High Input Impedance Single Supply Amp ?

On a sunny day (Mon, 14 Jun 2010 10:38:10 +1000) it happened "Phil Allison" wrote in :

Strange, on your planet physics works differently it seems.

$BAD SYNTAX

ABORT RETRY IGNORE

"Jan Panteltje = Poon "

The impedance is virtually the same as the resistance of the wire making up the voice coil.

( One exception is "dual element" mics that have two transducers and a crossover network internally )

Diaphragm motion damping is all mechanical.

Snip rest of this poon's diabolical verbal diarrhoea.

.... Phil

On a sunny day (Mon, 14 Jun 2010 22:24:29 +1000) it happened "Phil Allison" wrote in :

ABORT, RETRY, IGNORE ^

Phil AllesWrong randomly pressed some keys:

Yo ushould see all this in teh context of J.Lurking's remork tha the wanted to see wa thread abiout dynamic mikes. His mentioning of thousands of FTES i nparallel to lower the noise suggest we need to look at the smallest details. And theen there is inductance in any wound coild. You could (OK I could) model it in spice even.

Almost is not good enough when you are usin g2500 FETS in parallel, audio philes are unforgiving.

No it is not.

Sorry to hear that, drinking less oil may help I suppose.

"Jan Panteltje = Psychopath "

The impedance is virtually the same as the resistance of the wire making up the voice coil.

( One exception is "dual element" mics that have two transducers and a crossover network internally )

Diaphragm motion damping is all mechanical.

Snip rest of this poon's verbal diarrhoea.

Wot a sad little autistic.

.... Phil

ABORT RETRY IGNORE ^

ABORT RETRY IGNORE ^

On a sunny day (Mon, 14 Jun 2010 08:28:11 -0700) it happened John Larkin wrote in :

ABORT RETRY IGNORE ^

To all.

So I guess I'll use high enough imput impedance, like 10 times or more...The application is neither critical nor Hi-Fi, but it would be good to make the best of the components I have available...and that excludes any of those JFETs mentioned before. So long as the circuit's noise isn't audible enough compared to the actual signal it's OK. the idea is to plug it in a 100W guitar power amp for band rehersal, and mix it with the guitar signal...I know it's not the best solution but I can't afford another Amp.

opamp

But

one

Thank you for that information. This mic is of the low-Z dynamic class. high-Z inputs for such are not a correct application. Actually, your best result will be from a low-Z input discrete mic amp. You can get reasonable performance from ultra low voltage noise opamps. Much simpler to work with. The load impedance presented to this mic should not be much above 1k to 2k, and it works reasonably well into about 750 ohms to as much as 10k. If i can find circuit to the low-Z mic inputs to my Ampex AX-300 i would post it. =20

with

opamp

input

input...and

The

any

SM58

I find i mostly agree. They are all piss poor designs.

opamp

But

Not at all. About 1k to 2k. BJT input as well. Part of the issue is that you have to load the microphone properly, otherwise all of the low-Z dynamic microphone properties go to hell. =20

Use good low (voltage) noise parts, and any reasonable topology will work pretty well. For you i recommend a low noise opamp and a mic load resistor DC coupled to the microphone. First stage gain should be from

But

Ah, that information brings up another solution. You should be able to get low-Z to high-Z in-line transformers for a reasonable price. Try rooting around in school kid band garage sales. Easy, reliable, works.

"JosephKKK"

.... Phil

"JosephKKK"

Person would have to be a mental retarded to even imagine it could be true.

.... Phil