

Quote:
Originally posted by makinson1
Now for the controversial IMHO part. A bass with good single coil pickup wants to look into a valve stage.
Bollocks.
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Old 9th April 2008, 07:59 AM   #8
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Bollocks! Well, I'm prejudiced. I think tubes sound better than solid state devices. I think black vinyl sounds better than CDs. I think mag tape sounds better than a hard disk. So there. Bollocks? Is that a Britishism? Something like ********? Is there a translator out there that can translate that into American?
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Old 9th April 2008, 02:23 PM   #9
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Quote:
Originally posted by makinson1
Bollocks! Well, I'm prejudiced. I think tubes sound better than solid state devices. I think black vinyl sounds better than CDs. I think mag tape sounds better than a hard disk. So there. Bollocks? Is that a Britishism? Something like ********? Is there a translator out there that can translate that into American?
Well you have two of them, and they hurt a LOT if kicked!

Bear in mind the OP has an active bass, not a passive one, so no need (or use) for a high impedance input as you would need for a passive bass. Most amps though have sockets for both, so it might be an idea to add both?.

Valve amps have their uses, but it's mainly personal choice, and a decent transistor amp would be my choice for bass, as I like a clean sound, not the distortion and colouration of a valve amp.
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Old 9th April 2008, 07:35 PM   #10
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Quote:
Originally posted by Nigel Goodwin


Well you have two of them, and they hurt a LOT if kicked!


Little brothers !?! They're both boxers and will respond in kind. Over here that's called hitting below the belt.

I'm learning Irish so bear with me. I found out that in Ireland its called a Wan*er, but in England it's called an MP, whatever that is. And in Australia it's called a banana bender. i didn't even know they had bananas in Australia.

Bear in mind the OP has an active bass, not a passive one, so no need (or use) for a high impedance input as you would need for a passive bass. Most amps though have sockets for both, so it might be an idea to add both?.

I had a Music Man Sabre with humbuckers and a Sadowsky preamp. It did in fact reduce the differences between tube and solid state amps.

Valve amps have their uses, but it's mainly personal choice, and a decent transistor amp would be my choice for bass, as I like a clean sound, not the distortion and colouration of a valve amp.
Either amp should be able to be adjusted for the amount of drive (distortion). It's just that when solid state amps are overdriven they clip the signal like a limiter rather than a compressor. I don't know if that simile works for you.
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