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MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Wed Apr 06, 2016 1:47 pm

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There’s been some discussion here recently about using an in-line preamplifier when you require significant amounts of gain for your less-sensitive ribbon or dynamic mics. For those with respectable, but not stellar, microphone preamplifiers in either recorders, interfaces or mixers, high gain settings can result in hiss and a definite increase in the noise floor.

A simple solution is to use one of these ‘cascode’ preamplifiers in-line between the mic and the mic input. Powered by the receiving device’s phantom power-supply these preamps will give you varying amounts of additional gain depending on the make and model, meaning that you can use lower gain settings on the microphone input of the device itself.

The names most often associated with these devices are Cloudlifter and FetHead. However, a UK-based micro-business – MARTiAUDiO – has also been attracting some interest for their similar product. Having read and seen some reviews I decided to buy one as a solution to my own ‘need more gain’ issues. In passing, mine was delivered within 48 hours of placing the order although as they’re often made to order then you may have to wait longer. This is made quite clear on the EBay site – the only way of purchasing in the UK.

The microphone preamps are respectable in my various devices, but all exhibit some noise artefacts when cranked-up if using a dynamic mic. To give some context, I’m in a treated room and usually recording single-voice read material in a conversational style. This coupled with me being somewhat softly-spoken means that I need all the gain I can get!

The MARTiAUDiO preamp couldn’t be simpler. It’s effectively a short barrel (8.5 cms) with an XLR 3-pin socket on one end and a corresponding plug on the other. You connect it between the mic and the existing preamp. It puts me in mind of the XLR ‘gender-changers’, attenuators and polarity inverters that can be found in many an audio-tech’s box of bits.

The MARTiAUDiO preamp is powered by the device that the mic and preamp combo is connected to. This means that 48-volt phantom-power is a must at the receiving device. Note that the MARTiAUDiO preamps are specified to run at 48-volts. In some of their literature they state that the device may work with lower phantom voltages, but this is not guaranteed. Unlike the cascade preamps from some other manufacturers there is no option for phantom-power ‘pass through’. This means that the MARTiAUDiO device is strictly for use with mics that need no external DC voltage. But then the price is much less than the ‘pass through’ equivalents from other companies!

To test the MARTiAUDiO preamplifier I decided to use my Zoom H5 digital recorder and a Beyerdynamic M201 hypercardioid dynamic microphone. The M201 gives a very smooth unhyped sound, but has the Zoom preamp working hard to get acceptable level. Noise then becomes a slight, but irritating issue.

It took me all of 30 seconds to connect the preamp between the mic and the mic input on the Zoom and another few seconds to adjust the gain. To my ears there is a distinct improvement which has reduced the noise without producing additional unacceptable artefacts. (Input gain was set to average at around -12dB with peaks no more than -6dB. This was the same for all recordings – the aim being to get as much gain-matching as possible at the front-end rather than later in the DAW. That said, all recordings have been normalized to -2dB to give some consistency. No other processing, eq or dynamics processing has been applied.) However, there are some artefacts that I detect as I listen to the recordings. The preamp does introduce some slight hiss (compare it with the benchmark LDC which has a very low self-noise figure) but I had to listen on headphones at relatively high volume to become aware of it. Also, compared to the ‘native’ recording of the M201 I feel that there’s a little boost been given in the low-mids which another review has characterized as ‘warmth’. But those are observations rather than criticisms. Using this preamp will allow me to use some of my preferred dynamic mics for spoken word without having to resort to noise reduction in post-processing or investing in additional expensive high-gain, low noise preamps.

There are three recordings in the attached sample file: The first is a benchmark using a low self-noise LDC set to a hypercardioid pattern. The second is the M201 straight into the Zoom. The third is with the MARTiAUDiO preamp in-line. In all cases a high-pass filter at 80Hz was set on the Zoom H5

I am very pleased with this purchase and it more than meets my needs. And at the price of £35 plus £5 postage it’s a bargain and I’m happy to recommend it. MARTiAUDiO also make a deluxe version which is electronically identical, but uses Neutrik connectors. That one is £42 with the same postage costs. All prices include VAT.

As I mentioned in the introduction, similar products are available from Cloudlifter and Tritonaudio with their FetHead range. FEL also have some products. However, in the UK all are more expensive than the preamps from MARTiAUDiO.


Audio Samples: https://soundcloud.com/rhemasound-productions/martiaudio-tes...

Independent Review: https://www.youtube.com/watch?v=UgUrMuNkiJo

Facebook: https://www.facebook.com/pages/MARTiAUDiO/469574086408107

Buying: http://www.ebay.co.uk/itm/In-Line-Mic-Preamp-Booster-XLR-Bar...

