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I am designing a "mic activator" with some design goals that are not satisfied by the simpler ones (e.g. FetHead, CloudLifter), but are possibly already done by the more complex ones like SE Electronics DM1 / DM2 (but I don't know the schematic of that one, if anyone knows, please share). In short, I want decent CMRR, PSRR and low output impedance. I have a schematic I could build, but the part count to satisfy these requirements is pretty high.
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So I don't think I can fit it into the regular XLR male-female "tube" adapter, e.g. this one on , which is similar to what FetHead uses. The PCB that can fit inside that one is 13mm wide by 15mm long, but 5.5mm of that length are used by the XLR connector. I could have a second PCB ride on the first, but I'd lose some area for the header connectors between the two.
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Ideally, I would like a longer tube, e.g. like , which is ~36mm longer than the FetHead. Even 10mm longer would probably be enough for this circuit. Is there any way to source such a body?
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Ideally, I would like a longer tube You might be able to find “mini” sized guitar pedal enclosures more easily than cylinders or tubes. See attached photo. — matt.
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What about something like the Neutrik NA-Housing?
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You can match it with their D-shape modules, like the NM3MD-B and NM3FD-B XLR connectors, to make a full enclosure. It'd give you something like 65mm by 30mm, roughly -- there's a dimensioned drawing on the product page. It's a little expensive, but worked well when I used one for a BNC to XLR adapter.
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There are also these enclosures on Ali:
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https://pl.aliexpress.com/item/32961610296.html?spm=a2g0n.order_detail.order_detail_item.3.577743cexag7lb&gatewayAdapt=glo2pol
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Cheap and sturdy.
Note, there are several options to choose from: plastic or aluminium and male/female conectors variations.
Connectors are plastic even with aluminium bodies.
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Yuo might even consider using the enclosure of one of these: ? ?
It's a sort of Cloudlifter 'clone', and is a robust enclosure - complete with XLRs etc.
Just replace the internal PCB....
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On Wed, Aug 28, 2024 at 02:45 AM, Arjay1949 wrote:
It's a sort of Cloudlifter 'clone'
Thanks for the suggestions, this gave me the idea to look for other clones, and I found this: . It's not as cheap as the empty tubes (5x the price), but I am really partial to the "tube" form factor as it works well with plug-on transmitters such as . There are also some in a similar form factor, but they are twice the price.
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But it's nice to see that there are quite a few options in the "box" form factor as well.
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That's what I used for my MicBooster. The space is good for
conventional through-hole PCB.
Le 27/08/2024 à 23:44, Alex Reinhart a
écrit?:
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What about something like the Neutrik NA-Housing?
?
You can match it with their D-shape modules, like the NM3MD-B
and NM3FD-B XLR connectors, to make a full enclosure. It'd give
you something like 65mm by 30mm, roughly -- there's a
dimensioned drawing on the product page. It's a little
expensive, but worked well when I used one for a BNC to XLR
adapter.
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I bought a few samples. There is not much space for the PCB. I
don't want to go SMD so I had to give up. The price is quite
attractive compared to the Neutrik solution.
Le 28/08/2024 à 00:39, pmfalcman a
écrit?:
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There are also these enclosures on Ali:
?
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Cheap and sturdy.
Note, there are several options to choose from: plastic or
aluminium and male/female conectors variations.
Connectors are plastic even with aluminium bodies.
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They also have "barrel" bodies.
Note the extraordinary performance figures, such as "Sex to noise
ratio"
Le 28/08/2024 à 01:45, Arjay1949 a
écrit?:
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Yuo might even consider using the enclosure of one of these:
?
?
It's a sort of Cloudlifter 'clone', and is a robust enclosure
- complete with XLRs etc.
Just replace the internal PCB....
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Remember one thing: the smaller it is, the easier it is to be
stolen.
Le 28/08/2024 à 08:03, sergio_logic via
groups.io a écrit?:
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On Wed, Aug 28, 2024 at 02:45 AM, Arjay1949 wrote:
It's a sort of Cloudlifter 'clone'
Thanks for the suggestions, this gave me the idea to look for
other clones, and I found this: .
It's not as cheap as the empty tubes (5x the price), but I am
really partial to the "tube" form factor as it works well with
plug-on transmitters such as . There are also some
in a similar form factor, but they are twice the price.
?
But it's nice to see that there are quite a few options in
the "box" form factor as well.
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On Wed, Aug 28, 2024 at 12:01 PM, Jerry Lee Marcel wrote:
I don't want to go SMD so I had to give up.
I'm quite the opposite... I managed to squeeze 14 bipolar transistors (packaged in matched pairs), 21 resistors and 5 capacitors into a FetHead-style body. It's a true fully differential amplifier (phantom-powered), but the SNR is 12dB worse than FetHead because of the resistive feedback network. I have since come to my senses and concluded that the JFET differential pair with no feedback is probably the way to go, but it needs some "supporting actors" (output buffer, current sink) for improved performance. I have two devices into which the FetHead is NOISY probably because of the >10k output impedance, one is a P1 portable phantom supply, which I typically connect to a Shure transformer into a camera. The other is the . Other P48 mics and preamps are really quiet in the same setups. The FetHead is even noisier than this circuit in those setups, whereas in others (iRig Pre 2, TC-Helicon GO Vocal) I see the expected 12dB difference in the favor of FetHead (which matches what I expected from the simulations).
