This thing has been recommended to me by a friend as something I need in order to achieve technical correctness when playing with, say, a Shure SM57, into an amplifier? (Maybe that also goes for my Audix Fireball?) My friend knows a lot about these things -- but not particularly well related to harmonica.
If you are talking about a guitar amp, I think you want an impedance matching transformer (IMT). LowZ to HiZ. Sm57 to amp. But wait for a few more comments before relying on any of my advice.... ---------- Phil Pennington
i think with that you would have to run it backwards. you would need a standard mic cord. plug that in to your mic and the other end in to that unit there.
then use a guitar cord coming out the other side in to the amp. low to high impedance.
you can buy a transformer that will fit inside of your mic for next to nothing, or get an ultra super transformer for just a tiny bit more.
simply solder the wires, not hard at all. i bet you could buy one of your friends a beer and they would be happy to do it for you.
also you could just get inline matching transformer for 20 euros. no work involved.
Use an impedance matching transformer for a mic like a 57 that is using low z, xlr balanced cable in order to change it to a hi z, unbalanced cable to plug into pedals or a guitar amp.
Use a DI to go from a hi z guitar, bullet mic, or effects pedals using output to an unbalanced, hi z, instrument cable and change it to balanced, xlr cable to a PA mic input. ----------
Again Martin? :) This is my fav subject, so all good.
Listen to Doug, he has it right.
...although 1847 is right too and so is Fil. Personally I like the "DI box in reverse" idea because it's a robust box on the ground, rather than a massive, vulnerable sticky-outy plug going into your amp - ready to be bent by someone knocking into it. Or worse, damaging your amp's input socket.
If I had a tenner for every bent IMT I've seen, I'd be able to retire. Maybe you can buy them pre-bent, like distressed jeans. To show you've been around and paid your dues.
I think the technical reason for this odd arrangement is the idea that you should have as much balanced cable and as little unbalanced cable as possible - for the least noise and hum. So the IMT should be as physically close to the amp input as possible.
Last Edited by MindTheGap on Sep 15, 2017 2:03 AM
The interesting thing is that in all of Sweden´s (a Northern country, w/ some 9 million inhabitants) music stores there exist no such thing as an "impedance matching transformer". ("Impedansomvandlare".)
I have *zero* inclination to buy something I don´t need, so I guess this Palmer thing is off the table now, and I´ll have to revert to my somewhat tardy friend who has promised to build me something (but I´d like him to finish that before I´m dead, and by now I don´t really know ...). Or do I have to buy *two* things? If so, is this one of them: https://www.thomann.de/se/monacor_ma_100_15.htm?ref=search_rslt_impedance+matching+transformer_113716_3
And I wonder, isn´t Adam Gussow using a standard vocal mic into his (guitar) amp here:
and then maybe he is technically incorrect as well? -- but he´s got a bit of the sound I´m after (although i like it cleaner) and I see nothing apart from Adam himself, harmonica, mic and amp. I´m at the end of my tether here.
@timeistight: I already have two bullet mics (hi-Z, I take it?). I like none of them. Therefore I´m exploring other avenues.
Thanks to all of you who are taking the trouble, but I believe I don´t need any technical explanations, but just simple directions. Like you´re talking to a child or an imbecile -- pointing with a steady hand. And if that comes down to that I need stuff for, say, $500, then I´ll just check out discretly and continue as before. But I remain, as always, very grateful for your patience and input.
Martin yes that Monacor MA-100/15 is one of these things. And it has a rats-tail design which some like. Still unwieldy but less chance of damage.
I know you don't want the technical explanations, but actually you are doing a public service (seriously), as there seems to be a bit of confusion generally about mics/impedance matching/signal level/dB/volume controls etc. on here (not the company present on this thread though). It's been an opportunity to clear some of this up. After all, some people regard MBH as the premier diatonic blues harmonica site of the world. So it's good to be pedantically correct I think.
I can't remember what mic Adam uses but I seem to recall it was Hi-Z. You can get Hi-Z stick mics, and you can get dual-impedance ones too.
Here's a simple direction that may solve your problem: buy an Akai DM-13. It's 2nd hand, cheap, Hi-Z and sounds very nice for harp.
Last Edited by MindTheGap on Sep 15, 2017 6:34 AM
A short cable from the a95uf or the pigtail on the Audix going to the amp eliminates having a tall piece of gear sticking out of the amp jack that risks accidentally damaging the jack.
Now that's a very good suggestion. There's also the Behringer MIC200 Ultragain, similar but has 'voicings' too. I always meant to try one of these things.
