How did you establish that? Did you find a sensible datasheet somewhere? Do you mean the DC resistance? The impedance level a transformer is meant for is always well above the DC resistance.
By the way, measuring a signal transformer's DC resistance with a normal multimeter may magnetize the core and cause increased second-order distortion. You can then demagnetize it again by applying a large subsonic sine wave of which you slowly reduce the amplitude to zero.
You can, but not without increasing noise to some extent (and the distortion of the transformer). Besides, it should not be necessary.
No, see my previous post.
Many thanks! So:
Here is the test signal, recorded with the camera.
I checked it on an frequency analyzer on a ProTools System, roughly the drop starts below 125hz.
https://we.tl/t-uFuDtO7zbV
It was recorded without Mic, just the modded Xvive inserted in the balanced mono signal,
the sweep coming from a test CD. The player has balanced outputs.
I checked it being connected balanced to a Zoom recorder and unbalanced to the camera,
drop below 125hz is the same.
https://asset.conrad.com/media10/ad...ce-200-primary-voltage-12-v-content-1-pcs.pdf
What do they mean stating this, last page:
Source / load
impedance in Ω
200/2k, (600/10k)
????????????????
Correct! But I accidentally deleted the test signal from the first measurement, when the Xvive was unaltered, with the SMD capacitors of unknown value but without the audio transformer. Basically nothing has changed.
Yes. About 45V at pins 1+2, no voltage on the signal path. I assume it would have blown the camera and also ruined the audio transformer.
Here is the test signal, recorded with the camera.
I checked it on an frequency analyzer on a ProTools System, roughly the drop starts below 125hz.
https://we.tl/t-uFuDtO7zbV
It was recorded without Mic, just the modded Xvive inserted in the balanced mono signal,
the sweep coming from a test CD. The player has balanced outputs.
I checked it being connected balanced to a Zoom recorder and unbalanced to the camera,
drop below 125hz is the same.
Here is a datashheet:
https://asset.conrad.com/media10/ad...ce-200-primary-voltage-12-v-content-1-pcs.pdf
What do they mean stating this, last page:
Source / load
impedance in Ω
200/2k, (600/10k)
????????????????
That's a lot better than the datasheet I found on a Neutrik site!
I think they mean that the transformers are meant to be used with a 200 ohm source impedance and 2 kohm load impedance, or with a 600 ohm source impedance and 10 kohm load impedance. 200 ohm source impedance and 2 kohm load impedance is pretty typical when you put it between a microphone and a microphone amplifier, exactly as you want to use it.
If the primary inductance is 8 H, like the NTM1, then the input impedance with 2 kohm load will only drop below 400 ohm at frequencies below 8.12 Hz (and below 800 ohm at frequencies below 17.37 Hz).
I think they mean that the transformers are meant to be used with a 200 ohm source impedance and 2 kohm load impedance, or with a 600 ohm source impedance and 10 kohm load impedance. 200 ohm source impedance and 2 kohm load impedance is pretty typical when you put it between a microphone and a microphone amplifier, exactly as you want to use it.
If the primary inductance is 8 H, like the NTM1, then the input impedance with 2 kohm load will only drop below 400 ohm at frequencies below 8.12 Hz (and below 800 ohm at frequencies below 17.37 Hz).
Summarizing, I think your idea of shorting the capacitors and using the transformer should work fine. The extra resistors are not needed and would only degrade performance.
Edit: I overlooked one possible problem. Does your camera provide power for cheap electret microphones, so-called PiP (plug-in power)? If so, and if it can't be switched off, you need a capacitor between the secondary and the camera to keep the PiP DC current out of the transformer.
Edit: I overlooked one possible problem. Does your camera provide power for cheap electret microphones, so-called PiP (plug-in power)? If so, and if it can't be switched off, you need a capacitor between the secondary and the camera to keep the PiP DC current out of the transformer.
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Many thanks! Plug-in Power of the cam can be switched off!
This is how the signal path looks like now*:
So, the only original parts are the 100ohm resistors. Please compare the drawing to "image1.jpeg" in the first post:
The original capacitors, probably between 0.47µF and 1µF, replaced by 5.4µF, are to be found in the upper right,
above the number 20200814. There are even +/- markings next to them for electrolytics Xvive did not use.
