UPDATED: So You Want A Good Cheap Ribbon Mic: Upgrading the $69.99 MXL R40

UPDATE: since this article seems to get an enormous number of pageviews, I thought I should mention that we did in fact carry-out the intended shoot-out of the mod’d R40 versus a range of other similar ribbons (with a Royer R121 as the ‘control’ sample.  CLICK HERE to listen to some apples-to-apples action.

I love the sound of ribbon mics.  Friends and clients will often ask me why, or ‘what’s the difference’ (b/w a ribbon and other forms of mics) and I generally reply that good ribbon mics seem, to my ears/brain, to reproduce sound in a way that more closely resembles the actual event.  To my ears, a good condenser like my U87 or U47 FET sound fantastic – more spectacular than the actual sonic event, in many cases – and a good dynamic mic like a 441 or an SM7 can really improve the sound of an electric guitar speaker – but there are ways that they do seem distorted, especially on material with complex, aggressive high-frequency content, such as cymbals played with a heavy touch.  Ribbon mics also seem to respond better to additive EQ, and on bass instruments they also seem to create the impression of bigger, fuller bass without actually taking up as many DBs in the mix as you might expect.  Anyhow, I keep writing ‘seem’ because all of this is, necessarily, subjective.  That being said, these are opinions that more and more recordists and musicians have come to share since ribbon mics came back into vogue a decade or so ago.

FOLLOW THE LINK BELOW TO READ-ON AND LEARN HOW TO MAKE YRSELF A REAL-NICE SOUNDING RIBBON MIC IN 45 MINUTES FOR UNDER $100

Although condenser microphones were actually invented a few years before the first ribbon mics, ribbon mics are interesting in that they really haven’t changed in design since the 1920s.  Whereas today’s garden-variety condenser mics are much more sophisticated and hi-fi than their 1920s ancestors. A standard ribbon mic consists of a physical body or shell, a thin metal ribbon suspended in a metal frame alongside a magnets, an output transformer and output jack.  That’s really it in most cases.  And with these very few elements, sound can be turned into electricity with incredible realism.

Royer Labs claims to have been responsible for starting the uptick in popularity that ribbons have seen since the millenium; their R-121 was introduced in 1998 and sure enough it’s a great microphone.  I’ve owned one for years and yeah I use it on pretty much every session.  It sounds great, it has a lot of output, it’s very small, and it has survived a few 4-ft drops onto the oak with no ill effects.  It’s a very good product, if a little overpriced IMO (check out the Shinybox 46MXL for a mic that’s 98% as good for 40% the price of the Royer; I’ve used my 46MXL on sessions with my Royer for years).   Also shockingly good: the Cascade Fathead Two.  I bought one of these a few years back just to see what the fuss was all about, and while it’s not going to replace my Royer, or my vintage Beyer, Shure, and RCA ribbons anytime soon, it’s really pretty remarkable for a $200 microphone.  One caveat: with no apparent cause, my Fathead II has developed a slight slack ribbon which causes an audible rattle if the mic stand is bumped hard.  Now, realistically, if a mic stand gets bumped, you prolly have a bigger sound-problem than a rattle -40db below program level but it’s important to mention. 

Ok but let’s say you don’t have even $200 to spend on a microphone.  I sure didn’t when I started taking recording-studio classes in college.  There are a number of cheaper alternatives to the Fathead II, and I’ve tried many of them over the years, driven mainly by curiosity.  Mics in this category that I cannot recommend: The Nady RSM4.  Chalky, low output.   The Oktava ML52 (expensive now, but these were intially as cheap as $150 at GC): just awful.  So when I got some sort of promo-mailer from Musician’s Friend touting the “MXL R40 Ribbon Mic $59.99″ (still avail for $69.99).  I figured: what the hell.  Worst case scenario, I’m buying a sixty dollar shockmount.

So the mic came and it didn’t suck.  The output level was not so good but the sound was cool in a midrange-y, vintage-LP sorta way.  Way, way better then the Nady.  But not a very modern-sounding mic, so application would be limited.  You read some other folks’ assessment of the stock R40 at this link.

