Thanks!!! I wonder how small one could make this? Would it fit in a tube which would be an extension of the mic? Sync L/R?
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That's an interesting circuit and I'd be curious to hear the results. For my use I'd just go with a transformer (because I like them) but understand why other people might not want to. If built all SMD, it could be quite small. There would be some practical issues of signal transport and handling doing it that way, just something to work out.
Thanks for the tip on the Mavis software. I've never seen it but will certainly give it a try, it seems to provide some interesting info! Also, I'll hit you up via PM for more recordings. I'd like to hear one or two in more length. Cheers.
Thanks for the tip on the Mavis software. I've never seen it but will certainly give it a try, it seems to provide some interesting info! Also, I'll hit you up via PM for more recordings. I'd like to hear one or two in more length. Cheers.
While you could do that, it would seem impractical to do so. The thing is, if you put the ADC that close to the mic, then you don't need 48V or balanced line drivers. You just need to get the capsule powered up with 2.5-5V and feed the ADC a low impedance differential signal.
If you come digital out of the mic how are you going to get it into the recorder? How will you record more than one mic? You could simply build the recorder into the mic, but then you'd have to stack and time align your recorded tracks in post. It can be done, but is an extra step.
If you come digital out of the mic how are you going to get it into the recorder? How will you record more than one mic? You could simply build the recorder into the mic, but then you'd have to stack and time align your recorded tracks in post. It can be done, but is an extra step.
I don't know about the brand TNT uses, but the prepolarized (that is, electret) condenser microphone capsules used in the AKG C535EB have no amplifier built in and hence don't need a supply voltage. They do need a buffer/amplifier with an extremely small input noise current.
http://gyraf.dk/schematics/AKG_C535EB.GIF
Of course this doesn't relate to the main point Pano made, just to a detail.
http://gyraf.dk/schematics/AKG_C535EB.GIF
Of course this doesn't relate to the main point Pano made, just to a detail.
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One could just receive 1 stream each from 2 toslink cables... using e.g. a RME Digiface one can in the receiving DAW collect the two streams simultaneous to a stereo track!?
Digiface USB - RME Audio Interfaces | Format Converters | Preamps | Network Audio & MADI Solutions
I can worry about L/R frame synchronisation but I'm not sure its a lot in it if using high quality oscillators...
I use a Jekclin disc so mics are close - maybe a box out there giving cables about maybe 20 cm (8")...
What is the 48V used for - the fet interfacing the membrane? Why does it need so high voltage? I thought it was for the membrane polarisation... anyways - simplifying everything and making a really transparent recording of whats the membran is sensing is my goal.
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Digiface USB - RME Audio Interfaces | Format Converters | Preamps | Network Audio & MADI Solutions
I can worry about L/R frame synchronisation but I'm not sure its a lot in it if using high quality oscillators...
I use a Jekclin disc so mics are close - maybe a box out there giving cables about maybe 20 cm (8")...
What is the 48V used for - the fet interfacing the membrane? Why does it need so high voltage? I thought it was for the membrane polarisation... anyways - simplifying everything and making a really transparent recording of whats the membran is sensing is my goal.
//
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When the microphones have independent ADCs, you would need to synchronize them to a common clock or use asynchronous sample rate conversion. Otherwise when you have 5 ppm clock frequency difference and record for an hour, you would have an 18 ms shift between left and right at the end. Interaural time delays are less than a millisecond, so the stereo image would be messed up completely within a few minutes - unless samples get dropped or repeated, which causes clicks. In fact the RME Digiface would drop or repeat samples when the signals are not synchronized to the same master clock, see page 65 of https://www.rme-audio.de/downloads/dface_usb_e.pdf
In a "normal" condenser microphone, you need a relatively high voltage for membrane polarization and you need to provide a supply voltage to the buffer/amplifier with extremely low input noise current. In an electret microphone, the membrane is permanently polarized without any external voltage, so you only need to provide a supply for the buffer/amplifier with extremely low input noise current. The voltage can then be much lower, in fact the 48 V phantom supply is often regulated down to 10 V or so.
