Seeing Specs Before My Eyes

Last week, we talked about all the ways that the wattage on an amplifier can be grossly overstated and that finding out the true power capabilities can be a game of cat and mouse.  This is especially true of the manufacturers of lower end gear.

This week, I wanted to at least touch on some of the other specifications you will typically see on a power amp.  You don't see these exaggerated near as much...mainly because most folks never get past the wattage spec.  But, they are there, and I thought you might like to know how them impact the way an amp sounds.

First off, let's take a look at the specs our trusty Crown XLS 802.

So, for a live sound application which specs are we really concerned with?  While I can make a case to consider all of 'em, the first 4 are really the important ones.  Let's talk about what they are.

Sensitivity Training
The spec for sensitivity of an amp is actually one of the easiest to understand.  The spec for this amp is 1.25 volts.  What that means is that if you turn the gain controls on the amp all the way up, it will take 1.25 volts at the inputs to drive it to full power.  This is a reasonable spec, as most modern mixers and crossovers can output several times this. 

The trick is that console outputs are almost always spec'd as dBu.  To convert that to voltage requires....ah hell, I'll just give you the answer today.  My Presonus StudioLive can do +24dBu.  That works out to a little over 12 volts...plenty to drive the amp.  (We'll do an article on decibels for non-math majors one of these days).

But decibels are funny critters, being logarithmic.  That means they're kind of like the Richter Scale they use for earthquakes...where a 7 is a whole lot worse than a 6.  If your console can output +18dBu, then that's about 6 volts.  And if it can only do +4dBu...that's right at 1.25 volts...which means you'll have to have it floored to max your amps out.  It also means you're completely out of headroom on your console and you're probably clipping the signal.
And once the signal clips at the console there's nothing you can do to clean it up later. ...you're S.O.L. at that point. 

Freq Out
The frequency response of an amp is the range of frequencies that it can pass.  Almost every amp will have that spec, but 80% of them are incomplete.  A frequency response without a tolerance on it is really useless.  The spec for this amp is 22Hz to 20kHz, but notice the numbers after that...+0 dB, -1 dB.  That means the amp is flat to within 1dB which is incredibly good. 

Most amps are spec'd +/- 3dB which is still perfectly acceptable for live work.  But when you start seeing numbers like +/- 10dB...it's a BS spec.  That means you're going to have to put a lot of EQ in front of that amp to get it to flatten out.  And if there's no tolerance...well...that just means they're hiding something.

Now, how much frequency response do you need for live work?  Unless you're using concert grade subwoofers and doing electronic dance music, you're not going to need to reproduce much of anything below 40Hz.  And going to the other way, most PA systems start rolling off at 12 kHz.

So why do amp manufacturers spec the frequency response outside of this range.  While you may not be able to hear (or a speaker pass) anything about 15kHz, an extended high frequency response can be an indication of how "fast" an amp is.  There's a spec not mentioned about called slew rate, and you'll usually see it on consoles and preamps.  Slew rate can be a scary looking spec, but what it amounts to is "how fast can this amp move on a waveform".  It's usually expressed in volts per microsecond.  An extended high frequency response can mean that the amp has a decent slew rate.  What that that translates into sonically is amp that sounds clear and punchy.  The slew rate along with the damping factor (we'll talk about in a bit) has a large impact on the "sound" of a power amp.

Bring Da' Noise
The signal to noise ratio (frequently abbreviated S/N) gives you an idea how much background noise the amp produces on it's own.  Here again, a bigger number is better.  For this amp, they're saying that the noise is 100dB below the signal.  Putting that into more familiar terms, it means that the noise is 1/100,000th of the signal...pretty darned quiet.  The difference between weighted and unweighted is that the weighted number is filtered and limited to what we can actually hear.  The weighted number is more meaningful in the real world here.  But even the unweighted is still pretty impressive. 

Again, how much do you need?  Keep in mind that your system S/N can not be any better than the worst component in the chain.  So, if you amp is 100dB, but your Behringer console is only 55dB...then that's as good as your system can get.  Personally, I look for 80dB or better unless the client just has no budget and is only going to be playing $#!+ hole clubs.

Distorting The Truth
When most musicians here the term "distortion" they think of the pedal a guitar player steps on before the intro to "Satisfaction".  (OK, bad example...that's a fuzz box). But where I'm going with this is that while distortion is usually desirable to a guitar (and some bass) players, it's not in a PA system.  So this is where a smaller number is better.

Now, how many of you actually know what "distortion" is?  The technical definition for the intellectually curious is any non-linearties introduced into a signal.  For the mere mortals, it's probably easier to explain how it's measured.

To measure distortion in an amp, you input a single tone (1kHZ is the standard, but some folks use 400Hz) and measure the output signal level.  Then, you filter out the original tone at the output and measure the signal level again.  The crap that's left over...that's your distortion.

Again, how much (or little in this case)?  It depends on the application.  If this amp were going into a studio or other critical listening environment, I would want 0.1% or less.  But for live work, I'll generally accept anything at 1% or below.  This amp has 0.5%, so it's fine.

