Samuel Groner
Well-known member
Err, any chance for a description which at least gives a glance where to look at the mentioned site? :grin:
Samuel
FET opamp for condensor microphone?
- Thread starter Svart
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Samuel
Svart
Well-known member
in the downloads section? I search for "microphone" and it returns every single datasheet on each mic...
Yes, there is a opamp based circuit in the Neumann microphone book. I think that circuit was used in an earlier handheld (not the current Neumann stage mic).
As Gus said, CAD uses opamp circuits as well. They use pretty good opamps in their newer mics, such as the e300-2, and those mics sound quite nice and clean. But: Those opamps can draw more current than most P48 supplies deliver. CAD uses 9V batteries that buffer enough juice to supply sufficient current when the opamps need it and are charged by P48 when the opamps draw less current. Although that means the opamps must work class AB or class B, the mics acutally sound nice. On the other hand, that solution is definetly not cheaper than a discrete circuit. So I wonder what the advantages really are. Okay, you can use those mics for a couple hours without a power supply. But other than that? Maybe it's just so the mics are different.
As Gus said, CAD uses opamp circuits as well. They use pretty good opamps in their newer mics, such as the e300-2, and those mics sound quite nice and clean. But: Those opamps can draw more current than most P48 supplies deliver. CAD uses 9V batteries that buffer enough juice to supply sufficient current when the opamps need it and are charged by P48 when the opamps draw less current. Although that means the opamps must work class AB or class B, the mics acutally sound nice. On the other hand, that solution is definetly not cheaper than a discrete circuit. So I wonder what the advantages really are. Okay, you can use those mics for a couple hours without a power supply. But other than that? Maybe it's just so the mics are different.
Svart
Well-known member
any chance of someone having a cad schemo? I'm working on a schemo based on a lot of different sources at the moment..
EDIT.. interesting thing is that i see that neumann has elected to add a BJT servo type of circuit..
now to get rid of that pesky trafo.
EDIT.. interesting thing is that i see that neumann has elected to add a BJT servo type of circuit..
now to get rid of that pesky trafo.
http://www.groupdiy.com/index.php?topic=5574&highlight=cad+microphone
look for the m37
Cool little circuit.
lets see transformer out
Spilt from a E and C
Schoeps
AKG, Neumann, Rode, Oktava 021 type out.
Take a 71 add a push pull output pair set to a gain of one or - one
100 ohm 3 to ground and a little less than 100 ohm from the output of the 71 to 2
What is so hard?
look for the m37
Cool little circuit.
lets see transformer out
Spilt from a E and C
Schoeps
AKG, Neumann, Rode, Oktava 021 type out.
Take a 71 add a push pull output pair set to a gain of one or - one
100 ohm 3 to ground and a little less than 100 ohm from the output of the 71 to 2
What is so hard?
Svart
Well-known member
I don't recall saying anything was hard.. only that I was studying this and playing around.
http://www.gyraf.dk/schematics/Neumann_Handheld.GIF
Svart
Well-known member
Yeah Jakob that is the circuit I was talking about with the interesting BJT servo.
I found the fragments, pretty cool, I like that CAD schematic, interesting voltage regulation and step up converter, however I am going the photodiode route for the bias voltage.. but i have to figure out what the best way to isolate the grounds are..
I found the fragments, pretty cool, I like that CAD schematic, interesting voltage regulation and step up converter, however I am going the photodiode route for the bias voltage.. but i have to figure out what the best way to isolate the grounds are..
Svart
Well-known member
ah for those interested, I was thinking about a pair of source/sink BJT arrangements on the outputs of the opamps for extra drive, but the opa627 has pretty good oomph itself.. so do you think I would be ahead just using two opamps instead of a bunch of BJTs for drive?
Simple opamp microphone circuit inspired by the CAD M37
http://groupdiy.twin-x.com/displayimage.php?album=lastup&cat=1&pos=0
Low voltage at the capsule and set for low gain POSSABLE AB sound for a condenser microphone used on a KICK. I am thinking a MXL V67M, 1006 etc with this circuit installed. Some AB circuits can have a cool sound. I am thinking more of an effect than a clean circuit
Low capsule voltage means less signal voltage from the capsule.
