Making Shure PE54 a Dual Impediance Mic

[buck1110]

Hello,
I have a Shure PE-54 (High Imediance) microphone, and I was wondering if there is a way to make it dual impedance?
Would it be possible to replace the onboard transformer with one like the PE-54D has, with the 2 primaries and 4 secondaries (are they manufactured by Shure or 3rd party)?

Thanks for your input!

 

[MagnetoSound]

If you take it apart, you will most likely find the transformer has the low impedance wires cut short at the bobbin.

If you are lucky there will be just enough left to strip back and solder extensions to (without melting the bobbin and damaging the windings). If not you will either need to replace the transformer, or you can wire the capsule directly to the output connector which will give you around 30-ohms output impedance and reduced level.

 

[Walrus]

My memory is not what it used to be, but I thought the PE54 was just an ordinary 545S with a different label round the grille, in a plastic case with an XLR to unbalanced Jack cable.
As Dan says, just undo the connector insert retaining screw (it's an anticlockwise thread and screws down into the connector) then carefully pull out the insert and see what you find.
The Blue and Red wires may be just tucked back inside, then follow the 545 data sheet for rewiring.

 

[Tubetec]

A few of the semi-pro Shure mics have a three position switch in the handle , they have hi , lo and off in the middle position , the switch lock can be placed up or down leaving only the wanted impedence selection and off avialable to the end user . The PE53 only has the hi-z winding .

 

[GrannyGremlin]

The PE53 only has the hi-z winding .

Confirmed - the PE54 is (officially *) HiZ only (I have one)

More schems from the Unidyne series and how to convert various other models to Hi/Lo Z:

https://www.angelfire.com/music/harmonica/shure545.html#pe54orig

* unofficially, it is possible that they used the same dual secondary transformers, but a quick look inside is inconclusive: the only easy access to the transformer is by unscrewing the capsule (the whole black plastic bit, not just the basket at the end) and then you can only see the primary side. You would need to melt/scrape off the goop/epoxy/whatever it is that holds the trafo in place to check if the LoZ secondary winding exists - it seems doubtful but not impossible (it may have been cheaper to just use the same part vs stocking a whole other part and then just not show it on the official schem so folks would pay more for the higher end models with Hi and Lo Z options). You might be able to get the end cap off the butt end of the barrel (which would afford a view of the secondary side) but I doubt you could do that without gouging the metal a bit so I do not recommend that.

I would not hold out too much hope that a LoZ secondary exists however - your best bet is likely to replace the transformer; don't muck about in there getting the trafo out if you are not prepared to do that - shame to mess with it otherwise.

Replacement options include the OEM part as currently used by Shure (part# 51a303; $10.99):
https://www.avshop.ca/sound-amp-pa-...former-for-shure-sm58-lc-and-sm57-microphones

And the TAB Funkenwork upgrade (T58; $89):
https://www.tab-funkenwerk.org/product/t58/

Hi Z mics are useful though - I bought mine specifically to have a nicer HiZ mic to run into guitar amps and old tube PA heads with HiZ mic inputs for lofi/drity vocals or feeding an echo chamber (hallway or stairwell).

What I do when I really want to use the PE54 into a LoZ preamp is use a barrel style in line Hi to Lo Z adapter. Like the Shure A95U (there are cheaper options from Hosa, Rapco, Audio Technica and generics). You can make a higher end one by using the Neutrick NTE4 transformer and make your own barrel type adapter using their D Shape Adapter series or their modular adapter parts (see pg 13): https://www.neutrik.com/media/10091...ies and Patch Panels PG EN 202202-V22.pdf?v=5

 

[buck1110]

Thanks all for your input. I'll go more in depth below.

If you take it apart, you will most likely find the transformer has the low impedance wires cut short at the bobbin.
If you are lucky there will be just enough left to strip back and solder extensions to (without melting the bobbin and damaging the windings). If not you will either need to replace the transformer, or you can wire the capsule directly to the output connector which will give you around 30-ohms output impedance and reduced level.

