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Author Topic: Compact handheld XLR preamp w phantom?  (Read 3450 times)

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Offline Colin Liston

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Re: Compact handheld XLR preamp w phantom?
« Reply #15 on: May 31, 2020, 01:17:33 PM »
^ That thing is pretty cool! It would make an awesome small rig. I like how it can record to both the microSD and a phone/tablet. It's a shame you can't gang the gain for the two XLR inputs, though, and it would also be nice if it had a user replaceable battery. And some sort of more advanced level indicator.

Do you have one, Colin? I would love to hear some taper reports and ask a few questions...

I do not own one.  I saw one at Widespread at the Beacon at the end of February and would consider one if and when concerts start happening again. I think it would make a great 007 deck.  Unfortunately I have not heard the recordings of the Panic shows from the Beacon.
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Offline aaronji

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Re: Compact handheld XLR preamp w phantom?
« Reply #16 on: May 31, 2020, 06:00:30 PM »
Send a PM to TS member "dallman".  He is very happy with his R4R recorder.

https://taperssection.com/index.php?topic=190281.msg2297842#msg2297842

Thanks! I am somewhat embarrassed to see that I actually posted in that thread, although my post was about MixPre powering. I guess I glossed over the MixerFace entirely. I am going to post a couple of questions here and point dallman to them, so that his answers won't get lost in a PM.

I do not own one.  I saw one at Widespread at the Beacon at the end of February and would consider one if and when concerts start happening again. I think it would make a great 007 deck.  Unfortunately I have not heard the recordings of the Panic shows from the Beacon.

It's definitely small. Per the specs, it is about 18.7 cubic inches. For comparisons sake, (again from manufacturer's specs) an SD MixPre-3 is 34.6 cubic inches (plus power), a Zoom F6 is 46 cubic inches, and a TascamDR100 MKIII is 26.6 cubic inches.

Here are some questions I have:
  • What is the maximum input level for XLR mic-in?
  • Can you only get ISOs for two channels? If you also use the AUX input, from the manual, those levels appear to be mixed with the XLR inputs and you only get a stereo out.
  • Are the gain knobs stepped or continuous? How stiff are they (i.e. can they be moved easily)?
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Online morst

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Re: Compact handheld XLR preamp w phantom?
« Reply #17 on: June 01, 2020, 03:26:52 AM »
I like my Beyer MV 100. Basically the same as a Sonoxax but has a stepped gain instead of a variable gain and ICs instead of discrete. The Sax has XLR outs and the Beyer has RCA outputs. The sound is very similar and the MV100 is a lot cheaper on the used market. It's a nice little fool proof box.
I agree, but will point out that the +20 dB gain is sometimes too much for mics without pads at loud events, and that the MV100 runs off a pair of 9V batteries.
I usually got an easy 5 hours out of a pair of alkalines, powering Neumann KM140s.
User manual scan:
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Offline dallman

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Re: Compact handheld XLR preamp w phantom?
« Reply #18 on: June 12, 2020, 02:48:41 PM »
Send a PM to TS member "dallman".  He is very happy with his R4R recorder.

https://taperssection.com/index.php?topic=190281.msg2297842#msg2297842

Thanks! I am somewhat embarrassed to see that I actually posted in that thread, although my post was about MixPre powering. I guess I glossed over the MixerFace entirely. I am going to post a couple of questions here and point dallman to them, so that his answers won't get lost in a PM.

I do not own one.  I saw one at Widespread at the Beacon at the end of February and would consider one if and when concerts start happening again. I think it would make a great 007 deck.  Unfortunately I have not heard the recordings of the Panic shows from the Beacon.

It's definitely small. Per the specs, it is about 18.7 cubic inches. For comparisons sake, (again from manufacturer's specs) an SD MixPre-3 is 34.6 cubic inches (plus power), a Zoom F6 is 46 cubic inches, and a TascamDR100 MKIII is 26.6 cubic inches.

