re: "wired hot" (was: Octave Effects Question)

Date: Thu, 20 May 2004 08:06:15 -0700 (PDT)
From: Jp Pagan <jpl_pagan@xxxxxxxxx>
Subject: re: "wired hot" (was: Octave Effects Question)

hey all,

  both G. and M.N. (who've both been awesomely
informative and supportive all the years i've been on
this list - thanks guys) mentioned getting the Shure
545 (a dream of mine) "wired hot." does that just mean
wired hi-impedance as opposed to lo-impedance, or is
there a further step to "hot"-ness?

  (on a related note: i've noticed before that Tom
Ellis sells at least 2 kinds of 545's - i mean that in
the plural, not in the "545S" sense - one is the
"three pin, the original" and the other is the
"Butterfield Special, four pin". i'm wonderin' what's
the difference in terms of output or sound...)

   thanks all,

Thanks for the kind words JP.

My experience with the 545 is very limited, but after Pete Knapton paid me a
visit and leant me his for a day I got very interested.
There have been several models of the Shure 545 UNIDYNE® III.
The Shure PE54 UNIDYNE® III series for all intents and purposes are the same
microphone in almost every aspect,  have the same R45 dynamic cartridge, the
frequency response charts appear the same to my eye, and the output levels
are comparable.  That gives us a total of 8 models to choose from, the 8th
being the latest Shure 545SD.

IMHO tonally they're a great mic.  Its got a slightly different frequency
response pattern to both the SM57 (which has the R57 dynamic cartridge) and
SM58 (R58 dynamic cartridge) for different reasons (eg. range of response,
frequency response pattern) - but to my ear not all that different in tone
except for one key element - when you wire the earlier 545's high impedance,
the signal is hotter (ie. more dBs) than using an impedance convertor - and
THAT is the big difference with them.
It makes it a very versative mic indeed, and means that you get a lot more
punch and drive from it than any low impedance vocal mic, even with an
impedance convertor.

I've read here the latest Shure 545SD doesn't produce the same desirable
tonal characteristics as the earlier models even when wired hot,  despite
having the same R45 dynamic cartridge.   I don't have enough experience to
pretend I know anything much about this - its difficult to compare apples
with apples when comparing Shure's data sheets among the various models,
since they use different methods of measuring output with the lastest model
compared to the earlier ones.  So, from what I can see Shure have simply
reduced the signal level on the latest 545SD model when wired hot.   Part of
the reason why I believe this is even the modern Shure 520DX has a lower
signal level (and very limited response range!!) to earlier 520 (and
related) models.

All the 545 series and PE54 series have the same R45 dynamic cartridge.  (I
think) they all have the option to be wired low or high impedance.  And from
what I can see, they all have the same frequency response pattern.

Among the lot, there are three methods of wiring them high or low impedance:
* The original Shure 545 (wand) and 545S (mounted, on/off assembly) with 4
pin jack can be used with one of two cables. The way the cables are wired
are how low or high impedance signal is selected.
* The 545SH, PE54, PE54SH are mounted on an on/off assembly
with XLR jack - they require access into the assembly via the on/off switch
and cover plate, inside there is a black plastic impedance selection socket
mounted over two of three pins.
* With all the other models 545 & PE54 which are wands with XLR jack have
various ways of getting internal access to the same black plastic impedance
selection socket mounted over two of three pins.

If you want full detailed instructions for any of these models, and to
compare all the technical details I've written up a lengthy webpage
specifically on this subject quoting details, images of the diagrams,
instructions out of the datasheets AND links to Shure's online technical

What stops me rushing out and paying money for one of these (and I'd like to
have one of the wand models) is I can get a similar distorted tone from my
Bullets (CR, CM, crystal, or ceramic depending on flavour of the moment),
and I can get a warm clean punchy tone from either my SM58 (warmer) or SM57
(compressed, more bass end) - so it would be a luxury to have one, rather
than a critical addition.

Having a Shure 545 set up high impedance would mean one could use the same
mic for playing both clean AND overdriven.
But if I want both setups, I'd prefer to set up two mics seperately so I can
simply switch mics, and therefore rig setups without having to mess around
onstage between songs.

In terms of whats the deal on high and low impedance, and hot and not hot
signals, I'm first to admit I'm still learning the subject - to understand
it properly would mean learning about acoustic electronics.  But impedance
alone isn't the entire story, output levels measured in dB also plays a
part.  I cover impedance and matching impedance, covering the subject
broadly on my website about amplified tone (and fighting feedback)

Its easy to read and write emails about technical gumph like this, its a lot
harder to write and understand more esoteric subjects like building a good
solo, working on tone and learning to play by ear.  :)
- -- G.

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