balanced line to transmitter

[Detroit47]

I know that this has been beaten to death but here we go. Also before someone says did you check the archives yes I did. I have an Eq and a few other pieces that I would like to use with my assorted studio microphones. The output from my rack gear is balanced line. I am looking for a transformer that will match it to the input of my 32v2 or my Johnson stuff. I'm not looking for broadcast audio I just want to be able to use my studio mics without doing a lot of mods to the transmitters. So I am looking for a matching transformer. That will get me into the mic jack. I have seen all different types and I am overwhelmed with information, Help!!!!!!!!!!
   Thanks John N8QPC

[Opcom]

You may be able to use a 500 Ohm CT - to- 10K Ohm single ended transformer. An attenuation pad is probably going to be needed to keep a match on the line to the load and reduce the power of the line level signal (0dBm?) down to that of the microphone input (-50dBm?). I don't know the levels but the manual should give the voltage necessary at the microphone jack.

Those kind of transformers are pretty common. It may be possible to use a surplus 'plug-in' transformer from a PA mixer. It is not critical. You probably have something like that in the junkbox?

Here are some new parts:
http://www.hammondmfg.com/560.htm
http://www.mcmelectronics.com/product/555-2855
http://www.mcmelectronics.com/product/555-9235
http://www.triadmagnetics.com/catalog_template.php?productCategoryId=48

there are many others, but one of these may do.

[Steve - K4HX]

You can buy line (low Z) to Hi-Z transformers at radio shack and many other places. Get one with an XLR on one end (I'm assume your rack equipment is XLR out) and 1/4" phone on the other. You'll also need to pad (attenuate) the line level so you don't over drive the mic input. These pads can also be purchased or you can build one (as below).

http://www.tkk.fi/Misc/Electronics/circuits/line_to_mic.html

[k4kyv]

Before taking any action, check out "RaneNotes" at the following website:
http://www.rane.com/library.html

They have a wealth of information on balanced vs unbalanced lines, interconnecting balanced and unbalanced inputs and outputs, mixing balanced and unbalanced audio equipment, preventing and dealing with ground loops, rfi problems in audio equipment, Pin 1 problem and much more.

Here is an index of their entire library of RaneNotes by number and subject. Click on the link for an HTML version for the note.  At the bottom of the last page of each note is a link to a PDF version.  I find the PDF version more attractive and easier to read.  
http://www.rane.com/library.html#gpm1_2

I would particularly recommend downloading and printing out the following:

Note 151: http://www.rane.com/pdf/ranenotes/Grounding_&_Shielding_of_Audio_Devices.pdf

Note 110: http://www.rane.com/pdf/ranenotes/Sound_System_Interconnection.pdf

Note 165: http://www.rane.com/pdf/ranenotes/Pin_1_Revisited.pdf

Note 166: Rfi and shielded balanced lines

I am considering downloading and printing the entire library on front/back sheets, and taking the whole thing to some place like Kinko's and having them bind them into a permanent booklet.

Audiophools who browse the snake-oil websites could benefit from this excerpt from Note # 166:

...Yet another reason to avoid most HIGH FUTILITY loudspeaker cables! I never cease to be amazed at how little real science the purveyors of all that pseudo-science actually understand. After one of my rep friends went through the “training” sessions held by the manufacturer of one of the better known of these product lines, he asked them for some data he could show his technically inclined clients to back up their claims. They responded that they had no such data and no gear to measure it, but they would appreciate any data he could provide!

[kg8lb]

 The Radioshack transformers are a bit shy on bandwidth. Peerless or Altec transformers pop up every now and then..pretty good stuff.

[Steve - K4HX]

Shy enough to matter when used with stock Collins or Johnson iron?

[kg8lb]

Shy enough to matter when used with stock Collins or Johnson iron?

Probably. The Peerless transformers got much better reports on my 32V3 as well as the DX100B (The DX100B had a Thordarson 300 Watt CHT mod xfmr at the time )

[W1RKW]

I'm using this going from the mixer to the transmitter. It works 100% with no RF issues.
http://www.mcmelectronics.com/product/555-8485

Then there are these which seem to be more cost effective but I haven't tried them
http://electronics.mcmelectronics.com/?N=&Ntt=balanced+to+unbalanced&x=0&y=0

[Detroit47]

Thanks for all the input guys. As it turns out I have the proper junk in house to do it. I might get a Radio trash one to play with also. Their is a Hamfest Sunday in Toledo so I might find something there. http://www.tmrahamradio.org/Hamfest/2011_TMRA_Toledo_Hamfest_Flyer.pdf
Erin go Bragh
73 John

[WA3VJB]

John before using transformers and/or spending your money at Shady O'Rack (when you don't really need a cellphone anyway, right?), I'd recommend checking for boxes that have dual outputs and offer both balanced and unbalanced in/out.

I bought a ROLLS brand eq/compressor a few years ago that has XLR or 1/4" phone jack inputs, is switchable to accept mic or line level.
On the output, it has the same thing -- XLR or 1/4" for balanced or unbalanced, and a switch for mic or line level.

The output level has a slider next to the EQ sliders to find the best level of drive for the 32V2 I've been using it with.
Have used 421, RE50, RE-27, and a 635A as the mics, and it all works well.

My brother's got the same HR11C with an RE20 into a 32V3 and it also works well and sounds great, directly into the front panel Amphenol connector on the transmitter.

Other boxes are out there with the same capabilities, under $100.

http://www.rolls.com/pdf/M_HR11c.pdf

[kg8lb]

 Shure sold mic mixers for years with bal in to unbal out. eBay is usually loaded with them in the $10-$20 range. Search " microphone mixer Shure".

[WA3VJB]

Shure sold mic mixers for years with bal in to unbal out. eBay is usually loaded with them in the $10-$20 range. Search " microphone mixer Shure".

Yes, I thought about suggesting the M67 and its variants, but you may remember they're very noisy. The hiss from those germanium (?) transistors is really audible.  

They had a field mixer called the FP31 that I used to have, and Shure actually acknowledged the hiss and recommended keeping the master output pot as LOW as possible and using the individual channels at a higher level to minimize the problem.  They were right, but I wasn't pleased at the work-around.

Probably why today all that line is selling for $10-20.

Here are a couple good photos:

http://www.bigdmc.com/m67.htm

[kg8lb]

 I used one along with an Altec 670B ribbon mic for years on the Johnson 500 .Very low tech but workable. Yep, they are a bit noisy.