Here are some questions I have:
  • What is the maximum input level for XLR mic-in?
  • Can you only get ISOs for two channels? If you also use the AUX input, from the manual, those levels appear to be mixed with the XLR inputs and you only get a stereo out.
  • Are the gain knobs stepped or continuous? How stiff are they (i.e. can they be moved easily)?

 I do very much like the mixerface, it is rugged easy to use and sounds great. Sound wise I think it on a par with my MixPre6MKII, but also my hearing while still excellent is losing some nuance as I turn 65 in a few days. The mixerface does not have meters though so it may not be for everyone. It also has a lot of mixing functionality that I do not use and it is strictly 2 channel for recording. I have never used any of the associated programs, and have found the LED's allow me to set the levels without issue. Not everyone will like that, but I think it is fine.

There are lots of ways to use the deck beyond a stand alone. I often use is as channel 5 and 6 on my MixPre6II. Aside from synching the recording with my other sets of mics (I do not mix them, but tracking all at once is easier), and I also get an extra copy of the recording on the Mixerface although I have never needed it in that situation.

I am attaching some photos:
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Offline Niels

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Re: Compact handheld XLR preamp w phantom?
« Reply #19 on: June 12, 2020, 03:58:47 PM »
That’s very helpful. Thanks.
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Offline aaronji

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Re: Compact handheld XLR preamp w phantom?
« Reply #20 on: June 12, 2020, 08:45:57 PM »
I am attaching some photos:

Thank you very much! The photos are very useful.

One question: are the gain knobs stepped or continuous?

P.S. Happy Birthday!
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Offline jerryfreak

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Re: Compact handheld XLR preamp w phantom?
« Reply #21 on: June 12, 2020, 09:29:47 PM »
Thank you very much! The photos are very useful.

yeah they are. esp the first one, which really helps in gauging size (i have 4 of the others, and also had a mixpre at one point) :guitarist:
my facemask is a windscreen

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Offline OldNeumanntapr

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Re: Compact handheld XLR preamp w phantom?
« Reply #22 on: June 13, 2020, 01:39:30 AM »
I like my Beyer MV 100. Basically the same as a Sonoxax but has a stepped gain instead of a variable gain and ICs instead of discrete. The Sax has XLR outs and the Beyer has RCA outputs. The sound is very similar and the MV100 is a lot cheaper on the used market. It's a nice little fool proof box.
I agree, but will point out that the +20 dB gain is sometimes too much for mics without pads at loud events, and that the MV100 runs off a pair of 9V batteries.
I usually got an easy 5 hours out of a pair of alkalines, powering Neumann KM140s.
User manual scan:
http://www.taperssection.com/reference/pdf/Manual_BeyerdynamicMV100.pdf

I agree. I use the pads on my KM140s with the Beyer for everything except acoustic music.  The peak LEDs on the MV100 are supposed to light Before clipping so if they glow occasionally it's OK.

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Re: Compact handheld XLR preamp w phantom?
« Reply #23 on: June 13, 2020, 06:39:01 PM »
I agree. I use the pads on my KM140s with the Beyer for everything except acoustic music.  The peak LEDs on the MV100 are supposed to light Before clipping so if they glow occasionally it's OK.
Yes. According to the manual, the MV100 red peak lights come on at -6dB before the clipping point.
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Offline DSatz

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Re: Compact handheld XLR preamp w phantom?
« Reply #24 on: June 14, 2020, 01:52:11 PM »
OldNeumannTapr, the Neumann KM 140 can handle 138 dB SPL without the pad--and Neumann tends to specify things in a conservative way. So I really, really doubt that your microphones--themselves--are being pushed into overload if you're powering them properly. Based on what you wrote, I think that you'd probably agree. And in an emergency, using the pad switches on the microphones may be your only available solution. No dispute there.

