JTThirty
191 posts
Jan 02, 2013
3:49 PM
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Are there any drawbacks to micing an amp to p.a. with a HiZ Shure 545?
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Ricky B
http://www.bushdogblues.blogspot.com
RIVER BOTTOM BLUES--crime novel for blues fans available at Amazon/B&N and my blog
THE DEVIL'S BLUES--due out soon
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Joe_L
2298 posts
Jan 02, 2013
3:40 PM
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The only thing I can think of is cable length for long runs.
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The Blues Photo Gallery
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5F6H
1469 posts
Jan 02, 2013
4:06 PM
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The pick up pattern will shut right down in hi-Z mode, compared to lo-Z mode. You may have to have the source much closer to the mic diaphragm...may, or may not be an issue? Give it a go.
If it's an old 545 you could carry a hi-z cable and a lo-z wired cable? It only takes a minute or so to swap the solderless terminal on the new 545SD - do it in the comfort of your home, rather than having to crawl around the floor in a bar looking for your dropped grub screw ;-).
Some studios still use 545 for micing amps (they were general industry standard mics in the 60's), though I'd guess they are configured lo-Z for that application.
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Greg Heumann
1920 posts
Jan 02, 2013
8:51 PM
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Mark are you sure about the pick up pattern? The mic performs very similarly high-Z and low-Z. Still - I would use low Z for the better noise rejection, longer cable runs, and use of the PA's proper mic preamp. (My understanding is that the high-Z input on most PA's bypasses the preamp.)
As for the grub screw- all the modern Shure connectors, when you "unscrew" the screw it actually recedes into the connector so the connector can be removed - can't lose the screw.
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/Greg
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MrVerylongusername
2449 posts
Jan 03, 2013
1:37 AM
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The only reason the polar pattern would change is because the mic would be in free air (as it is intended) rather than cupped. Impedance setting makes no difference.
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5F6H
1470 posts
Jan 03, 2013
1:40 AM
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Hi Greg,
I have often sung into hi-z/lo-z mics with a transformer, into a hi-z amp input, you find you have to be right on the mic to get a good signal out, compared to the same mic in lo-z mode plugged into a lo-z amp/PA.
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JTThirty
192 posts
Jan 03, 2013
2:01 PM
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Thanks for the input guys. I can switch the 545 to LoZ. I've been using the 545 with Greg's Bulletizer straight into the p.a. along with a Lone Wolf Harp Break and delay pedal in a trio playing pretty eclectic stuff. It sounds well enough, but I feel like trying out my Kalamazoo with a bit of p.a. assistance. I can switch the 545 to LoZ, but if they prefer the straight to p.a. sound then I'd have to switch it back. The p.a.'s 1/4 inch inputs switch to either line or mic levels.
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Ricky B
http://www.bushdogblues.blogspot.com
RIVER BOTTOM BLUES--crime novel for blues fans available at Amazon/B&N and my blog
THE DEVIL'S BLUES--due out soon
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Greg Heumann
1921 posts
Jan 03, 2013
9:03 PM
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@JT: I would certainly try mic'ing the amp with the high-Z mic, ideally plugged into a DI box that goes to the PA's low-Z input. I think you'll find that very, very close to setting the mic up low-Z and going straight in. Given the reduction in hassle factor, it is certainly worth a try.
@Mark re: "I have often sung into hi-z/lo-z mics with a transformer, into a hi-z amp input, you find you have to be right on the mic to get a good signal out, compared to the same mic in lo-z mode plugged into a lo-z amp/PA."
It is possible the explanation is that most PA's have a fairly high gain mic preamps on their XLR inputs. They do not on the 1/4" inputs. I haven't noticed this phenomenon but then I've spent very little time trying! I ALWAYS sing through a low-Z mic straight in the PA.
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/Greg
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JD Hoskins
394 posts
Jan 03, 2013
9:56 PM
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In the 60's and 70's many PA's. like the original Shure Vocal Masters, Kustom, Sunn, Marshall, Peavy, had only HiZ inputs. I always noticed the same thing Mark describes, and I don't believe it was from lack of gain in the preamps.
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Greg Heumann
1923 posts
Jan 04, 2013
9:06 AM
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The one piece of gear I do NOT have in my shop is a simple PA. I test everything I make/mod through a Kalamazoo (the most beat up, ragged thing you've ever seen, gets turned off and on many times each day, every day - and has been going for many, many years now - with the same tubes!)
I guess I need to get one. I'd like to see this for myself. I trust Mark and JD's opinions.....
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/Greg
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5F6H
1475 posts
Jan 04, 2013
1:51 PM
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MrVLUN I don't recall anyone saying hi/lo-z affected the operation of the capsule, nor changed the pick up pattern. The mic's job is to turn soundwaves into electricity, so I don't see how you can arbitrarily exclude an "electronic" property? If you have some field data I'd be interested to see it & happy to stand corrected.
