<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body dir="auto"><div dir="auto">Yes, we have to pick our battles. The 150 Ohm that is talking about has near 0 DC.</div><div dir="auto">But the 6.8K resistor to 48V phantom your mic is connected to has DC... that is where material may matter. </div><div dir="auto">Yes, there is more to learn every day...</div><div dir="auto"> Regards</div><div dir="auto">Dan Lavry</div><div dir="auto"><br></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: David Josephson via ProAudio <proaudio@bach.pgm.com> </div><div>Date: 6/14/21 12:11 PM (GMT-08:00) </div><div>To: proaudio@bach.pgm.com </div><div>Subject: Re: [ProAudio] Microphones question </div><div><br></div></div>The microphone measurement standard recommends the use of A-weighted rms <br>noise specifications in addition to ITU-R BS.468-4, which specifies not <br>only a frequency weighting curve but a quasi-peak detector which <br>penalizes for low frequency pops and clicks, which can be a factor for <br>some poorly executed microphone designs.<br><br>Yes, even some of the experts in the standards world talk about "low <br>noise" resistors. We have to pick our battles.<br><br>On 6/14/2021 12:01 PM, Dan Lavry via ProAudio wrote:<br>> Excess noise is important in some cases, and it is material dependent. I <br>> agree that the 150 for the noise measurement can be "any: 150 Ohm.<br>> <br>> Regarding "A weighting", I just publish both figures. In most cases it <br>> is 2dB difference.<br>> <br>> Regards<br>> <br>> Dan Lavry<br>> <br>> On 6/14/2021 11:03 AM, Bill Whitlock via ProAudio wrote:<br>>> Dan, I'm glad you caught that one! Noise is a "stand alone" that <br>>> needs no reference except a unit of measure - and, as frequently <br>>> omitted by marketing types, a stated bandwidth. And I have no problem <br>>> in using weighted figures as long as it's clearly stated.<br>>><br>>> In my mind, the biggest barrier to understanding noise and its <br>>> implications is the lies, distortions, and half-truths perpetrated by <br>>> marketing folks! A measurement, with test conditions and references <br>>> fully disclosed, is not subject to interpretation. Sadly, many folks <br>>> are "educated" by such misleading information and will believe, for <br>>> example, that the 150 Ω resistor used for testing preamp noise must be <br>>> a special "low-noise" resistor. In fact, thermal noise has no <br>>> dependence on the resistive material at all. So-called "low-noise" <br>>> resistors are low in "excess noise" that occurs when DC current flows <br>>> in it - and there's a huge difference among those! Anyone whose ever <br>>> heard me lecture is well aware that no love is lost between me and <br>>> marketing people.<br>>><br>>> Bill Whitlock<br>>><br>>><br>>> -----Original Message-----<br>>> From: Dan Lavry via ProAudio <proaudio@bach.pgm.com><br>>> To: Mike Rivers <mm1100@yahoo.com>; proaudio@bach.pgm.com<br>>> Sent: Mon, Jun 14, 2021 9:27 am<br>>> Subject: Re: [ProAudio] Microphones question<br>>><br>>> I think you are confusing things. EIN does not need to be measured at <br>>> full scale, and it is a real representative of the noise contributions.<br>>><br>>> Micpre noise is low and not easy to measure directly. Say you test <br>>> system can measure down to 1uV, but your signal is 0.1uV. It would be <br>>> difficult to measure the noise directly. Say you set the gain at <br>>> 60dB, the noise will become 100uV, and a 1uV system can measure that. <br>>> At 40dB gain you get 10uV, still good enough to measure. In the first <br>>> case Ein is 100uV/1000, in the second case 10UV/100, both yield 0.1uV <br>>> which is the real input noise.<br>>><br>>> Of course that will not hold if the design is poor. Any reasonable <br>>> design will yield very similar ein at 60dB and 40db.<br>>><br>>> Regards<br>>> Dan Lavry<br>>><br>>><br>>><br>>><br>>> Sent from Samsung Galaxy smartphone.<br>>><br>>><br>>> -------- Original message --------<br>>> From: Mike Rivers via ProAudio <proaudio@bach.pgm.com><br>>> Date: 6/14/21 8:07 AM (GMT-08:00)<br>>> To: proaudio@bach.pgm.com<br>>> Subject: Re: [ProAudio] Microphones question<br>>><br>>> How about a little discussion on the value of knowing the EIN of a <br>>> preamp and how the figure is useful to the designer?<br>>><br>>> Here's why I ask:<br>>><br>>> When I was writing reviews regularly, EIN was (and still is) often <br>>> quoted in the product's specs. The numbers ranged from -125 dBu (just <br>>> a couple) to a majority being either -127 or -128 dBu. Manufacturers <br>>> liked to tout it because it was a nice low number with "noise" in its <br>>> name. And it was always measured at a level within a dB or so of <br>>> clipping since that's it looked the best.<br>>><br>>> But unless I missed the appropriate chapter, EIN is a calculated value <br>>> - the measured noise level with the gain subtracted out. So a preamp <br>>> with 60 dB of gain that advertised EIN=-128 dBu could be expected to <br>>> put out -68 dBu of noise, measured, of course to the advantage of the <br>>> marketing department with the appropriate input termination (0, 100, <br>>> or 150 ohms usually) and output load.<br>>><br>>> So, among design engineers, what's the big deal about EIN? Is there a <br>>> better way of measuring it that's more meaningful? And if you can <br>>> squeeze another dB of EIN out of a design, how significant will this <br>>> be to the user? I<br>>><br>>> , know "it depends."<br>>><br>>> -- <br>>> For a good time callhttp://mikeriversaudio.wordpress.com <http://mikeriversaudio.wordpress.com/><br>>> _______________________________________________<br>>> ProAudio mailing list<br>>> ProAudio@bach.pgm.com <mailto:ProAudio@bach.pgm.com><br>>> http://bach.pgm.com/mailman/listinfo/proaudio <br>>> <http://bach.pgm.com/mailman/listinfo/proaudio><br>>><br>>> _______________________________________________<br>>> ProAudio mailing list<br>>> ProAudio@bach.pgm.com<br>>> http://bach.pgm.com/mailman/listinfo/proaudio<br>> <br>> <br>> ------------------------------------------------------------------------<br>> Avast logo <https://www.avast.com/antivirus> <br>> <br>> This email has been checked for viruses by Avast antivirus software.<br>> www.avast.com <https://www.avast.com/antivirus><br>> <br>> <br>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2><br>> <br>> _______________________________________________<br>> ProAudio mailing list<br>> ProAudio@bach.pgm.com<br>> http://bach.pgm.com/mailman/listinfo/proaudio<br>> <br>_______________________________________________<br>ProAudio mailing list<br>ProAudio@bach.pgm.com<br>http://bach.pgm.com/mailman/listinfo/proaudio<br></body></html>