I remembered that EDCOR made a 1:37 ribbon mic transformer that only cost $23 and promised perfect frequency response.  I ordered one along with some other bits and bobs that I needed from America’s premier manufacturer of low-cost audio transformers, and a month later it arrived: the RMX1  (see here for spec sheet: RMX1).

EDCOR makes some great products, and some not so great.  Search for EDCOR on this site and you can see many, many opinions of mine regarding their various wares.  That being said, I am a big supporter of theirs, because the products are all made in America, carefully packaged, well supported, and really an incredible bargain if you use them correctly.  As for the RMX-1: I am giving this product the full two thumbs up.  WOW what a difference it makes in the MXL R40.  Here’s how I did it:

With 8 turns-of-the-wrist the R40 opens up to reveal a 4-point terminal board positioned above a transformer housing.  Above, two wires extend from the head (these be the two ends of the ribbon, I imagine…) into the body cavity.

Here’s the reverse view.  This is the original factory transformer.  It has two primary wires and two secondary wires.  The EDCOR RMX1 is EXACTLY the same size and fit in pretty easily once I removed some of the shrink-tubing that EDCOR used to protect the exiting wires.  Other than removing some of the shrink tubing and re-securing the wires with electrical tape there was no mechanical work to be done.  Simple.

The wire color-codes on the EDCOR don’t match the colors on the stock transformer, so I drew the above schematics in my super-embarassing ten-yr-old-boy handwriting.  Feel free to laugh at my apparent total lack of fine motor control.  ANYway, that’s about it.  Sub the new trans in for the old, solder the wires to the correct places on the terminal board, and yr done.

Here’s how it sounds, recorded right into ye olde MBOX2.  You are hearing a solo finger-picked acoustic-guitar performance of a gospel classic.  Put on some decent headphones and take a listen.  First, the original transformer, with 4.6 db of gain digitally added (no other processing whatsoever):

LISTEN TO ORIG TRANS WITH 4.6 DB ADDED: MXL R40 Original Transformer plus4pt6db

…and after I did the modification, which took 45 minutes…  here I am with a 2nd performance, same mic position, same input level on the MBOX, etc…  but with no gain added:

LISTEN TO EDCOR TRANS: MXL R40 Edcor Transformer

Was this test scientific?  No.  I could have been a little off-position for the 2nd take.  I could have played a little harder.  Sure.  But this is a dramatic difference.   It feels like there is a whole additional octave both top and bottom with the EDCOR;  it also sounds smoother and more polished.  Plus I had to add 4.6 db of gain to get the original transformer take at the same average program level.  That means that the mic’s output with the EDCOR is around 50% louder in volume.   These are substantial improvements for an easy-to-install $23 part.

If I ever get the chance, I will do some sort of listening-test in the studio with this modded MXL, the Fathead II, the Shinybox, and the Royer.  Don’t hold yr breath on that one tho…

Further Reading

Michael Joly (ribbon microphone upgrade service-for-hire) ***

DIY Ribbon Mic Kits and Plans ***

Ribbon Mic Rennaisanse coverage in the popular press (c/o WIRED)

( *** n.b: I have no experience with these companies/services, but it’s interesting reading at the least)

PREVIOUS RIBBON MIC COVERAGE ON PRESERVATIONSOUND DOT COM:

Vintage RCA Ribbon Mics (the standard in professional American ribbon mics)

The American R331 (an obscure American ribbon mic from circa ’50)


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31 Responses to UPDATED: So You Want A Good Cheap Ribbon Mic: Upgrading the $69.99 MXL R40

  1. Pingback: Przerabiamy MXL R40 « 0dB.pl – twój poziom odniesienia

  2. Jono says:

    Great article. Thanks for the sound clips. I’m thinking of doing this same procedure on the R144. Don’t see why that wouldn’t work. :)

  3. jon says:

    Be sure to check the polarity of the mic once you have swapped the transformer. Whenever I see red connected to white (from the manufacturer), it certainly makes you scratch your head and think they either installed the magnets backward, put the motor in backward, or wired the microphone backward.

  4. Mike K says:

    Unfortunately the Edcor RMX1 is not $23 anymore try $31 + shipping on top of that which even if you are in the USA will be at least another $10 cause they send everything by courier so your looking at $41 or more for the Edcor RMX1. There are cheaper transformer alternatives to be had like the ones here: http://www.pfsonics.com

  5. Robert Murray says:

    Do you have any experience with the MXL R144 or R77 Ribbon Microphones?

  6. chris says:

    nope… just the R40… c.

  7. Yeah, I did this, except I used a Shinhom T25 from PFSonics (Google it) which is pretty much a clone of the transformer in this article. And YES IT WORKS. The output was massively greater and suddenly there was a whole lot more there in terms of frequency. Now I love this mic. I would also suggest pulling off the internal pop/windshields that protect the ribbon — no real danger as long as you always use an external pop shield (or double pop shield) which I always do anyway. Put the mic in a ziploc bag for moving it around if you’re worried. Thank you for the excellent article.

  8. Dan says:

    Thanks for posting this! I was inspired to install two RMX-1 in my R40 pair. The cost is now $32 per transformer with a hefty $15 shipping fee. Totally worth it though. Especially considering comparable US transformers are in the $100 range. The wiring guide was helpful in this post. I actually removed all the old wires in mine and just wired the transformer directly to the ribbon motor and XLR connector. Less wire. I am in love with these microphones! You can here some sound demonstrations I posted here http://www.gearslutz.com/board/so-much-gear-so-little-time/597135-mxl-r40-ribbon-microphone-4.html

  9. Dan says:

    Sorry, $31.03 to be precise.

  10. Eric says:

    I still love this mod and did it myself. A recommend europe source for this rmx1 trafos
    http://www.don-audio.com/Edcor-RMX1
    The difference is a nuance and in a nice direction. It sounds more flat after this mod. The highs are also better interpreted with some nuances i could not hear witht he stock one. In comparison the original seems to have a bit boosted low mids and the highs are a little bit muddy. With the rmx1 the frequencies are almost more natural. Good sound with transformers is often to find the perfect impendance balance and it must fit to the circuit anyhow… this post made me realise that experimenting and modding gear with a little effort and $$ can be really worth. Thank you!
    Hope this helps.
    E.

  11. Larry Ayres says:

    I got an R-40 as a Musiciansfriend.com stupid deal of the day for $50 with the aim of doing this mod. Before doing it I tried to use it in some recording. I would say, unmodified it is almost unusable. The signal is so weak that it is barely above the noisefloor of the amplifier. It also had a dark, closed in sound in the high frequencies.

    I put the edcore in this weekend. Easy mod. Two tips, you unscrew the bottom of the mic to get inside and note that the body of the mic is keyed at the top to the part with the ribbon in it. That ensures that the front of the ribbon lines up with the lettering on the body.

    After the mod it is a great mic. Easily twice the level, it is no longer in the noise. The high end opened up, as I hoped it would and sounds very natural. It is my favorite mic now for my voice. I’ve got condensors and dynamics, but this records great, and as others have said it takes EQ very well. It also sound great on a weak voice, seems to thicken it up. This is a very worthwhile project! Thanks!

  12. Kevin says:

    This is a great article as I am in search for a nice ribbon mic in my budget. I have been told that the ribbon mics are great for micing saxophone and other wind instruments (as I play) also they respond very well to Eq changes. So I am going towards the Cascade Fat Head, but…Here’s my question: Does the MXL R40 with EDCOR mic transformer sound better then the Fat Head? Also, would the transformer work on the Fat Head, would it make a noticeable difference/does it even need it?

    Thanks again for this great article!

  13. Stephen Cole says:

    Great article, but you missed the boat along with everyone else on the web. I can’t find the information I’ve shared below – I had to figure it out myself but it wasn’t difficult and my experiments prove my theory correct.

    Was the mic preamp input impedance taken into account? Most professional mic preamps have a low input impedance, usually 100, 600, 1K or 1.5K ohms. I come up with about 2.7K output impedance for the transformer secondary (2 ohms reflected through a 37:1 turns ratio transformer) that is being required to drive a low impedance load. This is not good for the reasons below.

