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|previous: Adam Ziegler LM386-1 Chip for Active Pickups? -- 11/12/2002 1:17 AM||View Thread|
|11/13/2002 5:47 PM|
|Dr. Strangelove||General opamp notes|
ne of the early problems with EMG pickups was their reliance on a mediocre opamp (National Semi LF441?) in order to get acceptable battery life.
Many opamps draw too much current for use in active pickups, often needing 4-8 ma to stay alive while the average carbon-zinc battery has a 400 ma-Hour capacity -- 100 hours is the very best you can hope for from one cheap battery.
Eveready's 9V batteries have these capacities:
400 maH - carbon-zinc
565 maH - Alkaline A522
655 maH - Energizer E2
1200 maH - Energizer Lithium
If possible, select the opamp for 1-2 ma quiescent current and remember that you need 2-3 pickups in a guitar. Avoid them.
Finding a good-sounding low power opamp will take time because the lowest current opamps often have poor bandwidth, distortion, and noise qualities.
A rough selection guide could be:
8+ Mhz GBP (gain-bandwidth product)
4+ Mhz unity gain bandwidth
<1-2 ma quiescent current
<200 nv/hz noise voltage
5-30 volts supply voltage
As audiophile opamps go, these figures aren't impressive, but they are the compromise you must make if you want more than 10 hours on one battery.
|Adam Ziegler Dr. Strangelove |
Dr. Strangelove More opamp notes -- 11/15/2002 5:36 PM