A couple of comments, do with them what you want:
1. In my experience, it is fairly easy to solder 1206 multilayer ceramic SMD capacitors to the copper side of 2.54 mm pitch perfboard with one copper island per hole. If it helps, C6 could be replaced with an X5R SMD capacitor, but preferably not C4.
2. As 1206 SMD resistors are the same size as 1206 SMD capacitors, they can also be soldered to perfboard. In the case of thin film SMD resistors, you have to make sure to treat them gently and not to overheat them, though, as they are easily damaged.
3. You can do what you want, but you hardly gain any signal-to-noise ratio by recording at -9 or -6 dB, you just use more bits to quantize the noise. The same holds for increasing the gain of the circuit of post #88. (Recording at +6 dB with that circuit is comparable with -12 dB with the present set-up, when you change the 15 kohm resistors to 30 or 33 kohm, +6 dB corresponds to -6 dB with the present set-up.)
4. I would change the voltage divider to 1.3 kohm and 1 kohm or 750 ohm (depending on whether the line input is also 2200 ohm or much more than that). The load that the op-amp sees is then at least 1044 ohm and the cut-off frequency at the output at most 6.93 Hz with 22 uF, 3.24 Hz with 47 uF, 1.52 Hz with 100 uF or 0.693 Hz with 220 uF.
1. In my experience, it is fairly easy to solder 1206 multilayer ceramic SMD capacitors to the copper side of 2.54 mm pitch perfboard with one copper island per hole. If it helps, C6 could be replaced with an X5R SMD capacitor, but preferably not C4.
2. As 1206 SMD resistors are the same size as 1206 SMD capacitors, they can also be soldered to perfboard. In the case of thin film SMD resistors, you have to make sure to treat them gently and not to overheat them, though, as they are easily damaged.
3. You can do what you want, but you hardly gain any signal-to-noise ratio by recording at -9 or -6 dB, you just use more bits to quantize the noise. The same holds for increasing the gain of the circuit of post #88. (Recording at +6 dB with that circuit is comparable with -12 dB with the present set-up, when you change the 15 kohm resistors to 30 or 33 kohm, +6 dB corresponds to -6 dB with the present set-up.)
4. I would change the voltage divider to 1.3 kohm and 1 kohm or 750 ohm (depending on whether the line input is also 2200 ohm or much more than that). The load that the op-amp sees is then at least 1044 ohm and the cut-off frequency at the output at most 6.93 Hz with 22 uF, 3.24 Hz with 47 uF, 1.52 Hz with 100 uF or 0.693 Hz with 220 uF.
Dear Marcel,
many thanks for your input.
The -12dB setting of the camera is quite right for recording loud environments - like the busy street junction close to my home.
A motorcycle blasting by will clip, but be safe on the second channel because of the voltage divider.
For softly spoken interviews, soft environments I'll need the range of 18db. (+6dB at the camera)
BTW the noise can be reduced during mixing with special plugins that "learn" the self noise
of the preamp and subtract it from the signal.
Check my documentary, it was almost completely recorded with the MKH-416,
though being independently mixed in Stereo for streaming and Surround for cinema.
Funnily, a scene with larger than life sounds - an old lady that cannot pass a busy street -
was recorded with onboard mics.
To get -9dB on the second channel the divider will be 1000Ω / 750Ω. Impedance of the camera is about 2200Ω.
I can only buy packs from 10 pieces for SMD and do not like the waste of material. But very likely I'll have to.
All the best and many thanks,
Salar
When it is 33k, I would get the present "-12dB" setup with R2, R4, R5 being 39k, correct?
Being driven by 3.3V, the LME49721 can still handle the peaks?
BTW-what load will the Mic see with the LME49721 circuit attached?
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That's exactly where I disagree with you.
Measuring the noise levels in your test recordings with an MKH-416 in quiet surroundings (left channel, not the attenuated channel), expressed in decibel A-weighted with respect to a full-scale sine wave:
-12 dB setting: -76.25 dB(A)
-9 dB setting: -73.85 dB(A)
-6 dB setting: -71.16 dB(A)
-3 dB setting: -68.4 dB(A)
0 dB setting: -65.47 dB(A)
+3 dB setting: -62.75 dB(A)
+6 dB setting: -59.8 dB(A)
Now suppose you would record some very soft sound not in the +6 dB gain setting, but with a lower gain setting and correct that afterwards by digitally amplifying the signal (which, of course, also amplifies the noise). For example, record at +3 dB and add 3 dB of digital gain afterwards, or record at -6 dB and apply 12 dB afterwards. The noise levels would then end up at:
-12 dB setting, 18 dB digital gain: -58.25 dB(A)
-9 dB setting, 15 dB digital gain: -58.85 dB(A)
-6 dB setting, 12 dB digital gain: -59.16 dB(A)
-3 dB setting, 9 dB digital gain : -59.4 dB(A)
0 dB setting, 6 dB digital gain: -59.47 dB(A)
+3 dB setting, 3 dB digital gain: -59.75 dB(A)
+6 dB setting, no digital gain: -59.8 dB(A)
That is, compared to recording at +6 dB, the signal-to-noise ratio gets worse by this amount:
-12 dB setting, 18 dB digital gain: 1.55 dB degradation compared to recording with the +6 dB gain setting
-9 dB setting, 15 dB digital gain: 0.95 dB degradation compared to recording with the +6 dB gain setting
-6 dB setting, 12 dB digital gain: 0.64 dB degradation compared to recording with the +6 dB gain setting
-3 dB setting, 9 dB digital gain : 0.4 dB degradation compared to recording with the +6 dB gain setting
0 dB setting, 6 dB digital gain: 0.33 dB degradation compared to recording with the +6 dB gain setting
+3 dB setting, 3 dB digital gain: 0.05 dB degradation compared to recording with the +6 dB gain setting
+6 dB setting, no digital gain: 0 dB degradation compared to recording with the +6 dB gain setting
That is, you lose less than 1 dB by only using the -9 dB and -12 dB settings and only 1.55 dB when you only use the -12 dB setting.
