ReedSqueal
66 posts
Jan 30, 2011
8:27 PM
|
Would "Low Z" SM57 behave differently than a bullet mic when plugged into a tube amp? I think I was reading somewhere (on Greg's site?) where a Low Z mic power is essentially cut in half? (I forget under which circumstance though)
I picked up a SM57 from ebay, but haven't received it yet. Just wondering if I need to do anything to play. i.e. impedance matching or whatever.
----------
Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
|
Swezey8
58 posts
Jan 30, 2011
8:46 PM
|
Short answer: the SM57 is lowZ and will need an impedance matching transformer to convert the load to HiZ, which is what the tube amp will need to see for optimum results. Something like this will work:
http://www.guitarcenter.com/Audix-T-50K-Inline-Impedance-Matching-Transformer-103670980-i1128417.gc?source=4WFRWXX&CAWELAID=439938290
Try to stay away from ones without the cable on it (just the connectors) as they often snap off in the input jack.
|
Greg Heumann
1024 posts
Jan 30, 2011
10:23 PM
|
As Swezey says you need to a cable with XLR connectors at both ends and an Impedance matching transformer at the amp end of the cable - all will be well.
The only time a low-Z mic gives you half output is when you connect it to an amp using a cable that was designed for a high impedance mic. That cable has an XLR connector at the mic end and a 1/4" plug at the other. It isn't so much the impedance mismatch that cuts the signal, it is that the wiring for low and high impedance mics is different and this cable doesn't even connect to one of the low impedance mic's signal leads.
----------
/Greg
|
rharley5652
380 posts
Jan 31, 2011
12:45 PM
|
@ReedSqueal,.
In general, a high impedance microphone will have an output level around 20-25 dB greater than a low impedance microphone.
So yes by all means get the Impedance matching transformer ,.be heard over that lead guitar player <> LOL
----------
Simply Unique Kustom Mic's By Rharley
|
Greg Heumann
1026 posts
Jan 31, 2011
5:29 PM
|
"In general, a high impedance microphone will have an output level around 20-25 dB greater than a low impedance microphone. "
This is simply not true.
RHarley - I don't know what low impedance mics you're using but I wonder if you're using an XLR-to-1/4" cable to hook them to your amp. That WILL cause a big output drop because it is wrong. Hi vs low should make no practical difference, and certainly should NOT be anywhere near 20-25dB less than a high-Z mic. The output of a 545, a 533SA vs SB, an Ultimate 57 set up hi-Z compared to stock 57 - are all within a few dB of each other.
----------
/Greg
|
ReedSqueal
68 posts
Jan 31, 2011
5:54 PM
|
@Greg - Aren't all SM57 mic's XLR? But regardless, that's the kind I just picked up. And using a XLR-to-1/4" cable... isn't that the only option?
I have a hard time believing that every Tom, Dick and Harry is going to automatically know that a impedance matching adapter is needed?
Admittedly I fell into the 'Tom, Dick and Harry' category because I just plugged it in and assumed it would work in my lil' ol' Kay 703. But it didn't. Well it didn't have any oomph, that's for sure. First thing I thought was the mic was hosed. Then I remembered reading on your site a long time ago (before I was amplified) about impedance matching - hence why I just brought up the topic.
----------
Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
Last Edited by on Jan 31, 2011 5:55 PM
|
Swezey8
60 posts
Jan 31, 2011
6:37 PM
|
@Reedsqueal-
No, a XLR to 1/4" cable is NOT the only option. What I mentioned (and Greg) was using a standard mic cable, XLR to XLR, as well as an impedance matching transformer (see link I gave above, has and XLR and 1/4" connections but is not the same as a high impedance mic cable you're mentioning.
I'm sure "every Tom, Dick, and Harry" doesn't know about using an imp match trans when using a lowZ mic into a highZ amp input. They'll either find out somethings wrong when they notice they're not getting any output from the setup or they'll search online, etc and found out what they're doing wrong. That's why it's nice to have a forum like this to find out all that info! Grab what we're suggesting and you'll notice the difference immediately.
|
ReedSqueal
70 posts
Jan 31, 2011
6:56 PM
|
@ Swezey8 - makes sense in retrospect ;-)
XLR to XLR just didn't make sense to me though, as in how the how do you plug it into an amp? The link you supplied shows and XLR to 1/4".. but I simply drew some incorrect assumptions.
Thanks for the info and link btw.
----------
Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
|
Greg Heumann
1028 posts
Jan 31, 2011
8:46 PM
|
@ReedSqueal - You might get a lot out of my document "All About Harmonica Microphones, and then some...." It covers this topic. All you really need to know is what Swezey and I have said - use an XLR<-->XLR cable and an impedance matching transformer.
