Rockbox Technical Forums

Support and General Use => Recording => Topic started by: gnu on March 27, 2007, 11:05:47 AM

Title: Dynamic microphone preamp DIY?
Post by: gnu on March 27, 2007, 11:05:47 AM
Since line-in works on my nano, but mic input does not, I need a cheap, small preamp that brings my mic to line-level. I don't want to buy anything, but I got lot's of old devices with almost any type of transistor, resistor etc.
I searched the web, but I couldn't find a working (simple) one anywhere. Can you provide me with a plan for a preamp? I doesn't need to have good quality or be stereo.
Any suggestions?
Title: Re: Dynamic microphone preamp DIY?
Post by: saratoga on March 27, 2007, 11:40:02 AM
I've built a few of these for lab projects.  Generally a pair of 741s or better opamps in series does the trick.  INA122 or similar if you don't mind spending 2-3 bucks extra.  Not sure if this is ideal, but I've had good results.

You're not going to be able to build one of these with salvaged parts though.
Title: Re: Dynamic microphone preamp DIY?
Post by: gnu on March 28, 2007, 11:26:41 AM
Ah crap..
OK, I'll have to buy some opamps...
Title: Re: Dynamic microphone preamp DIY?
Post by: gnu on March 29, 2007, 01:08:53 PM
I looked through all my salvaged parts and I found a tl082 opamp - now I only need a simple preamp...
Title: Re: Dynamic microphone preamp DIY?
Post by: BenJenkins on March 29, 2007, 06:03:11 PM
I don't know what kind of parts you have sitting around, but here is a recycled preamp. http://sneaktime.net/2007/03/13/homemade-preamp
Title: Re: Dynamic microphone preamp DIY?
Post by: gnu on March 31, 2007, 10:08:58 AM
OK, I made a small preamp with one transistor.
It didn't work until I realised that my microphone wasn't a dynamic one at all - it was electret!
Knowing this, I made my preamp work!!! But it has lot's of noise, so I think I'll build another one with an opamp in it.