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Posted by Bob Gollihur on August 23, 2001 at 07:08:21:
In Reply to: Pre-Amp? posted by Mark on August 22, 2001 at 22:23:51:
: I'm new to this board. I have been playing upright bass about 6 years now. I have been plugging in with a fishman pickup and a fender combo amp. I know I should know this, but what is the purpose of a pre-amp? Does it 'tweak' the signal so that you can control the tone better than just using the EQ on the amplifier? And what pre-amp would you recommend? I play mostly bluegrass, some folk, a little rockabilly...
It's a matter of impedance matching. Most bass guitar amplifier's preamps are designed only for magnetic pickup impedances, in the vicinity of 50,000 ohms. Your Fishman, and other piezo-based pickups are in the millions of ohms. When you plug something into a preamp, it becomes part of the circuit, and if the device's impedance is not in the range of the preamp's specs, unusually things can happen.
Typically, with bass, you get a sort of thin, quacky and brittle sound, not the nice round bass tone you deserve. To properly match, and buffer the pickup, you need a preamp with an input impedance of 1 megohm (1,000,000 ohms) or better. You'll find further info about this on my Preamp page, linked below.
Unless you require extensive features at the preamp, nothing fancy is required. Personally, I use the K&K Power Pack and do little if any EQ'ing at the preamp, and just use if for buffering purposes and a convenient local volume control, and do my major EQ'ing, if necessary, at the amp.
Your Fishman will sound much better with an appropriate preamp.
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