Any microphone experts out there?
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From: Phil Hobbs on 18 Jul 2010 14:33 Jim Thompson wrote: > On Sun, 18 Jul 2010 13:36:42 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> Jim Thompson wrote: >>> On Sun, 18 Jul 2010 08:37:46 +0100, "Midge" <midge(a)somewhere.com> >>> wrote: >>> >>>> Have a small microphone mixer http://www.audiomate.co.uk/PDF/G105C.pdf >>>> >>>> I've been using a couple of dynamic microphones on it, but I wondered if it >>>> was possible to either get a tie-clip microphone (these seem to be electret >>>> condenser) which can be plugged straight in OR match the different >>>> technologies somehow. >>>> >>>> Thanks, Midge. >>>> >>> If the electret has a built-in FET buffer, all you'll need is power >>> for the FET. >>> >>> Otherwise the Audiomate input impedance is too low. >>> >>> ...Jim Thompson >> As an aside, does the standard explanation of how electret mics work >> bother anyone but me? It's usually stated that the 'frozen in' >> electric polarization in the material works just the same as the applied >> voltage in a real capacitive mic. This is of course nonsense--charges >> such as air ions migrate around and eventually neutralize any E field >> external to the electret material, so that waving it around does nothing >> whatever. (Leakage--that's why you have to keep the capacitance mic's >> supply connected for it to work, duh.) >> >> The reality appears to be that they work by a combination of the >> piezoelectric effect (like a quartz crystal) and the variation of >> capacitance with stress (like coaxial cable with a DC voltage on it). >> >> Any comments from audio folks? >> >> Cheers >> >> Phil Hobbs > > I've used them many times in hearing-aid chip designs, but I have no > idea of how they actually work. The leader, in hearing-aid usage is > Knowles... > > http://www.knowles.com/search/technologies/tech_condenser.jsp > > But I've also used a MIMS equivalent (Akustica) which was simply a > capacitor biased with a _very_high_valued_ "resistor", powered from a > 4X charge-pump (my part of the design). > > ...Jim Thompson I just did a design for a startup making radiation sensors from conductive polymers--it used a $5 CCFL inverter with a bridge rectifier and a rail splitter to form half of the readout bridge. It makes 600V from a 5V supply. There are a lot of things you can do with those, for very little dough. (Maybe even make capacitive mics.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Jim Thompson on 18 Jul 2010 14:37 On Sun, 18 Jul 2010 14:33:20 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >Jim Thompson wrote: >> On Sun, 18 Jul 2010 13:36:42 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> Jim Thompson wrote: >>>> On Sun, 18 Jul 2010 08:37:46 +0100, "Midge" <midge(a)somewhere.com> >>>> wrote: >>>> >>>>> Have a small microphone mixer http://www.audiomate.co.uk/PDF/G105C.pdf >>>>> >>>>> I've been using a couple of dynamic microphones on it, but I wondered if it >>>>> was possible to either get a tie-clip microphone (these seem to be electret >>>>> condenser) which can be plugged straight in OR match the different >>>>> technologies somehow. >>>>> >>>>> Thanks, Midge. >>>>> >>>> If the electret has a built-in FET buffer, all you'll need is power >>>> for the FET. >>>> >>>> Otherwise the Audiomate input impedance is too low. >>>> >>>> ...Jim Thompson >>> As an aside, does the standard explanation of how electret mics work >>> bother anyone but me? It's usually stated that the 'frozen in' >>> electric polarization in the material works just the same as the applied >>> voltage in a real capacitive mic. This is of course nonsense--charges >>> such as air ions migrate around and eventually neutralize any E field >>> external to the electret material, so that waving it around does nothing >>> whatever. (Leakage--that's why you have to keep the capacitance mic's >>> supply connected for it to work, duh.) >>> >>> The reality appears to be that they work by a combination of the >>> piezoelectric effect (like a quartz crystal) and the variation of >>> capacitance with stress (like coaxial cable with a DC voltage on it). >>> >>> Any comments from audio folks? >>> >>> Cheers >>> >>> Phil Hobbs >> >> I've used them many times in hearing-aid chip designs, but I have no >> idea of how they actually work. The leader, in hearing-aid usage is >> Knowles... >> >> http://www.knowles.com/search/technologies/tech_condenser.jsp >> >> But I've also used a MIMS equivalent (Akustica) which was simply a >> capacitor biased with a _very_high_valued_ "resistor", powered from a >> 4X charge-pump (my part of the design). >> >> ...Jim Thompson > >I just did a design for a startup making radiation sensors from >conductive polymers--it used a $5 CCFL inverter with a bridge rectifier >and a rail splitter to form half of the readout bridge. It makes 600V >from a 5V supply. There are a lot of things you can do with those, for >very little dough. (Maybe even make capacitive mics.) > >Cheers > >Phil Hobbs I don't the luxury of a wall socket for my hearing-aid designs ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Friday is Wine and Cheeseburger Day
