An Old Friend Revisited

Many years ago, I helped my Rhythm Dawgs band mate Dana Vandiver package up his pedal collection and put together a proper pedal board.  Keep in mind that this is long before options like Pedaltrain or Trailer Trash Pedalboards were available.  No, we laid things out, got a sheet of plywood and started fabricating the whole thing.

  

It's been through some minor changes over the years....a pedal swapped out here and there.  But recently Dana changed his main amp, and the controller for it is much larger than the one currently on the board.  The good news is that the two foot switches on the far left (for Mute and Delay) can come off the board, as their functionality is now available on the new amp controller.  Dana also wanted to add an EQ pedal to use with some of his guitars to even out the high end.

Once we agreed on a signal path, I ordered wire and connectors and got to work.  Step one, strip the existing board down....

I've got to admit, it was a little strange to see it like this after all these years.  A couple of things I should point out...mounted in the top cavity is an MXR Microamp that stays on all the time.  It serves to give a bit of a boost to overcome the inevitable signal loses that are are going to occur.  The silver panel to the top right is a patch panel that gives access to the input/output jacks (located on the right side of the board) and the Microamp.

While I had it open, I gave the board a good cleaning.  There were a lot of "souvenirs" in there...namely leaves, dog hair, and over a dozen various guitar picks.

Since the new amp controller was going to dictate where everything else went, I located it first, and then the rest of the pedals around it basing their locations on what made the best sense for signal flow.  Here's everything dry-fitted in.




 

As is, it would be difficult to access the pedals in the top row without bumping the amp controller.  The pedals in this location previously were on risers, so I made new ones with the appropriate dimensions.  The pedals determined the width.  The height was picked to clear the amp controller, and be tall enough if we wanted to add an isolated output power supply later.  They're just 1/2" BC grade plywood that's glued and nailed. 

Here's one of the pedals mounted up.  I used the bottom plate of the pedal as a template to mark the riser and then drilled clearance holes in two corners.  I replaced those screws with 1" long 6-32 machine screws (which most pedals use) to attach the pedal from the bottom.  The riser will then get mounted to the main board with wood screws through the bottom, so that they can be removed if needed.

I used Mogami 2319 shielded cable to make all of the audio interconnects.  This stuff is just the best...very easy to work with, small diameter, and sounds good.  When working with it, you have to be careful how you strip it...that black covering around the center conductor insulation is conductive (which provides 100% shielding).  If you don't strip it back from the wire, you'll get shorts.  Connectors are Switchcraft 228 right angle, and one Switchcraft 380 short barrel straight connector.

Dana already had a power supply he likes on the board, so we stayed with it.  I had to add another splitter to accommodate the new EQ pedal.  

DC coaxial connectors rely on friction fit, which just sucks in my book.  I used heat shrink over the connections to make sure they stayed connected.

Ten plus years of use had worn the feet on the board down to pretty much just the screws.

So, I put new tread on it.

Here's the completed board.  For those interested, the signal comes in through the MXR Compressor first, then the Microamp.  Then it's the 6-band EQ, Fulltone Full Drive, Wah, MXR Uni-Vibe, and finally the Voodoo Labs Tremolo.  From there, it's back to the amp.




The silver toggle switch in the upper right corner is what I refer to as the "aw $#!+" switch.  It completely bypasses the board, connecting the input directly to the output.  In the event of a power supply or pedal failure, you can take everything out of the signal path and at least finish the set.  The large silver flange on the left is where a boom mic stand gets inserted.

With any luck, this will last Dana another 10 years!  If you would like to see and hear the board in action, come on out to a Rhythm Dawgs or SUIT show.
 

Until next time, keep the meters out of the red!

Ken

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area with The Rhythm Dawgs and Fire Flight. You can reach Ken at itsjustlogistics@gmail.com

Testing 1, 2, 3...Is This Thing On?

I know, I know....when I "wrapped" up this blog back in 2013 I said I would still write from time to time when I came across and interesting repair or other event.  And it's not that I haven't had anything interesting happen or come across the bench...on the contrary, it's been almost non-stop.

In the past several months, I've gotten to work on a couple of really cool old amps...including a late 60's Fender Princeton Reverb that was in immaculate condition (it just had a loose solder joint).  I'll be writing an article about that repair a bit later.  But today, I feel compelled to share an experience from this past weekend.

