-lachy- Posted June 17, 2005 Report Share Posted June 17, 2005 hi does anyone know what the input impedance of a guitar amp is, i am working on a preamp for a microphone on my double bass so i cal use through a guitar amp but i need to know what the impedance is to get it working. thanx lachlan Quote Link to comment Share on other sites More sharing options...
thedoctor Posted June 17, 2005 Report Share Posted June 17, 2005 It depends to a huge extend on the amp but the rule with modern guitar amps is that they are all happy with hi-Z inputs. For preamp design, I would think you would be more interested in voltage and sensitivity. DR and that kinda stuff. Quote Link to comment Share on other sites More sharing options...
crafty Posted June 17, 2005 Report Share Posted June 17, 2005 Usually 1 Meg Ohm. BTW, my brother-in-law's name is Lachlan. You're only the second person I know now with that brilliant Scottish name. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 17, 2005 Report Share Posted June 17, 2005 What kind of microphone are you trying to match? As crafty pointed out, anything marginally below a Meg or so should work fine, provided the levels are about right. Are you trying to adapt a balanced mic, or is it single-ended? If you can be a little more specific about your needs, I've probably got a design or two lying about that you can use as a starting point and tweak to your own specs. Quote Link to comment Share on other sites More sharing options...
thedoctor Posted June 18, 2005 Report Share Posted June 18, 2005 Sounds like he just needs a DI box schematic. If you insist on building it, it shouldn't be too bad a project but the factory made ones are down to $29.00 thanks to some new one-chip preamp/gain thingy that is happy running on a 9 volt battery. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 18, 2005 Report Share Posted June 18, 2005 Point taken - but an impedance matcher is the matter of about 20 minutes of work and about $15.00 worth of Radio Shack parts (if you include the $8.00 Hammond box), and it can be optimized for the application in size, operating voltage, frequency response and headroom. To each his own, I suppose. Quote Link to comment Share on other sites More sharing options...
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