It's got Hi-z and Lo-Z inputs AND outputs, so should be good for any of your mics, going to amplifier or PA.
...and it's got a tube in it (cue heavenly choir). If only it had an effects loop in/out, it would be perfect.
Martin - buy one of those.
Last Edited by MindTheGap on Sep 15, 2017 8:17 AM
The gain is adjustable and you need to add some or there is no sound. The settings for gain and output are usually set at about the 12 O'clock position. I think it warms the sound.
I usually use it with a condenser style mic for vocals or acoustic harp playing and then into a PA for a very clean sound. Mic is always on a stand and not cupped.
I have an SM57...I'll try it with that to see if feedback/overdrive is an issue and report back. ---------- MBH member since 2009-03-24
We just had a whole thread about impedance matching.
If I can remember the summary: -
Sometimes balanced signals and unbalanced signals need to be matched, but it's usually not crucial at low power. An unbalanced cable (like coax) is shielded: a balanced cable isn't necessarily, so that's an argument for minimising the length of balanced cable. Except that you can get shielded balanced cable.
Impedance matching maximises power transfer, but a pre-amp doesn't care about power, it only cares about voltage - the power amplifier is the current amplifier.
The impedance matching transformer acts mainly as a voltage transformer, and that's why it appears to "work".
But ironically, I forgot in that thread to mention that transformers have less than 100% power efficiency, so even with one, you still aren't getting maximum power into your preamp (but as I said, it doesn't matter).
Possibly a guitar amp will have a relatively high level input for a mic (rather than a high impedance input).
Summary: just stick your mic into your amp. If it ain't loud enough, use a cheap impedance transformer to boost the voltage. ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 15, 2017 10:57 AM
Yes, it's great isn't it. I'm better at this than playing the harmonica, so it's good.
Correct about the impedance matching (power and voltage etc.) But more so: with mics you specifically don't want to match impedance and maximise power - because that would gives a lower fidelity signal. Of course for harp, we like lo-fi signals but the likely effect would be to 'rob tone' as people say.
The Hi-Z mic signal IS about right for a guitar amp, used for vocals - but not when cupping as that boosts the signal considerably.
Re balanced cables, it's not so much about the shielding, although they are shielded. The whole point of the balanced scheme (using three conductors rather than two) is to minimise picking up electrical noise. So they are best for long cable runs. The unbalanced (e.g. guitar cable, with two conductors) is also shielded so it does reject some electrical noise, but isn't as good as balanced.
My own experience, playing alongside two guitarists, is that they are generating so much electrical noise with their guitar cables, single coil pickups, pedals, switched-mode power supplies, that they provide enough hum, hiss and buzz for everyone.
Last Edited by MindTheGap on Sep 15, 2017 1:04 PM
Martin - You can get a microphone impedance transformer (rat tail) in Sweden at the Thomann website. The Audix T-50K sells for 26 Euros, or 248 SEK.
I use one with my SM57 when plugging into a tube amp. Works fine.
Dougharp' s explanation (4th entry in this string) is perfect.
The question about whether you NEED it, depends on the mic/amp combo. You may or may not need it, but its a valuable tool to have in your kit bag.
Last Edited by AppalachiaBlues on Sep 15, 2017 1:47 PM
Mind the gap says "The whole point of the balanced scheme (using three conductors rather than two) is to minimise picking up electrical noise. So they are best for long cable runs. The unbalanced (e.g. guitar cable, with two conductors) is also shielded so it does reject some electrical noise, but isn't as good as balanced.
My own experience, playing alongside two guitarists, is that they are generating so much electrical noise with their guitar cables, single coil pickups, pedals, switched-mode power supplies, that they provide enough hum, hiss and buzz for everyone."
Thanks I'll look into that. All I know is that my fluorescent desk-lamp went in the bin the day I bought my SM57, lol! ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 15, 2017 11:41 PM
Yes, well nothing's perfect. Could be your desk lamp was polluting the mains, or your body was acting as an aerial and putting a signal on the 'ground' of the mic. It's all fun.
Where we rehearse the mains often seems noisy. Machinery? Dimmer switches? "Doesn't do this at home" We often take a happy few minutes of precious rehearsal time for people to take their hands on and off their guitars and mics, switch on/off pedals - in an attempt to identify the culprit.
Fluorescent lamps are well-known for the interference they throw out.
It's an arc (in an ionised gas, initiated by the starter), so it's a very efficient radio transmitter. ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 16, 2017 3:41 AM
Just to follow up regarding the preamp option. I did try it with an SM57 to a tube amp and the PA and the preamp works great to provide a clean acoustic sound.