To answer in (probably way too much) detail:
All Stock SM57's are low impedance. All low impedance mics use XLR connectors. SOME high impedance mics use XLR connectors too. The Hohner Blues Blaster, late model JT30's, some Shaker mics, a late model Shure 545 (which can be configured for either high or low.) One of the features of my Ultimate Series conversions for the SM57, 58 and 545 is that I can set them up with a choice of impedance and a choice of connector.
Here's your problem. A cable that is XLR at one end and 1/4" on the other is made for those HIGH impedance mics. It gets its signal plus and minus from Pin 1, and EITHER (but not both) Pin 2 or Pin 3 of the XLR connector. However all low impedance wiring is standard - the signal plus and minus are on pins 2 and 3. Pin 1 is ground and is NOT part of the signal path. The signal is allowed to "float" with respect to ground - although the plus side is roughly half way above ground and the minus side is roughly half way below.
When you use the XLR-to-1/4" cable, you're getting about half of the available signal from your low impedance mic. When you use an XLR-to-XLR cable with an impedance matching transformer, the IMT performs TWO important functions. First, it does match the impedance so the mic and amp are both happy and will perform as specified. Second, the wiring is corrected so that the low impedance signal on pins 2 and 3 coming from the cable ends up coming out on the 1/4" plug's tip and sleeve.
----------
/Greg
|
ReedSqueal
72 posts
Jan 31, 2011
9:04 PM
|
Thanks again - after re-reading everything here... twice.. ok 3 times and reading the all about mic's I get it.
Thanks again!
----------
Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
|
Miles Dewar
676 posts
Feb 01, 2011
12:01 AM
|
Usually a good idea to trust Greg on these things.
|
rharley5652
382 posts
Feb 02, 2011
1:43 PM
|
@ Greg ,..
I said :
So yes by all means get the Impedance matching transformer !!
NO,.I'm not using an XLR-to-1/4" cable to hook them to My amp,..I use a Shure A85F low-to-high impedance transformer on the low Z's<>into a tube amp,.
As for the :
"In general, a high impedance microphone will have an output level around 20-25 dB greater than a low impedance microphone. "
YA gotta take that up with the Shure technician that I spoke to a few yrs ago,..<> .
----------
Simply Unique Kustom Mic's By Rharley
|
Matzen
9 posts
Feb 02, 2011
1:55 PM
|
-A little off topic!!-
The Shure 545SD UNIDYNE® III (newer version Paul Butterfield mic) makes a great harp mic. The microphone is shipped connected for low impedance operation, but is designed to be switched easily to high impedance by simply disconnecting and reconnecting plugs on different sockets! Here's a great link with a lot of info on these mics pertaining to harmonica: http://www.angelfire.com/music/harmonica/shure545.html
The current Shure 545SD UNIDYNE® III comes with the same Mexican R45 element used in the later discontinued models. It's a very good and highly recommended harmonica microphone. Unlike most good bullet mics its available brand new in music shops that stock Shure products. The Mexican made R45 elements are just as good as the original US model, with no difference in tone or performance.
Last Edited by on Feb 02, 2011 1:56 PM
|
REM
35 posts
Feb 02, 2011
3:53 PM
|
This probably won't help you now Reedsqueal , but I would advise people against buying SM57s or SM58s on Ebay. Ebay is filled with counterfeit SM57s & SM58s and it's getting harder and harder to tell if they're real or not by examining them. This isn't to say that all of them on ebay are fake, but a whole lot of them are. You best off buying them from a Shure retailer, like guitar center (and of course Greg Heumann ensure's that his ultimate mics are genuine Shure mics).
Last Edited by on Feb 02, 2011 4:32 PM
|
MN
45 posts
Feb 02, 2011
4:03 PM
|
Have any of you folks tried the ELS Audio ES-57 mic? I've read good things about them and they run less than $40 shipped on eBay.
|
rharley5652
383 posts
Feb 02, 2011
10:12 PM
|
@ MN,..I like how they say :
They were designed to sound just like the standard in the industry, the Shure SM-57.
@ REM ,..yes I agree:
ebay counterfeit SM57s & SM58s and it's getting harder and harder to tell if they're real or not by examining them.
I just worked on one,. a SM57 that was a fake !!
----------
Simply Unique Kustom Mic's By Rharley
|
MN
46 posts
Feb 04, 2011
3:11 AM
|
@rharley5652:
I've read some good reviews of the ELS Audio ES-57 online. Hence the question. I have an SM-57 already and thus am not in the market for either. But for someone who's really on a tight budget, the ELS Audio ES-57 (or their 58 model) MIGHT be worth checking out for use as a harp mic.
