Topic: Line Match? Or not?

[skiphunt]

er... um... I don't understand all of this. Can anyone tell me which cable I likely "should" be using for the best results given the 200ohm rating of the Senn ME66 mic and the 20k input of the H2? Looks like there's about 5-6 varieties of cables I can choose from on bhphotovideo. Just wondering which one is the correctly matched cable.

NO cable will work with that.. get a transformer... 1:1 RATIO low impedance to High or get a preamp..



Ps.. And I dont make a preamp that can do what you need it to do so I am not just giving you this advice to "sell you something"

Chris

The Shure LMT cable I have has this printed on it: Wired for 150 Ohm on low Z side. For 600 Ohm exchange Orange and Yellow wires. On the High Z end (pointed toward the miniplug end) it says 3k Ohm.

The HOSA cable I found on bhphotovideo has the following specs:

ine-Matching Transformer, 600ohm Low-Z to 2500ohm Medium-Z.  Matches microphones with XLR connectors to 3.5mm inputs found on personal portable recording devices, camcorders, and computers.


Should I rewire the Shure? Stick with it? Or get this HOSA cable instead?

thx,

Skip

The SHURE is fine the way it is 150:3k is fine... Now. that should work you might find you need more gain you also need an adaptor to go from the output of the Shure to a stereo 3.5 mm jack both the ring and the tip of the jack must be shorted so you get your audio on both left and right..

Chris

it's got a 1/8" mono plug on it. I get audio to both L and R if I select "mono mix" on the H2. However, even with the Mogami XLR to 1/8" stereo mini I had to select "mono mix" to get it to both channels. Doesn't seem let the plug really matters. Or, does it?

[skiphunt]

Just called up a local Pro Audio house.. and told them everything I outlined here, and they said I shouldn't even need a LMT.. and that the plug tip wouldn't matter between mono and TRS. I'm really confused now... I think I'll just take it all to them and let them check it all out and tell me what's best for my setup. I didn't think the question as to which cable and or a LMT was going to be all that complicated. The guy at the Pro Audio shop told me all the LMT is going to do is boost my signal a little, but that I really should be using a standard cable with no transformer.

[Church-Audio]

Just called up a local Pro Audio house.. and told them everything I outlined here, and they said I shouldn't even need a LMT.. and that the plug tip wouldn't matter between mono and TRS. I'm really confused now... I think I'll just take it all to them and let them check it all out and tell me what's best for my setup. I didn't think the question as to which cable and or a LMT was going to be all that complicated. The guy at the Pro Audio shop told me all the LMT is going to do is boost my signal a little, but that I really should be using a standard cable with no transformer.

NO offence but if your not going to listen to us why ask? I am a "pro sound engineer" who has been doing it for 20+ years now so are alot of people on this board.. Your pro audio shop guy sounds like a clown.. His advice is WRONG.. Save your money SAVE YOUR TIME listen to me take your shure adaptor and plug it into the cable you have that goes from your TF to your 3.5 mm stereo plug DO NOT USE A MONO PLUG... use a stereo plug with the tip and the ring shorted you can use the mono setting on your recorder but dont use a mono jack in a stereo input because you are shorting the input to ground on the ring side.. This might not cause any problems but its better to just wire it like I said.. This is not rocket science.
In the end two things are going to happen your going to end up using the Shure adaptor.. Or your going to buy a preamp.. Then you will say dam I should have listened to the guys at Taperssection they actually know what they are talking about when it comes to connecting a microphone to a recorder... But that's just my opinion.. 

Chris

[skiphunt]

Just called up a local Pro Audio house.. and told them everything I outlined here, and they said I shouldn't even need a LMT.. and that the plug tip wouldn't matter between mono and TRS. I'm really confused now... I think I'll just take it all to them and let them check it all out and tell me what's best for my setup. I didn't think the question as to which cable and or a LMT was going to be all that complicated. The guy at the Pro Audio shop told me all the LMT is going to do is boost my signal a little, but that I really should be using a standard cable with no transformer.

NO offence but if your not going to listen to us why ask? I am a "pro sound engineer" who has been doing it for 20+ years now so are alot of people on this board.. Your pro audio shop guy sounds like a clown.. His advice is WRONG.. Save your money SAVE YOUR TIME listen to me take your shure adaptor and plug it into the cable you have that goes from your TF to your 3.5 mm stereo plug DO NOT USE A MONO PLUG... use a stereo plug with the tip and the ring shorted you can use the mono setting on your recorder but dont use a mono jack in a stereo input because you are shorting the input to ground on the ring side.. This might not cause any problems but its better to just wire it like I said.. This is not rocket science.
In the end two things are going to happen your going to end up using the Shure adaptor.. Or your going to buy a preamp.. Then you will say dam I should have listened to the guys at Taperssection they actually know what they are talking about when it comes to connecting a microphone to a recorder... But that's just my opinion.. 

Chris

My Shure LMT has a cable screwed into the end opposite the XLR end. I don't remember where I got the Shure LMT and was just calling to see if they had the same size screw-in cable but with a 3.5mm stereo plug instead.. So... I WAS FREAKIN' taking your advise. The one I have has a mono-plug. Then the guy starts asking me what I'm trying to do and why. I explained what you told me, and he said that was false. So I decided I'd just take it to them and see if they have something that will work. I wasn't diss'in you Sir. Just reporting back what the Pro Audio shop told me.

ps. don't think I don't appreciate your help though. It's just a little frustrating trying to get a simple answer and instead getting a half-dozen conflicting answers... who to believe?

Figured I'd just go to the pro audio shop.. they've got about 5-6 options in stock. The music store I went to only had one. Figured I'd just plugin each option and decide for myself what worked and sounded best. No offense to you though. I'm sure you're very experienced and know what you're talking about.