Example of a condenser microphone, now obsolete AKG model that actually regulates down the supply and then converts it up again:
http://gyraf.dk/schematics/AKG_C451EB.GIF
Professional electret (a.k.a. prepolarized) microphone, also obsolete and from AKG:
http://gyraf.dk/schematics/AKG_C535EB.GIF
In a "normal" condenser microphone, you need a relatively high voltage for membrane polarization and you need to provide a supply voltage to the buffer/amplifier with extremely low input noise current. In an electret microphone, the membrane is permanently polarized without any external voltage, so you only need to provide a supply for the buffer/amplifier with extremely low input noise current. The voltage can then be much lower, in fact the 48 V phantom supply is often regulated down to 10 V or so.
Example of a condenser microphone, now obsolete AKG model that actually regulates down the supply and then converts it up again:
http://gyraf.dk/schematics/AKG_C451EB.GIF
Professional electret (a.k.a. prepolarized) microphone, also obsolete and from AKG:
http://gyraf.dk/schematics/AKG_C535EB.GIF
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Actually I mentioned that professional electret microphone capsules do not necessarily have a FET inside, unlike the electret capsules used for consumer equipment. For example, the buffer amplifier of a C535EB is on a PCB inside the microphone, but outside the capsule. It also needs more than 3 V.
Makes 48 volt overkill
I suppose there is some old reason for the standard 48 volt figure :-D//
48 volts is still useful for some mic circuits. But as mentioned above, it is usually regulated down to 10-12V in most mics.
Seems to me that if you are using a barrier mic rig like the Jeklin, then a small box of electronics at the mic rig would not be a big problem. Even the whole recorder could be there. Otherwise if you really want to ADC at the mic, then maybe AES is the best cable transport to use back to your DAW. AES is robust enough for medium long runs.
True! I've gotten so used to using those that do have a FET, I had forgotten about the others without. They are often of quite good quality. I think I have a couple, probably Primo.
Seems to me that if you are using a barrier mic rig like the Jeklin, then a small box of electronics at the mic rig would not be a big problem. Even the whole recorder could be there. Otherwise if you really want to ADC at the mic, then maybe AES is the best cable transport to use back to your DAW. AES is robust enough for medium long runs.
Line Audio answers that no special version will be made due to workload. Good for them
Well, maybe I have to open one. Or get me 2 pcs of really good capsules and forge my own. I think I don't worry to much about the FR - I can see myself calibrate them to a really good reference which I have access to and I'm not afraid of doing EQ afterwords.
But I will probably need some handholding putting it together... if you may ?
I would like to build a super short, super clean, super simple (but not to!!!) as possible for a completely transparent and open capture. Be gone caps, diodes, trafos, long line cables, connectors, potentiometers and what not - welcome brutal reality.
Please help me to something new - made possible by leaving old standards and thinking..
The topology I think will need to be one common box close to the mics with room for battery power. Laptop say < 10 meter away so only digital interface out from the box - preferably opto - 24/192 max. 24/88 OK.
Maybe the PCM4222 evaluation board can be used. I would primarily need help with the mic-PCM4222 interface... pretty please...
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Well, maybe I have to open one. Or get me 2 pcs of really good capsules and forge my own. I think I don't worry to much about the FR - I can see myself calibrate them to a really good reference which I have access to and I'm not afraid of doing EQ afterwords.
But I will probably need some handholding putting it together... if you may ?
I would like to build a super short, super clean, super simple (but not to!!!) as possible for a completely transparent and open capture. Be gone caps, diodes, trafos, long line cables, connectors, potentiometers and what not - welcome brutal reality.
Please help me to something new - made possible by leaving old standards and thinking..
The topology I think will need to be one common box close to the mics with room for battery power. Laptop say < 10 meter away so only digital interface out from the box - preferably opto - 24/192 max. 24/88 OK.
Maybe the PCM4222 evaluation board can be used. I would primarily need help with the mic-PCM4222 interface... pretty please...
//
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