Show 130 – Microphone Impedance Adjustment and more

This week Ryan experiments with altering impedance between microphone and preamp for tonal changes.
In the Rapid Fire section: Favorite non-standard vocal effect; Favorite cheap outboard gear; Favorite non-audio related studio item.
Joining us for discussion this week is Kim Lajoie; Australian composer and producer.

Download Show #130

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[consultation and assistance to other composers, producers and engineers]
HRS episode 106 with Kim Lajoie interview
Magneto Audio Labs VariOhm – Microphone Impedance Tool
Microphone to Preamp resistor calculator (google doc spreadsheet)
Download full resolution audio examples from the show

12 thoughts on “Show 130 – Microphone Impedance Adjustment and more

  1. Once again great show guy, although you did loose some credibility buy not mentioning Lava lamp as favorite non-audio item.

    Really interesting about the impedance, one question though.
    You mentioned high impedance in clean preamps, do you know if increasing the impedance would help making a preamp cleaner.
    I got an old piece of crap laying around and if increasing the impedance would somehow made it useful, it would be a nice way to spend an afternoon.

  2. I just wanted to point out that you can achieve the very same results as the VariOhm for about 20% of the cost. First, at $289, you are better off spending a couple hundred dollars more and buying something like a Focusrite ISA 1 which gives you 4 of the same impedance settings while also being a top quality, fully functioning pre amp AND DI box (both have separate ins and outputs and can be used simultaneously…) as well as offering phase reversal, a 75hz. roll off, and a whopping 80dbs of gain. The 200,300,and 500 ohm settings on the VariOhm are pretty redundant and it really is unnecessary to have all three as with most mics, there will be little difference between those settings and 500 is all one really needs. I assume they are also using resistors to change the impedance which is how most pres with variable impedance do it. They might be using transformers, but that is doubtful. However, there is an even cheaper and much more simple DIY way to alter impedance. Some time back Recording Magazine had a DIY article on the “Gizmo”, a simple resistor based mod to change the impedance on a Shure SM 57. The mod can actually be made out of a simple adapter so it can be used with a variety of mics. They also give the formulas for precisely matching the correct impedance between any mic and any pre, although it is obvious that such precision is really not necessary, the VariOhm even demonstrating that by its “general” impedance settings. To save space, here is the link.

    The article also goes into much more specific detail about the hows and whys of variable impedance than the Magneto site. Don’t get me wrong, I am not knocking the VariOhm, I’m simply presenting some much more economical choices to achieve the same results. Again, you can make a Gizmo for every impedance setting the VariOhm offers (a total of 6) or even perfectly matched for specific mics/pres for a total of about $50 as opposed to the $289 cost of the VariOhm. At that price, I still say it makes more sense to spend $499 and just buy an ISA 1. I will also add that VariOhm is a little misleading in their promo material as the Gizmo article makes clear that a transformer-less condenser really won’t be affected that much by changing impedance and if nothing else, go to a music store first and try an ISA 1 (or any other pre with variable impedance) with the mics you use because as the Gizmo article points out and I have found by testing a variety of mics with my ISA 1, changing the impedance doesn’t do that much with many mics. At any rate, before purchasing a VariOhm, you owe it to yourself to at least read the Gizmo article to learn more about the entire concept. Then make your own for about 20% of the cost of the VariOhm…..

  3. Great show as always and yes my head is spinning. It would be awesome if you did a video of the mic and cable mods you’ve done! I know i could probably get something similar on YouTube but rather see it done by you guys. Donating now!

  4. Are the impedance settings on the VariOhm fixed with detents?

    I have a ART Digital MPA at home. I know it’s not an elite piece of gear, but I don’t have an elite budget either. Anyway, I just bring it up because it has infinitely variable impedance within the allowed range. The idea being that you can match it to the impedance of whatever mic you are using. But it works the same as you were demonstrating.

  5. Hey, great show again, guys. I have a few variable impedance and the results of sweeping that dial around are always different for different sources. However on my pre73, I always check it, but so far I’ve always gone back to the low-z mode.

    And about the tube driver pedal, I’m not talking about the bk butler design. Those I’ve played with, they’re pretty nice, but the effectrode “tube drive” is a totally different thing. Here is a link with a video:

    Note the three tubes all swappable right on the top of the unit, all six triodes used in series, and the active tone control. It’s not like the tone on that other pedal or like you have on a guitar. Very complex circuit, very simple interface. Watch how he uses it in the video.
    (and then note the price tag!)
    Now to resist the urge to buy a ksm32…. So smooth… So much money I don’t have….

  6. Hi guys, first time commentor, long time listener. Actually about the small room acoustic show, as most of us listening are probably relegated to a spare bedroom or the garage, its a pretty important topic. I took a closet in my studio bedroom, and turned it into an iso/vocal booth. Not exactly knowing what i was doing, i covered every square inch of wall and ceiling with acoustic foam, and carpet on the floor. I also installed a 2 ft by 1 ft double paned window in the door. It looks cool, and it is dead as a coffin in there. Mostly it keeps me from worrying about a car driving down the street, or the ac kicking on. But is it ok for vocal recording? Its a little unnerving hearing your voice so dead, so i usually add some reverb (but don’t print it) Would love to hear a show on DIY iso booths.

    Thanks for cranking out a show every week – love it.

  7. Instead of using a fixed resistor for modding a xlr cable why not use a pot? That way adjustments could be made on the fly. just a thought

  8. Great show guys. Impedance is something I’ve never really messed with but it’s fascinating how much it changed the sound! When using the KSM32 on the cymbal – the higher the impedance level the louder it got! Well in my crappy car stereo each level seemed to add some gain. Around 500 ohms you could REALLY hear the initial crack/attack (insert Ryan’s dirty joke here) of the cymbal. Pretty cool stuff! Great episode and it’s always nice to hear Kim’s opinions in the audio realm. Thanks!

    • If you can find a used cassette tape deck with 1/4″ microphone inputs from the 80’s or early 90’s… preferably cheap and poorly built, you are in the money! The one that I had as a kid was from K-mart. The one that I am using now was from a JC Penny catalog. Just plug in a guitar or output line level signal from your DAW then send it back in from the tape player’s RCA outputs on the back. Two channels of distortion. I got this one for $6 at a second hand store. That is only $3 per channel!

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