It may not be as convenient as an impedance matching transformer due to size and it requires power, however it does provide other cabling options that may be desirable. ---------- MBH member since 2009-03-24
Thank you to all who have (once again!) taken the trouble to answer my endless queries of things technical. I have taken notes and will proceed with a few investments in the near future.
Next time I raise a subject I hope it will be in more of a "harmonica nature": I´ve been going on to much with the electrical stuff lately. (In fact I thought of sharing a short video from Facebook right now, just to show my good will, from a gig this Saturday, then playing through a Roland Mobile, with no greater issues than the usual feedback when I tried to get louder, but of course that didn´t work, because of ... things technical.)
Hope to not complicate things but technically a low Z balanced mic's signal "floats" without a true ground reference. You would need a guitar preamp with a special amp called a differential (diff) amp to use it to it's full potential. It responds to the difference in voltage between the two wires. It's more immune to noise because any noise picked up will be picked up equally in both wires.The amp will see there is no difference between the wires and thus no amplification. The transformer "unbalances" the signal and gives it a true ground reference and your conventional guitar amp is happy.
Last Edited by Tuckster on Sep 18, 2017 11:02 AM
If you don't liike the sound of your existing hi-Z mics, have you considered that adding a transformer (or anything else into the chain) will alter the sound of your preferred microphone into a sound that will no longer be pleasing to you?
Last Edited by Joe_L on Sep 18, 2017 11:34 AM
@Tuckster: You can very easily complicate things for me in this area, and that´s something I´ll just have to live with. As of now I´ve put stuff into the hands of a friend who´s guiding me (along lines indicated here above: he´s a capable guy) and I´ll send your comment to him. Thanks.
@Joe L: I don´t particularly care for any of my mics. Especially not the Shure 520 DX -- and a cheapo knock-off that I got. Right now I´m waiting for delivery of an EV PL35 -- recommended to me on this forum. We´ll see how that turns out. The only one I´ve really liked was an old Beyerdynamic M160, ribbon type -- and what I liked was how it sounded straight into the PA. It died on me rather quickly though. Another old Beyer is good, but a bit weak. The Audix Fireball is strong, but not very ... intimate.
Are you suggesting that I don´t need extra equipment?
Tuckster - although what you say is true, this really does confuse things for Martin. A cheapo XLR-1/4" cable will do the job of getting a signal from mic into the amp, demonstrably - it's just the signal voltage isn't normally high enough to get the kind of sound you want out of the amp. Although Martin is happy enough with his.
Last Edited by MindTheGap on Sep 18, 2017 2:28 PM
Martin wrote: "Right now I´m waiting for delivery of an EV PL35 -- recommended to me on this forum. We´ll see how that turns out."
You know that the PL35 is a low-impedance mic, right? You still should be using an impedance matching transformer if you're running it into a high impedance amp or pedal.
@Martin - at this point, I'm not sure any of us can help you. I will say this, if you expect the equipment to provide the intimacy or the conversational nature of you're playing, you're looking in the wrong place. That really needs to come from you.
Well, I think Martin should get an IMT *and* a DI like the Palmer so he's ready for anything, but what he needs to plug the PL35 into his Memphis Mini is an IMT like the Shure or Audix recommended by dougharps.
You know, Martin has been getting advice on impedance matching on this site for at least four years and he's still paralyzed by indecision. I think he needs clear, simple options and not bunch of edge-case scenarios.
The Palmer is a DI, for routing a high-impedance, unbalanced output into a balanced, low-impedance input. Some DIs (the Palmer is probably one) can be hooked up backwards to match a low-impedance output to a high-impedance input but why would you buy it for that purpose when a simple rat-tail IMT would do the job for less money and be less confusing to set up?
timeistight - Martin got the clear advice right at the top of the page. But the rest of the discussion is interesting I think. Lots of technical info being laid out, as an aside.
For one thing, gmacleod15 mentioning those preamps has made me think about reassessing them. I don't think that's right for Martin BTW, I agree that Martin should get a conventional IMT and a DI box.
I have to mention that every time I hear an example of Martin's playing, I think it's good. So I'm not sure what he's worrying about. But that's musicians for you.
Fil (2nd post in the thread) is right, but he hasn't said enough for us to know if he's right for the the right reasons?
The impedance is a red herring.
I just Googled guitar output voltages. There's lots of guff out there, but everyone seems agreed that it's a significant proportion of 1 Volt.
An Sm57 will ouput millivolts, I'm guessing. So your amp is just not sensitive enough for an SM57. Either a preamp OR an impedance matching transformer WHICH SALIENTLY, BY COINCIDENCE, IS ALSO A VOLTAGE TRANSFORMER will do!
