mikolune
125 posts
Apr 26, 2012
4:13 PM
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Following recent threads on using impedance transformers - I am wondering where is the best place to put it: on the mic, or on the amp ?
I understand that a cable connected to a Hi-Z mic is susceptible to noise and therefore should be short, so one is better off with a Low-Z mic connected when using a long cable.
Does that mean that if I have a Low-Z mic, it is better to connect the impedance transformer to the amp and not to the mic if I want to use a long cable ? Reasoning is that if I connect the impedance transformer to the mic, then it is exactly as if I have a Hi-Z mic, and the cable should be short. I had the impression that people actually connected the transformer to the mic.
Any comments on that ?
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MrVerylongusername
2348 posts
Apr 26, 2012
4:40 PM
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The amp end seems the most logical - especially given the design of a lot of IMTs
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atty1chgo
320 posts
Apr 26, 2012
5:59 PM
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Billy Branch uses an impedance matching transformer, because he uses an Electrovoice 635A (Lo-Z) microphone into a Peavey Special 130 solid state amp. I took a look at the way he sets it up, and he has the transformer at the end of his mic cord, plugged straight into his delay pedal and octave pedal, and then runs the line back to his amp. The IMT is not directly connected to the amp.
Last Edited by on Apr 26, 2012 6:00 PM
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mikolune
126 posts
Apr 26, 2012
7:17 PM
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thanks guys - makes all sense! cheers
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isaacullah
1933 posts
Apr 26, 2012
7:34 PM
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Hey, while we have this thread open, anyone got opinions on the different brands of IMT's out there? Are the Shure one really worth $40? What about the Audix T-50K? Is it worth the $25? What about the cheaper $12.95 Audio Technica one? Is it any good? Is it noticeable worse than the more expensive brands? Any other brands out there that are known to be quality?
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Greg Heumann
1593 posts
Apr 26, 2012
7:34 PM
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You CAN connect an IMT at or near the mic. It has the advantage of allowing you a long cable run from mic to whatever. But it can also add weight and length to the handheld portion of your gear - which can be uncomfortable to hold.
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/Greg
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MrVerylongusername
2350 posts
Apr 26, 2012
11:48 PM
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Er... If the imt is on the mic, then the line is hi-z. How does that allow long cable runs? Long cable runs are balanced low-z lines.
Obviously if you use effects the imt goes into the pedal not the amp, but the op don't mention pedals.
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5F6H
1172 posts
Apr 27, 2012
3:24 AM
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@ Isaac "Are the Shure one really worth $40?" well you do get adaptors to allow either male or female 1/4" connection, so you can use an XLR to XLR, or a 1/4" to 1/4" cable. I have noticed a tangible difference with other brands. Not tried the 2 you specifically mention though.
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isaacullah
1935 posts
Apr 27, 2012
10:38 AM
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@5F6H: Thanks for answering! The adaptability of the Shure IMT's is definitely one of the advantages I could see... I was wondering about tone, though, and it's interesting to read that you've heard differences between brands. That's something I wasn't sure about, whether there would be differences in tone. I guess what I wanted to know was if there was a real tonal reason to buy an IMT that costs about as much as the mic I'd be buying it for, or if I would be okay with a cheaper alternative... The cheapest ones I've seen are all at the $10-15 range, and the most expensive ones I've seen are $40-80.
FYI, I'm using a Behringer XM-8500, which is a really great mic considering that it only costs about $20. I A/B'ed it against an SM-58, and IMO, there wasn't a significant difference between the two. If anything, the XM-8500 was a tad bit hotter... But really not much difference at all... I've been using it straight into my Z00M G3, and then from there into a portable PA. It sounds quite good this way, but I'm thinking that I could get a little better tone out of the G3's amp models if I use an IMT (this was suggested to me by Richard Hunter over on his site). But, you can see why I'd be leery of spending $40 on an IMT for a $20 mic! :)
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Saqqara
12 posts
Apr 27, 2012
1:05 PM
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I picked up the HOSA IMT-435 on Amazon for $13.90 shipped. Labelled "200 ohm - 50k ohm Taiwan". Don't trust my noob opinions, but it seems to work well, seems sturdy, big boost in volume, no hum or other noted ill effects (well of course it is more apt to feedback because it is hotter). Lacking a lot of info from harp players on these cheaper choices, I picked it over the Audio Technica because the two reviews on Amazon were somewhat better, but mostly because the impedances were labeled and seemed right for the application. I have not tried any other brand.
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isaacullah
1937 posts
Apr 27, 2012
1:16 PM
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@Saqqara: Thanks! Yes, I'm looking at the ones on Amazon, as that's where I'll be purchasing it from (I've got an amazon rewards credit card, so I get to buy some stuff for free from time to time!). I was also looking at the Hosa, but didn't include it in my list since most of the reviews were about using it to connecting XLR mics to camcorders... All reviews were very positive, and I do like the design better than that of the AudioTechnica one (i.e., with the little pigtail cord to the TRS plug). You have really helped me make up my mind on this: I'll go for the Hosa. Thanks!
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easyreeder
313 posts
Apr 27, 2012
4:18 PM
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@Issac
The Shure's are worth the money. The money goes into a quality transformer, rugged construction, and the switchable male/female connectors. For your application ruggedness might be a consideration.
Shure also offers the A85F, without the switchable connectors, for about half the cost. I've never used that one though.
If you don't hear a difference between the SM58 and the Berrigner mic you might not notice the difference between a the Shure and a less expensive transformer. But when you hear the difference between a high quality transformer and a really bad one you'll understand. The bad ones are really awful. I've been using the Shures in my work for years; they get abused and I've never had to repair one. I've repaired several less expensive units because they just can't take abuse, or they weren't well made.