Many thanks for the options here. In wiring the capsule directly to the output connector, is impedance that low still usable? Would the reduced level be correctable without noise issues?

My memory is not what it used to be, but I thought the PE54 was just an ordinary 545S with a different label round the grille, in a plastic case with an XLR to unbalanced Jack cable.
As Dan says, just undo the connector insert retaining screw (it's an anticlockwise thread and screws down into the connector) then carefully pull out the insert and see what you find.
The Blue and Red wires may be just tucked back inside, then follow the 545 data sheet for rewiring.

Thanks! I'll check out that wiring before digging more deeply.
I wonder if the PE54 family all used the same transformer, now that it's been mentioned. There were 4 different models: the high pistol grip (PE54), dual pencil (PE54D), low pencil (PE54D-CN), dual pistol grip (PE54SH). Even though the descriptions duplicated here (https://www.angelfire.com/music/harmonica/shure545.html) specify certain models and not others as being convertible through the use of jumpers, I also wonder if that was just a selling point (the leads had been clipped and the transformer covered with epoxy).
That leads me to the next question: 1) the purpose of the epoxy/silicone/mystery substance (was it for potting or acoustic properties or to keep everything in there solid)

and 2) the best way to get the epoxy/silicone out of the tube. I've noticed that some of the older ones (e.g. my old Pat Applied 545-S) seem to have a different colored, whit-ish, type of substance in there. Is it asbestos, or would that have made no sense to use in a microphone application?
I was thinking of gently using a pick (with maybe just a little acetone on a q-tip swab to help break it up).
Even if the transformer is un-convertible as is, it looks like it's possible to try several other options.
Are those replacement transformers of the same quality as the originals (and will sound quality change)?
Thanks again for all of your input.

 

[buck1110]

Thanks for this! I was only familiar with the "On/Off" switches in some of the "pistol grip" models before. Was this maybe in some of the lower priced models (compared to the 545 and PE54) or maybe an option in others?

A few of the semi-pro Shure mics have a three position switch in the handle , they have hi , lo and off in the middle position , the switch lock can be placed up or down leaving only the wanted impedence selection and off avialable to the end user . The PE53 only has the hi-z winding .
View attachment 132577View attachment 132578

 

[buck1110]

Thanks! I agree, regarding the usefulness of Hi-Z mics and their sound. Does the additional cable run to a barrel style inline transformer have an appreciable effect on signal loss or noise? I can't really tell with my ears.
I've used this method for years successfully, too.
Thanks for the parts links, btw.

Confirmed - the PE54 is (officially *) HiZ only (I have one)


* unofficially, it is possible that they used the same dual secondary transformers, but a quick look inside is inconclusive: the only easy access to the transformer is by unscrewing the capsule (the whole black plastic bit, ......

Replacement options include the OEM part as currently used by Shure (part# 51a303; $10.99):
https://www.avshop.ca/sound-amp-pa-...former-for-shure-sm58-lc-and-sm57-microphones

And the TAB Funkenwork upgrade (T58; $89):
https://www.tab-funkenwerk.org/product/t58/

Hi Z mics are useful though - I bought mine specifically to have a nicer HiZ mic to run into guitar amps and old tube PA heads with HiZ mic inputs for lofi/drity vocals or feeding an echo chamber (hallway or stairwell).

 

[GrannyGremlin]

Thanks all for your input. I'll go more in depth below.


Many thanks for the options here. In wiring the capsule directly to the output connector, is impedance that low still usable? Would the reduced level be correctable without noise issues?