But remember, for the distortion numbers to be meaningful it has to be a rated power.  And this is where you can get tripped up.  The Crown spec above is written to say that distortion will never be worse than half a percent.  But other manufacturers will bound the distortion measurement by doing things like spec'ing it at a lower power or not over the entire frequency bandwidth of the amp.

If you don't see this number on a spec sheet...it's likely because the manufacturer doesn't want you to know that it sucks.

Et All
The other numbers (IMD, Damping, Cross Talk, and Input Impedance) are still important, but unless you're putting a very large system together (I'm talking 10 power amps or more), don't concern yourself too much.  Most folks getting into a system that big are going to hire a geek like me to do it for 'em anyway.  But just for giggles, here's what they are and how the affect what comes out of the speakers.

• IMD - Intermodulation Distortion.  Dang...that hurt.  IMD is one of one of those distortions that is really uncool.  To explain it, you have to have a quick primer on the concept of Intermodulation.  Whenever you mix 2 different frequencies together, you wind up with 4!  Yep...it's magic.  You get the original 2, plus the sum and difference of them.  So..if you mixed 800Hz and 1200Hz, you would also get 400 Hz (1200-800) and 2000Hz (1200+800).  To bad we can't do that with currency.  Anyway, it's an annoying artifact, so the more negative this number is the better.
• Damping Factor - I would tell you how this number is derived, but you would just want to throw something at me.  Let's just go with this...the damping factor is an indicator of how well an amp can physically control a speaker.  Think about what's happening with a speaker...it's travelling one direction and then all of a sudden has to go the opposite way.  If the amp doesn't have enough control to do this, then the first thing you notice is that the low end is muddy and undefined.  The Damping Factor (sometimes written as DF) is one of those "bigger is better" numbers.  There are a lot of other things that affect the system Damping Factor (when you add in the speaker and the wire that hooks it up).  If you see an amp with 200 or better, you're in good shape.  Don't look for this spec on a budget amp...it would reek if they printed it.
• Crosstalk - This one is actually pretty easy to understand.  On a stereo (or multi-channel amp), the crosstalk is a measure of how much of the signal on one channel gets into another one.  Again, the more negative the number the better.  I only pay attention to this spec if the amp is going into a critical listening environment (like a studio).  But live...all the noise coming off the stage is going to mask the minor amount of crosstalk in the PA system.  As long as it's at least -40dB I'm not gonna sweat it for a PA.
• Input Impedance - This is almost useless to spec now unless you plan on hooking up 10 amps in parallel.  Back in the 60's when stuff had real transformers in it for the audio, this mattered.  Now...no so much.  It's just another big number to confuse the average user. 

I realize the last couple of weeks have been really tech-heavy.  Those of you who got through this...kudos.  Regardless of how much of this sank in, I hope this helps those of you buying equipment in the future.  Again, I hate seeing people get ripped off or wind up with less than they thought they were getting.

Next week...I promise no (OK...very, very little) math.  We'll talk about working with sound and lighting companies.  I recently played a show where we hired in the production (and man oh man was it nice to not have to pack a PA at the end of the night).  A lot of what we'll discuss also applies to playing on house systems at a club. 

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

Watts The Meaning Of All This

I'm going to let you in on a little secret about most consumer grade electronics manufacturers. They're counting on most people having absolutely no idea what all of those numbers on a specification sheet mean. They're banking on the fact that most people believe a bigger number is a better number.

Now before you beat yourself up over this, just keep in mind that unless you've got an electronics background and understand how specifications are derived then terms like S/N ratio and Total Harmonic Distortion are just buzzwords.

Furthermore, consumer grade audio manufacturers are really bending the rules nowadays...all in the quest of that all mighty big number. The pro grade guys...not so much. Because the guys that are ready to spend a few thousand dollars on a power amp can spot a B.S. spec in a split second.

So for the next couple of weeks, I'd like to impart a little bit of this inside information to you. We'll talk about what certain specifications are, whether a bigger number is actually better (not always), and how a spec affects how a piece of gear sounds. We'll also talk about the ways that manufacturers "fudge" the numbers...especially wattage.

I had originally planned to cover all of the major specs of a power amp in one article, but after I started writing this I realized that it would wind up being a very long post.  So we're going to split it up.  This week, we'll talk about wattage and power ratings.  Next week, the other specs.

Which Watt?
The output power of an amp is the most manipulated, massaged, and maladjusted spec on a power amp.  After all, that's the first thing people look at.   "Ooooo....2000 watts for just $100...I'll take it".  Yeah, you'll take it all right...but I'm not going to say where you're going to take it.

First, let me clear the air here. A watt is a watt...period. There are no "tube" watts, "solid state" watts, "British" watts, or "American" watts. Anyone who uses these terms falls under the category of "repeats whatever they read on bathroom walls". The formulae for calculating power does not contain a variable for any of these terms (but maybe there should be an "moron" variable). You hear these terms used with guitar amps mostly, but be aware they're out there and they're bunk!

There are several variations of the power formulae, depending on the variables that you know, but at the end of the day it boils down to this:

Power (watts) = Volts * Amps

 

 

Like I said, there are variations of that if you know the load that the amp is operating into.  The most frequently used is:

 

 

Power (watts) = Voltage Squared / Resistance (ohms)

 

 

You'll see that one written as P= E^2/R, and we'll be using that one later.