    If the preamps have 600 ohm inputs (switchable to 100 ohm for ribbon mics for more gain) how is a 2.7K source (transformer secondary) going to drive that? It can’t. Look at the transformer freq response specs that are posted for some of these cheap transformers and you’ll see that a source of A FRACTION OF AN OHM was used to drive them to get those specs. A fraction of an ohm source will reflect back to the secondary as a much lower impedance than 2.7K, so the freq response plots that are published are all bogus. NO ribbon mic motor has an output impedance of 0.1 ohm. Most are ten to twenty times that (about 1 or 2 ohms) so you can expect a good amount of high frequency roll-off if you use a mic preamp with a low input impedance. A mic pre with a high impedance input would prevent the highs from “sagging” on the primary of the transformer due to the fact the current draw is much lower. I use a homemade TI chip with JFET inputs as a “pre”-preamp.

    Using a homemade low noise JFET input high impedance preamp/buffer on the secondary of the transformer causes the high frequencies to become much more pronounced and open compared to loading it down with a professional mic-pre having very low input impedances. The transformer gives a “noise free” voltage boost, but the output driving current is reduced by a factor of 37 – there is no “free power”. Conversely, condenser mics have a lower output impedance at the XLR mic connector and more importantly, a relatively constant output impedance with respect to frequency (active circuitry as opposed to a transformer coil). Transformers tend to have rising output impedances with frequency, so loading them down with a low impedance resistive and capacitive loads will simply create a low pass filter and make the mic sound dull and muddy.

    If you have a high impedance preamp such a a guitar pedal with a 1 Meg input impedance try plugging (any) ribbon mic into it before going to the mic preamp. You might get a lot of noise due to the noise the pedal creates, but you’ll also notice that the treble is no longer being “sucked away” by your $5,000 mic pre that sounds worse than a $4 Texas Instruments Op-Amp circuit that costs about $15 to build. If you build one use a non-inverting circuit configuration to avoid resistor noise on the input and a TI LME49860 Op-Amp with an input noise density of 2.7nV/sqrt(Hz). This is one of the quietest op-amps you can buy. The input bias current is high, but with the *relatively* low impedance of the source (assuming 2.5K), current noise is not an issue.

    http://www.lundahl.se/pdfs/datash/1927A.pdf

    The Lundahl above specs a flat frequency response – flat with a 0.3 ohm source and a 10K load. These impedances are FANTASIES. In real life they are VERY different. Try about 2 ohms for the source (about 7 times higher than the 0.3 ohms used for the specs) which reflects to the transformer secondary at about 2.5K. So a 2.5K source is supposed to drive a load as low as 600 ohms on the input of a good mic pre PLUS the cable capacitance. NOT GOING TO HAPPEN without problems. This is basic stuff.

    All the above means two things: 1)The response curves and specs on transformers is MEANINGLESS, 2)You can fix the problem using a good transformer AND a buffer amp between the mic and the mic preamp. A buffer alone may solve all your problems better than a new transformer but it takes more time to build.

    http://www.ti.com/lit/ds/symlink/opa627.pdf

    The above is another good op-amp that won’t load down your transformer, the OPA627. This Op-amp has the advantage of a very low input bias current although in this application that spec isn’t as important than the voltage noise.

    http://www.lundahl.se/wp-content/uploads/2013/05/7903.pdf

    This transformer specs the freq response using a 30K ohm load!!! I believe that, but as soon as you plug it into a mic pre with a low impedance input the first thing that will happen is that your treble will be attenuated. A device designed to drive a 30K load will NOT PROPERLY drive the 600 ohm load of a mic pre. If your plugging a ribbon mic into a low impedance input mic pre you WILL experience loss of high frequencies. If you buffer the secondary so that it feeds a load in excess of 30K ohms then you’ll get a flat response. The main problem here is that the output impedance of the transformer is not flat with respect to frequency, and if the load is too large (low impedance) the high frequencies will drop off. Also, transformers are poor drivers of long cables. I also use a very short cable (about 5′) from the mic to the homemade buffer/preamp to avoid picking up noise or loosing treble in the cable capacitance.

    Summary: Build a high impedance preamp/buffer with an XLR input and output. It need not be balanced. Set the circuit to get a reasonably high gain (40dB is a good compromise), and plug the output of the preamp/buffer into the mic preamp. Presto – the high frequencies are there is spades and the mic sparkles.

    Can you tell us the input impedance of the mic pre you are using?

    Thanks.