The 100Ω resistors can be found in the lower right, above the right connector. The audio transformer is not on the photo.
*I think I can see on the photo a resistor/capacitor combo to drain noise to ground from the audio lines, but have to check.
I thought consensus was not to omit/short the capacitors and keep DC from the transformer?
This is how the signal path looks like now*:
So, the only original parts are the 100ohm resistors. Please compare the drawing to "image1.jpeg" in the first post:
The original capacitors, probably between 0.47µF and 1µF, replaced by 5.4µF, are to be found in the upper right,
above the number 20200814. There are even +/- markings next to them for electrolytics Xvive did not use.
The 100Ω resistors can be found in the lower right, above the right connector. The audio transformer is not on the photo.
*I think I can see on the photo a resistor/capacitor combo to drain noise to ground from the audio lines, but have to check.
You draw it as if there is a grounded centre tap on each side, but the NTE1 has only four wires.
No, there is no center tap. GND goes straight from one end to the other.
Conversion from balanced to unbalanced happens elsewhere, so that that the modded Xvive can be used in
a balanced setup as well.
Conversion from balanced to unbalanced happens elsewhere, so that that the modded Xvive can be used in
a balanced setup as well.
For the case with shorted capacitors, the two outputs of the modified Xvive phantom supply circuit should ideally be at the same DC potential, so you would ideally get no DC current through the primary winding. In practice, there will be some DC offset. If that offset is big enough to drive the transformer core close to or into saturation, then you need a capacitor. There is not enough information to calculate if this is the case, but I suspect that the offset is small enough, because schematics where transformers are connected directly to phantom supplied microphones are not unusual.
The two 5.4 uF capacitors are effectively in series in this circuit. To completely block DC current from the transformer primary, it suffices to have a capacitor in one branch and a short in the other. If you put all the capacitors in one branch and a short in the other, you effectively go from 2.7 uF to 10.8 uF.
Checked the signal path again, there do not seem to be resistors to drain the signal to ground.
As far as I understand I should insert some when replacing the Foils with electrolytics.
The resistors in the signal path are not 100Ω but 47Ω.
As you might guess, soldering is unnerving. What happens when I put a 10K resistor between the right windings of the NTE-1?
Impedance rises on the left side, correct. But output impedance will be too high for the camera?
As far as I understand I should insert some when replacing the Foils with electrolytics.
The resistors in the signal path are not 100Ω but 47Ω.
As you might guess, soldering is unnerving. What happens when I put a 10K resistor between the right windings of the NTE-1?
Impedance rises on the left side, correct. But output impedance will be too high for the camera?
I would not bet XVIVE took care of that...
You mean shorting to ground, not bridging? Like I would run the mic unbalanced?
No, I meant shorting the two terminals of one of the capacitors and using all the available film capacitors for the other capacitor. This circuit looks asymmetrical, but it has no DC path through the primary winding of the transformer.
You can also just replace the film capacitors with 47 uF, 63 V electrolytics and leave everything else as is.
You can also just replace the film capacitors with 47 uF, 63 V electrolytics and leave everything else as is.
Merci Beaucoup! I‘ll take electrolytics. But shouldnt I make a connection to GND, I think2.2k in parallel with a 2nF to drain the leakage current?
Last image in this thread
https://gearspace.com/board/geekzone/1239527-phantom-power-blocking-capacitors.html
Last image in this thread
https://gearspace.com/board/geekzone/1239527-phantom-power-blocking-capacitors.html
Not if you always use it with the transformer. Leakage current of the electrolytic capacitors may cause a 48 V DC voltage to occur on both primary terminals of the transformer, but that won't affect the performance of the transformer.
Dear Marcel,
many, many thanks, especially for the quick respones I got while being in town.
I was able to buy the parts very quickly and already replaced the Wima foils with electrolytics.
It is even two 47µF/63V Caps in parallel for each signal, so 94µF each line.
There is however some heavy distortion in the lower frequencies of the sweep,
I assume due to the transformer? I think it vanishes @60Hz.
BUT: The level is line, not mic.
The mic will never get that hot. Also with pink noise, I do not hear
distortion. Attached are the waveforms, how the Xvive looks like now (looks awful, hand-soldered) and both soundfiles,
with 5.4µF and with 94µF.