So with that said, lets look at a good set of wattage numbers, and then some not so good.

In With The Good
I consider Crown and QSC to be amoung the best amp manufacturers out there.  You'll see their amps on a lot of pro touring rigs, and the care they put into those high end products are reflected in their consumer grade stuff.  Since we've been talking about the Crown XLS 802 for the last couple of weeks, we'll give 'em a little more free advertising.

These are the average power numbers and are very conservative.  Most amp manufacturers use RMS (root-mean-square) power (which would result in a slightly higher number). Either measurement is a good indicator of what the amp can pump out all day long without breaking too much of a sweat.  Crown specs the frequency, the distortion level, and the loads they test into.  If it looks simple, it's because it is.  These are honest numbers without any trickery involved.

Taking A Peek At Peak To Peak
Prior to the mid 70's, amp manufacturers had no guidelines on how to spec power.  So how did they do it?  Easy, by using methods that would make for the biggest numbers! So you saw wattage ratings expressed in either Peak Power, or the notorious Peak To Peak Power.

So what are these numbers?  This is definitely one of those cases where a picture is worth a thousand algebra equations, so let's look at a sine wave:

The point at which the waveform crests and reaches it's maximum (or minimum) value is the peak.  Peak to Peak is 2 times that.

So lets say that I'm testing an amp into a 8 ohm load (typical for a loudspeaker), and I measure the peak value at 28.28 volts (there's a reason for that weird number).  OK, so how much power is that?  If you plug in the numbers you'll see:

 

(28.28 * 28.28) / 8

 

800 / 8

 

100 watts

 

 

So, the peak power of this amp is 100 watts.  Any guesses as to the Peak to Peak power?  Anyone?  Yep, 200 watts.  Sound pretty impressive, doesn't it.  But there's a slight problem with this number.

 

 

Not So Peak Performance

The problem with the Peak power numbers is that for most amps they're not sustainable.  What I mean by that is they can produce that power for a very short period of time (a few hundredths of a second).  If you tried to produce that continuously, you would burn the amp out pretty quickly. 

 

Looking at the sine wave above...you can see that the amp actually spends very little time (relative to the rest of the waveform) at the peak value. 

 

At some point in the mid 70's, the Federal Trade Commission finally stepped in and put some rules in place about how manufacturers can specify the power of their amps.  And with that came two new values...RMS and Average. 

 

Sustainable Power

RMS and Average values are what an amp can produce over an extended period of time without destroying itself.  So...what are they and how do they compare to the Peak numbers?  Glad you asked:

 

 OK...so that graph looks a little intimidating, but here's the bottom line.  The RMS (root mean squared) power is about 71% of the peak, and that is by far what most amp manufacturers use.  The average power is even more conservative, and is about 64% of the peak.  Crown uses the average power, but then again they've always been very conservative with their specs.

Hey Man, What Happened
So lets use what we just learned on the example I gave earlier.  Prior to about 1975, a manufacturer could have advertised the amp in my example as a 200 watt amp, and not told you how they came up with that number other than to say it was Peak to Peak.  But what can this amp really do?

First, anytime you see Peak to Peak, divide it in half.  Again...it's a BS number.  Now, take the 100 watts you have left and multiply it by .7, which leaves you with 70 watts.  That's a much more realistic number.  But what's more impressive...70 watts or 200 watts (sounds like one of those phone commercials with the kids, doesn't it)?  So now you know how the game is played.

Full Disclosure
A wattage rating alone is useless without knowing at a bare minimum the load you're operating into and the distortion.  The example from Crown, that's a complete spec.  But that's not so much the case with our next contestant.  And I don't mind calling them out, because Pyle is one of the worst offenders as far as manipulating their numbers and playing off the average consumer's lack of electronics knowledge.

What A Pyle Of...
OK, we saw a good wattage spec.  How's about something from the other end of the scale:

Two things to point out.  First, they are not doing anything illegal.  Second, keep in mind that they are advertising this amp as a 1,400 watt product.

Under the section for "Continuous Output Power", they list the amp as being able to produce 70 watts per channel into an 8 ohm load, and 110 watts into a 4 ohm.  That alone tells me that the power supply for this amp is under designed.  On a decent amp, it would produce about twice the wattage into 4 ohms as 8.  On this amp, the power supply runs out of gas before then.  That's a red flag.

There's another flag on this as well.  In the 8 ohm mode, they spec that the amp can deliver 70 watts over the full audio bandwidth (20Hz to 20kHz).  But, on the 4 ohm ratings, the 110 watt figure is only spec'd at a single frequency.  So that does that mean?  It means that the distortion figure likely goes to hell at frequencies above and/or below this.  That's a bad sign.

Anyway, we have power and load.  The Total Harmonic Distortion (THD) is listed as 0.1% at "rated output power".  So, that infers that it's at the 70 watt / 110 watt figures.  But then they throw out "Maximum Power" for the two loads.  And guess what, there's no definition for "Maximum Power" other than what they define.  Most likely, that wattage is at a higher distortion value...probably 1% (which still isn't terrible).