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PCB side assembled by JLCPCB:
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PCB side hand assembled by me:
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Plase find attached the schematic of my MicBooster.
It's not the most perfect in the world, it can always be
improved, but it's used by hundreds of discerning users around the
world.
I had one of the earlier Fethead's. I recognized two significant
problems. Due to the high Vdg, it was very noisy, and the high
impedance output made it sensitive to load.
In the second version, they have solved (very inelegantly IMO)
the first issue, but made the second even worse.
I reckon my solution is pragmatic and efficient. There are
probably many other ways to skin that cat, though.
Le 28/08/2024 à 12:18, sergio_logic via
groups.io a écrit?:
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On Wed, Aug 28, 2024 at 12:01 PM, Jerry Lee Marcel wrote:
I don't want to go SMD so I had to give up.
I'm quite the opposite... I managed to squeeze 14 bipolar
transistors (packaged in matched pairs), 21 resistors and 5
capacitors into a FetHead-style body. It's a true fully
differential amplifier (phantom-powered), but the SNR is 12dB
worse than FetHead because of the resistive feedback network. I
have since come to my senses and concluded that the JFET
differential pair with no feedback is probably the way to go,
but it needs some "supporting actors" (output buffer, current
sink) for improved performance. I have two devices into which
the FetHead is NOISY probably because of the >10k output
impedance, one is a P1 portable phantom supply,
which I typically connect to a Shure transformer into a camera.
The other is the . Other P48 mics and preamps are really quiet in
the same setups. The FetHead is even noisier than this circuit
in those setups, whereas in others (iRig Pre 2, TC-Helicon GO
Vocal) I see the expected 12dB difference in the favor of
FetHead (which matches what I expected from the simulations).
?
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PCB side assembled by JLCPCB:
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PCB side hand assembled by me:
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Sergio, what mike do you need to increase gain with this device?
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I have a simple design at /g/MicBuilders/files/Ricardo/ActiveRibbon which probably meets your requirements.? It's VERY low noise.? But I also pontificate on when it is sensible to use such a device and present an alternative .. and also when you might as well just increase the gain in your DAW ?
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I’m experimenting with some dynamic mics as budget indoor boom mics for interviews. Typically, the mic for this application would be a hypercardioid/supercardioid SDC with 20-25 mV/Pa sensitivity, e.g Audio-Technica AT4053b or Sennheiser MKH50.?
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Some of the more directional dynamic mics (Audix OM2, Shure Beta 58a) also seem to also have a decent bass respose even at 30cm (1ft) from the source.
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I think with the BJT base feedback design you presented, because the output impedance of dynamic mics varies by ~2x over the frequiency range, the gain would vary by the same ratio and would colour the respose a lot. I guess the ribbon mics you designed this circuit for have a much flatter Zout(f) than dynamics, right?
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I think with the BJT base feedback design you presented, because the output impedance of dynamic mics varies by ~2x over the frequiency range, the gain would vary by the same ratio and would colour the respose a lot.
This just reduces the LF around the 'bass resonance' of the dynamic mike by 6dB.? Using an OM2 or Beta 58a at 30cm or less for speech, you probably need to reduce bass even imore ndoors.? Certainly you need to do this outdoors.
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Ribbon2.gif is optimised for high quality ribbons which need VERY low noise and amplification.? Most high quality ribbons need some LF cut.? eg see the comments about Royer in my README.doc and also BBC Engineering monograph No4 on the 4038 (IMHO, the best ribbon ever made)
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If you're happy with the LF performance of your dynamics and just need a little more gain, Jerry's circuit is probably best.
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Ribbon2.gif can have quite a bit of bass boost built in without degrading the noise but needs a couple of extra resistors & capacitors.
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For dynamics, it’s not just a LF effect, it’s also a HF issue:
(source for impedance curve: )
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Sergio, what circuit are you using ?
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Matthew McGlynn at Recording Hacks had a big review of several such devices.
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It showed the Cloudlifter as the best and the FEThead sorta second with some caveats.? It also showed several were made from liquid BS so that's probably why he's taken the mass review down.
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Matt, you should have a search facility for your blog ... but I enjoyed going through all of them and checking out the treasures within :)
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Triton FetHead is what I am using. Like I said, the performance is as expected with some XLR input devices and pretty bad with others.?
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I build those kinds of things in guitar pedal type enclosures.? Plenty of space for whatever circuits you need.
Triton FetHead is what I am using. Like I said, the performance is as expected with some XLR input devices and pretty bad with others.?
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Paul E Marchman