As most of you know, I've had the pleasure of playing alongside a very talented guitarist and genuine nice guy, Dana Vandiver, in The Rhythm Dawgs for the past 16 years.  About 5 years ago, Dana started up a side project where he got to play his favorite music...blues.  And ever since I upgraded my PA system to a digital console, I've been saying that we should record his band SUIT sometime.  This sometime finally happened on Saturday, July 25th.  And since my system is so tightly integrated, we decided it would be easier for me just to do sound that for that show rather than trying to hook up two different systems that we had never put together before.  Besides, that freed the band up from PA duties and let them concentrate on playing.

The idea of loading in and setting up an outdoor show on an afternoon where the heat index was about 105 wasn't super appealing, but what was appealing was the thought of getting to run sound for what I consider a good band.  You see, I've had my Presonus Studiolive for a couple of years, and never have really had a chance to drive it for another band.

After everything was connected and mic'd, I fired the system up.  Since I've had that system in the venue (Junior's Icehouse & Grill) many times before, I already had a house EQ curve that worked so that saved having to run SMAART analysis.  And while it was tempting to try to adapt one of my other band's settings to this show, I decided to start with a clean slate and zero out the board completely.  That's a little scary...at least it was for me.

Keep in mind, this is a 3 piece band (guitar/bass/drums) with 3 vocals.  But since we're recording I ran some extra sources that normally wouldn't be there (snare bottom, both mic and DI on the bass, and stereo crowd mics).  We wound up using 21 channels that night.  Yep, you read that right.

Before bringing up the channels, I went through and applied my best guesses for high pass filtering on all the channels (100Hz on guitar channels, 180Hz on vocals, 80Hz on snare and toms, 40Hz on kick and bass guitar).  Otherwise, every channel had flat EQ, and no compression or gating.  I also set up groups for the drums and vocals, and did a rough in on the monitors for the guys based on what they told me they liked.

We were ready to start sound check at 5:00PM (we started loading in at 2:30).  I brought the kick drum up, and even though we were using a inexpensive mic (a Shure PG-52) I didn't have to touch it.  It was clear and punched you in the chest, but didn't boom like a Roland 808 drum machine.  We were through a 5 piece kit (9 channels total) in about 10 minutes.  Guitar was about the same (2 very different amps, a Mesa Mark V and a very old Magnatone). 

Bass was equally as quick.  A quick song, and 40 minutes after we started we were done.

During the course of the night, I tweaked a couple of things (a bit of presence peak on the vocals and kick), and added some bus compression across the drums and vocals.  People were coming up during the night wanting to know if the band was performing to backing tracks, because in their words "...it's sounds like a record".  

So....how did this go so easy and so well for a first time working with this band?  Actually, the "secrets" are pretty easy.

Start with a great sound source from a great player

Everyone in this band has good gear and good tone. And major plus, the drummer actually knows how to tune his kit for live performance.  

Drums are traditionally the hardest thing to get right in a PA as they're a purely acoustic instrument.  They have to be tuned and played correctly.  I did a festival gig a couple of years ago where the drum kit was provided for all bands.  We thought we had the kick mic'd up and EQ'd well, but it sounded like crap for the first band.  During change over, we checked everything again and couldn't find anything wrong.  The second band started up, and things sounded great.  The only thing that changed was the drummer.  And while I'm picking on drums...

Drums are 1 instrument, not 5 or 6.

You want to know what drives me crazy as a player and a sound man?  A 1 hour sound check that spends 50 minutes on the kick drum!  Seriously, I seen it dozens and dozens of times over the years.  I'm sorry, but unless you're playing in a death metal or thrash band, the kick drum is not the lead instrument!  And even if you are playing that style of music, I've never heard anyone leave a concert humming the kick drum part.  Just make it work within the context of the drum kit and the band.
 

And before I get off this rant, don't go crazy with gates and expanders trying to isolate each drum.  OK, maybe that's important in an arena setting...but you're reading my stuff so you're not likely playing there...yet;).  In a club, the drums are going to be heard acoustically off the stage (unless you're playing behind a shield).  Don't worry about bleed...it's gonna happen.

Along the above lines, it's 1 band, not several instruments

Everything has to work together.  When the players understand that, it makes a sound man's job so much easier.  Once the show starts, nobody is listening to individual instruments in the mix (except the other musicians that don't have a gig that night).  The way I mix a band live, the vocals are going to sound a little thin on their own, but are clear and understandable when the band is playing.  The vocalist that demands that their voice sound like Pavarotti through the PA is missing two key points...we ain't playing opera music and they can't sing like that.

Likewise, every drum is not going to sound like an explosion.  In case you haven't noticed, they're supposed to be different pitches.  And for the guitarists that insist on cutting all of the mids on their amp...they'll sound great when they're playing alone.  But once they band kicks in, they'll be eaten alive.