And then there's that Peak Power....which I'm at a loss on how they came up with.  If you take the 100 watt figure as an RMS value and work the math backwards, the Peak value I come up with is 142 watts.  So how the hell did they come up with 700 watts?

Hey Rocky, Watch Me Pull A Spec Out Of My A$$
Here's how they did it.  If you measure the power supply rail of the amp at idle, it's likely coming in at around 75 volts (a typical value for a 200 watt amp).  Now, if you plug that number into the power formula we used earlier, then you get:

(75 * 75) / 8

5625 / 8

703 watts

 

 

So in effect what they are saying is that the amp has the "potential" to produce a peak output of 700 watts.  However, there's a whole lot wrong with this:

• As soon a you put a signal in the amp, the supply rail is going to drop a bit
• Even if the supply rail didn't drop initially, it will in a few thousaths of a second
• Assuming they've got a really good power supply that maintains it's voltage under load(which they don't), you're going to have switching losses through the output transistors.

So the 700 watt spec is valid...until you actually try to amplify something.  That's real useful...not!

 

You should be on the lookout for other obscure power ratings.  There's no official industry definition for "Music Power".  Some manufacturers will make that 6 or 7 times their RMS and then come up with some tech-speak about non-recurring non-simultaneous power excursions in typical program material.  Screw you guys...you're trying to sell a 200 watt amp (on a good day) as a 1400 watt amp.

Levelling the Playing Field, And Then Not
As I said earlier, the Federal Trade Commission standardized how wattage could be advertised around 1975.  Amp makers either played by the rules or got fined for false advertising.

However, in the last couple of years the FTC appears to be bowing to pressure from electronics manufacturers.  They are now considering no longer requiring the distortion figure in print or radio advertising.  Their "rationale" behind this is a crappy as Pyle's power numbers:

• Most equipment produced today has a low distortion value.
• Most consumers don't understand that number
• Consumers that want to know the figures can find them on the Internet.

As to the first point, it should be noted that most equipment made today is capable of low distortion.  But if you're going to advertise it at a power level that 10x of reality...that goes out the window.  The other two points, I unfortunately can't argue with.

A Dead Give Away...
I've gotta give Behringer the "Most Exaggerated Wattage" award for their new iNuke series amps.  And here's why.

There's a basic law of energy conservation that says you can't get more power out of something than you put into it.  Keeping that in mind, and the fact that a watt is a watt regardless of how it's being used take a look at this spec sheet for what they claim is a 3000 watt amp:

There are a lot of numbers here, but I've highlighted the two of interest.  First is the claim that the amp can produce 1500 watts per channel into 2 ohms (and don't get me started on 2 ohm load measurements).  Then look down at the Power Consumption at 2 ohms...they're stating that it's 350 watts total.

If there's one number you can usually trust on a spec sheet, it's the power consumption number.  You see, if the manufacturer wants to get a UL (Underwriters Laboratories) sticker or equivalent, they have to state the max power the amp can draw under worst case conditions. 

So, what Behringer is saying is that they can put 350 watts into the amp, and get 3000 watts out.  Really?  Where did the other 2,650 watts come from?  OK...here's how they do it.

They're using the same trick as Pyle, and basing that 1500 watt per channel number on the power supply rail voltage (probably about 110 volts) The power supplies used in light weight amps (switching power supplies) can deliver a lot of power instantaneously, but can only do it for maybe a 1/10,000th of a second.  And then that's it...it's out of juice until it recharges on the next power cycle.  So it's a completely useless number other than for marketing.  If someone could make a device that could continuously output more power than it took in, they wouldn't be jacking around with amps.  They would be making trillions of dollars selling cheap energy to the world.

The bottom line here is that you can't have more continuous power out than you take in.  If you read anything to the contrary, it's more marketing BS.  In fact, the true power output of an amp should always be less than the power it draws from the AC outlet.  No amp is 100% efficient.  Some really good (and expensive) ones approach 90%...but most are in the range of 50% to 70%.  So, expect a true 500 watt amp to draw between 700 to 1000 watts.  The difference between the two figures is what's lost as heat.

Oh, and what do our friends from Pyle list as the power consumption for their "1400 watt" amp:

Wow...it's blank! Go figure.  Losers....

I realize we've covered a lot of stuff today, but to me this is important stuff.  I'm really tired of seeing decent working musicians spend their hard earned money with these companies thinking they're getting 3000 watts of power only to find out it's really less than 1/10th of that. 

In fact, it bugs me so much I'll make this offer.  If you're considering buying a power amp and you're not sure of what you're getting, then email me at the address below.  Either tell me the make and model or the amp or send me a PDF of the spec sheet.  I'll read it and tell you what you're really getting, not what the magazine ad wants you to believe.

Next week, we'll wrap up our discussion on specifications and how they impact the way an amp sounds.

Until then, keep the meters out of the red.  Especially if you don't have as much power as you think!


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

Change The Oil...Rotate The Tires

In my last article, I had mentioned that I was going to write on lighting for a band.  Well...two things happened.  First, it's been pointed out to me that very few bands on the circuit I play now actually carry any lighting (their loss).