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Greg Heumann
1594 posts
Apr 27, 2012
5:20 PM
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re: "Er... If the imt is on the mic, then the line is hi-z. How does that allow long cable runs? Long cable runs are balanced low-z lines."
I guess we need to clarify. There are two cases here.
1) High impedance mic into low impedance input - then if the IMT is at the mic you have a low-Z balanced line running to the PA. For some reason I was thinking of this when I wrote the above but it is less common. Also - the IMT in this case is usually called a "DI" box but with a device like the Shure where you can change connector sex, some people might call it an IMT.
2) Low impedance mic into high impedance input (guitar or pedal) - you're correct - then it makes almost no sense to run the IMT at the mic end.
Sorry if I confused things.
I sell a cheap Whirlwind IMT and it holds up perfectly well against the Shure. I used to sell the Audix T-50 which is attractive because of the pigtail between the 1/4" plug and the transformer - but I found it was NOT very good tone wise.
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/Greg
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Saqqara
14 posts
Apr 27, 2012
10:18 PM
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Isaac I think that makes the Whirlwind the one to get.
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hvyj
2363 posts
Apr 28, 2012
10:58 AM
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I'm a long time aficionado of low Z XLR style mics. For the last 25 years or so, I've been using Peavey rat tail style IMTs. They work great, sound great, and have a LIFETIME warranty. If one goes bad after 10 or 15 or 20 years you just bring it back or send it in and they give you a new one. They cost about $30.
Btw, the place to put it is at the end of the XLR mic cord.
Last Edited by on Apr 28, 2012 10:59 AM
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isaacullah
1938 posts
Apr 28, 2012
1:15 PM
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Thanks for the extra input guys! If Greg sells the whirlwind, then it has to be good! I've heard good things about the Peavey too... Unfortunately, I'm stuck with having to buy through Amazon (it's the way their rewards point thing works), so I'll likely still be buying the Hosa. All very good stuff to know though! :)
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isaacullah
1956 posts
May 16, 2012
3:15 PM
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Just a follow-up to this discussion: I ended up getting the Hosa unit from Amazon. So far it seems to work really well. I'm using it with my Behring XM8500. It gives that mic the boost it needs into my Epi Valve Jr head, and sounds really good with the amp models on my G3.
One word of caustion: The Hosa unit has a 1/8" stereo male TRS plug on the end of the "pigtail". This plug has the "hot" signal from the mic routed to both the left and right "rings" on the plug. This means you need to buy a 1/8" to 1/4" adapter that is meant to convert stereo to mono. If you use a mono to mono adapter, the hot lead will short to ground, and you won't get a signal to the amp. Of course, if you are handy with a soldering iron, you can replace the stock stereo 1/8" plug with a standard mono 1/4" plug. Personally, I prefer to use an adapter because it allows me to also use this IMT to plug my mic directly into the sound card of my computer via the "line in" jack (not the "mic in" jack!). This gives me much better recording sound than using the mic jack and no IMT.
Cheers,
~Isaac
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laurent2015
202 posts
May 17, 2012
9:04 AM
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Hi,
I'm using a Roland Cube 20X that's supposed to be rated
1Mohm impedance (?) and notably a Shure sm57 mic that's supposed to rate "actual" 300 ohms, so low impedance.
With that pattern and nothing else it yields a good sound, however not the sound I'd like (Adam's, Digg's, Frank's, Studebaker John's, Magic Dick and a lot of others).
If transforming my mic's impedance, what could actually change in the sounding?
I also use a Superlux mic with a volume control, so, does transforming the impedance here make sense?
Last Edited by on May 17, 2012 9:08 AM
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timeistight
575 posts
May 17, 2012
9:16 AM
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You should use a transformer for the 57, not for the Superlux when going into the high impedance input on your amp.
Last Edited by on May 17, 2012 11:05 AM
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Greg Heumann
1612 posts
May 17, 2012
9:26 AM
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Impedance needs to be "matched" for both systems to work properly. Failure results in reduced output and altered frequency response. This CAN then change the tone but it really isn't the way to go about it.
When you have a high impedance INPUT (the 1/4" jack on your amp or pedal for example) and a low impedance MIC (like the SM57) then you should use an impedance matching transformer.
When you have a low impedance INPUT (the XLR jack on your PA) for example) and a HIGH impedance MIC then you should use an impedance matching transformer.
When both mic and input are low impedance, or when both mic and input are high impedance, then no matching transformer is required.
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/Greg
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laurent2015
203 posts
May 17, 2012
10:40 AM
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Great advices...I never heard about that, except here.
I'll try it in principle, let's say: by curiosity.
Thanks!
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Greg Heumann
1614 posts
May 18, 2012
8:18 AM
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Very important to note that, aside from impedance mismatch, the mic's signal comes out on different pins of the XLR connector depending on whether it is low or high impedance. Low impedance mics need a cable that is XLR at BOTH ends. The impedance matching transformer provides the 1/4" plug. High impedance mics need an XLR-to-1/4" cable. Using this cable to plug a low Z mic into a high-Z input will only deliver half of the mic's output.
Just because you can physically plug both ends of a cable into something doesn't mean it is correct.
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/Greg
Last Edited by on May 18, 2012 8:20 AM
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laurent2015
206 posts
May 18, 2012
10:31 AM
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Well Greg, I think this is an important notice.
XLR means the stuff with 3 pins? that end of the cable goes into my mic.
The other end has a "jack" that I stick in the amp so not the BOTH ends have XLR connection.
Beeing that so, should the sm57 be considered high impedance?
As I said, the sound I get is good as far as I can judge.
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