Not built yet not tested designed for about a 3ma draw
Just saw a mistake the two 5.1Ks should be about 10K to 12Ks
* means match relative match
Bend the input pin in the air and make the High Z connection in the air
Lets post
I checked and another picture shows at the link. I guess I linked the schematic the wrong way. What is the right way?
http://groupdiy.twin-x.com/displayimage.php?album=lastup&cat=1&pos=0
Low voltage at the capsule and set for low gain POSSABLE AB sound for a condenser microphone used on a KICK. I am thinking a MXL V67M, 1006 etc with this circuit installed. Some AB circuits can have a cool sound. I am thinking more of an effect than a clean circuit
Low capsule voltage means less signal voltage from the capsule.
Not built yet not tested designed for about a 3ma draw
Just saw a mistake the two 5.1Ks should be about 10K to 12Ks
* means match relative match
Bend the input pin in the air and make the High Z connection in the air
Lets post
I checked and another picture shows at the link. I guess I linked the schematic the wrong way. What is the right way?
> another picture shows at the link. I guess I linked the schematic the wrong way. What is the right way?
I'm not sure. That album system has layers within layers.
You cited:
.....displayimage.php?album=lastup&cat=1&pos=0
This link appears to reference "album=lastup", which may be "Album last updated". That was a logical way to find what you just posted, and worked at the moment you looked, but some other album was updated after that. So that link will keep changing.
I think you mean:
.....displayimage.php?album=174&pos=0
That seems to be "your" album, and the first (zero-based) image on that page. It has your name, the image looks like phantomed opamps.
Page with image
just the image
I'm not sure. That album system has layers within layers.
You cited:
.....displayimage.php?album=lastup&cat=1&pos=0
This link appears to reference "album=lastup", which may be "Album last updated". That was a logical way to find what you just posted, and worked at the moment you looked, but some other album was updated after that. So that link will keep changing.
I think you mean:
.....displayimage.php?album=174&pos=0
That seems to be "your" album, and the first (zero-based) image on that page. It has your name, the image looks like phantomed opamps.
Page with image
just the image
Make the 5.11Ks 10Ks I was thinking the parallel value of the two.
The 10ks might work ok for a opamp current of about 3ma and maximize the voltage for the capsule without a DC to DC. One can add a cap an another resistor to gain about 7.5VDC for the capsule.
It is untested a min part circuit
The 10ks might work ok for a opamp current of about 3ma and maximize the voltage for the capsule without a DC to DC. One can add a cap an another resistor to gain about 7.5VDC for the capsule.
It is untested a min part circuit
Svart
Well-known member
sorry guys, I've been so busy with work these days I haven't been keeping up with the threads and other projects. It should settle down soon though. I have an idea in a schematic that I have been thinking about and if I get time tonight I will post it. quite different from what you guys have posted so far..
I will try to get thing going here.
Look at the 2.2k and the 5.1ks In analag's nice picture
A TL072 should work OK with the 5.1Ks as 10Ks (the resistors to change for the current draw of the opamp lower values for higher current draw opamps) Also the 2.2 and 5.1(10K) acts as a voltage divider. Lets think about this The overall gain is less than one first the swing at the outputs of the opamp sums up to X2 but the dividers after them reduce that.
The CAD circuit is clever look at the top left of the CAD m37 the first opamp has > than gain of one and set to gain of one an overall gain of -20Db
Also the 72s don't "like" to drive lots of current but in the CAD the 2.2Ks limit the max current
Clever circuit CAD designed.
The one I wrote down is made to stick more in High SPL areas and to be as simple as possable and cheap.
Look at the 2.2k and the 5.1ks In analag's nice picture
A TL072 should work OK with the 5.1Ks as 10Ks (the resistors to change for the current draw of the opamp lower values for higher current draw opamps) Also the 2.2 and 5.1(10K) acts as a voltage divider. Lets think about this The overall gain is less than one first the swing at the outputs of the opamp sums up to X2 but the dividers after them reduce that.
The CAD circuit is clever look at the top left of the CAD m37 the first opamp has > than gain of one and set to gain of one an overall gain of -20Db
Also the 72s don't "like" to drive lots of current but in the CAD the 2.2Ks limit the max current
Clever circuit CAD designed.
The one I wrote down is made to stick more in High SPL areas and to be as simple as possable and cheap.
