Discussion in 'Basses [BG]' started by Danham, Mar 22, 2003.

1. ### DanhamGuest

Feb 11, 2003
Shreveport LA
I recently ordered an EDA905 and am wondering something. It has 18V circuitry but only takes one 9V battery so I am assuming it has a transformer that steps up the voltage. Why not just use two 9V's in series? What is the difference between using a transformer and using batteries in series?

2. ### tim4003

Apr 30, 2002
Dawsonville , GA
Well, you'll buy half as many batteries!!

3. ### WoodseyGuest

I might have got this wrong but as far as i kno u need ac current to use a transformer and batteries use dc, so how does that work?

4. ### E.O.M.

Dec 7, 2001
Grand Rapids, MI
Wouldn't drawing 18v out of a 9v battery make him buy twice as much?

5. ### tim4003

Apr 30, 2002
Dawsonville , GA
But you can't draw 18v out of a 9v batterey, so there's something else going on in there!
What, I don't know?

6. ### JOME77

Aug 18, 2002
Georgia
The primary advantange of powering a preamp with 18 Volts in lieu of 9 Volts is to get more headroom. Since P(power)=I(current) X E (voltage). Twice the voltage (18V) means you require 1/2 the current. I know that EMG pickups can be wired either 18V or 9V. Maybe the bass pre is capable of being wired for 18 volts but is currently wired for 9 volts.

7. ### Tim__x

Aug 13, 2002
No, to get the same power output yes but according to Ohms law

I = V / R

the circuit will draw twice the current

And no you don't need a transformer to up voltage you can double voltage with something called a charge pump its a combo of diodes and capacitors that when fed ac current outputs double voltage
and to make ac from dc all you need is a basic osc. this could be made from a 74ls14 hex inverter or a 555 or even just a npn and pnp transistor

Although for this particular situation I'd say that it has a pre-amp capable of 18v but currently running at 9v

8. ### Sanctum

Jan 25, 2002
Conjunction Junction
I have the same thing in my Spector with the Aggie OBP-1 - 18V circuit with one 9V battery. It has a Fishman voltage step dealie in it - uh, yea, that's a technical term

oh wait, i found the info - its a Fishman Voltage Doubler

http://www.stewmac.com/freeinfo/i-5185/