But once you realize that your "downstream" equipment--your preamp, mixer or recorder--is at risk of input overload, then if that downstream equipment has no setting that fixes the problem, you need to use balanced, in-line resistive pads at the inputs of that equipment. Those are available from all pro equipment dealers. Shure makes them, Audio-Technica makes them, Whirlwind and many lesser brands offer them as well for less money (e.g. ~$20). They're very good to have in your bag at all times. I'd suggest a pad value of 15 or 20 dB for typical situations (technically 12 dB is the minimum for ideal impedance relationships, but if 10 dB floats your boat, so be it).

And then turn your microphones' pad switches off, and leave them off! Unless, as I said, you have a situation in which the microphones themselves are in danger of being overloaded--which should be exceedingly rare; 138 dB SPL causes severe hearing loss within minutes.

The reason this is not just a "matter of opinion" or "personal preference" is that using the internal pad in a condenser microphone reduces the output levels, while the self-noise (noise floor) of the circuitry remains the same. The pad switch works "early on" in the circuit to prevent the capsule's output from overloading the first stage of the amplifier, i.e. the FET or vacuum tube. Thus, relative to the signals that you're recording, the noise floor of the microphone goes UP by the same amount, e.g. 10 dB, whenever you throw the switch--and the noise floor of your microphones is distinctly greater than the noise floor of the MV 100 preamp. Your recordings also become 10 dB more vulnerable to any interference that's being radiated into the cables.

By comparison, a resistive pad at the input of the preamp, mixer or recorder will reduce BOTH the signals (that threaten to overload the device) AND the self-noise of the microphone AND any induced interference all by the same amount--thus preserving the full dynamic range of the microphone's signals, and reducing noise due to any interference.

--best regards
« Last Edit: June 14, 2020, 02:10:16 PM by DSatz »
music > microphones > a recorder of some sort

Offline OldNeumanntapr

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Re: Compact handheld XLR preamp w phantom?
« Reply #25 on: June 14, 2020, 02:15:55 PM »
OldNeumannTapr, the Neumann KM 140 can handle 138 dB SPL without the pad--and Neumann tends to specify things in a conservative way. So I really, really doubt that your microphones--themselves--are being pushed into overload if you're powering them properly. Based on what you wrote, I think that you'd probably agree. And in an emergency, using the pad switches on the microphones may be your only available solution. I'm not quarreling with that.

But once you realize that your "downstream" equipment--your preamp, mixer or recorder--is at risk of input overload, then if that downstream equipment has no setting that fixes the problem, you need to use balanced, in-line resistive pads at the inputs of that equipment. Those are available from all pro equipment dealers. Shure makes them, Audio-Technica makes them, Whirlwind and many lesser brands offer them as well for less money (e.g. ~$20). They're very good to have in your bag at all times. I'd suggest a pad value of 15 or 20 dB for typical situations (technically 12 dB is the minimum for ideal impedance relationships, but if 10 dB floats your boat, so be it).

And then turn your microphones' pad switches off, and leave them off! Unless, as I said, you have a situation in which the microphones themselves are in danger of being overloaded--which should be exceedingly rare; 138 dB SPL causes severe hearing loss within minutes.

The reason this is not just a "matter of opinion" or "personal preference" is that using the internal pad in a condenser microphone reduces the output levels, while the self-noise (noise floor) of the circuitry remains the same. The pad switch works "early on" in the circuit to prevent the capsule's output from overloading the first stage of the amplifier, i.e. the FET or vacuum tube. Thus, relative to the signals that you're recording, the noise floor of the microphone goes UP by the same amount, e.g. 10 dB, whenever you throw the switch. The recording also becomes 10 dB more vulnerable to any interference that's being radiated into the cables.

By comparison, a resistive pad at the input of the preamp, mixer or recorder will reduce BOTH the signals (that threaten to overload the device) AND the self-noise of the microphone AND any induced interference all by the same amount--thus preserving the full dynamic range of the microphone's signals, and reducing noise due to any interference.