    Stephen

    • chris says:

      Hi stephen. thanks for the info. i don’t doubt any of what you are saying, but anecdotally, i use many many different models of vintage and modern ribbon mics in the studio all the time with a wide variety of different mic preamps (input impedance of which varies roughly between 150 ohms and 1500 ohms) and they all sound good, plenty of high-end. The mics that don’t sound good I leave at home and call that a day. So i don’t think it’s necessarily that case that every ribbon mic demands an unusually high input impedance to sound its best.

      If you feel that you have an idea for an affordable device that will make a generic mic preamp sound markedly better than a “$5,000 mic pre” when used with a ribbon mic, you should market it. You could sell a lot of them.

      good luck, c.

      • Stephen Cole says:

        Hmmm, not a bad idea! The basic problem of ribbon mics is low output voltage, and using a transformer to amplify the voltage to compensate causes problems that an active device will solve. To back up my point, there are now ribbon mics that use 48V phantom power. They eliminate the problem of high output impedance on the secondary by buffering the transformer INSIDE the mic instead of outside in a separate box like I do, but the theory is EXACTLY the same: put a buffer between the output transformer and the mic pre-amp.

        Condenser mics have active buffer amps INSIDE the mic and now ribbons are starting to do the same, as they should. Perhaps some of those limited bandwidth mics would sound awesome if they weren’t being asked to drive a load that the laws of physics says they can’t.

        Great discussion. I’ll try to post some comparisons of my MXL R40 through low and high impedance preamps to demo the difference when I get a chance.

        Cheers!

    • Mike K says:

      Hi Stephen, Regarding your comment;
      “Most professional mic preamps have a low input impedance, usually 100, 600, 1K or 1.5K ohms. I come up with about 2.7K output impedance for the transformer secondary (2 ohms reflected through a 37:1 turns ratio transformer) that is being required to drive a low impedance load. ”

      Most “Professional” mic preamps I have come across have at least 1.5k input impedance available, a lot have more, eg AEA ribbon mic preamp has more than 10k.
      Also 2 ohms is a large number for ribbon motor output impedance and sounds like an inaccurate measurement. There are lots of ribbon motors that have been properly designed that have much lower output impedance. In my opinion a passive ribbon mic with a motor properly designed for even a cheap step up transformer can hold its own against the best active ribbons that cost many times more.

  14. Stephen Cole says:

    Sorry for the back to back posts but I just performed an experiment that uses no home brew equipment. I own a Studio Projects VTB1 Mic pre. Not the best in the world but not too shabby. It has a high impedance (Hi-Z) 1/4″ input of 1.5 Megohm. The XLR input impedance is 300 ohms by contrast.

    I made a simple cord with an XLR on one end and a 1/4 inch on the other so I could plug the MXL R40 into the Hi-Z input. Pin 3 and pin 1 (ground) of the XLR went to the 1/4 sleeve and pin 2 went to the tip.

    Plugging the mic into the Hi-Z 1.5 Meg input yields a wider, flatter response, and noticeably so from the stock transformer. The bass and treble are enhanced, and there is less “boominess” in the lower mids, to my ears anyway. On a 12 string acoustic the difference is immediately apparent.

    If you’re mic pre has a hi-Z input (usually for instruments like guitars and usually 1/4″) you can try it yourself. I stand by everything above with the exception of the statement that “condenser mics have a lower output impedance than ribbon mics”. This is not true in general, but it is true at high frequencies, which is why they are attenuated more than the mids by the same resistive loads. I’m not certain why the bass is enhanced, but the treble is simple physics and using a Hi-Z input with a ribbon mic is almost exactly analagous to a guitar player installing a buffer preamp in a guitar to prevent the cable capacitance from “sucking all the highs” out of the tone. The guitar pickups present a rising output impedance with frequency. Combined with a capacitive load this is a recipe for dull sound.

  15. Stephen Cole says:

    BTW, I did a side by side shoot out of the MXL R144 vs. the R40 a year or so ago right after the R40 came out.

    The R40 sounds noticeably better. It had a more detailed high end and just sounded better in general to me. The difference was significant. I returned the R144 and bought another R40, which was more expensive, but worth it. Now I see the R40 for $70 and the R144 for $100. What happened? The price seems to have flip-flopped, but I would take the R40 over the R144 any day.

