<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body dir="auto"><div dir="auto">You mentioned digitizing at the mic. It is interesting to see the TDK mics, sending one bit stream, and the 4 ch ic that receives that signal and decimats it with 4 or 5 pole filter to i2s or tdm. </div><div dir="auto"><br></div><div dir="auto">Dan Lavry</div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div id="composer_signature" dir="auto"><div style="font-size:85%;color:#575757" dir="auto">Sent from Samsung Galaxy smartphone.</div></div><div dir="auto"><br></div><div><br></div><div align="left" dir="auto" style="font-size:100%;color:#000000"><div>-------- Original message --------</div><div>From: Scott Dorsey <kludge@panix.com> </div><div>Date: 6/11/21 5:35 PM (GMT-08:00) </div><div>To: proaudio@bach.pgm.com, dan@lavryengineering.com </div><div>Subject: Re: [ProAudio] Microphones question </div><div><br></div></div>The answer is partly that microphones vary all over the place in their<br>output impedance. Effective output impedance of some condenser microphones<br>is around 50 ohms. But an RCA ribbon wants to see 2K or higher or you'll<br>lose high frequencies because the high frequency impedance is higher than <br>the impedance at 1kc.<br><br>So... 150 ohms seems like a nice reasonable middle ground that more or less<br>represents a wide range of microphones. If I was going to pick a value for<br>a standard to measure noise at, I'd pick something in that range.<br><br>And yes, there are cases where preamp A is quieter with the Schoeps and<br>noisier with the RCA compared with preamp B. <br><br>It is stuff like this which drives the Neumann Solution-D and other attempts<br>to digitize signals at the mike and eliminate the whole mike/preamp interface.<br>--scott<br><br><br><br></body></html>