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Repairing a Shure 545?


I recently bought an older Shure 545 (4-pin Amphenol era) on eBay, and while it works, it sounds a bit of the dog with voice: a greatly diminished low end, and reminiscent of talking through a paper towel tube.

Given there's only three parts to the mic: cartridge, transformed and wiring, it seems eminently repairable (by me), but I have no idea what's wrong with it. So I'm looking for pointers, links or URIs of forums that might help me diagnose the trouble with microphone.

So if you could help, I'd be greatly appreciative!

Thanks, Charles


Boswell Wed, 11/30/2016 - 06:02

 It's possible that you have it set for high-impedance output ("H" position) and you are connecting it to a standard low-impedance microphone input (needs "L" position). See figure 4 on

Can you give details of how you have it connected to your pre-amp, specifically, which pin numbers on the microphone are wired to which pins on the pre-amp input?

Charles Turner Wed, 11/30/2016 - 06:24

Thanks so much for your kind responses.

Connections are as follows:

4 2
3 3
1 1

I've doubled checked these quite a few times, so while a mistake is always possible, I'm pretty sure that the above is correct.

I've been testing these microphones with a Focusrite ISA 2, and also directly into my MOTU Hybrid MkIII.

I should say also that with respect to my other 545, which I very much like the sound quality of, it's out of phase. I originally thought it was exactly 180 degrees, but after looking at a stereo recording of both microphones through the Voxengo 979 phase plugin, there remains a lack of correlation in the low frequencies. Adjusting phase with the plugin improves the situation, but it never approaches the correlation of a pair of EV 635a (omnis) in the same stereo configuration.

I've also reversed the polarity of the plus and minus leads as Shure suggested. This fixes the phase issue, but the output of the questionable microphone is then maybe 6-12dB lower than the good one.

I should go back over all this territory with a closer eye now.

Thanks again! Charles

Boswell Wed, 11/30/2016 - 07:20
I'm sorry to say I didn't look carefully enough at the data sheet before talking about the H and L jumper positions. The sheet I found was for the 545D model, the one with the native XLR connector. The original 545 has the 4-pin connector, and the high and low impedance functions are achieved by wiring to different pins rather than by a jumper. That said, it looks as though you have the correct pinning for the low-impedance connection, leaving phase apart.

Assuming the rest of the microphone's internal wiring is correct, it may be that your particular unit does have a mechanical fault, as Marco suggested. I've never tried dismantling a 545, so I don't know how easy or difficult it is to get to the voice coil to give it a detailed optical inspection.

Many years ago I was given a old good-quality dynamic microphone (I forget the make and model) on the basis that I could keep it if I could get it to work and bin it if I couldn't. I was a little more carefree in those days, and wired it to the headphone output of a tape recorder to se if it would work backwards, i.e. produce sound. When it didn't, I took it apart by breaking a glue seal, and found a broken wire. Having fixed the wire and re-assembled it, it did work as a headphone, and I could listen to all my favourite recordings in glorious lo-fi. Needless to say, it also worked as a microphone again. When I told the person who gave it to me the story, he asked for it back, and I haven't seen either him or the microphone since.

Charles Turner Wed, 11/30/2016 - 07:54
Thanks. I intend to run over all this ground again, because it's mostly stuff I've noticed while trying to record with the mic, and not so much a controlled experiment where I'm trying to reproduce or measure what's actually going on.

I took the end of my good 545 (an XLR Unidyne) and found everything swamped in "goo." Others have noted this, but I can't determine whether Shure actually put goo in the mic barrel, or it was some sort of insulation that's liquified over the years.

Anyway, Shure has instructions for taking the cartridge off, and also for dismantling the windscreen. At some point I may attempt all this, and I'll report back with whatever I find.

Best and thanks again, Charles

pcrecord Wed, 11/30/2016 - 08:14
Charles Turner, post: 445265, member: 50149 wrote: Others have noted this, but I can't determine whether Shure actually put goo in the mic barrel, or it was some sort of insulation that's liquified over the years.
I know that SM57 must be boiled to remove what you call goo...
There's a mod for the transformer removal and it's part of the steps.
If your old one has it and this one doesn't it might be that someone tried to fix it or mod it... I'd be sure to validate if it's the right capsule Inside if you're at it. Hope it wasn't replaced with a cheap chinese capsule.. lol

Charles Turner Wed, 11/30/2016 - 18:54
pcrecord, post: 445267, member: 46460 wrote: I know that SM57 must be boiled to remove what you call goo...
There's a mod for the transformer removal and it's part of the steps.