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Many thanks, but so what? This was recorded with the crappy Mic - Level
circuitry of the Lumix. But as we found out Line - Level will only amplify or dampen the self noise of
the MKH-416 including your Mic-preamp which I hope will be inaudible.
Working with a Nagra had much worse noise levels - thousands of films were made with it.
Second: To push everything just to gain 1.5dB more S/N is completely unpractical for editing
or roundtripping interviews for transcription.
The norm for recording sounds, no matter if whispering or a rock concert:
-9dB headroom. Room-Tones on the level of what was recorded before in the room.
So no one has to deal to grab to the volume knob every second while editing.
Later you can bring things to a natural level - but would find out that mixes without
blockbuster explosions are very even and the whisper will be close to the rock concert.
With Interviews I prefer to go close to 0dB so that the Limiter of the S5 can clip the loudest peaks.
Still the attenuated channel holds the "unharmed" sound as a backup.
So, will 39K will get me close to the -12dB setting?
What load will the MKH-416 see?
All the best,
Salar
So you have a reason not related to sound quality why you have to record whispers loudly, the reason being that large level differences are inconvenient for whoever does the editing, and using volume normalization before doing anything else is impossible or inconvenient. Fair enough.
Rounded to E24 values, assuming 3.7 V supply voltage, your choices are roughly:
R4 = R5 = 15 kohm, R2 = 16 kohm or 15 kohm:
gain 28 dB, recording in the +6 dB setting is comparable to -12 dB now, hard clipping of the microphone amplifier at 100 dB SPL (the 9 dB attenuator doesn't help when it is the microphone amplifier that clips).
R4 = R5 = R2 = 30 kohm:
gain 34 dB, recording in the +6 dB setting is comparable to -6 dB now, hard clipping of the microphone amplifier at 94 dB SPL.
R4 = R5 = R2 = 56 kohm:
gain 40 dB, recording in the +6 dB setting is comparable to 0 dB now, hard clipping of the microphone amplifier at 88 dB SPL.
R4 = R5 = R2 = 100 kohm:
gain 45 dB, recording in the +6 dB setting is comparable to +6 dB now, hard clipping of the microphone amplifier at 82 to 83 dB SPL.
The microphone sees a load of R1 + R2 + R4, so always above 30 kohm.
Rounded to E24 values, assuming 3.7 V supply voltage, your choices are roughly:
R4 = R5 = 15 kohm, R2 = 16 kohm or 15 kohm:
gain 28 dB, recording in the +6 dB setting is comparable to -12 dB now, hard clipping of the microphone amplifier at 100 dB SPL (the 9 dB attenuator doesn't help when it is the microphone amplifier that clips).
R4 = R5 = R2 = 30 kohm:
gain 34 dB, recording in the +6 dB setting is comparable to -6 dB now, hard clipping of the microphone amplifier at 94 dB SPL.
R4 = R5 = R2 = 56 kohm:
gain 40 dB, recording in the +6 dB setting is comparable to 0 dB now, hard clipping of the microphone amplifier at 88 dB SPL.
R4 = R5 = R2 = 100 kohm:
gain 45 dB, recording in the +6 dB setting is comparable to +6 dB now, hard clipping of the microphone amplifier at 82 to 83 dB SPL.
The microphone sees a load of R1 + R2 + R4, so always above 30 kohm.
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Everyone has this reason. This is the final timeline of the edit my last documentary, prior before mixing, blue is image, green is sound,
assembled from 130 hours of footage that had to be catalogued, transcripted, etc. Editing took 6 months, mixing about three weeks.
also heavily edited.
When you zoom in, you´ll find sometimes 46 edits in sound but only 7 edits in image, during 136 seconds:
Supply voltage will be 3.3V.
What will I get with 39k and 47k?
I do not understand R11. Shouldn't it be only "active" as long as the Phantom Power
powers on and gives unnecessary load to the 3.3V supply?
All the best,
Salar
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With 3.3 V, the clipping levels will be about 1 dB lower.
R2 = R4 = R5 = 39 kohm, 3.3 V supply:
about 36.5 dB of gain, +6 dB similar to -2.5 dB now, clipping around 90 dB SPL.