    • Mike K says:

      Stephen,
      Next time get your facts straight before posting 10 pages of misleading rubbish.
      Then coming back and telling everyone you were misinformed.

  16. Stephen Cole says:

    Phantom powered ribbon mics and why ribbons need phantom power:

    The AT4081 – “Phantom-powered active electronics provide STABLE IMPEDANCE
    and higher output for MAXIMUM COMPATIBILITY WITH MICROPHONE PREAMPLIFIERS ” (from the product literature).

    The key words here are “stable impedance” (caps by me) and “maximum compatibility with microphone preamplifiers”. AT is doing it right – finally! This is the future of ribbon mics.

    This strongly implies that there is an incompatibility between some ribbon mics and some mic preamplifiers (and there is). To be specific, they are referring to an inadequate (less than 10:1 ratio) impedance mismatch. This is the Achilles heel of ribbon mics – they use transformers to drive a low impedance preamp designed for condenser mics which the ribbon mics can’t drive, then they are labeled as junk and cast aside when in reality they may sound great with a proper high impedance preamp. Incompatibility has nothing to do with phantom power. All new ribbon mics can handle phantom power. I would recommend either not using it or plugging the mic in before turning it on so the transformer doesn’t see a pulse of DC, but otherwise it’s perfectly acceptable to run the transformer coil at 48VDC on a ribbon mic. It will not harm the mic or the ribbon. The 48V is applied to BOTH ends of the transformer secondary so the transformer actually has zero VDC across it. The voltage is isolated by the transformer so it can’t get to the ribbon – only AC is passed.

    A transformer is a HORRIBLE device to drive a cable or a low impedance load unless the transformer has a very low output impedance itself. This is because the output impedance changes with frequency. An inductive source (transformer) typically has a high frequency roll off if connected to a load it can’t drive. A source in general as a RULE OF THUMB should have less than 1/10 the impedance of the load it drives to avoid altering the frequency response. While a ribbon transformer may be able to deliver the mid-band frequencies because it has a lower impedance at those frequencies, SOME ribbon transformers simply can’t drive a 2k or 3K load on a mic pre, even one costing $5000. A $10 circuit made with a $2 op-amp will sound better IN THIS PARTICULAR CASE than a $5000 pre with a 2K input impedance, simply because the cheap op-amp isn’t requiring that the transformer supply current and voltage it simply can’t supply to the $5000 preamp.

    Tube circuits in general are very simple. The tube preamps in the range of $500 to $5000 are overpriced and unnecessary – again, MY OPINION. If you want the prestige of owning one and you have the bucks – go for it. I don’t want the prestige – just a clean, natural sound, or in some cases a dirty, distorted sound. I can get that with a $180 Preamp and a $150 mic. Moving the mic just one inch can improve the sound more than substituting the most expensive Neumann for a Behringer B2 Pro (a cheap mic with a hyped high end but very detailed sound – you need to EQ DOWN the treble but the result is beautiful). Keep that in mind when you’re recording.

    My point is that with experience, good ears, patience, and LOTS of experimentation one can now locate in 2014 very inexpensive products that in many cases OUT PERFORM very expensive “vintage” equipment. Just because it’s old doesn’t mean it’s magic or sounds good. In fact, most old equipment sounds bad. There are a few very well made preamps that are sought after for their high quality sound, but newer designs sound as good or better to my ears. The ONLY reason I can think of for a preamp to cost thousands of dollars is if it is filled with a compliment of NOS Mullard tubes or some other popular NOS tubes. I’ve seen ONE 12AX7 NOS listed on eBay for $450! Would YOU buy a tube you can get for $12 for $400 just because it’s old? Maybe 20 years ago I would if I were rich, but tubes have gotten a lot better in the last 10 years due to the resurgence of the use of tubes in guitar amps and the lack of anyone’s ability to create a convincing simulation of tubes using transistors. The Rockman is the closest thing I’ve heard to real tubes, but it still doesn’t quite nail the tube distortion of a real tube amp. There are a couple of digital modelers that sound pretty good and could fool the ear, but they cost a lot more than a real amp. I simply build the preamp circuits I find online for $50-$100 each and can get real tube distortion. I cloned Mesa’s Triaxis Lead 2 circuit and an A/B comparison with a real Triaxis reveals that my rip off sounds the same as the Triaxis with just some minor difference in the EQ. The character and quality of the distortion are the same. If you’ve ever played this amp you’d appreciate the quality of the distortion. It goes from clean to totally distorted using only picking dynamics. It’s very touch sensitive and expressive. I digress…

