Sound Skulptor forums

Build help and troubleshooting => AB528 Microphone preamplifier => Topic started by: Alaska on September 28, 2024, 07:20:05 AM

Title: 300 vs 1200 ohms?
Post by: Alaska on September 28, 2024, 07:20:05 AM

I know, “use your ears”, but Im curious some specific mics you would use 300 with or 1200 with.  What is the general usage rule of thumb for choosing these?  I have all manner of mics, and 1200 just seems to be more open sounding in my limited testing.  

Title: Re: 300 vs 1200 ohms?
Post by: JPK on October 01, 2024, 09:46:09 AM

300 ohms gives 6 dB more gain if the mic has low impedance, but loads the mic more, which can result in restricted bandwidth if the mic has high impedance.

Title: Re: 300 vs 1200 ohms?
Post by: Alaska on October 23, 2024, 06:30:55 PM

What is considered “high impedance”.  Any specific mics you would use 300 on?

Title: Re: 300 vs 1200 ohms?
Post by: JPK on October 24, 2024, 10:20:34 AM

The mic impedance should not be higher than the preamp input impedance divided by 10.
Pre on 1200: use mics with less than 120 Ohms (most mics)
Pre on 300: use mics with less than 30 Ohms (ribbon mics generally)