Thanks! I'll check out that wiring before digging more deeply.
I wonder if the PE54 family all used the same transformer, now that it's been mentioned. There were 4 different models: the high pistol grip (PE54), dual pencil (PE54D), low pencil (PE54D-CN), dual pistol grip (PE54SH). Even though the descriptions duplicated here (https://www.angelfire.com/music/harmonica/shure545.html) specify certain models and not others as being convertible through the use of jumpers, I also wonder if that was just a selling point (the leads had been clipped and the transformer covered with epoxy).
That leads me to the next question: 1) the purpose of the epoxy/silicone/mystery substance (was it for potting or acoustic properties or to keep everything in there solid)

and 2) the best way to get the epoxy/silicone out of the tube. I've noticed that some of the older ones (e.g. my old Pat Applied 545-S) seem to have a different colored, whit-ish, type of substance in there. Is it asbestos, or would that have made no sense to use in a microphone application?
I was thinking of gently using a pick (with maybe just a little acetone on a q-tip swab to help break it up).
Even if the transformer is un-convertible as is, it looks like it's possible to try several other options.
Are those replacement transformers of the same quality as the originals (and will sound quality change)?
Thanks again for all of your input.

The goop is for mounting only so the Tx does not rattle around in there; it does not completely cover the tx, so it can't be for potting, just sort of to tack it to the inside walls of the barrel.

The current OEM part is a modern version of the original; maybe a numetal core vs iron but generally the same and of the similar quality - litterally what they use in modern 57/8s. The TAB is (allegedly, I haven't tried it myself but do not doubt it) an upgrade and "sounds better." Lots of threads about it online especially at GS if you want the opinions of people who have tried it, vs second hand. There's also threads with at least high level if not step by step instructions on how to remove the old transformer. It's been a while since I read those, but I seem to recall heat to soften the goop up being involved. This was in reference to modern 57s tho; possibly the older Unidynes used a different substance.

Thanks! I agree, regarding the usefulness of Hi-Z mics and their sound. Does the additional cable run to a barrel style inline transformer have an appreciable effect on signal loss or noise? I can't really tell with my ears.
I've used this method for years successfully, too.
Thanks for the parts links, btw.

The main effect of using the adapter is that the signal is now LoZ and you can use cables longer than 10-20 feet without it becoming a noise antenna (place the adapter as close to the mic as possible; shorten the original cable to 6 feet or something for best results; just long enough that the weight of the adapter won't stress the mic's jack because it is resting on the floor.... or shorter still but attatch it to the mic stand for strain releif with a zip tie or velcro strap etc).

In theory the quality of the transformer could have an impact, but it is such a low level signal that I do not think I have ever noticed a difference.... granted I am not sure I ever used such an adapter for micing anything other than vocals or guitars and any effect of cheap tx would likely be noticed in the low end response first (I have a couple $10 cheapies I got at a local surplus store as well as 'nicer' brand name ones). That said, the 60s Gibson Les Paul basses (loZ pickups) came with the Shure A95U adapter for use with 'normal' hiZ amps (the 70s ones, AKA the LP Triumph bass, had that same transformer built into the control cavity on a Hi/Lo switch - I have one of those) and I can tell you that the thing does not lack bass and is clean. The pickups are also much higher output then a mic capsule so if that doesn't saturate the tx I 'm not worried. If you are worried, go the Neutrik route.

 

[Tubetec]

There may be a chance of asbestos and glass fibers in very old wire insulation , its normally ok if its not disturbed , if its perished and you move it it can start to break down to powder .

There might be bits of it in older Shure mics like the 55' , try not to disturb it or bend it as it may crumble .
You can paint it with hot wax and use a hair dryer to seal it to prevent it shedding nasty crap . Heatshrink tubing can be used to patch up damaged areas , if its too far gone replacement is the only option .

I dont think you have to worry about any noxious substances in the PE series ,

A lenght of cable on a hi-z mic will load down the highs due to capacitance , but the presence of a controlled amount of capacitance can give a useful treble lift in conjunction with the transformer/ load resistance . Id try and keep any hi-z mic to less than 10 foot of cable if possible .
Another alternative use a lo-z mic with conventional balanced mic cable , then a few feet from the amp use an inline transformer bal to unbal /low to hi-z , you can adjust the lenght of cable on the high-z end to present the correct capacitive load for the transformer .
See the Beyerdynamic microphone transformer catalog in the document section .

Theres a few models have the dual impedences ,
588sdx is one 565SD also , 515SDX is the one I have .