Pick the right mic for the job

You don't have to spend $6000 for a pair of studio condenser mics for your drum overheads, but you're going to have to do better than those "7 drum mics for $100" kits (unless you're buying used).  If you're using a mic on your drums that has an aggregate cost of about $14, there is nothing in the world you can do to make that sound good other than throwing it away (and the sound of it going into the trash can is the only good sound it will ever produce).  If you've got the budget then Shure, AKG, or Sennheiser condenser mics are the ultimate for drums.  But if you're of more modest means, the Shure PG series is the best bargain out there.

 

Likewise, there's not excuse not to be mic'ing your guitar amps with SM-57's ($90) or e609's (about $110).  Even the PG-56 on a guitar cab sounds very good.

Finally, build the mix on what's already there

Again, I'm mixing in a club.  I can't "replace" the stage sound with the PA without getting the system so loud that I would drive off the patrons.  My philosophy is to give the sound coming off the stage a bit of a lift to carry it to the back of the room.  Want to know my "secret weapon" for mixing in a room like this?  I delay the main speakers so that they're time aligned with the amps.  It doesn't take much...I believe I used 12mS at this gig.  But it really gets rid of the "smear" that I hear a lot of times in the upper midrange and the bass build up.  

The only thing I really had to fight was the guitarist's vocal mic picking up a lot of his amp when he wasn't singing.  It took me a while to figure out why the guitars were so bright in the PA when I had done some pretty significant EQ cuts, but once I realized it was his mic I added a downward expander to drop the channel level about 10dB when he wasn't singing...that seemed to do the trick.  Next time, I'll try an Audix OM-7 on the vocals to combat that problem.

After listening back to some of the 2-track recordings from the board, I was very happy with what we captured that night.  I'll be distributing these to the band over the next week or so.  From that, they'll pick what we're going to go back to the multi-tracks and mix down.

I had a lot of repairs and a couple of custom engineering projects I've gotten to work on since we last visited.  I'll update you on those in a couple of weeks!

Until then, keep the meters out of the red!

Ken

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com

I'd Like To Thank The Acadamy...

It's hard to believe it, but it's been over a year since I started throwing these (for the most part) weekly tidbits out for general consumption.  I made a commitment to myself to see if was disciplined enough to do it for a year.  Except for those Saturday mornings when I got in at 4:30 from a gig, it's been a pleasure to do this. 

Please know that this exercise has been educational for me as well.  It's forced me to stop and think "how do I actually do (fill in the blank)" as opposed to just going through the motions.  As a result, I've gotten more efficient in the way I do certain things.

And what has amazed me is hearing from people that have absolutely no connection to performing or audio that say they enjoy reading the articles.  For that, I'm extremely grateful.  It's funny, because I wasn't a big fan of writing when I was in school.  But now, I find it quite therapeutic.

So...for now I think I've said everything I've needed or wanted to.  But before I close this out, I did want to share a few things with you.

And The Winner Is...
People ask "What has been your most read article?".  By far, it was Pedals To The Metal from February 23rd, with Part 2 right behind.  After that, the recent rant on power amp companies, Watts The Meaning Of All This would be in third place.

In general, the popular articles tended to be the ones about monitors, personal gear, and rehearsals.

Far & Wide
The most mind blowing part of this year long exercise for me is that this blog has attracted readers from every state, as well as South America, Mexico, Russia, Italy, Denmark, Norway, England, and a host of other places around the globe.  That tells me that crummy clubs, broken gear, and neurotic bandmates are universal!

And Now...
I want to thank everyone for the feedback, advice, and ideas for articles.  I've gotta give props to my wife Barb for understanding why I disappeared into the studio on Saturday mornings after breakfast.  A big thanks to Michael Ingalls for coming up with the title.  And of course, to everyone who has kept up with these morsels of information along the way.

I'm still going to write, albeit on not as much of a schedule now.  If something interesting comes along or a cool piece of gear comes across the bench, I'll share it with you guys.  If I run into a club owner that's figured out a new way to screw a band over, I'll let you know.  Conversely, if I play a venue that really knows how to treat musicians I'll share that as well.

If I had to summarize the last year, and boil it down into a bite-sized piece of advice, I would just say this...

 - Take care of your gear
 - Take care of your bandmates
 - Take care of business

Do that, and everything else will take care of itself.

Thanks for a great year!  And even though I'm not around here weekly now, you can always email questions to me.  If I don't have an answer, I probably know someone who does!

As always, keep the meters out of the red.