Wow, boiling! I used lighter fluid and Q-Tips and it came off very quickly.

If you have time, could you send me a link to the transformer mod? I searched about on the internet and found some 545/57/58 "take-aparts," but they actually weren't that informative.

Best wishes, Charles

Charles Turner Thu, 12/01/2016 - 04:29
Appreciate the link pcrecord. I see now that taking apart the sm57 is pretty narrowly centered around the transformerless mod. My searches for a more general "take-apart" found very little.

I also see that there's hard glue in the body. When I checked the impedance of my XLR 545, there was a brick red syrup ("goo") in the body, so I guess it had melted? Purpose is to keep the parts from rattling in the body, I suppose, which it does.

A little off topic: is the transformerless mod done mostly to the newer Mexican sm57s? Idea being it fixes many of the complaints you hear about the character of the newer mics?

Thanks all!

dvdhawk Fri, 12/02/2016 - 12:58
Boswell, post: 445397, member: 29034 wrote: Whaddya mean "must have been"?

I'm trying to recall which SexPistols song screams, "I was a little more carefree in those days!!!!"

OK, trying desperately to not derail Mr. Turner's thread:

As far as wiring XLR to the Amphenol, here's a thread from a few years ago that has 2 pinouts for the 545 - neither of which match yours FWIW.

Sometimes mics of a certain age lose some of the luster in their sound simply because the diaphragm gets dry, brittle, torn, gunked up by old deteriorating windscreen foam, etc. All those gaps and vents are by design, and if they're not clear it has a negative effect on the sound and/or pickup pattern. Getting that style of grill/windscreen off for that visual inspection is disturbingly easy. (Be prepared to catch that spring-loaded retaining ring) Getting it back together may try your patience, and possibly your vocabulary of swear words. (*see, spring-loaded retaining ring) Shure still sells a complete (R45) replacement cartridge for the 545, but at around $75, I would consider it prohibitively expensive vs. the cost of a brand new 545 ($95), or SM57 ($99).

The transformerless mod to an SM57, allegedly puts it more in the realm of the SM7b. It trades off one tonal characteristic for another. It may be more a little (or a lot) more articulate, but as pcrecord has said, without the transformer it then requires a significant amount of gain to get a comparable level. (you need a preamp with about 60dB of clean gain to get the most out of an SM7).

How that information applies directly to a 545, I couldn't say. Shure has manufactured other transformerless handhelds along those lines, like the SM78, which if I recall correctly, uses a ultra-lightweight aluminum diaphragm to make it more sensitive and increase the output.

paulears Sat, 12/03/2016 - 02:48
Old microphones come in two categories. Those worth saving and working on and those not! My elderly 545 that I bought second hand in the 70s, managed to connect with a bodge connector, was sitting on the shelf. It sounds truly horrible compared to a 20 year old SM57, and that 57 sounds different to a new 57. Different enough that a quick one-two says ok or not ok. Too many people seem to expect these old mics to sound somehow 'special'. Old ribbons are worse still - very few sound like they should. I have a brand new Grampian DP4 handheld omni sitting on the shelf too - very popular PA mic in the 60s/70s and it is a dreadful mic by today's standards.

Thinking about it, even the counterfeit Shure mics at pennies price sound more contemporary than some of the old ones.

Charles Turner Sat, 12/03/2016 - 04:02
For the record, I got my info for adapting the Amphenol to XLR from Shure's knowledge base:>

So I assume it's authoritative.

I haven't read the entirety of the post you mention, dvdhawk, but one of the combos simply reverses the polarity, which Shure mentions might be necessary when running several microphones at once:

"It is recommended that the polarity of the 545 be checked after the XLR cable is fabricated. If the polarity is reversed when compared to other mics, like the Shure SM57 or Shure SM58, reverse the wiring of XLR pin 2 and XLR pin 3 on the 545 cable."

And FWIW, I agree with paulears comment that the fascination with these old microphones is possessed of quite a bit of mythology and phony connoisseurship. I read a very funny post recently on Gearslutz that pointed out most of the EV RE20s for sale on eBay had spent their long lives inside a kick drum or next to a bass cab, and were worthless really.

paulears Mon, 12/05/2016 - 03:48
Shure's reverse wiring in the 70s was a real pain in the rear - it being the only popular brand here that had the problem, and lots of mixers back then did not have polarity reverse switches. It actually got worse when people started to convert them, but not label them up - so you used a converter cable on an already converted mic!

If you find a polarity reversed mic - swap the wiring IN the mic, if you have a box full of cables, reversed ones are a nightmare to manage. Shure's advice is, for once, rubbish, and trouble!


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