Soundfiles:
https://filetransfer.io/data-package/2IXi0sO7#link
many, many thanks, especially for the quick respones I got while being in town.
I was able to buy the parts very quickly and already replaced the Wima foils with electrolytics.
It is even two 47µF/63V Caps in parallel for each signal, so 94µF each line.
There is however some heavy distortion in the lower frequencies of the sweep,
I assume due to the transformer? I think it vanishes @60Hz.
BUT: The level is line, not mic.
The mic will never get that hot. Also with pink noise, I do not hear
distortion. Attached are the waveforms, how the Xvive looks like now (looks awful, hand-soldered) and both soundfiles,
with 5.4µF and with 94µF.
Soundfiles:
https://filetransfer.io/data-package/2IXi0sO7#link
Attachments
Great that it did the trick! The distortion very probably comes from the transformer; the datasheet you linked to shows that it can't handle line level at low frequencies.
By the way, if you should ever unintentionally magnetize the transformer core, a sweep like this should fix it.
By the way, if you should ever unintentionally magnetize the transformer core, a sweep like this should fix it.
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Well, happy to energize - this is how the finished setup looks like.
Can be mounted on the camera rig or on a boom pole.
My last documentary was entirely shot with the MKH-416, using
a SIE MP232 field mixer.
Unfortunately the German company SIE is long forgotten and competed with SQN and Shure.
Very sturdy, warm and precise sound. But very heavy.
Though the MKH-416 is mono, it was the main base for the stereo and surround mix:
Film can be watched here worldwide, also with French subtitles:
https://fishermansframe.gumroad.com/l/abtyf
Can be mounted on the camera rig or on a boom pole.
My last documentary was entirely shot with the MKH-416, using
a SIE MP232 field mixer.
Unfortunately the German company SIE is long forgotten and competed with SQN and Shure.
Very sturdy, warm and precise sound. But very heavy.
Though the MKH-416 is mono, it was the main base for the stereo and surround mix:
Film can be watched here worldwide, also with French subtitles:
https://fishermansframe.gumroad.com/l/abtyf
I made a new test today.
Source plugged in directly and with the modded Xvive (94µF Caps and NTE-1 audio transformer) inserted.
It reveals that the modded Xvive is now linear, but the mic preamp of the Panasonic Lumix S5 camera is not that good.
The mic preamp of the S5 dampens the low end.
But both mono waveforms now look identical, see above.
As the camera's mic preamp is highly integrated,
I assume there is nothing that can be done here.
But I hear a slight distortion no matter if the Xvive is inserted or not.
It sounds like aliasing, but with the Xvive inserted it is more audible.
Best to be heard when played back from 37 seconds.
The two wav mono files you can see in the image are linked below:
https://filetransfer.io/data-package/DzbOV9Ty#link
Still distortion? If so, of what kind?
Source plugged in directly and with the modded Xvive (94µF Caps and NTE-1 audio transformer) inserted.
It reveals that the modded Xvive is now linear, but the mic preamp of the Panasonic Lumix S5 camera is not that good.
The mic preamp of the S5 dampens the low end.
But both mono waveforms now look identical, see above.
As the camera's mic preamp is highly integrated,
I assume there is nothing that can be done here.
But I hear a slight distortion no matter if the Xvive is inserted or not.
It sounds like aliasing, but with the Xvive inserted it is more audible.
Best to be heard when played back from 37 seconds.
The two wav mono files you can see in the image are linked below:
https://filetransfer.io/data-package/DzbOV9Ty#link
Still distortion? If so, of what kind?
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Yes, but everything is switched off.
Also, a "Wind Cut" would be more aggressive.
It is very likely a design flaw, because
noise level is also bad.
As far as I remember -65dB with the highes damping allowed, -12dB.
Interestingly the noise level does not change when you switch from "Mic" to "Line".
So they very likely put some "One Size Fits All" - ish stuff into the cam.
Also, a "Wind Cut" would be more aggressive.
It is very likely a design flaw, because
noise level is also bad.
As far as I remember -65dB with the highes damping allowed, -12dB.
Interestingly the noise level does not change when you switch from "Mic" to "Line".
So they very likely put some "One Size Fits All" - ish stuff into the cam.