Ken

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com

And The Answer Is....

So...how did everyone do on last week's test? 

I know you're waiting with baited breath (or is that coffee breath).  Anyway, here are the answers.

---

1. When does the show start?
   1. On the downbeat of the first song
   2. At the last rehearsal before the gig
   3. At load-in
   4. After everyone has had a shot of Patron or Jack Daniels

Like it or not, you're in the spot light as soon as you start rolling into the venue.


2. What should you do before hooking up to power at a new venue?
   1. Check that the outlets are wired correctly and have a functioning ground
   2. Determine what outlets are on the same circuit
   3. Both a. and b.
   4. Get everyone a shot of Patron or Jack Daniels

Use that handy dandy outlet tester that you ran out and bought last year.  It's cheap insurance against frying a piece of gear...or worse yet, you!


3. How should you "build" your stage setup?
   1. Back to front, top to bottom
   2. Stage Left to Stage Right
   3. From the middle out to the edges
   4. The same way you play Jinga

Don't make any more obstacles than you have to.  Hang your banner and lights from the back wall, run your upstage cross connections, and then work to the front of the stage.


4. You've determined that two normally well behaved pieces of equipment start humming as soon as they are connected together. The cause is most likely:
   1. An power supply failure
   2. A faulty cable
   3. A ground loop
   4. A fruit loop

A power supply failure can cause hum, as can a faulty cable.  But the hum would be there before you connect the gear. 


5. When performing at private parties, the key to a successful gig is:
   1. Remaining patient and flexible
   2. Getting half the money up front
   3. Loading in and out through the kitchen
   4. Doubling up on your Prozac before leaving the house

You will likely be dealing with people that have no idea what's involved in putting a live band's production together.  I will also accept answer D, as it helps with A.


6. The function of a compressor to:
   1. Limit the dynamic range of a signal
   2. Re-equalize a signal
   3. Correct the pitch of a singer
   4. Make up for a crappy pack in the trailer

By reducing the dynamic range of an audio source, it's easier to get it to sit in the mix.


7. When should you use sub-groups?
   1. When you need to control the level of several sources without changing the balance between them
   2. When you need to apply processing or effects to several sources
   3. Both a. and b.
   4. When the main group is late to the gig and you need a replacement

Drum kits, big keyboard rigs, and horn sections are all good candidates for sub-grouping.  Vocals work really well in a sub-group with compression across the bus.


8. What is "Power Alley"?
   1. 20Hz to 50Hz
   2. 200Hz to 500Hz
   3. 2000Hz to 5000Hz
   4. Where most of the crack dealers in Austin hang out

Power Alley is the portion of the audio spectrum where just about every source (except cymbals) has fundamental frequencies.  This is where your mix can get away from you.


9. When your band picks a song to cover, make sure everyone learns:
   1. The same version and key of the song
   2. All of the lyrics so anyone can sing it
   3. English and Spanish versions
   4. The entire Phil Collins catalog

Nothing makes you want to throw things at rehearsal more than to find out you've learned the radio edit version, while the rest of the band picked up on the extended dance remix.


10. Generally speaking, when assembling a pedal board which effect should go last in the signal chain?
    1. Compression
    2. Distortion
    3. Delay
    4. The on/off switch for the fog machine

While there are no hard and fast rules, your time-based effects will have the greatest effect at the end of the pedal signal chain or in the effects loop of your amp.


11. When discussing "American" watts and "British" watts, it's important to remember:
    1. American watts are louder
    2. British watts are louder
    3. It has to do with the differences in line voltage
    4. The person talking about the two terms is a idiot

Power equals volts multiplied by amps. There's no variable for "country of origin" in any of the formulae.


12. When EQ'ing monitors stop when:
    1. All of the sliders are at the top or bottom of their travel
    2. You've moved about one-third of them
    3. The peak detect light comes on
    4. There's blood coming from the lead vocalist's ears

Once you've reached that point, you're really not going to get anymore out of the system.


13. From a reliability and noise stand point, the best way to power a pedal board is:
    1. Batteries
    2. A switching power supply (like a 1-Spot)
    3. A linear power supply (like a Voodoo Labs Power Plus)
    4. A tank of electric eels being aggitated by a trained monkey

Batteries will give you the quietest performance from a pedal. However, they are not the most reliable (and it's easy to forget to change them before a show). The switching supplies are the most efficient, but can be a noise source. The linear supply is the best compromise (but I'd pay money to see that eel power supply).