Two...you have to keep in mind that I built automated lighting for 8 years, so once I started into this it became an endless string of acronyms, buzz words, and technical jargon that at times required trigonometry.  And seeing that this comes out on Saturday morning (which is prime hangover time), I didn't want to risk exploding any heads.  So, maybe another time.

In the last couple of months, I've gotten back into servicing other peoples gear (albeit on a limited and referral only basis).  It starts off with "hey...I heard you know how to fix amps...can you look at mine?"  The next thing you know, I got gear waiting to be looked at. 

As many of you know, I'm an Engineering Electronics Technician by trade.  At my day gig, I'm dealing with very low power, and units of measure that are ridiculously small like nanovolts, picoamps, and femtoseconds.  That's all well and good, but when I get the chance to get my hands on something in the range of hundreds of watts...well, this is where you insert that Tim Allen grunt.  I'll admit it...there's a certain rush to working on a piece of equipment that has the potential to kill you!

Lots of gear snobs go on and on about how good the "vintage" amps from the 60's sound.  And some of them are really great.  If I had a few thousand dollars laying around I would love to score a mid 60's Marshall JTM-45.  But I would never take it out...so much of that stuff from that era was so fragile. 

It was in the late 70's that manufacturers figured out how to build good sounding amps that could stand up to being thrown in the back of a van and driving down 200 miles of washboard road by a ticked off roadie who has been up for 3 days on bathtub crank.

Recently, I've had a couple of bass amps from the 80's come across my bench...an SWR and a Gallien Kruger that I'm finishing up today.  Both of these amps represented some really outstanding engineering and manufacturing processes.  I mean, we're talking 30+ year old equipment that's been working...not sitting in a closet some where.

Both of them just needed some TLC to their power supplies.  The GK had a blown output transistor, but it was one of the originals from with a date code on it from 1984!  The owner really loves this amp, so we're completely rebuilding the output section in addition to the power supply.  This amp will hopefully run another 30 years.

Which brings me to the heart of the article today...what can actually wear out in a piece of gear? 

First, let's get the vintage thing out of the way.  If you have a 30 plus year old amp that gives you a tone that defines "your sound", then by all means keep it running.  It pains me to know that thousands of pieces of vintage instruments and gear have been bought up by foreign investors and have left this country.  So anything we can do to keep part of our history here is OK by me.

Stuff Wears Out
In general people think that tubes in amps are the only things that wear out and require replacement.  Solid state amps (like most bass amps) just keep running forever.

WRONG!

Even the solid state stuff will wear out after time.  You want to know the number one enemy of electronics?  It's heat.  Yep...it wears things out more than you realize.  This is a real generalization, but for every 10 degrees Celsius (18 Fahrenheit) that you can reduce the temp on electronics, you double the life!  Yeah, you read that right.  This is why tube amps typically need to be serviced more...they just run hotter.  And this leads to...

The Power Supply Is Everything
Without adequate and clean power, the rest of the amp can't perform.  I've seen some brilliant designs that were compromised by cheaping out the power section (although one amp, the Vox AC-30, actually capitalized on this as part of their sound).

Here's the power supply from the GK amp I'm working on now:

All of those blue cans...those are the electrolytic filter capacitors, and that's the primary component that wears out (or should it say drys out) in amps.  Yeah, there's actually a liquid in those things that makes them work.  Their job, when they're working right, is to take all of the ripple and junk out of power that's going to amp.  When they're not working, you'll notice an increase in hum in your amp even when all of the controls are turned down. 

They're also used between the stages in your preamp to couple the audio through.  When they start failing there, your sound tends to start getting thinner.  In tube amps, your gain is all off because the tube stages are getting voltages there weren't designed to take (the technical term is "incorrect bias").

These things aren't the cheapest things in the world ($5 to $10 each, depending on the value and size), but if your tube amp is over 10 years old or solid state amp is 15 years or more, it's probably time to change these things out.  If you let them completely go, they can eventually short out and take out a lot of other stuff in the amp.

Hey Man...You Got Any Scratchy Pots?
Noisy potentiometers (you know...those knobs on the front of the amp) are a very common complaint.  Now, if you take your amp in for service, a good technician will clean these for you while he has the amp open (and I'm a good technician).

But whether it's on your amp, one of your guitars, or an effect this is something you can take care of yourself if you're so inclined.

First, I'm guessing that most of you don't know how a pot actually works.  Well, it's not really that complicated.  And it doesn't matter if it's servicing as a volume, tone, balance, or whatever control...the hardware is pretty much the same.

This is what's going on inside of potentiometer...or as they're also know a variable resistor:

Not the greatest picture in the world, but the important parts are that black semicircle and the wiper arm.  The semicircle is called the resistive element.  It can be carbon, conductive plastic, or a number of other proprietary things.  The wiper arm is what actually moves when you turn the knob.

If you get a bunch of dust / dirt / nicotine / body fluids on either the resistive element or the wiper arm at the point of contact, you get that oh-so-annoying scratch when you turn the knob. 

So, how do you clean it?  Well, the good news is that most pots have an opening in them, like this one:

That slot right under the terminals is where you can shoot some cleaner in.  And speaking of that, my favorite hands down is DeOxit D5.  You'll pay about $15 for a can of the stuff (Guitar Center sells it, along with Fry's, and some Radio Shack stores).  Squirt a little in the slot, then turn the knob all the way back and forth to distribute the cleaner.  If it's really dirty, shoot it again and repeat.