If you've been indecisive for 4 years, I don't blame you - forums like this will always give more answers than there are responders, but in 4 years, maybe you could have saved enough money to buy some good gear? ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 19, 2017 3:43 AM
Andrew, you're definitely on the right track there - it's about the voltage and not the impedance. As I say, Martin's threads have done a service to MBH by getting down to some brass tacks and uncover some nuggety truths.
So, on the subject of voltage. Yes that's right about the guitar voltage. But it's not a 'standard' - so in the guitar world they have prized 'hot pickups' like we have 'hot mics'.
Thing is, and this IS the thing: everyone says it's technically correct to use an IMT with a Lo-Z mic, they are right, sort of, that's what it's designed for. That is if you want to sing into a guitar amp. But when you cup the mic, you end up with a signal voltage that is quite a lot more than a guitar and is often too much for a guitar amp (feedback, can't turn up past 3) Hence all the after-market tube swaps and mic attenuators.
It appears to be that the 'Lo-Z' signal is too weak, and the 'Hi-Z' a bit too strong for amped harp into an unmodified guitar amp. I don't think that's news really. IMO that's why the Lone Wolf pedals and kit are so good - they are designed to be right for the amped harp signal level. SM57, IMT, Harp Break - and everything is in the Goldilocks zone.
But I repeat that I've got good results with a Lo-Z mic, XLR-1/4" cable into a gainy guitar amp. And I know why.
Last Edited by MindTheGap on Sep 19, 2017 6:17 AM
...that's why I say although Tuckster is correct with his description of differential amplifiers, noise rejection, floating signals etc, it's not that that's going to dominate Martin's amped harp sound. It's going to be the signal voltage ending up in his amp, the distortion that produces and whether Martin likes that or not.
@timeistight: Yes, I´m aware that the EV PL35 is low impedance. But that is being taken care of. (And no, I have not been getting info on impedance matters for four years -- but I adsmit to an accretion these last weeks. However, several people seem to think it´s an OK subject; and I don´t think I´m the only one playing a vocal mic (lo-Z) into a guitar amplifier.)
@JoeL: Are you introducing that old hobby horse "It´s all in the player, never in the equipment"? If so, let me assure you I´m aware of the perils of losing yourself in stuff and disregarding the playing -- but there are ways to adjust amps to sounding less obnoxious, I´m sure you´ll agree? If this link works you can hear a clip of Audix into a small solid state amp, and I´d certainly like more warmth/intimacy here. Also, I know how to get it -- change mic! -- but the Audix gives more volume:
Martin See, you sound great. Very musical. I wish I could play like that. Seems like you've got that bit sorted - so totally justified in having multiple threads about these technical details to get a different sound. I like that current sound, but it's subjective and I can also imagine that you think it's a bit harsh.
Last Edited by MindTheGap on Sep 19, 2017 6:49 AM
The problem with a forum like this is, it is very difficult to post circuit diagrams and mathematical things like calculus. People might not understand the math, but circuit diagrams might help people to understand why impedance is irrelevant in this situation. ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 19, 2017 6:51 AM
Martin - call it a hobby horse, if you wish, but it's a proven fact. The players that have warmth and intimacy have that through pretty much any equipment. You've been given a bunch of great advice, but you seem sort of dismissive
I'm not going to critique your playing. If you don't dig your sound, you can work on it or keep chasing equipment until you find what you're looking for. Good luck in your quest.
Martin wrote: "And no, I have not been getting info on impedance matters for four years"
On October 7, 2013 you started a thread titled "Need more bass -- badly". In that thread, dougharps told you
"It isn't that the signal gets weaker, it just is that XLR is for a balanced, low impedance mic, and the 1/4" jack for guitar amps is for a high impedance unbalanced mic. If you don't match the impedance of the mic to the input, you lose signal.
If your mic is high impedance (high-z)then you don't need the transformer unless going to an XLR input, and the XLR is not the right cable to go straight from mic to PA.
If your mic is low impedance, and you use an XLR to 1/4" cable with no transformer, then you lose half the signal."
So, four years was an exaggeration. Three years and forty-nine weeks is more accurate.
Last Edited by timeistight on Sep 19, 2017 7:25 AM
Are you also asserting that you believe that impedance is not at all important in matching a crystal mic or ceramic mic (needing very high impedance to not lose low frequencies) with a lower impedance guitar amp? A similar well documented issue is piezo guitar pickups that sound thin and "quacky" until they encounter a very high input impedance in a preamp or unity output op amp.
There is a reason that Greg Heumann makes different volume controls with different pots for different kinds of mics. There is a reason that LW pedals for 1/4" inputs have high input impedances.