[skiphunt]

skiphunt, the H2 has four gain settings, according to its manual:  -40, -30, and -20 on the mic input, and -10 on the line input.  Your Senn mic is listed as -26dBV/Pa, which is its output with a 94dBSPL input (measured at the capsule).  Therefore, if you are recording a 94dB source, try the -20 setting (least sensitive).  If you are recording a quiet source, try the -40 setting.  If no setting works on the mic input, try the mic through the transformer into the line input.

At any rate, my money is on the guys at the pro shop being correct, it should work unless your sources are so quiet that you do need gain, in which case the transformer should help, if the H2 is used at the appropriate setting.  This is called "gain staging" and proper gain staging is always critical for a quality recording.

Now, would your signal quality increase with an external preamp?  Possibly, but there is no technical reason why the gear you already have cannot play nicely together.

Recording is a technical discipline, so technical details really can't be avoided . . .

Yes it is the "turns" basically addes resistance.

If you have 10K on the load and attach it to a 20K input you get more voltage on the input than the open circuit load gives you.

A good discustion here: http://sound.westhost.com/impedanc.htm

Scroll down to Impedance Matching

It's interesting when they're talking about why a 600Ohm mic needs a 1.2k-2k input .

ethan, turns add resistance, but turns ratio does not necessarily, and in fact does not usually equal the impedance ratio, except for matching transformers.  This is because it's often desirable to have a larger change in impedance than change in voltage (or is it simply of function of getting the side with higher turns to fit in the core), so the gauge of the wire used to wind one side will be different.

Thus, for a transformer it is turns ratio, and not impedance ratio, that determines gain.

At any rate, I fail to see what your link about mic preamp and power amp input impedance has to do with this, but without a transformer in the chain, there is no "gain" whatsoever, just lesser degrees of signal loss as input impedance of the preamp increases, which is a diminishing effect as input impedance increases.  Thus, for example you might see a 3dB difference between 600 ohms and 1K ohms, but only 1dB between 1K ohms and say 3K ohms, and almost no difference at all as impedance further increases.  The tonal effect of varying input impedances is dependent not only on the source impedance, but also whether the source is resistive or inductive in nature.

Thanks! Yeah, I think I'm putting too much into this cabling issue and not enough into just refining my settings more. Seems like I should probably at least get an adaptor cable with the TRS plug instead of the mono one I'm currently using. Wondering if the erratic "clipping" is really just that mono plug shorting out like Church-Audio warned. And a TRS plug seems to just "fit" better.

Appreciate the explanation and help!

Skip Hunt
Austin, Texas
http://www.skiphuntphotography.com

[Roving Sign]

Well, I'm trying to keep this as portable as possible. The Sennheiser is self-powered, is there such a thing as a small pre that's self powered in-line and small?

also, are you saying that there is NO way I can use a self-powered shotgun mic to get good/natural/warm dialogue recordings using ONLY the pres in the Zoom H2?

The H2 shipped - what - last week?

The H2 has yet to be psyched out by tapers - just not enough of them in use yet - but Im sure there will be more concrete answers in the following weeks...

At this point I would just report your findings to one of the H2 threads...comments will follow...

Probably not too many answers out there yet...

[George2]

The output from the Senn ME66 is very hot. My guess is you are overloading the input.

[skiphunt]

I have a couple more questions. I've tried my Sennheiser ME66 (self-powered) with and without a line-matching transformer. I've also tried a RODE NT2 and NT3. Both self-powered but the RODE NT2 shotgun gives me such a low signal when powered that it's completely unusable. I thought maybe there was something wrong and it wasn't getting power. But I tried it on my friend's HVX200 without camera-supplied phantom power and it worked just fine. Must be some incompatibility with the H2. Strange that my ME 66 works fine though.

I've also tried a little Sony ECM-717. It's a little consumer mic powered by a watch battery. http://reviews.cnet.com/microphones/sony-ecm-717/4507-6469_7-20038201.html?tag=nav

It doesn't seem to matter much if the "plug-in" power is turned on or not. With the H2s plugin power turned on and the Sony turned off.. it's not really supplying the mic with anywhere near enough juice to get a decent signal. If the plugin power doesn't help with a little powered consumer mic.. what the heck is it for? And, even with it self-powered I have to have the H2's gain on HI and the level cranked up to about 125.

I also tried a little Sony ECM-DS70P http://reviews.cnet.com/microphones/sony-ecm-ds70p/4505-6469_7-20648800.html
This mic is not self-powered and I get nothing from it unless I turn on the "plug-in" power. Even still, the signal is pretty weak and I have to have "plugin" power turned on.

I've also noticed that with any and all of these mics so far.. when recording and getting an acceptable level.. if ANYTHING jumps up a bit, I frequently get this sound like the mic has hit some "ceiling"? It just abruptly sort of gives you this jarring sound like you've just thumped the end of the mic. You can get a good recording if you're very careful and the source audio is fairly steady. However, the mics on the H2 seem to be MUCH more forgiving. If I get out of range, it just distorts a little. Never this jarring "thumped" sound. Do you know what's going on? Someone said I might be overloading the preamps.. but doesn't the external jack use the same pres as the onboard mics? If so, why would I ONLY have the problem with external mics?

It's appearing that not just any mic will work well as an external mic with the H2. I'm hoping that someone with access to many more mics dials in the perfect external mics to use, because my results have been all over the place.

Thoughts about what's going on? And or, a suggestion on the best all-around external mic to use with the H2? Best shotgun for dialogue to use with the H2? Best external mic for environmental ambient sounds?

[SparkE!]

The comments I've seen in this thread indicate to me that some people here do not understand transformers and how turns ratio affects voltage gain and how turns ratio and load resistance affects the impedance looking into a transformer.  The following two pictures tell the story: