I need to build an amplifier/power source to connect a condenser microphone to a recorder such as the Zoom H4N.
I am looking at several mic capsules at places like digikey and they generally specify from around 2 to 10V to power their FETs or Amps. Most recorders however supply 48V "phantom" power.
I am a little confused why the 48V. My inclination is to just divide down or reduce the voltage at the mic to meet the voltage spec. And then of course couple to the recorder with a capacitor.
Is this what is generally done inside a commercially built mic or am I missing something here?
Thanks
Fritz
I am looking at several mic capsules at places like digikey and they generally specify from around 2 to 10V to power their FETs or Amps. Most recorders however supply 48V "phantom" power.
I am a little confused why the 48V. My inclination is to just divide down or reduce the voltage at the mic to meet the voltage spec. And then of course couple to the recorder with a capacitor.
Is this what is generally done inside a commercially built mic or am I missing something here?
Thanks
Fritz
Hello Fritz. 48 volts comes from the old days and has stuck with us. There is also 12V, but it's rarely used,
If you are going into something like a Zoom just use the 1/8" inputs and turn on the "Plug in Power". It's about 2.5V and works great with most of the electret capsules on the market. Nothing else needed. I've used it with Panasonic, PUI and Primo capsules with very good results. Most video cameras also have the 2.5V plug in power on the 1/8" mic jack.
Let me know if you need any help.
If you are going into something like a Zoom just use the 1/8" inputs and turn on the "Plug in Power". It's about 2.5V and works great with most of the electret capsules on the market. Nothing else needed. I've used it with Panasonic, PUI and Primo capsules with very good results. Most video cameras also have the 2.5V plug in power on the 1/8" mic jack.
Let me know if you need any help.
Thanks Pano. I did not know about the 1/8" input voltages (only the XLR) so I will look into that. I assume I still will need the capacitor coupling just like I would with an XLR setup?
I think the 48V was a common plate voltage on vacuum tubes--back in the days when you could almost "see" the electrons!
Thanks
Fritz
I think the 48V was a common plate voltage on vacuum tubes--back in the days when you could almost "see" the electrons!
Thanks
Fritz
You're welcome! The 1/8" with Plug in Power has everything you need already in line, the blocking cap, the resistor etc.. It's dead simple. On my first try I was surprised how it's all just there, no need for anything else - just connect the mic capsule and you're ready to go.. If you need to run very long lines then the XLR is a better choice, but I've done 6 feet unshielded 1/8" with no noise at all, and 25 feet shielded 1/8" dead quiet. It's simple and fun to use. Results can be excellent.
48V is old telephone power. It was commonly used for small chores in broadcast studios (who often networked through telephone lines). At the time it was generally considered "safe", at least for paid workers. Today fashion favors 24V max around non-technical users.
48V phantom was never about tubes. The power is too low for good results. (There IS today a 48V tube microphone, so...) The field opened with JFET transistors. While these will run on much lower voltage, the capsule needed "high voltage" bias, and 48V was about the lower end of good results.
No, the 2V-10V electret capsule mikes do NOT direct connect to Phantom. Aside from voltage, these mikes are unbalanced and Phantom demands a balanced circuit.
As Pano says, nearly any "bootleg concert recorder" has an easy way to use electret capsules.
48V phantom was never about tubes. The power is too low for good results. (There IS today a 48V tube microphone, so...) The field opened with JFET transistors. While these will run on much lower voltage, the capsule needed "high voltage" bias, and 48V was about the lower end of good results.
No, the 2V-10V electret capsule mikes do NOT direct connect to Phantom. Aside from voltage, these mikes are unbalanced and Phantom demands a balanced circuit.
As Pano says, nearly any "bootleg concert recorder" has an easy way to use electret capsules.
Thanks for the update. I an never sure where the 48V started. About 30 years ago I did some telecomm work up in Maine in the US. Some pretty old equipment there-I was a fiber engineer but I was amazed to see some huge glass "battery jars" with characteristic electrodes in the exchanges. These were power failure backups as I was told and i vaguely remember them being 48V! Would not be surprised is they still are running up there.
cheers
Fritz
cheers
Fritz
> I was amazed to see some huge glass "battery jars" with characteristic electrodes in the exchanges. ... Would not be surprised is they still are running up there....