From: Phil Hobbs on 18 Jul 2010 14:41 Jim Thompson wrote: > On Sun, 18 Jul 2010 14:33:20 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> Jim Thompson wrote: >>> On Sun, 18 Jul 2010 13:36:42 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Sun, 18 Jul 2010 08:37:46 +0100, "Midge" <midge(a)somewhere.com> >>>>> wrote: >>>>> >>>>>> Have a small microphone mixer http://www.audiomate.co.uk/PDF/G105C.pdf >>>>>> >>>>>> I've been using a couple of dynamic microphones on it, but I wondered if it >>>>>> was possible to either get a tie-clip microphone (these seem to be electret >>>>>> condenser) which can be plugged straight in OR match the different >>>>>> technologies somehow. >>>>>> >>>>>> Thanks, Midge. >>>>>> >>>>> If the electret has a built-in FET buffer, all you'll need is power >>>>> for the FET. >>>>> >>>>> Otherwise the Audiomate input impedance is too low. >>>>> >>>>> ...Jim Thompson >>>> As an aside, does the standard explanation of how electret mics work >>>> bother anyone but me? It's usually stated that the 'frozen in' >>>> electric polarization in the material works just the same as the applied >>>> voltage in a real capacitive mic. This is of course nonsense--charges >>>> such as air ions migrate around and eventually neutralize any E field >>>> external to the electret material, so that waving it around does nothing >>>> whatever. (Leakage--that's why you have to keep the capacitance mic's >>>> supply connected for it to work, duh.) >>>> >>>> The reality appears to be that they work by a combination of the >>>> piezoelectric effect (like a quartz crystal) and the variation of >>>> capacitance with stress (like coaxial cable with a DC voltage on it). >>>> >>>> Any comments from audio folks? >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> I've used them many times in hearing-aid chip designs, but I have no >>> idea of how they actually work. The leader, in hearing-aid usage is >>> Knowles... >>> >>> http://www.knowles.com/search/technologies/tech_condenser.jsp >>> >>> But I've also used a MIMS equivalent (Akustica) which was simply a >>> capacitor biased with a _very_high_valued_ "resistor", powered from a >>> 4X charge-pump (my part of the design). >>> >>> ...Jim Thompson >> I just did a design for a startup making radiation sensors from >> conductive polymers--it used a $5 CCFL inverter with a bridge rectifier >> and a rail splitter to form half of the readout bridge. It makes 600V >>from a 5V supply. There are a lot of things you can do with those, for >> very little dough. (Maybe even make capacitive mics.) >> >> Cheers >> >> Phil Hobbs > > I don't the luxury of a wall socket for my hearing-aid designs ;-) > > ...Jim Thompson Your customers just aren't plugged in. (This isn't a wall socket application either.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Tim Wescott on 18 Jul 2010 15:49 On 07/18/2010 10:36 AM, Phil Hobbs wrote: > Jim Thompson wrote: >> On Sun, 18 Jul 2010 08:37:46 +0100, "Midge" <midge(a)somewhere.com> >> wrote: >> >>> Have a small microphone mixer http://www.audiomate.co.uk/PDF/G105C.pdf >>> >>> I've been using a couple of dynamic microphones on it, but I wondered >>> if it was possible to either get a tie-clip microphone (these seem to >>> be electret condenser) which can be plugged straight in OR match the >>> different technologies somehow. >>> >>> Thanks, Midge. >> >> If the electret has a built-in FET buffer, all you'll need is power >> for the FET. >> >> Otherwise the Audiomate input impedance is too low. >> >> ...Jim Thompson > > As an aside, does the standard explanation of how electret mics work > bother anyone but me? It's usually stated that the 'frozen in' electric > polarization in the material works just the same as the applied voltage > in a real capacitive mic. This is of course nonsense--charges such as > air ions migrate around and eventually neutralize any E field external > to the electret material, so that waving it around does nothing > whatever. (Leakage--that's why you have to keep the capacitance mic's > supply connected for it to work, duh.) > > The reality appears to be that they work by a combination of the > piezoelectric effect (like a quartz crystal) and the variation of > capacitance with stress (like coaxial cable with a DC voltage on it). > > Any comments from audio folks? Some piezoelectric materials do need to be polarized to work. I suspect that the "charge frozen in" explanation is valid to the extent that anything else could be without going into the details of the physics, and it has the desirable property that it confuses people into shutting up while still using the device correctly. Do you accept the "trapped charges on a floating gate" model of EEPROM behavior? How is that different from the "frozen-in charges" of the piezo microphone? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Midge on 18 Jul 2010 16:08
Thanks for the advice guys. Midge. "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:cf76465fpcqdhm2oun7dfiicuc3kfka2aa(a)4ax.com... > On Sun, 18 Jul 2010 08:37:46 +0100, "Midge" <midge(a)somewhere.com> > wrote: > >>Have a small microphone mixer http://www.audiomate.co.uk/PDF/G105C.pdf >> >>I've been using a couple of dynamic microphones on it, but I wondered if >>it >>was possible to either get a tie-clip microphone (these seem to be >>electret >>condenser) which can be plugged straight in OR match the different >>technologies somehow. >> >>Thanks, Midge. >> > > If the electret has a built-in FET buffer, all you'll need is power > for the FET. > > Otherwise the Audiomate input impedance is too low. > > ...Jim Thompson > -- > | James E.Thompson, CTO | mens | > | Analog Innovations, Inc. | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | Phoenix, Arizona 85048 Skype: Contacts Only | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > "What would happen to [Obama's] vanity if he didn't have us to > throw alms to? What would become of his strength if he didn't have > weaker people to dominate? What would he do with himself if he > didn't keep us around as dependents? It's quite alright, really, > I'm not criticizing him, it's just a law of human nature." > > -Ayn Rand, "Atlas Shrugged" > |