--best regards

I agree that the downstream preamp is prone to overload, but I never thought about the fact that the pad on the microphone reduced the output significantly, enough to limit the sound quality.
Point taken.
I leave them off most of the time. I've noticed that the musical events that draws us old folk tends not to have earsplitting SPLs.
Of course, I haven't recorded Anything for over a year and with everything that is currently going on, not to mention the use of metal detectors, sometimes I wonder if I will ever record anything again.

I do miss  >:D recording David Lindley. :(

Offline jerryfreak

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Re: Compact handheld XLR preamp w phantom?
« Reply #26 on: June 14, 2020, 02:34:18 PM »
dont mic pads usually only reduce output voltage?

isnt max SPL at the capsule constrained by the same physical limitation?
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Offline DSatz

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Re: Compact handheld XLR preamp w phantom?
« Reply #27 on: June 14, 2020, 02:54:16 PM »
jerryfreak, the SPL limit of a condenser microphone is nearly always the limit of its electronics, not its capsule. There are some exceptions, but capsules typically can handle 150 dB SPL or more, with only gradually increasing distortion. By contrast, the circuitry tends to clip fairly hard at some given voltage, especially in transistorized microphones. The limiting factor is generally the first stage of the electronics (if there's more than one), i.e. the FET or tube--although when an output transformer is present, it also sets a certain voltage ceiling, which (in small microphones especially) may be significantly lower at low frequencies. In any case, the job of the pad is to reduce the voltage feeding the input of the microphone's amplifier circuitry.

There are two general ways that pads work. The traditional way is that a fixed capacitance is added to the capsule's capacitance, thus reducing the voltage changes that reach the first stage FET or tube. The entire amplifier then operates at 10 dB (or whatever) lower signal levels. But most of the noise of the electronics comes from that first-stage device, and that isn't affected by the pad one way or the other. Thus the noise floor stays the same while the desired signal is 10 dB lower. Result: 10 dB more FET or tube noise relative to the desired signal.

The more modern way is to reduce the polarization voltage going to the capsule. But it has the same effect on dynamic range.

It would be possible for a pad switch to put an H-pad in series with the modulation leads at the output of a microphone. However, this would need to be a multi-pole switch, since not only the two series resistors but also a shunt resistor would need to be switched in. And those switches themselves would inevitably become a real source of problems, both in terms of reliability and size. I've never seen or heard of any microphone being made that way, and I'm not sure that I would buy one if it existed, because that switch (even if I never used it) would be a recording disaster waiting to happen.

In any case it's better to put a pad like this at the preamp end of the cable, because then the signals in the cable remain at higher levels (thus overcoming interference that much better), plus that's usually closer to where the recording engineer is, allowing for adjustments without having to pull the mikes down first.

--best regards

P.S.: Noise is a complicated subject, since it's never fully described by just one number/amount. It's always time-varying to some extent, and its frequency spectrum isn't inherently flat. The FET or tube at the front of the microphone circuitry is usually the main source for the microphone's noise at and above some midrange-y frequency. At lower frequencies the capsule's capacitance dominates quantitatively--but at such low levels, the ear is largely insensitive to low-frequency sound. So as a rough first approximation you can consider the FET or tube noise as "the noise" of the circuitry as a whole, because the ear is so much (several tens of decibels) more sensitive to noise at upper midrange frequencies.
« Last Edit: June 18, 2020, 03:00:39 AM by DSatz »
music > microphones > a recorder of some sort

Offline dallman

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Re: Compact handheld XLR preamp w phantom?
« Reply #28 on: June 15, 2020, 04:36:32 PM »
I am attaching some photos:

Thank you very much! The photos are very useful.

One question: are the gain knobs stepped or continuous?

P.S. Happy Birthday!

Thanks!
They are continuous and feel very snug and fluid.
Somewhere there is a video of someone driving a car over the deck with no damage. I have no plans to test that out though  8)
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