I'm sure they are. I'm on a "newer" route and the 1990s technology keeps crapping out. It is entirely possible the investor-owned telcos have abandoned all the glass-jars they know about, but the Telephone Museum on Winkumpaugh Rd will have some.
--------------------------------------------------
-48VDC Power and the Backbone of the Telecommunications Industry | Server Technology
This link is a little short-sighted; before Central Battery there was Local Battery, 3V 6V 12V (as needed) of large carbon/zinc doorbell cells inside the user's telephone.
On short runs the telco has the choice to supply a lower voltage. But the rise of line-powered toys restricts how low they could go even if they gave us efficient instruments. I have read of logging camps etc being fed 96V, which I suppose is safer than dull axes or angry bears or poker games.
In the US we think of 48V battery and 52V from the charger. UK apparently calls it all "50V".
Telco 48V always (where you can mess with it) has a current limiting resistance. For nominal use this is the line relay which senses that you have seized the line and might like service (operator, dialtone, etc). In studio microphone Phantom there is a 3.4k in series with the transformer center tap.
I'm sure they are. I'm on a "newer" route and the 1990s technology keeps crapping out. It is entirely possible the investor-owned telcos have abandoned all the glass-jars they know about, but the Telephone Museum on Winkumpaugh Rd will have some.
--------------------------------------------------
-48VDC Power and the Backbone of the Telecommunications Industry | Server Technology
This link is a little short-sighted; before Central Battery there was Local Battery, 3V 6V 12V (as needed) of large carbon/zinc doorbell cells inside the user's telephone.
On short runs the telco has the choice to supply a lower voltage. But the rise of line-powered toys restricts how low they could go even if they gave us efficient instruments. I have read of logging camps etc being fed 96V, which I suppose is safer than dull axes or angry bears or poker games.
In the US we think of 48V battery and 52V from the charger. UK apparently calls it all "50V".
Telco 48V always (where you can mess with it) has a current limiting resistance. For nominal use this is the line relay which senses that you have seized the line and might like service (operator, dialtone, etc). In studio microphone Phantom there is a 3.4k in series with the transformer center tap.
48 V (with 3.3 kohm or 3.4 kohm series resistance) phantom power is still very common for professional condenser microphones. The microphones sometimes have an internal converter to increase the voltage to some higher value for biasing the condenser microphone capsule and an internal series or shunt regulator to supply the internal buffer/amplifier.
Electret capsules for consumer equipment are typically supplied by a 3 V supply with 2.2 kohm series resistance.
Edit: the (now obsolete) AKG C451 and C452 have such a converter, but it actually only produces 38 V:
http://gyraf.dk/schematics/AKG_C451EB.GIF The circuit around T4 and T5 is a basic shunt regulator.
Electret capsules for consumer equipment are typically supplied by a 3 V supply with 2.2 kohm series resistance.
Edit: the (now obsolete) AKG C451 and C452 have such a converter, but it actually only produces 38 V:
http://gyraf.dk/schematics/AKG_C451EB.GIF The circuit around T4 and T5 is a basic shunt regulator.
Last edited:
Two things:
- the ZoomH4N has VERY good built-in microphones, you'd be hard pressed to find anything significantly better at the usual hardware suppliers - at least for the "plug-in-power" minijack connector.
- if you go the (higher possible quality) XLR route with "real" condenser microphones, you should be aware that the phantom power delivered by ZoomH4N is only at 24V, which makes some mics struggle to work well. Neumann KM84 and AKG C414-P48 comes to mind. Setting Up: Input [1], [2] Connections And Phantom Power Source - Zoom H4n Operation Manual [Page 33] | ManualsLib
/Jakob E.
- the ZoomH4N has VERY good built-in microphones, you'd be hard pressed to find anything significantly better at the usual hardware suppliers - at least for the "plug-in-power" minijack connector.