If you're doing this in an amp, make sure it's been off for a while and unplugged.  DeOxit isn't conductive, but you shouldn't be monkeying around in a powered amp unless you're looking for trouble (literally).

If you have slide pots (like on a mixer or EQ), just shoot it in the front and move the slider.  There, that was easy.

If your pot is still scratchy after this, it's likely that the resistive element has worn out (it happens).  At that point, you're looking at replacing the part.

DO NOT USE WD-40!  I've made a small fortune replacing pots (especially the slider type) because someone thought it was a good idea.  Don't get me wrong, WD-40 is a great product...on case casters.  But not electronics for two reasons.  First, it attracts dirt, and that's what we were trying to fix in the first place.  Two, it's reactive with some modern conductive plastics.  I once replaced 32 very expensive slide pots (these were $50 each my cost) on a guy's mixing console thanks to WD-40.  What's sad was he knew he was supposed to use something like DeOxit, but the WD-40 was "so much cheaper".  Yeah, right.  I think that total bill was almost $2,400.  Tell me again how much you saved?

Speakers....not usually.
Here's something that doesn't wear out unless you blow them, and that's speakers.  Sure, the cones can be damaged.  Sometimes the glue holding them together fails.  And although you typically don't see speakers with foam surrounds in pro audio gear, occasionally I come across one where the surround has rotted away.  In all those cases however, the speaker can be saved with a recone.  They take the frame and give you a new cone, voice coil, and dust cover where applicable.

But here's what cracks me up, and that's when someone claims that their speaker's magnets have lost their power.  I'll ask them if they've had an MRI done on their amp, or if they've been close to a nuclear detonation (in which case we wouldn't be having this conversation).  In every case so far, then answer has been "no". 

Good, it ain't the magnet.

In full disclosure, I used to wonder about this too.  So I called a friend at Electro-Voice, another at Meyer Sound Labs, and emailed an engineer with Celestion in the UK.  I got the exact same answer from all three, which I will paraphrase here.

 - When you initially power a speaker up, it will loose about 1% of it's magnetic flux
 - It will loose another 1% during the first year or so of operation
 - It will take about 100 years of continuous operation before it looses another 1%!

Yeah...100 years!  So OK, maybe Keith Richards' amps are getting close, but none I've come across.

Here's The Good News
I can say that audio techs and amp repair guys are (in general) the most honest service people out there.  TV Repair, automotive, appliance...I've had attempted rip-offs by all of 'em, but never another amp tech.  I guess I attribute that the fact that most of them, like myself, are musicians.  They understand how import your gear is to you, and know that 99% of us are not swimming in money. 

A good tech will walk you through everything they've done, and hand you the parts they pulled out when you pick up your gear.  Just things to keep in mind.

Next week ought to be interesting.  We'll talk about fixing stuff, but not equipment.  Let's talk about taking care of ourselves.  I've been fighting shoulder and arm pain in my right arm since 2009, and haven't found answer for what's going on.  Recently, I've been very lucky to meet a musician who is an Orthopaedic Physician's Assistant by day.  I'm going to see him next week, and want to share what we find out.  Because after all, you can have the best gear in the world...but if you ain't working....

Until next week, keep the meters out of the red moving!

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

2012 In Review

Here's another year in the books.  And music-wise for me this year, it's been quite a bit different than past years.  Since everyone does their end-of-the-year wrap ups and "best of" articles about now, I felt somewhat obligated.

So, in no particular order in my Top-10 Music/Gig moments of 2012

1. In March, The Rhythm Dawgs take their first extended break in their 13 year history
2. The same Rhythm Dawgs reunite in December and play to a packed house, basically picking up exactly where we left off.
3. After roughly a year, I parted ways with Triple Play. Still love the folks and will support the band wherever I can....things just weren't panning out like I had hoped.
4. I did my first major PA upgrade in 10 years, discovering the beauty of digital consoles and modern power amps that weigh a fraction of what they used to.
5. Proved that it's possible to get frost bite from bass strings by playing an outdoor wedding reception back in February.
6. Once again confirmed at the same gig that the more upper class a venue is, the more they treat their bands like crap.
7. Via the Michael Ingalls Band, have seen first hand that Motorhead is a guilty pleasure that more people than let on really really like.
8. Drank the Apple Kool-Aid and found out that iPads are all they're cracked up to be...especially when they let you replace 3 large notebooks of music.
9. Proved to myself once again that I'd much rather play with good musicians who are great people than great musicians who are full of themselves.
10. Rush will finally be inducted into the Rock-n-Roll Hall of fame. That doesn't have anything to do with me, but it's freakin' cool!

So, what's ahead in 2013 for me?  The Rhythm Dawgs will be playing out albeit at a much reduced pace from previous years.  In the next week or two, I'll be starting work on an album with Michael Ingalls which should be cool.  And I'm planning on continuing writing these tidbits weekly.  Oh yeah, I'm sure there will be a new gadget in there somewhere.