14. You've just fired up your PA. The drum and instrument mics are working, but none of the vocal mics are coming through. The problem is likely:
    1. The main power amps did not get turned on
    2. The monitors are not connected
    3. The vocal sub-group on the board is muted
    4. President Obama's fault

If the main amps weren't on, you wouldn't hear anything. Not having the monitors up shouldn't affect the mains. Check for a button on the mixer that shouldn't be pushed.


15. The #1 enemy of electronics is:
    1. Humidity
    2. Temperature
    3. Vibration
    4. A 1st semester electronics student with a Radio Shack soldering iron.

For every 18 degrees F you can drop the temperature of a component, you essentially double it's life. Cold can affect some electronic components (mainly electrolytic capacitors), but you've got to get down below -100 F before it's a problem.  Unless you're doing an outdoor gig in Siberia, don't worry about it.


16. When should you learn your parts to a song?
    1. On your own time
    2. During rehearsal so the rest of the band can help you
    3. During sound check
    4. On the way to the gig

Showing up to a rehearsal unprepared is unfair to your band mates. Don't be that guy!


17. When working with a house sound man or hired PA, the most helpful thing you can give them is:
    1. Verbal instructions on how your band is set up
    2. Nothing...they're pros and will figure it out
    3. An up to date stage plot
    4. Weed

A stage plot is a prime example of a picture being worth a whole lot of words.


18. PA speakers should be aimed:
    1. Straight ahead to minimize bleed onto the stage
    2. Toward the main audience area
    3. At the bar
    4. Right at the guy yelling for "Freebird"

You're there to entertain the audience, not the bar staff. Remember, if they can't hear the drink orders, your night is going to go down hill really fast.


19. When booking an extended tour, the first thing you should look at is:
    1. Routing
    2. Accomodations
    3. Getting plenth of merchandise to sell after the shows
    4. Having a "connection" in each city you're playing in

You have to know where you're going before any other plans can be made. The routing will make or break you on a tour.


20. Keep the meters out of:
    1. The green
    2. The red
    3. The black
    4. Your corn hole

Please tell me you got that one right!


---

All right folks...the winner of the iTunes gift card is Murray Jones from right here in Austin!  Congrats Murray.


Next week, random thoughts. 

Until then....see question #20.




Ken







Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com

Open Your Test Booklets

All right gang...you were warned last week.  And here it is, the official "It's Just Logistics" Quiz.  The first person to email the results of the test back and get 'em all right will get an iTunes gift card...a small one, but a gift card none the less.

In the event that nobody gets a perfect score, the gift card will go to the highest score with the earliest time stamp.

Good luck.  And....begin!

---

 

1. When does the show start?
   1. On the downbeat of the first song
   2. At the last rehearsal before the gig
   3. At load-in
   4. After everyone has had a shot of Patron or Jack Daniels


2. What should you do before hooking up to power at a new venue?
   1. Check that the outlets are wired correctly and have a functioning ground
   2. Determine what outlets are on the same circuit
   3. Both a. and b.
   4. Get everyone a shot of Patron or Jack Daniels


3. How should you "build" your stage setup?
   1. Back to front, top to bottom
   2. Stage Left to Stage Right
   3. From the middle out to the edges
   4. The same way you play Jinga


4. You've determined that two normally well behaved pieces of equipment start humming as soon as they are connected together. The cause is most likely:
   1. A power supply failure
   2. A faulty cable
   3. A ground loop
   4. A fruit loop


5. When performing at private parties, the key to a successful gig is:
   1. Remaining patient and flexible
   2. Getting half the money up front
   3. Loading in and out through the kitchen
   4. Doubling up on your Prozac before leaving the house


6. The function of a compressor to:
   1. Limit the dynamic range of a signal
   2. Re-equalize a signal
   3. Correct the pitch of a singer
   4. Make up for a crappy pack in the trailer


7. When should you use sub-groups?
   1. When you need to control the level of several sources without changing the balance between them
   2. When you need to apply processing or effects to several sources
   3. Both a. and b.
   4. When the main group is late to the gig and you need a replacement


8. What is "Power Alley"?
   1. 20Hz to 50Hz
   2. 200Hz to 500Hz
   3. 2000Hz to 5000Hz
   4. Where most of the crack dealers in Austin hang out


9. When your band picks a song to cover, make sure everyone learns:
   1. The same version and key of the song
   2. All of the lyrics so anyone can sing it
   3. English and Spanish versions
   4. The entire Phil Collins catalog


10. Generally speaking, when assembling a pedal board which effect should go last in the signal chain?
    1. Compression
    2. Distortion
    3. Delay
    4. The on/off switch for the fog machine


