shure 57 transformer in bo dI

[kepeb]

anyone used one in the BO DI?

 

[kepeb]

no one?
from what i gather the transformer from the 57 is around 5:1 the same ratio as the di specifies.
is it too small?

 

[PRR]

Can we buy another clue?

Who is BO?

What 57 from Shure? The SM-57 microphone?

 

[kepeb]

apologies, yes i accept cheques or postal orders

yes the transformer from the shure sm57 microphone,
I have read over a couple of threads from way back about the mods for this mic and the effects of removing the transformer. i just wondered if i could put it to use if i did.
I'm out of funds for projects till next year so i was scraping the barrel

it looks as tho the transformer may be rolling off some low end in the mike from what i got from the previous discussions but that shouldn't be a problem, the 57 does it and is still used.

it looks like the ratio may be very similar,
i may have got the project name wrong sorry... Bo Hansen?
http://www.hansenaudio.se/techpage#active%20DI-box,%20my%20work%20horse%20from%201975

the diagram from this page

 

[Kingston]

perhaps you should read up on sm57 and its history, and what tremedous r'n'd effort it was. The research put into that mic was extensive, and that is an understatement.

Modifying it in any way will only make it worse. I think may have been reading too much gearslutz bull since you're even asking about it.

 

[zebra50]

I never understood that mod either, the idea that completely removing the transformer makes it better? I can't believe that Shure wouldn't know this and save themselves a few dollars if it were true.

I haven't tried that mod myself, but personally I don't want a SM57 to sound different or 'better'. I do want t it to sound & behave like it should when I grab it.

They're maybe unloved, and take a lot of abuse, but every studio has a handful of these and there's a good reason. They sound OK on most sources, are reliable, and are a 'go to' mic for many engineers when they don't have a fancy mic to hand, or time to experiment.

 

[kepeb]

I have only ever read one page on that site and that was a discussion with one of my favourite producers.

The first i heard of the mod was via TapeOp which arrived in the mail. i can take a picture of the article if you like.

I respect the position the SM57 holds regardless of your, or my opinion of the microphones performance.

I am currently in possession of a redundant back end of an sm57 (the part with the transformer in) which I was idly thinking about uses for.

I have used the search function and read... at length, discussions between more respected members on THIS forum about both removing and modifying the SM57's transformer.

eg.
http://www.groupdiy.com/index.php?topic=14541.0

I am into DIY and I also like to make sure I create little waste. as it will cost as much to replace the front end of this spare part as it would to buy a new one, i was curious about how useful it may become.

 

[kepeb]

guys, this is nothing to do with the use of the extracted transformer in the DI

the subjective opinions over the effect on the old 57 have already all been voiced before.

i am not about to mod a 57, thats up to whoever does it

i am simply asking about the transformer and possible use in the DI

 

[zebra50]

guys, this is nothing to do with the use of the extracted transformer in the DI

the subjective opinions over the effect on the old 57 have already all been voiced before.

That's true enough - if you have one kicking about then try it and let us know how it works. I think you'll probably be the first to try that.

 

[Kingston]

I was trying to find it just now, a great article about sm57 predecessors and development leading to sm57. In the article it was pointed out that it was not originally meant to be a cheap mic. Only the 30-40 years of volume sales have made it so: they no longer have to make up for the ridiculous r'n'd costs. If you were to develop a mic in an equally extensive way today, you would be looking at the price in the order of magnitude higher.

If someone remembers that article, please post a link.

 

[Rossi]

Well, it's a step-up transformer, so you lose about 12 dB sensitivity when you remove the tranny in the SM57. People say it makes the mic sound cleaner with better bass response. That may be true. It's not a super-hifi-tranny, and Oliver Archut acutually makes a SM58/57 replacement that's supposed to sound better. On the other hand, if you want cleaner and more bass, you might as well buy a different mic to begin with, such as a Beyer M201.

The best way to find out if the SM57 tranny works (as step-down) in the Bo Hansen DI is to just try and see if you like the sound. Being that the SM57 tranny is a low-Z step-up tanny (about 12 ohms to 250 ohms), I would expect significant bass loss at higher impedances. So it really depends on the driving impedance; if it is low enough, the SM57 tranny may work okay.

 

[kepeb]

lol,
ok so you think just try it?
if there is a better use for the transformer? or should i be aware of any potential issues i have over looked?

i am still unfamiliar with much in electronics, transformers really stump me.
should i be aware of operating conditions for such a different use of this transformer for a different application?
edit: apologies, writing as you posted.

 

[kepeb]

the SM57 tranny is a low-Z step-up tanny (about 12 ohms to 250 ohms), I would expect significant bass loss at higher impedances. So it really depends on the driving impedance; if it is low enough, the SM57 tranny may work okay.

i see, i was just looking at the similar ratios so i guess this answers the question 250ohm will be way too low for a guitar/bass pickup.

 

[zebra50]

The transformer in the DI is buffered by the active circuit - the guitar pickup doesn't see the transformer directly.

Also, you might want to have a look at this thread for some good teaching about how transformers work...

http://www.groupdiy.com/index.php?topic=41086.msg509909#msg509909

 

[kepeb]

thanks very much.
i'll try and take it in

ok so if there is a buffer for the transformer there is hope for this.
its sad to think people have 'modded' the 57 and just thrown this piece away.

EDIT: yeah... PRR's post on the subject is melting my brain, I better keep reading it over

 

[Bo Hansen]

Kepeb,

Shure SM-57 transformer with a step-up gain of about 12 dB, which could fit in my DI box if it had been designed for 200 ohms to approx. 5 kohms, (use backward)
but the SM-57 transformer is designed for approx. 12 ohms to 200 ohms, and this is totally the wrong area.
(it is also very little to reproduce good bass at high levels)

--Bo

 

[kepeb]

well there i have it, from the man
ta very much

 

[Rossi]

Still, it can't hurt to just try. With its emitter follower output, the driving impedance may actually be low enough for the transformer. Or maybe you'll like the shaved-off low end. Maybe you'll also like the added transformer saturation. Just make sure you wire the transformer correcty for step-down operation.

 

[QUEEF BAG]

i did the mod to the (SM)57...

i can't believe how much "better" it sounds with out the transformer
that transformer adds so much mid range oink it's amazing.

that said, with out the tranny, it is no longer an SM57  and you would
hafta learn what to use it on all over again.

that transformer sounds so bad i wouldn't even put it in my mother-in-law's butt.

but we have learned to use that ugly color... on snare and distorted guitars...hahahaha

 

[Nick Franklin]

That transformer isn't really appropriate (wrong impedance) for a DI box.

However, for future reference there's a tried and tested method of testing transformer suitability that I like to call the 'suck-it-and-see procedure'!