Thanks to all who have taken to reading this blog...it's much appreciated.  And to all my friends, band mates, clients, and lurkers out there I wish you all the best in 2013.

Until next year, 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

Is The Party Over There????

'Tis the season.  Whether it's office parties, house parties, or Grand Openings this is the time of year a lot of bands find themselves in the position of getting out of the clubs and performing at privately hosted functions.  It's a welcome change of scenery for a lot of us, and it's usually better money than you'll pull down at a club.  And of course, there's the opportunity to play in front of people that haven't seen you before (and possibly recruit some new fans).

But these affairs can also be royal pains in the neck.  If you're lucky and it's a pretty big shindig, then likely the host will have hired someone to put the party together for them.  Those people will usually have had experience dealing with bands, and have some idea what goes into putting on a great performance.  But then again, there are folks who while they might be good at planning appetizers and center pieces, may have never dealt with a band (or think it's the same as a DJ), and then be totally shocked with you roll in with 20 or 30 road cases.  This is where you have to be as much a diplomat and counselor as an entertainer.

I've played parties at those two extremes and everything in between.  So in the spirit of the holiday season, let me pass along to you a few of my survival tips for playing private affairs:

You're Not The Center Of Attraction
Just get over it now.  As much as our fragile egos want to think it's all about us, it ain't.  Unless you're an established artist, your importance falls somewhere between the crab dip and the door prizes.  Depending on the agreements (and you got everything in writing, correct?) you may be anything from background music during dinner to the jukebox for the company limbo contest.  No, it ain't about us tonight, it's about the guests and making sure they have a good time.

Take Your Usual Set Up Schedule...Now Double It
Hotel gigs are the most notorious for this, but be ready for delays at any party.  I've waited two hours for the stage to be erected, only to be delayed another hour because the party planner wants everything moved 12 inches to the left.  You'll wait on dance floors, decorations, and sometimes skit rehearsals.  On second thought...better triple your setup time....she might want it all moved back where it was.

Find Out Who The Boss Is Early
That's the wonderful thing about private parties...you'll get conflicting information from several well meaning folks.  This is why when I book these things I specify that there's one person for me to deal with throughout the night.  And that's either the person writing the check or an appointed representative that has the authority to make decisions on the spot.  That way, when the cousin of the CEO's neighbor's brother comes and tells you to move something, you simply say "I'd be happy to do so...I just have to clear it with the boss".  

Make Sure They Know What They're Getting
Once the deal is put together, I send 'em a contract, rider, and stage diagram.  They're required to sign everything and send me a copy back.  Make sure they know exactly what you need in order to put your production on (stage size, power, set up / tear down time, sound levels, etc). That's saved my bacon many times, but two that really stick with me are: 

• The event coordinate starting raising holy hell with us when we put the front of house console in place.  "That can't go there...it's ugly.  Does it have to be out front?".  Well lady, that's why it's called "Front Of House".  I pulled out the contract package and showed where the client had signed off on it.  I said we would be happy to pack it up, along with everything else, take our money and leave (that's how it was spelled out).  That ended that discussion.
• I booked a company Christmas party with a young lady, making sure she understood we're a rock-n-roll band (and including that in the contract).  We got the deposit and contracts back and thought we were good to go.  We show up for the gig and start rolling in.  The owner of the company comes up and says "Y'all don't look like a country band."  Well Billy Bob, there's a good reason for that.  He tried to start a fight with us for misrepresenting ourselves, but I showed him the contract his representative had signed.  The asshole wrote us a check for the balance and sent us on our way (fine).  He also fired the girl that hired us right there (not cool).  His company went bankrupt in 6 months.  Karma, baby.

Now, don't get me wrong...if the client needs something moved or changed and we can do it in a reasonable fashion then fine.  In the case of setting up front of house, I've suggested to event coordinators that they could drape the racks with table linens and add other decorations to the area as long as it doesn't impede our sound man.  That's smoothed over a lot situations.  But putting artificial Christmas trees on the stage that we have to maneuver around...I gotta draw a line there.

Make Sure You Know What You're Getting Into

If there's anyway to advance the gig...do it.  Go to the venue and look it over.  If you're playing at a hotel, talk director to the special events manager.  Find out where you're loading in and out from (don't assume it's the closest door...we had those blocked by catering before).  Ask if they've had other bands with production similar to yours and find out how they set up.  

 

If you're playing a venue that's out of town, talk to the manager there.  Most places that host a lot of parties will be able to send you a drawing of the room with dimensions, location of power, and load in/out locations.  It's better than nothing.

 

And review my post from September 30 (Before You Leave For The Show).  Don't be a rookie and have to ask for an extension cord.

Trust, But Verify
If you've negotiated for the client to provide sound & lights for you, be sure to get the name of the company / person providing that and call 'em at least 2 weeks prior.  Just because you send a technical rider to the client doesn't mean they're going to send it to the sound company.  