11. When discussing "American" watts and "British" watts, it's important to remember:
    1. American watts are louder
    2. British watts are louder
    3. It has to do with the differences in line voltage
    4. The person talking about the two terms is a idiot


12. When EQ'ing monitors, stop when:
    1. All of the sliders are at the top or bottom of their travel
    2. You've moved about one-third of the sliders
    3. The peak detect light comes on
    4. There's blood coming from the lead vocalist's ears 


13. From a reliability and noise stand point, the best way to power a pedal board is:
    1. Batteries
    2. A switching power supply (like a 1-Spot)
    3. A linear power supply (like a Voodoo Labs Power Plus)
    4. A tank of electric eels being aggitated by a trained monkey


14. You've just fired up your PA. The drum and instrument mics are working, but none of the vocal mics are coming through. The problem is likely:
    1. The main power amps did not get turned on
    2. The monitors are not connected
    3. The vocal sub-group on the board is muted
    4. President Obama's fault


15. The #1 enemy of electronics is:
    1. Humidity
    2. Temperature
    3. Vibration
    4. A 1st semester electronics student with a Radio Shack soldering iron.


16. When should you learn your parts to a song?
    1. On your own time
    2. During rehearsal so the rest of the band can help you
    3. During sound check
    4. On the way to the gig


17. When working with a house sound man or hired PA, the most helpful thing you can give them is:
    1. Verbal instructions on how your band is set up
    2. Nothing...they're pros and will figure it out
    3. An up to date stage plot
    4. Weed


18. PA speakers should be aimed:
    1. Straight ahead to minimize bleed onto the stage
    2. Toward the main audience area
    3. At the bar
    4. Right at the guy yelling for "Freebird"


19. When booking an extended tour, the first thing you should look at is:
    1. Routing
    2. Accomodations
    3. Getting plenth of merchandise to sell after the shows
    4. Having a "connection" in each city you're playing in


20. Keep the meters out of:
    1. The green
    2. The red
    3. The black
    4. Your corn hole

---

OK...put your pencils down...or however you're doing this.  Don't forget...the first person to get 'em all right and email their answers to itsjustlogistics@gmail.com  gets the glory and the iTunes card.

The answers will be posted next week.

Until then....you know.

Ken

 



Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com

Phantom Of The Microphone

I've never really liked the term "Phantom" power.  It makes it sound like it's not really there, or that it's just a figment of someone's imagination.  But since I don't have a better suggestion (and apparently neither has anyone else), we're stuck with it.

If you're using condenser microphones in your set up, you're going to need phantom power to them.  Condenser mics will not work without some kind of power source.  Period.

Condenser mics aren't the only thing that can take advantage of phantom power.  Some active DI boxes can use it as their power source, as can a few preamps and effects pedals (the Sansamp Tech 21 series being a good example).  So lets start the discussion today with exactly what phantom power is.

Special Delivery
Phantom power is a way to deliver DC power down a balanced audio connection without causing problems for the audio coming back the other way.  The original specification was written to allow 1mA (.001 amps) per connection, but as with everything else electronic, power demands have increased over the years, and now that power budget is 10mA.

Thinking back last week to our discussion of balanced and unbalanced connections, keep in mind that phantom power can only be done through a balanced system.  The positive voltage is applied to pins 2 and 3, and the shield carries the ground return current.  At the mixer (or voltage source end), the DC is blocked using capacitors as a high pass filter (DC is essentially a 0Hz signal, so we can filter that out long before we get to audio frequencies).

Electrically, here's what it looks like:

 

At the microphone end, the transformer that's built in keeps the DC from messing with the output of the preamp (DC can't cross a transformer, only AC / audio can).  At the mixer input side, you see the blocking capacitors I talked about.  Capacitors don't pass DC after they've charged (which only takes a few microseconds in a circuit like this).

 

So now you can see "how" we get the phantom power down to the mic and get the audio signal back.  I suppose you could think of it like a double-decker highway.  The audio is riding down the upper deck, and the DC the lower deck. 

 

Did You Want Medium, Large, or Extra Large?

I was brought up thinking that phantom power was always supposed to be 48 volts DC.  When you're using phantom for condenser mics, that's where they operate best.

 

However, it's a well know fact that most consumer grade electronics don't put out that much...it's typically 15 volts or so.  Why?  Easy...it saves them the cost of putting another power supply in their product (as most audio electronics run off of +/- 15 volts or less).  And in all fairness, you're not going to hear the difference with a mid-grade mic in a live situation.