For miking an amp, I guess I'm just old school, but I'll stick with my Shure every time.
|
rharley5652
387 posts
Feb 04, 2011
1:34 PM
|
@MN,.
Don't take what I said the wrong way,..There are mics out there designed to sound Just as Good as the big $$ name !
& I agree ,. "someone who's really on a tight budget, the ELS Audio ES-57 (or their 58 model) MIGHT be worth checking out for use as a harp mic."
Listen to the Ol' great harp players ,..hell they played through any mic that was plugged into the amp ,.they didn't care what brand it was !
----------
Simply Unique Kustom Mic's By Rharley
|
hvyj
1226 posts
Feb 04, 2011
1:43 PM
|
I don't like to disagree with Greg, either, but in my experience (which is certainly MUCH more limited than Greg's) i have found that hi-z 545s sound a little bit "hotter" than low-z 545s played through an IMT into the same amp. Certainly not a night and day difference, but audible to my ear.
Personally, I prefer using a lo-z 545 with an IMT because to my ear it sounds a little smoother, and makes it easier to control feedback. But YMMV.
Last Edited by on Feb 04, 2011 1:44 PM
|
Greg Heumann
1035 posts
Feb 04, 2011
8:34 PM
|
@hvjy and rharley - A 545 hi or low is within a one or two dB. Yes, a difference,, but a very small one, not 20-25. As I said - they do vary like that - sometimes hi-Z is higher output, I think I know where the confusion comes from.
The Shure 545 spec says the output is:
L-58.0 dB (1.3 mV)
H -35.0 dB(17.6 mV)
That suggests their difference is 23dB - a HUGE, HUGE difference. "Every increase of 3 dB is a doubling of the sound pressure level (twice as many micropascals). A sound of 23 dB is twice as much energy as a sound of 20 dB. Every increase of 10 dB is a tenfold increase. A sound of 30 dB is ten times as loud as 20 dB, and 100 times as loud as 10 dB." (from http://www.speech-language-development.com/decibel-scale.html - definition of the decibel scale.)
However that spec is a measure of OPEN CIRCUIT VOLTAGE, NOT POWER. It is the nature of high impedance mics to have higher voltage - but lower current. Low impedance mics the reverse. POWER is the product of current times voltage. What matters is the "power level". Inexplicably, the 545 spec does NOT clarify this.
However the spec from an earlier Shure mic, the 533SA (high impedance) and 533SB (low impedance) does clarify it. It starts out the same way, listing "open circuit voltage" level:
H: -55dB
L: -77dB
A similar difference to the 545, 20dB in fact. Like the 545 spec, the words "open circuit voltage" have an asterisk. Unfortunately and inexplicably in the 545 spec, editors eliminated the text the asterisk refers to!!! But the 533 spec asterisk actually DOES point to the clarifying text and it sheds important light: It says that the "power level" of the SA is -55dB and the SB is -56dB. Only 1dB difference. The spec goes further to define how power output is calculated. For the high Z mic it is "0dB = 1 volt per microbar" and for the low Z mic it is "0dB = 1 milliwatt per 10 microbars" - and reaffirms that high-Z output is -55dB and low-Z power is -56dB.
In other words, the "open circuit voltage" spec does not compare apples to apples. You have to use a power level computation to do so - and the Shure mics, including the 545, have very similar power outputs whether set up high or low-Z.
Sorry to get so pedantic, but I suspect this is where the confusion lies. All you have to do is try a 545 in both settings (I certainly have) to know that the difference is nowhere near "20-25dB".
----------
/Greg
Last Edited by on Feb 04, 2011 8:44 PM
|
rharley5652
389 posts
Feb 05, 2011
1:44 AM
|
Yes Greg ,.
also from (from http://www.speech-language-development.com/decibel-scale.html - definition of the decibel scale.)
# 3. Conversational speech is at about 60-70 dB; a whisper is around 20 dB
So we're not talking about a huge difference (20dB) either way,.
certainty not enough to argue about.
So lets say the Shure tech got it wrong,.what he should have told me is high impedance microphones will be a whisper (20dB) louder than a low impedance microphone. LOL
For someone like hvjy that whisper (20dB) may just be audible to his ear from Hi-Z to Low Z.
----------
Simply Unique Kustom Mic's By Rharley
|
MrVerylongusername
1545 posts
Feb 05, 2011
6:03 AM
|
Decibels are a logorithmic scale, not a linear one. When describing sound pressure levels, 20dB is actually around 4 times louder than 0dB
1 dB is the smallest perceptible difference in sound pressure.
The use of decibels in the context described here is NOT however a measure of sound pressure level - how does a microphone output sound?
Last Edited by on Feb 05, 2011 6:33 AM
|