Let's try to avoid over generalizations either way. The discussion can get really technical and confuse many of us, but let's not throw out valid information that works.
Depending on the mic and amp combinations sometimes the exception to the rule is correct. Most of the time our sound benefits from following the general rules. ----------
I agree that great players will sound great through pretty much any equipment. And they may even sound distinctively them - because there are other musical qualities that don't depend on kit.
But is it fair to say that these players will actually sound the same through different kit? Genuine question, not polemic.
One of things that really caught me about amped harp in particular is the wide range of actually different sounds available even under the umbrella of archetype Chicago blues harp. I don't have a wide range of kit, but even I've got first-hand experience of the different sound of different mics and amps.
Take that brilliant Blue Dadi software. It has a feature where you can record a raw signal and Re-Amp it through different virtual amps. It's easy to get radically different sounds.
Last Edited by MindTheGap on Sep 19, 2017 7:44 AM
doug - Re crystal mics. No I'm not asserting that. In that case the impedance issues are very real.
And the general rule is: to get good frequency response and good signal voltage strength, the load impedance needs to be much higher than the source impedance. That's often not the case with crystal and piezo elements. The effect will be to reduce the signal strength overall, and affect the frequency response, as you say.
So, yes there is a general rule and it works in all the situations. The LW pedals have very high input impedance, so they work for all types of mics.
I'm speculating here (so shoot me down in flames if you feel so inclined) but I could believe that the reason people find a beloved crystal mic works really well with one amp, and not with another is because of different input impedances. The good amp puts the signal in sweet spot. I don't have access to enough kit to experiment with this though.
Last Edited by MindTheGap on Sep 19, 2017 7:45 AM
When going from higher to lower impedance, more than half the signal is lost by this voltage divider.
When going from lower to higher impedance, less than half the signal is lost by this voltage divider.
When the two impedances are 1k and 10k the first loses 10/11ths of the signal; the second loses 1/11th of the signal.
But when the impedances are identical you lose precisely 1/2 the signal! You actually want to feed a low impedance device into a high impedance one.
If you have a really high impedance mic, then you have different problems from Martin's.
For mics such as the SM57 the real probem is, when a guitar amp expects a 1V input and you give it a 50mV input, its output will be 1/20 of what it should be (simplifying). The effect of the impedance mismatch from an SM57 is trivial and irrelevant. If an amplifier were intended to output 10V from 1V, i.e. if it had 10x magnification/amplification, it would output 0.5 V from 50mV.
In this situation, the impedance-matching transformer ONLY works by dint of being a voltage transformer. If it multiplied by 20 times, then lost half the signal (as above), the net result would be 10x the signal, which would look like success.
A theoretically perfect operational amplifier has infinite input impedance and zero output impedance. How would you expect to match those?
You wouldn't.
The point of the infinite input impedance is so that there is no voltage division, no matter what the impedance of the input device feeding the op amp. And the point of the zero output impedance is exactly the same, no matter how low the impedance of the thing the op amp is feeding into, e.g. a 2 ohm speaker. ---------- Andrew. -----------------------------------------
Last Edited by Andrew on Sep 19, 2017 8:04 AM
but why would you buy it for that purpose when a simple rat-tail IMT would do the job for less money and be less confusing to set up?
that's a great question ..........
the audix may be cheaper initially but if it is unreliable it is not cheaper in the long run. i own one, let me re-iterate... it is a cheap piece of $^%#.
i also have a radio shack imt. it is like mind the gap says... bent, but it still works.
i have never seen the palmer so i cant comment... but i will.
it appears to be built like a tank.there is a good chance it has a better transformer inside. i would not hesitate to try one. it is not necessary to buy this and another imt. it will do the job at hand.
Just what are you looking for in your ultimate mic? You said you prefer the sound of the Audix and the Beyer. Those are both very clean undistorted mics. You said the Audix lacks intimacy. Could you elaborate on that?
"but why would you buy it forthe audix may be cheaper initially but if it is unreliable it is not cheaper in the long run. i own one, let me re-iterate... it is a cheap piece of $^%#."
So buy the Shure then, or one from Hosa or the Whirlwind one that Greg sells.
"i have never seen the palmer so i cant comment... but i will.
it appears to be built like a tank.there is a good chance it has a better transformer inside. i would not hesitate to try one. it is not necessary to buy this and another imt. it will do the job at hand."
Not if the job at hand is running a low-impedance mic through a high impedance effects chain into a low-impedance mixer input, which is an application Martin asked about in another thread. You'd need two transformers to do that.