 

It's interesting to note that the first mic to use phantom power (the Schoeps CMT-20) was built in 1964, and was designed to use 9-12 volts.  It was built for French radio, and that value was picked because that's what was easily available in the studio.

 

It was in 1966 that Neumann Audio of Berlin built a mic with a transistorized preamp for the Norwegian Broadcasting Network.  That mic was designed for the now accepted 48 volts.  Again, why?  Because the emergency lighting in their studios ran off of 48 volts.  Again..it's what they had available.  And you thought there was a bunch of math and egg heads involved in picking these values.

 

There was a 24 volt standard proposed in the 1970's, but it never really caught on.

 

But I Don't Want Any...

So, what happens when you hook a plain old dynamic mic (that doesn't require phantom) up to a cable that is providing it?  Nothing.  Since the same voltage is being applied to both sides of the mic's transformer, there's a net zero potential across it.  In other words, it doesn't need it so it ignores it.

 

Big Bang Theory

Now, it's never a good idea to connect or disconnect an audio cable unless the channel is muted.  But with phantom power on a cable, it's worse.  Even if you're working with something that doesn't use phantom power, connecting or disconnecting the cable with the channel unmuted is going to sound like a .22 caliber weapon going off.  You won't damage the device you're hooking up to, or the mixer.  But, there's a good chance you'll blow a high frequency horn out.  This is why (when the equipment allows it) I only turn phantom power on the channels that need it.  Most digital and higher end consoles allow this.  But for less expensive gear, it's typically all or nothing.

 

You've been warned.

 

No, You Can't Do That

I mentioned earlier that some active DI boxes and preamps can use phantom power instead of their internal batteries.  This is cool (as anytime you can take a battery out of the equation is a good thing in my book).  But, there's one major drawback.  That is, when using phantom power you can not use the ground lift if you need to.  Phantom counts on the ground being there as the return path for the current.  If you have to use the ground lift, you'll have to run the device on batteries.

 

We've been at this for almost a year now, and I've wondered how much of this stuff I've been writing about has stuck with the readers.  So next week...we're having a quiz!  Yeah, you read that right.  It will be multiple choice, and all of the questions come from what we've covered here. 

 

And just to give you a little more motivation, the first person to email me with all of the correct answers....heck, I'll send you an iTunes gift card.  In the event no one aces the test, the highest score with the earliest time stamp wins. 

 

Study up and get some rest.

 

Ken

 

 

 

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com



 

 



Lost My Balance...

There's a long list of buzzwords in audio that people toss around, but really don't understand what they mean.  Two of those terms are "balanced" and "unbalanced".  Now, if you're talking about your band mates...then everyone knows what you mean.  But if you're talking about an audio connection or interface...that's where a lot of people's understanding gets a little murky.  So, this week we'll try to bring some understanding to these terms.  I'll attempt to keep it light on the math and heavy on the practical applications.

First off, lets start with an unbalanced audio connection.  Every time you hook up a guitar to an amp, an iPod to a computer or mixer, or anything else that just uses a 2 conductor cable, you're using an unbalanced connection.  This is what that type of cable looks like:

A balanced connection requires three conductors.  If you're hooking up a professional mic to a mixer (especially if it's going down a long cable), then you're likely using a balanced connection. Here's what that type of wire looks like:

OK, we've identified the physical difference between the two types of cable.  But what's going on here electrically, and why is one better than the other.

Let's look at the unbalanced (also called single-ended) connection first, since it's a little easier to understand.  With unbalanced connections, the shield is performing two functions.  It's serving as the return path for the signal (the "negative" side of the audio if you will), and it's shielding the center conductor (the "positive" side) from external noise.  It does a pretty good job, but if the interference is strong enough, it's going to start bouncing the ground around...and you're going to hear that in the audio.

Here's a very basic premise...the shield is only going to do so much to protect the signal from interference.  Unless you're using wire with a solid outer shield (which would make the cable extremely stiff), then some amount of noise is going to get through.  And the longer the cable, the more chance for garbage to get in.  That's one of the reasons why you rarely see unbalanced connections longer than 30 feet.

OK, so why is a balanced audio connection so much better?  It has to do with the fact that there's a second line of defense against noise that's built into the architecture.  It's a concept called Common Mode Rejection.   No, I'm not talking about when you got turned down for dates back in high school.  This is far more useful and much less painful.

Before we talk about common mode rejection, we're going to have to have to touch on a mathematical concept here (sorry...I've put it off as long as I can).  That concept is Vector Addition.  OK...let that sit for a moment...the sting will go away.

