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Who makes the Mic Pre with the best DI?

Who makes the Mic Pre with the best 1/4″ direct sound?

Well before I answer this question let me bend your ear a little bit.

When I first became interested in recording I picked up an old Tascam mixing board.   It had inputs and outputs galore.  At the top was a row of XLRs that read “Mic” and a row of 1/4″ inputs that read “Line.”   I understood the concept of the mic amp and had a vague and incomplete idea of what the line amp was for.   As an instrumentalist I’m primarily a bass player, but I was clueless how I could use this board for recording my bass.   Like all electric bassists and guitarists I was very familiar with a 1/4″ cable.    There was a 1/4″ input on the board just begging me to plug into it, so I gave it a shot.  I threw on a pair of headphones and monitored through the board.  What did I hear?   After cranking the line input gain knob pretty high my Fender Jazz Bass didn’t sound so jazzy anymore.  It sounded dry and boxy with not top end at all.   What the heck?  My microphones sounded pretty good through this board and the tape returns always sounded realistic so why did my bass, so heavenly through an amp, sound so crappy?

I remembered that at my live shows the sound guy always temporarily unplugged my bass and threw a little black box between my guitar and my amp.  Off of this little box, there was a long xlr cable that ran off into the distance.   Sometimes he’d flick a switch on the side of the box and the PA would start or stop buzzing.   I knew that this was a way to interface my bass to the PA system.   Now back in my home studio I thought that I needed one of those boxes.  I asked a friend that had a lot more gear than me and he loaned me a small direct box.  He explained that this box didn’t require any power and there was a transformer inside.   I was instructed to plug my bass into the 1/4″ input and run the outpur xlr into a microphone amp on my console.   There might have been a more technical description of why I needed this thing but for whatever reason it didn’t sink in.  I went back into my studio and did exactly as I was instructed.  You know what?  My bass sound got significantly better.  Still a little boxy but much improved.  I continued to use this device until I wore out my loan period and had to give it back

Now around this time I was starting to do bass session work around town.  I found myself at a studio in San Francisco’s Mission district called The Studio That Time Forgot.  It was owned by a guy named Kevin Ink that wore a little porkpie hat and dressed in thrift store highwater pants and 50’s Florida retiree style short sleeved shirts.    This studio was packed with cool old equipment that I only remember because Kevin was so passionate about it all:  A Neve broadcast board out of a South African BBC station, Lang EQs, a HUGE Ampex MM1000 2″ tape deck with a “Kelvinator” refrigerator badge glued to the side and some mysterious gear by companies with awesome names like Sphere, Electrodyne and Spectra Sonics.   He also had a workbench with an oscilloscope, soldering iron and various other instruments absolutely littered with spare parts.  This heap of equipment would influence me for years to come.

I was a few years off from starting down the audio design road, but had always worked with my hands.  My day job at the time was working for a cool cat by the name of Jeffrey Ruiz building custom furniture out of recycled wood.  We were way ahead of our time on that trip.  I had more fun than I may ever have in my life at that job, but I was also a musician that had caught the studio bug.   Now Kevin had formerly been a tech for a guy by the name of Dan Alexander.   Dan was San Francisco studio legend that went on to start Coast Recorders and made a small fortune importing old microphones and equipment from around the world in the 80’s.   I’m talking about stacks of U47s and Neve modules.   That picture of piled up mics is real!  I mean so much gear that I would would not be surprised if an ELAM 251 had been used as a doorstop.    Dan himself was not a tech so he started hiring young guys to repair equipment and help him assemble his line of racked vintage modules. A few years later I was racking solid state Telefunken modules myself and selling them like hotcakes to friends and on a new online auction site that you may have heard of.   A story for another time.

Kevin had worked for years as one of these indentured techs and had accumulated a fair amount of equipment.    Back in the Mission Kevin plugged me into one of these units.   It was a Telefunken V72 on one of Dan’s branded faceplates with a 1/4″ jack on the front.   There we’re wires dangling from the back but this thing looked super cool.  It had a big silver lever on the front that I just wanted to pull.    I was tracking in the control room right in front of the speakers and this is where I got to hear some serious electric bass sound.   I had made a slight improvement with my passive direct box at my home studio but this old tube unit was incredible.  Full frequency and not boxy at all.

It was at this point that I started to educate myself and here are some things I learned.   Each piece of equipment has a different input and output impedance.  Here’s a good primer since this post is long enough as it is.   In modern studio interfacing based on impedance bridging as opposed to the power transfer ideal of ye olde phone company, we are looking to send a low impedance source into a higher impedance load.  Something in the order of 10x magnitude is a good place to start.   EG.   A microphone (source) has an output impedance of 150 ohms.   The mic input impedance of a Pacifica (load) is 1500 ohms.  1500/150=10.  We’re looking good here.

Now with passive guitar pickups(also a source) there is a much higher impedance due to the  windings.   5000-10000 ohms is not uncommon.   Now going off of the 10x formula the pickup wants to see a load of at least 100,000 ohms but in reality engineers have found that this ratio should be in the order of 100x or more when dealing with passive pickups.   The line input on my Tascam was 10,000 ohms or 10k.  I was running a 5k pickup into a 10k load and losing a ton of high frequency because of this.  The first passive direct box I had probably had an input impedance if about 50k which improved things and the V72 was 500k ohms which improved things even more.

Now you knew I was going to come around to the question of who makes the best DI on a mic pre?  Well we do, of course!

Many mic pres on the market have a 1/4″ input on the front that is only suitable for low impedance sources such as synths, drum machines or active pickups.  When we designed the Pacifica and all of our 500 series mic pre modules we wanted a direct circuit that could hold its own against the best dedicated direct boxes including our own REDDI (which frankly is the best standalone DI for electric bass in the world).  We’re bass players at A-Designs and if it can’t make a P or Jazz sound good then to hell with it.  We added an elegant, discrete circuit that presents a 2 million ohm load to your pickups and runs the signal through the input transformer which adds a touch of musical harmonic distortion.  Thats good distortion.  This full frequency sound via impedance bridging along with subtle distortion is what I liked in that old V72 and what I love in the REDDI and on our mic pres.  The direct sound is so good that you might just find yourself leaving your amp out of the mix.

As Fletcher would say ‘your mileage may vary’ but with A-Designs you’re hitting the highway with a full tank of high octane.

4 Comments Post a comment
  1. Eric Hill #

    Interesting read 🙂

    March 28, 2012
  2. do you recommend hitting a direct box before the Reddi when tracking bass?

    March 28, 2012
  3. @dobianchi The REDDI is a direct box, but of the highest caliber. We recommend plugging your bass straight into the REDDI and then into one of your DAW’s line inputs. If you have a good compressor, you might try that after REDDI’s output but to start you should hear what this box can do all on its’ own. Thanks for your comment!

    March 29, 2012
  4. Thank you for opining up this topic.

    June 7, 2012

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