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Hugh Robjohns » Wed Apr 06, 2016 3:21 pm

Nice review, Mike. Thanks

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Guy Johnson » Wed Apr 06, 2016 10:13 pm

Indeed, and very useful.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Martin Walker » Thu Apr 07, 2016 3:42 pm

Yes, fascinating! Always good to find folk who are producing small audio devices that fill a need without breaking the bank 8-)


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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Wonks » Fri Apr 08, 2016 2:25 pm

Can I say that I preferred the sound of the M201 straight into the Zoom. To me, there seemed to be more low level noise (plus more lip noise) on the sample with the in-line device being used.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Fri Apr 08, 2016 5:55 pm

Wonks wrote:Can I say that I preferred the sound of the M201 straight into the Zoom. To me, there seemed to be more low level noise (plus more lip noise) on the sample with the in-line device being used.
You can say what you like... no skin... etc :D

Your post has caused me to do some further work on the posted samples.... I chopped out everything but the two silences I left deliberately when recording with the 201 - ie one without the preamp in circuit and one with the preamp in circuit.

I then gave the resultant short audio sample a global boost of 20dB. Hearing the two 'hiss' sections back-to-back it's clear to my ears that:

a) As already noted, there is hiss in both sections.
b) The hiss with the preamp in circuit is less than with the preamp not in circuit. I don't have anything like precision tools, but such as I have shows about a 6dB-9dB difference.

The lip noises can be discounted I think for two reasons:

a) It's two separate recordings with all the attendant variations that will inevitably be present.
b) I was/am getting over a bad cold which inevitably affects the vocal production apparatus.

Of course, as noted there is definitely some low-mid boost going on - and my spectral analysis now confirms this - so maybe that in itself means that the lip noises get more emphasis.

So each to their own, but I can't agree that there is more low-level noise with the preamp in circuit than without.

Cheers!

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Fri Apr 08, 2016 10:58 pm

IMPORTANT UPDATE

Following Wonks's comments I have been doing some more detailed evaluation of the preamp this evening.

I stand by the comments I've made about more gain and reduced (but not eliminated) hiss.

However, on doing more tests this evening using another 'end' preamplifier and monitoring through headphones at high volume I can detect some faint 'motorboating'.

This may be due to RF pickup - there is a wireless modem about 2 metres away - or it could be down to an issue with the electronics of the MARTiAUDiO preamp.

I shall be contacting the manufacturer/supplier tomorrow, but as of now I cannot recommend the product. :frown:

(I have checked the 'end' preamplifier with other phantom-powered mics and, although I can still hear some noise at these high levels, there is no trace of 'motorboating'. Thus it must be down to the MARTiAUDiO preamp.)

Watch this space...
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Tim Gillett » Sat Apr 09, 2016 12:33 am

After a casual listen I thought the one with the inline pre was quieter.

But I feel it would be better as far as highlighting the difference in noise to record a much quieter source. Then you can increase gain at the record stage to bring the pre noises right up. In other words highlight the noise at the record stage so it's well above any other possible sources of degradation further downstream, including mp3 conversion, the limitations of listeners' own gear, situation etc.

Even the natural ambience of your location could be used as source, so long as it's constant in level over the course of the test. Then if necessary gain match the ambience in the two samples and any difference in pre noise should now stand out clearly, even with a less than stellar listening situation. HTH

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Wonks » Sat Apr 09, 2016 9:19 am

This 'motorboating' noise. Could it be caused by some outboard gear? ;)
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Wonks » Sat Apr 09, 2016 9:22 am

Listened to the wav version and the noise I thought I was hearing had disappeared, so maybe it was an MP3 thing.

It would be interesting to know if either of the two other in-line preamp types exhibited the same 'motorboating' noise when used in the same location.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Sat Apr 09, 2016 10:18 am

Thanks for the comments...

... and a further update...

All credit to MARTiAUDiO for their VERY fast and detailed response to my expressed concern about extraneous noises.

To summarise:

1) They recognise that the version I bought - with the budget plug casing - may not be all it could be in terms of screening. They are seriously considering producing only the version with the Neutrik plug casing.
2) In five years of manufacture and selling they have had only one other concern expressed about extraneous noise - this with the same model as I have. This problem was traced to radiated RF from a mobile phone in the same room.
3) They tactfully pointed out that a chain is only as strong as its weakest link and stressed the importance of using good-quality cable and connectors.

So... this morning I switched-off the wireless modem and removed my phone from the room.

(I should mention that my recent and present tests are being conducted using a small and recent Yamaha mixer with decent preamps.)

I had the gain trim and fader/pot set to maximum and the headphones at silly volume. For this - and last night's - tests I used a Rode Procaster which is my mic of choice for personal spoken voice. Clearly at these settings I was not speaking but just listening to the ambient noise pick-up.