The classic (and simplified) definition of a vector is a ray with magnitude and direction.  Putting that concept into a real world example...a car heading north at 50 MPH could be considered a vector.  You have both magnitude (50 MPH) and direction (north). 

So far so good, but how does vector addition work?  For that example, let's use a tug of war game.  Let's say that there are 4 people on each side of the rope pulling.  Pulling from the left side, it's 4 Marines.  On the right side, it's 4 members of the Austin Botanical Society.  When we say "go" there's force being applied from both directions, but guess which way the rope is going to go.  Yeah, I'm betting the that vector force coming from the Marines side is going to be a little greater.

Now, let's even this up.  We'll send the Botanical Society home and bring in 4 Army Rangers to stand in for them.  And now let's assume it's a dead even match and both teams are pulling with the same force.  Which way will the rope go?  Right, it doesn't move because the 2 forces are cancelling each out.  (Now, in reality I know that one team will probably prevail...but I have friends who are ex-Marine Corp and ex-Army...so I'll just let them talk trash to each other).

Back to the world of electrons.  A balanced audio connection works by running the same signal down 2 wires, but they're running opposite of each other.  If you've heard the term "out of phase"...this is it.

By the way, here's another tech term you can throw around and impress people.  Whenever you have two signals like this that are compliments (opposite) of each other, it's called a Differential Pair.  That's going to turn some heads at your next beer bust.

I know...you're thinking "if those signal cancel out, then how do we hear anything?".  Well, you're right, but this is just to show you what happens to two signals that are out of phase with each other when they're added together.  I'll show you how we recover the signal in a bit.

Now, we've got our two out of phase signals running down the cable.  All of a sudden, noise decides to show up and join the party.  Now, our otherwise pristine signal looks something like this:

I want you to notice something very important here, because it's key to understanding how we're going to get rid of the noise.  While our audio signals are out of phase with each other, the noise is the same (or in phase) on the 2 lines. 

So what do you suppose would happen if we could flip one of those audio signals over so that is was in phase with the other one.  What would happen to the noise? 

Now our two audio signals are in phase with each other, but the noise is now out of phase!  When we add those two signals together...the noise is cancelled out.  And just to throw another tech term out there for you, the specification that describes how well a piece of equipment does this job is called the Common Mode Rejection Ratio, or CMRR.  That's one of those specs where the bigger the number the better.

The "phase flip" and signal addition was done with a transformer in the olden days.  Now, it's typically done with a ....wait for it...differential input amplifier.  Electrically, what's going on looks like this:

Given this significantly improved method of getting rid of noise on audio lines (along with a couple of other electrical characteristics), we're able to run much longer cables without degrading our signal.  How much longer?  If you've got a good pro mic and you're plugging it into a decent mixer, you can typically run up to 2000' feet of cable before you start messing the signal up.  Yeah, you read that right...about 4/10ths of a mile!  This is why you have to used balanced audio connections when you have a console out front to mix the band.  In that application, it's not uncommon to have 120 feet of wire between the mic and mixer.

So, can unbalanced and balanced connections ever mix?  The short answer is yes.  You can unbalance a balanced connection through wiring:

You would use a cable like this if you wanted to plug a balanced microphone into a guitar amp.  You loose the noise cancellation and some signal, but it works.  When you do this, though, the rules for unbalanced wiring apply...especially the length of cable limits.

Going the other way from unbalanced to balanced can't be done through wiring alone.  You're going to have to have some electronics or a transformer.  If you're a bass player or keyboardist, you've like already used a device that performs this function.  You just probably know it by it's common name...a Direct Injection (DI) box.

The transformer does the job of converting the signal from single-ended (unbalanced) to differential (balanced).  It also electrically isolates whatever you're hooking up to prevent ground loops.  And again, this can be done with electronics to...which would make this an active DI box (as opposed to a passive one shown above). 

I want to leave you with one final thought here.  If you happen to have a balanced cable that's had one of the signal conductors fail, you will continue to get a signal through it, because that that point you've got an unbalanced connection.  It's going to be quite a bit lower in level, and likely have more noise on it (since you've lost the ability to cancel it out).  So, if you're setting up your PA and happen to notice that a mic is quieter than you expected, it's probably a good idea to bust out the handy dandy cable tester that I'm sure you have now and check that cable.

This is has been a pretty heavy installment, and I've only covered a small part of theory behind all of this.  If you have additional questions, you're always welcome to email me.

Next week, as long as were talking about these connection schemes we might as well tackle another "mystery subject" to a lot of people, and that's phantom power.

Until then, keep the meters out of the red.

Ken

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at itsjustlogistics@gmail.com