    Here are the specs on the 48V phantom powered ACTIVE ELECTRONICS ribbon mic for anyone interested:

    http://eu.audio-technica.com/en/resources/0001_0261_01_at4081_ss.pdf

    While I’m on pre-amps, I’d like to go slightly OT again. I’ve been doing a lot of experimentation with mic preamps prior to a large project I’m just beginning to work on (which led me to become interested in this discussion) and I’m very surprised at what I’ve found. It’s now my OPINION that spending anything over $500 for a mic pre is simply a waste of money. I’m talking here about PREAMPS – NOT the compressors that are found in many high end models. I’ve done tests with borrowed gear costing several thousand dollars (albeit with built in compressors which push up the price) all the way down to the ART Tube MP Studio for $30. For mics I would set the “inaudibly better” price point at about $300 for condenser mics with dual diaphragms. I haven’t had much experience with ribbon mics and have no idea how much I would have to pay before the improvement in sound proves negligible.

    The best price/performance ratio in preamps goes to the ART Tube MP Studio – hands down. I am extremely impressed with the quality of the sound. It is very quiet and transparent. I honestly don’t know how they can make and sell these for $30. Note: the lights burn out on EVERY unit within a few months, so don’t expect an illuminated meter for very long. I own 4 of these for various uses, mostly to interface guitar preamps I build with tube power amps I build to control the relative levels of preamp/power amp distortion. If you’re on a budget and want crystal clear sound (albeit hyped treble that may need downward EQ) buy an Art Tube MP Studio for $30 and a Behringer B2 Pro for $150. You’re out $180 plus tax but IF YOU USE THEM CORRECTLY you can produce EXCEPTIONALLY high quality recordings. The B2 Pro is almost the opposite of a ribbon mic – it has a very sterile, accurate presentation but the treble is strong. However, as mentioned, if you EQ the treble down just a little you can get great results. The B2 Pro is one of the best deals in mics and one of Behringer’s best products. Junk this is NOT.

    Next up I would say the PreSonus V2 for $99 (on Amazon today), regularly $150, takes second spot. The difference between the PreSonus and the ART is minimal. A/B listening tests on various instruments revealed it was hard to tell which was which. With the +20dB button engaged the ART gets a little noisy at high gain settings, but if you set your levels correctly and aren’t trying to record a pin drop it shouldn’t be an issue.

    The Studio Projects VTB1 gets my third place for price performance, plus it has a very quiet front input that’s 1.5 Megohm which can be used to track guitars or use for ribbon mics.

    When I get more high end than the VTB1 I hear no sonic improvement. The preamps on all my mixers sound horrible. Other cheap preamps I’ve tried sound bad although I haven’t tried them all there are so many. The PreSonus sounds as good as the VTB1 but is noisier. The VTB1 and the PreSonus also have a tube circuit that is supposed to warm up the sound. The PreSonus tube drive sounds horrible, however, the Studio Projects tube drive sounds great. It actually does what it’s advertised to do! I think this is my favorite preamp and it’s what I always use unless I need multiple mics.

    High end preamps sound great, particularly the good tube preamps. But lets face it, there are only a finite number of different designs using tubes, tube circuits are simple compared to transistor based circuits, and there is NO REASON based on the components used that a preamp needs to cost several thousand dollars to sound great. Most high end preamps I’ve used are subtle effects boxes that impart a certain tonal quality to the signal, particularly when pushed hard. They may do this well and sound better to the ear if used properly in certain situations, but they are technically not as accurate in the reproduction of sound as much less expensive solid state preamps are.

    Happy New Year everyone, and thanks for the website and tips on ribbon mics. I’ve learned a lot. If my EE degree causes me to get too technical sometimes I apologize. I try to keep things simple but don’t always succeed. I also plan to post the recordings of the MXL R40 using both inputs (1.5 Megohm and 300 ohm) on my VTB1 using the stock transformer so everyone can hear the difference when the transformer is unloaded (a 1.5 Megohm load is almost like having no load at all).