I'm pleased to report that all of the 'noises off' had disappeared. Of course at these settings and volume levels, hiss from both preamps was noticeable, but this wasn't a real-world test - no-one with any sense would ever be recording, mixing or playing back spoken voice at these levels.

So I'm happy to reinstate my recommendation with two caveats:

Be careful of any radiated RF in the vicinity; perhaps spend the extra £7 on the Neutrik plug version.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Hugh Robjohns » Sat Apr 09, 2016 12:34 pm

Mike Stranks wrote:They tactfully pointed out that a chain is only as strong as its weakest link and stressed the importance of using good-quality cable and connectors.

Absolutely true, of course, but IF -- and I stress the IF -- the problem wasn't apparent without the in-line gain stage that implies the gain stage is the weakest link! No? And it seems they are aware of an issue with the screening of the cheaper casing.

Effective screening is not as easy as it seems, and a lot of equipment manufacturers fall foul of it -- especially mic manufacturers!

The EMC regulations are in place to ensure manufacturers make their products workable in the relatively hostile RF environments in which we now find ourselves. For that reason, I have a wifi router at the back of my test room and I routinely keep my mobile phone close to hand. I don't get many problems with most review gear, although I have on occasions. (I also have a DAB radio to hand which is good for detecting radiated shash from equipment too!)

John Willett is a big fan of the Neutrik EMC XLR connectors, and there's no doubt that they provide better RF screening than standard plugs and sockets... but I don't have John's budget ;) and stick with standard X-series for almost everything. Not had any real problems. In fact the only time I can recall a problem was when I heard the classic dit-dit-dit noise of a mobile phone during a rehearsal, which I tracked down to a lady 'cellist who had placed her handbag (containing the phone) directly on top of her spot mic's cable! I suspect it wouldn't have got through had I been using a star-quad cable, but moving her handbag 12 inches away from the cable cured the problem completely.

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Martin Walker » Sat Apr 09, 2016 2:51 pm

Hugh Robjohns wrote:I tracked down to a lady 'cellist who had placed her handbag (containing the phone) directly on top of her spot mic's cable! I suspect it wouldn't have got through had I been using a star-quad cable, but moving her handbag 12 inches away from the cable cured the problem completely.

Just as many people notice the Noise Margin of their router varies with the time of day, the sort of interference problem mentioned by Hugh above can also be time-sensitive - hence the well-known and often dire warnings about 'handbags at dawn' Image


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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Sun Apr 10, 2016 11:43 am

Further update...

This morning I have been doing some extensive testing with different mics - both dynamic and condenser - different cables and with the MARTiAUDiO preamp in circuit and not in circuit.

The end result of all of that is that I am pleased to report that the MARTiAUDiO preamp is not contributing to the RF pickup in any way at all.

About 75 cm from the router there is very significant RF intrusion on four different dynamic mics and, to a lesser extent, also on the condenser mic. Having the MARTiAUDiO preamp in circuit makes no difference to the breakthrough.

At the usual mic position I use there is NO RF breakthrough with any mic or whether/not the preamp is in circuit.

False alarm! Sorry to all for this blind alley. :blush:

My recommendation of the cheaper version - as tested - thus remains intact.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Hugh Robjohns » Sun Apr 10, 2016 1:09 pm

Well done for refining the tests to sort out what was going on. It is very easy to get lured into false assumptions -- we've all been there I'm sure! Hence the big IF in my previous missive... Anyway, glad the Martiaudio product has come through successfully. Thanks for the update Mike.

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby shufflebeat » Mon Apr 11, 2016 12:31 am

Thanks, Mike for your well conducted and conscientious piece. I had been planning to pick one of these little fellers up to facilitate trying my ribbon mic as a live drum o/h and after reading your experience I went ahead, it sounds great to me.

I bought the Neutrik version because they never let me down.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Bob Bickerton » Mon Apr 18, 2016 10:28 pm

Thanks Mike and a fascinating thread.......

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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Fri May 13, 2016 12:16 pm

Another quick update....

Further recent tests have revealed that the MARTiAUDiO preamp is inverting the polarity (aka phase) of the signal as it amplifies it.

Of course, if you're using just one mic for a recording then it isn't of great significance. But if it's on one mic in a multimic setup then you might get some strange artifacts as I did this week. It was those artifacts that alerted me to a possible issue. Detailed testing has now confirmed my suspicions.
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Mike Stranks » Fri May 13, 2016 8:03 pm

I raised this polarity issue with MARTiAUDiO... no-one else has raised this with them so they're going to conduct some tests of their own and come back to me...
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Re: MARTiAUDiO In-line Microphone Preamplifier

Postby Hugh Robjohns » Fri May 13, 2016 8:15 pm

Thanks for the update mic. Surprised they weren't aware! :shock:
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