- if you go the (higher possible quality) XLR route with "real" condenser microphones, you should be aware that the phantom power delivered by ZoomH4N is only at 24V, which makes some mics struggle to work well. Neumann KM84 and AKG C414-P48 comes to mind. Setting Up: Input [1], [2] Connections And Phantom Power Source - Zoom H4n Operation Manual [Page 33] | ManualsLib
/Jakob E.
All modern professional condenser mikes work with 48V Phantom power, Neumann, Sennheiser, AKG ....They have XLR connectors and must be balanced.
The other types (those mentioned here) are called elektret mikes and they require around 5V which is called bias usually. They are single ended and connect with a mini jack.
The other types (those mentioned here) are called elektret mikes and they require around 5V which is called bias usually. They are single ended and connect with a mini jack.
Thanks all for the further replies. I cannot use the h4N internals nor commercially prepared mics---- I need very small, independent mics--at least 4 or maybe 6 for this project. - I am building an acoustic sensing array for underwater imaging where each capsule is permanently spaced, linearly, at 1cm and 3cm. So I must control the placement.
I will be reading the mics with a homebuilt ADC hence I need to wire them myself. I also will need to record them in a separate leg of the experiment and will use a commercial recorder (don't want to build that!) I liked the H6N since I use an H4N when recording our orchestra. But looking further at the spec sheet I don't think I can really put 6 mics on it (there aren't 6 XLRs o 6 -1/4" jacks).
I didn't realize that the H4N only supplied 24V (never had need to measure mine). I checked the H6N and you can choose the power (12,24,48V). Everybody seems to have there own standard! Maybe I should just use a battery jar
At any rate I will have to look around for a 6 port recorder--hopefully under $2000 US.
I am guessing commercially enclosed mics (never disassembled one) have a converter which can handle a reasonable range of voltages-say 12 to 48.
Looking through Digikey it seems to be that the capsule vendors just want to receive a lower voltage (2-10V) and in the case of the recorder I must provide this from the 12-48V and then capacitively couple it to the digitizer. (It seems like a lot of vendors do provide the internal FET or amplifier). So I will just use "converter" box in the case of the recorder. For my ADC circuit which I build, I have total control of what I feed the mic of course.
cheers
Fritz
I will be reading the mics with a homebuilt ADC hence I need to wire them myself. I also will need to record them in a separate leg of the experiment and will use a commercial recorder (don't want to build that!) I liked the H6N since I use an H4N when recording our orchestra. But looking further at the spec sheet I don't think I can really put 6 mics on it (there aren't 6 XLRs o 6 -1/4" jacks).
I didn't realize that the H4N only supplied 24V (never had need to measure mine). I checked the H6N and you can choose the power (12,24,48V). Everybody seems to have there own standard! Maybe I should just use a battery jar
At any rate I will have to look around for a 6 port recorder--hopefully under $2000 US.I am guessing commercially enclosed mics (never disassembled one) have a converter which can handle a reasonable range of voltages-say 12 to 48.
Looking through Digikey it seems to be that the capsule vendors just want to receive a lower voltage (2-10V) and in the case of the recorder I must provide this from the 12-48V and then capacitively couple it to the digitizer. (It seems like a lot of vendors do provide the internal FET or amplifier). So I will just use "converter" box in the case of the recorder. For my ADC circuit which I build, I have total control of what I feed the mic of course.
cheers
Fritz
By coincidence I have a thread about P48 power and measurement mics here> DIY Brüel & Kjær measurement mic kit.
But since this thread is such a fount of historical information I may as well ask here-
Anyone know where the standard used in measurement mic capsules came from?
The earliest I know is Bruel and Kjaer, who started in 1940s Denmark (but not sure when the capsules were introduced)
However the 1", 1/2" and 1/4" diameters and 60 TPI UNS thread form hint at an American precursor.
Anyone familiar with the history?
Best wishes
David
Last edited:
Maybe you could contact Marco C. van der Hoeven, the writer of this book:
www.witnessesofwords.com
He knows more about historic microphones than anyone else I've ever met.
www.witnessesofwords.com
He knows more about historic microphones than anyone else I've ever met.