    Cheers!

  17. Stephen Cole says:

    I’m wrong about a couple of things I misspoke about and would like a chance to correct my mistakes, after which I’ll no longer post – my intent is not to hi-jack the discussion.

    First, this is one of the best things any tech or engineer could read regarding audio, especially microphone, transformers:

    http://www.jensen-transformers.com/an/Audio%20Transformers%20Chapter.pdf

    The entire book is there.

    Second, a VTB1 Hi-Z input is too noisy to use – it does however demonstrate the radical change in sound when a ribbon mic is used with it.

    Last, a 1 MegOhm load (or greater) isn’t always desirable. If phantom power is used the absolute lowest impedance of a mic pre is 6.8K (from either of the balanced lines to ground). If it’s switchable then there’s no limit to the upper end of the input impedance.

    A continuously variable load impedance across the transformer secondary (output), from about 10K down to 500 ohms yields a wide range of tones from the MXL R40. This can be accomplished with a 10K pot. If you put the pot in different positions you get a different EQ for each. The optimum impedance that you choose is SUBJECTIVE although frequency response plots can be run to choose the “flattest” response.

    MOST TRANSFORMERS ACTUALLY BENEFIT FROM A SMALL AMOUNT OF LOAD, and the only way to figure out where yours sounds best is to listen to it using different values of resistance shunted across the primary to provide a resistive component to the load. This allows an opposing flux to develop, and provides damping to prevent ringing. An unloaded transformer may exhibit instability and ring at certain frequencies. The square wave test (usually 10kHz) looks a lot better with just the right amount of resistance across the secondary and the transformer (and mic) sounds better.

    Thanks for letting me clear that up.

  18. Peter says:

    So I have a pair of R40s, and I just modded one of them. I got a pair of new transformers but figured I would do just one of them and do some tests with modded versus stock test before doing the second. I thought this would be a cool way to get some more “scientific” samples.

    Unfortunately, after doing one and then comparing, I don’t seem to have any increased output from the new transformer. In fact it may be 1-2 dbs less output. It might be a tiny bit brighter and less muddy, but any difference is super subtle. I was really hoping to get a lot more output since I often run into noise problems with those mics.

    I followed your instructions and diagram exactly as far as I can tell. Is there anything I could have messed up that would be lowering the output?

    Thanks

    • chris says:

      Hi peter. the only thing that occurs to me is maybe one of the transformer secondaries is wired to ground? If so, this would result in a mic that works fine, but has 6db less output. Other than that, I have no idea. It’s entirely possible that in the 2+ years since I wrote that article, MXL started using a different transformer in the mic. That’s about it for ideas,,,,

      • Peter says:

        Well if you got +4.8 dbs and I’m -1.2dbs that definitely sounds plausible right? What would that look like in terms of your wiring diagrams? If I was gonna check it with a multi-meter across what two points should I check to see if there’s an accidental connection? I wouldn’t be too surprised if something accidentally got crossed since I had to cram the thing in there more than I would have liked.

        And judging from your pictures the original transformer still appears to be the same.

        Thanks!

        • chris says:

          hey man. i couldn’t really tell ya “What would that look like in terms of your wiring diagrams.”

          but

          don’t trust a continuity tester either. the tester may SHOW continuity even tho the leg is not actually shorted to ground.

          Try the cont tester first, and if there is no cont, then there is no wiring error. if there IS cont, then also measure the DC resistance from pins 2 and 3 to ground. if the figure is not roughly the same, then there may be an error. Also just look at yr work carefully. good luck. c.

          • Peter says:

            Sorry, I guess the better way to ask that question would have been: which of the wires, what color(s), are the secondaries? I really don’t know much about transformers.

            Thanks a lot for your help!

  19. chris says:

    Hi Peter. I can’t say for sure yr transformer looks like, or what its colors mean, since i don’t have it to examine. But I can tell you that in my hand-drawn diagram above, the green and yellow wires are the secondaries.

    c.

  20. Peter says:

    Thanks a lot man!

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