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tmf714
1420 posts
Jan 04, 2013
2:00 PM
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GENERAL
POLARITY
CERTIFICATION
The Model 545SD is a dual-impedance, unidirectional, dynamic microphone. Shipped connected for low-impedance operation, it features a silent magnetic reed on/off switch.
The Classic Unidyne is a favorite for instrument pickup and recording,and can be used on lecterns for public address systems such as those used in political conventions and legislatures, convention halls, hotels, public auditoriums, stadiums, schools, and churches.
FEATURES
Exceptionally uniform cardioid pattern minimizes feedback in PA applications•
Selectable dual-impedance operation•
Silent magnetic reed on/off switch with lock option•
Cardioid dynamic•
Frequency response: 50 to 15,000 Hz•
CONNECTIONS
When using the microphone with a balanced input, pins 2 and 3 are the audio signal carriers. When using the microphone with an unbalanced input, use a cable wired with pin 2 as the signal carrier and pin 3 connected to the cable shield (ground), such as the Shure C20AHZ high-impedance cable.
The microphone is shipped connected for low impedance operation. To change to high impedance, proceed as follows:
Remove plug element at receptacle end of microphone by turning slotted setscrew in 1. (counterclockwise) and carefully withdrawing plug element from case.
Disconnect 2–terminal impedance selection socket from rear of plug element.2.
Reconnect 2–terminal impedance selection socket in reverse position so that pin 3 of 3. plug element is inserted in socket terminal “H” (White).
Reassemble plug element into microphone and seal setscrew securely by turning out 4. (clockwise).
IMPEDANCE SELECTION
RECEPTACLE END OF MICROPHONE
All cables and microphones should be tested to ensure that they have the same polarity. To test two microphones and/or their cables for proper polarity, connect them to an amplifier and talk or sing into them while holding them three or four inches apart. The sound from the speakers should be the same when talking into either microphone or directly between them. If the sound drops drastically, or if a dead spot is found when talking between the two microphones, either the microphones or their cables have opposite polarity.
To change the polarity of a microphone cable, either use a Shure A15PRS phase reverser or interchange the wires connected to pins 2 and 3 of the three-pin connector at one end of the cable. To change the polarity of a microphone, the microphone cartridge leads must be interchanged. This should be performed by your dealer, the Shure Factory Service Department, or other qualified service personnel.
SPECIFICATIONS
IMPEDANCE SELECTION
Type
Dynamic
Frequency Response
50 to 15,000 Hz
Polar Pattern
Cardioid (unidirectional)-uniform with frequency, symmetrical about axis
lmpedance
Dual. Microphone rating impedance is 150 ohms (250 ohms actual) for connection to microphone inputs rated at 19 to 300 ohms and “High” for connection to high-impedance microphone inputs.Wired for low impedance as supplied. To change impedance, see sections on lmpedance Selection and Connections.
Output Level (at 1,000 Hz)
Open Circuit Voltage*
L-58.0 dB (1.3 mV)
H -35.0 dB(17.6 mV)
*0 dB = 1 volt per Pascal (1 Pa = 94 dB SPL)
Polarity
Positive pressure on diaphragm produces positive voltage on pin 2 (with respect to pin 3).
Switch
Built-in magnetic reed on/off switch with lockplate. To lock switch in the ON position, remove screw on lockplate and turn lockplate 180°. Reassemble and tighten screw.
Cartridge Shock Mount
Internal rubber vibration-isolator
Swivel Adapter
Positive action, adjustable through 90° from vertical to horizontal, permits easy removal for handheld use, suitable for mounting on stand with 5/8”–27 thread
Case
Chrome-plated die casting with ARMO-DUR® grille and stainless steel screen
Net Weight (less cable)
255 grams (9 oz)
SET SCREW
IMPEDANCE SELECTION SOCKET
PLUG ELEMENT
PIN 3
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MrVerylongusername
2453 posts
Jan 04, 2013
2:26 PM
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Mark, you wrote: "The pick up pattern will shut right down in hi-Z mode". Pick-up pattern = polar characteristic. Perhaps you just chose the wrong words?
I'm not arbitrarily excluding an electrical property, I'm saying the difference in perceived sensitivity (which since two people say they hear it sounds like it is there) has to be an electronic one, since the diaphragm will move exactly the same way and the pressure differential will be identical regardless of impedance setting. There would be a pressure differential (and hence a polar pattern) even if the mic wasn't plugged in - polar pattern is purely about the pressure differential and the venting around the diaphragm
Last Edited by on Jan 04, 2013 2:38 PM
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5F6H
1476 posts
Jan 04, 2013
2:54 PM
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Aha! Outwitted by my own hand! Apologies MrVLUN. Yes, poor choice of words, perhaps "sensitivity" or "range" would have been better. I didn't mean to imply that polar characteristic, specifically, changed from cardioid, unidirectional.
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Last Edited by on Jan 04, 2013 2:56 PM
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