Regarding cheap electret microphone capsules, there is a huge difference in the equivalent acoustical noise level between different models. Many have a noise of about 35 dB(A), but some as low as 14 dB(A), like the PUI Audio AOM-5024L-HD-R. That wouldn't be a bad value for a professional microphone, although the large-signal handling isn't even close to that of a professional mike.
I don't know if any of them survive submersion in water.
I don't know if any of them survive submersion in water.
Last edited:
Yes, the built in mics are rather good, but I find the PUI HD series to be even better, at least for my uses. You gotta use what works best for you. In the case of the OP, that is not going to be the built in mics.
DIY moderator Wintermute has built a quite good phantom power adapter for electret mics. With Primo capsules it sounds superb and allows the use of long mic cables and XLR balanced inputs. I hope to have a PCB for it before too long.
AFAIK, the leader was Bell System, Bell Labs, Western Electric. They had a studio condenser but wanted a measurement mike. After some work they came to the WE 640AA. And then decided they should not be making it. Did a deal with a company Brel Kjaer, who sold it to WE and the world as 4160.
Others worked these lines. Olson of RCA did a series of ribbon mikes to reduce calibration errors. Obviously European companies must have made instrumentation mikes but the 1940s were rough and after B&K got going there was less urge to DIY.
https://www.aes.org/aeshc/docs/mtgschedules/113conv2002/webb_12-microphones.pdf page 4
https://asa.scitation.org/doi/10.1121/1.4899681
The WE 640AA condenser microphone
AIP Handbook of Condenser Microphones : Theory, Calibration and Measurements
Having approximately one(+/-) mike model also helps see long-term trends in calibration.
Long-Term Stability of One-Inch Condenser Microphones Calibrated at the National Institute of Standards and Technology
Perhaps 48V was used because it doesn't count as high voltage. My suspicion is that after a lot of people suffered electric shocks from valve/tube microphones they chose to pick something safer for FET microphones.
Pretty much every mixing desk and studio mic preamp in the world supports 48V phantom power and most studio condenser microphones assume it.
True condenser microphones will require a sufficiently high voltage, near 48V, electrets often can handle anything from say 5 to 48V phantom power as the incoming power goes to a regulator to power the JFET stage.
The circuitry inside a microphone both handles using/regulating phantom power, and driving the balanced signal back - a bare capsule is not the whole story. Many studio microphones have pad switches and some have pattern selection switches too - all requires circuitry.
Pretty much every mixing desk and studio mic preamp in the world supports 48V phantom power and most studio condenser microphones assume it.
True condenser microphones will require a sufficiently high voltage, near 48V, electrets often can handle anything from say 5 to 48V phantom power as the incoming power goes to a regulator to power the JFET stage.
The circuitry inside a microphone both handles using/regulating phantom power, and driving the balanced signal back - a bare capsule is not the whole story. Many studio microphones have pad switches and some have pattern selection switches too - all requires circuitry.
The KM84i and 86i's that I've run have been OK on 36V (never tried them on 24V). No doubt somewhat worse S/N, but no evidence of premature clipping -- even close-mic'ing snare drums of loud players!
I'll be very surprised if powering the electret is your biggest problem. The boundary interface from liquid to air will cause problems, if there is one. If there isn't, there probably isn't an electret anywhere that will tolerate a conductive liquid on its diaphragm (as MarcelvdG mentioned).
I don't know what sounds you want to pick up, or what the fidelity requirements might be, but there may be no way around starting with microphones designed for underwater use, despite the likely high expense.
Cheers
I'll be very surprised if powering the electret is your biggest problem. The boundary interface from liquid to air will cause problems, if there is one. If there isn't, there probably isn't an electret anywhere that will tolerate a conductive liquid on its diaphragm (as MarcelvdG mentioned).
I don't know what sounds you want to pick up, or what the fidelity requirements might be, but there may be no way around starting with microphones designed for underwater use, despite the likely high expense.
Cheers