R2 = R4 = R5 = 47 kohm, 3.3 V supply:
about 38 dB of gain, +6 dB similar to -1 dB now, clipping around 89 dB SPL
The 3.3 V presumably comes from a voltage regulator and voltage regulators are normally designed to source, but not to sink current. The purpose of R11 is to sink the charging current of the coupling capacitors when the phantom supply goes from 0 V to 48 V (or 46.5 V or whatever). If there is already something drawing at least 12 mA from the 3.3 V domain, it can be left out.
A circuit with a resistor and a Zener diode would draw less current and be more elegant, but then you need an extra component.
R2 = R4 = R5 = 39 kohm, 3.3 V supply:
about 36.5 dB of gain, +6 dB similar to -2.5 dB now, clipping around 90 dB SPL.
R2 = R4 = R5 = 47 kohm, 3.3 V supply:
about 38 dB of gain, +6 dB similar to -1 dB now, clipping around 89 dB SPL
The 3.3 V presumably comes from a voltage regulator and voltage regulators are normally designed to source, but not to sink current. The purpose of R11 is to sink the charging current of the coupling capacitors when the phantom supply goes from 0 V to 48 V (or 46.5 V or whatever). If there is already something drawing at least 12 mA from the 3.3 V domain, it can be left out.
A circuit with a resistor and a Zener diode would draw less current and be more elegant, but then you need an extra component.
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Dear Marcel,
many thanks!
But before starting soldering, something maybe needs to be considered,
and sorry, this thought comes very late:
Will the single ended output also work with longer cable lengths, about 4-5m?
Or shouldn't it be balanced, to be more versatile?
But it would be still a single 3.3V supply-so maybe clipping levels fall dramatically.
All cables and connections I use are balanced, besides the 10cm cable that
leads from the box beneath the cam to the mic/line input
In 70% of all cases the MKH-416 will be mounted on the camera, cable length
is no longer than 30 cm. But sometimes the mic could be put on a stand for interviews,
close to the subject, but more far from the camera.
I have a field mixer for this, but it is heavy. Would be nice to leave it out.
If being balanced and attached to the camera, the negative line would be shorted to GND,
before the voltage divider, close to the cam input. Could the LME4921 output handle this?
Many thanks, all the best,
Salar
many thanks!
But before starting soldering, something maybe needs to be considered,
and sorry, this thought comes very late:
Will the single ended output also work with longer cable lengths, about 4-5m?
Or shouldn't it be balanced, to be more versatile?
But it would be still a single 3.3V supply-so maybe clipping levels fall dramatically.
All cables and connections I use are balanced, besides the 10cm cable that
leads from the box beneath the cam to the mic/line input
In 70% of all cases the MKH-416 will be mounted on the camera, cable length
is no longer than 30 cm. But sometimes the mic could be put on a stand for interviews,
close to the subject, but more far from the camera.
I have a field mixer for this, but it is heavy. Would be nice to leave it out.
If being balanced and attached to the camera, the negative line would be shorted to GND,
before the voltage divider, close to the cam input. Could the LME4921 output handle this?
Many thanks, all the best,
Salar
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It will work fine with 5 m cables as long as there are no ground loops.
In any case, a balanced output that has to drive an unbalanced input would have to be a floating balanced output to have any advantage at all over unbalanced, and I don't know how to make a floating balanced output without making the circuit considerably larger.
In any case, a balanced output that has to drive an unbalanced input would have to be a floating balanced output to have any advantage at all over unbalanced, and I don't know how to make a floating balanced output without making the circuit considerably larger.
Based on your comment, I'll post a possible improvement that requires only one extra 100 ohm, 5 % resistor later. I have no time to draw it now.
BTW, maybe there is enough space left in the Xvive. Could be possible to plug the NTE-1 transformer after the
balanced output of the LME49721 to go from balanced to unbalanced? Too much load / voltage @ 36 db gain?
balanced output of the LME49721 to go from balanced to unbalanced? Too much load / voltage @ 36 db gain?
You mean the distortion that was audible in the low frequencies with high gains?
The MKH-416 goes down do 40hz, but when I read the only
graph available, frequency response is down only about -2 db. But I am not sure whether there is enough space to stuff the transformer in…
The MKH-416 goes down do 40hz, but when I read the only
graph available, frequency response is down only about -2 db. But I am not sure whether there is enough space to stuff the transformer in…
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Yes.
Above 60 Hz, the op-amp will hard clip before you reach the level where the transformer distorts 1 %, but not below 60 Hz.
Above 60 Hz, the op-amp will hard clip before you reach the level where the transformer distorts 1 %, but not below 60 Hz.
Would the transformer simply replace the resistors and capacitors at the output without influencing the rest of the balanced circuits design? Then I would leave it to the point whether the transformer fits physically into the Xvive or not.
With a transformer at the output, you could probably do without R6, but you would still need C4 (and everything else).
Dear Marcel,
were you talking about a balanced design here? I came up with a transformer for a balanced design.
No need for a transformer when single ended. Will balanced really be that bigger? The circuitry of R2, R4, R9, R10 would still be needed?