 

One such incident happened several years ago.  I negotiated sound and lights for a party we were doing.  I sent a very detailed rider along with the number of channels we needed (16 minimum), mics, monitors, effects, etc.  Being the thorough guy I am, I called the sound company 2 weeks early and asked what they were bringing.  The guy on the other end of the phone said something to the effect of "they said there was 4 of you in the band, so I figured I could just bring a Peavey 6 channel mixer and we'd be good".  When I asked if he had seen the rider, he said that the client had attempted to read it to him and he quoted a price, but they said that was too much and asked what was the cheapest thing he could bring (yet, they thought nothing of a $3000 ice sculpture for the affair).  

I called the client back, and tried to explain how that was going to severely limit our ability to deliver the best performance we could, but they just said "oh, we just want some noise to fill the background at the party".  At that point I told them that we were not the band for their event, cancelled the gig and sent their deposit back.  As Kenny Rogers once said "...you've gotta know when to hold 'em, and know when to fold 'em."


Be Prepared To Be Interrupted
You know that killer set list you wrote out?  Be ready to toss it out the window.  Between awards, door prizes, "thanks for a great year" speeches and such, count yourself lucky if you get to play 3 songs in a row.  But hey, they ain't paying you by the song...so just smile and take the money.  I can recall one Christmas party I played where we contracted for 3 hours.  By the time the evening was over, I think we had played 9 songs. 

You're Not A Guest
As a rule, I don't approach the guests about anything.  Now, if they come to me and strike up a conversation, I'm more than happy to talk to 'em.  But it's their party, let 'em enjoy it.  And don't assume you've got access to the open bar or buffet unless you're specifically told that it's cool.

Welcome To Amateur Hour
If the function is like 99% of the ones I've played, you're going to have a room full of people who are not very good at holding their liquor.  The drunkest and most abusive a-holes I've ever played for are 7-figure company executives with 4 shots of tequila on board.  Keep in mind that these folks will have no recollection of what they did the next day, and unless they try to get physical with you best just to nod your head every now and then like you're agreeing with them, and then excuse yourself.  

"Thank You...Good Night"
Wrap the show up at the agreed upon time, and no encores unless your "boss" says OK.  Then load up and get outta there.  The guests who haven't passed out yet are lookin' for the hook up, and the rest of the hired help for the party want to get out of there too.  Don't linger and talk.  If someone asks how to hire you, hand them a card and explain you're on a dead line to get out but you would love to talk to them next week about their event.  Nine times outta ten, you're never going to hear from 'em.

Private parties can be fun if you don't stress over 'em, and as I said are usually much better money than club gigs.  Just be prepared to earn it.

This year has been a little unusual for me.  My band of 13 years, The Rhythm Dawgs, took a break in March and just picked back up a couple of weeks ago.  Consequently, I've done more "band hopping" this year than I have in quite a while, and also played a lot fewer gigs than the typical.  I was thinking about sharing some of my "lessons learned" for 2012 in next week's installment.

Until then, Merry Christmas (there...I said it).  And this time, just for the holidays, you can let the meters go into the red a little.

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
 

Go Go Gadget...

A few weeks ago, I did a post on some of my "must have" gadgets I keep in my tool box.  With us being in the thick of gift giving now, I thought I would throw out a few more of my favorite things to get me through a gig.  And by the way, I'm not compensated in any way for this...these are just things I like and consider quite handy.

LED Flash Light
Man, when these things came out I thought they were a bunch of hype.  Was I ever wrong.  My son gave me one about 5 years ago, and I wouldn't take anything for it.  And here's a real kicker...I've only changed the batteries in it once in that time (and it gets used a lot, even when I'm not gigging).  The color rendering on LEDs is so much better for actually reading the back of a power amp in a dark club.  The Maglite XL50 is the replacement for what I'm carrying.  About $30 at Frys.

Cab Grabber Mic Holder
If you're a sound man, or a guitarist who mic's up his cabinet then you'll love this.  It's a fairly new offering from Audix, and will run you about $50.  But then you've got something that holds the mic in place and you don't have to worry about knocking over a stand (and I'm all about getting rid of as many mic stands on stage as possible.  You can find 'em at Musician's Friend online.  And if Santa doesn't bring me a couple of these, I'll use any cash I get to score some.

 

 

Portable Guitar Work Stand

I've got a pretty nice bench at home where I can work on my guitars, but every now and then you find yourself having to restring at a venue.  Rather than try to balance your guitar in your lap and support the neck at the same time, just grab this little gizmo from your work box and set your guitar neck in it.  From Planet Wave, the Headstand Instrument Workbench Stand is one handy little tool.  You can find 'em for $10 at all of the major online music dealers.

 

 

Music Management Software

A lot of musicians I know are carrying iPads...myself included.  I originally got mine for remote control of my mixing console, but it's morphed into a whole lot more.  My iPad has now replaced 3 large notebooks of charts and lyrics, and made them more usable on stage then ever before. 

 

There are several programs out there, but the one I'm using is called OnSong (http://www.onsongapp.com/) , available for iPad, iPhone, and iPod.  It not only lets me organize all of my lyric sheets, but also lets me build sets and then scroll through the songs in order.  You can import Word, PDF, and most image files directly, but the magic really happens when you take the time to put your cheat sheets into Chordpro format.  Then, you've got display control of the fonts for the chords and lyrics separately.  You can even transpose the key of a song on the fly.  It's the best $8 I've spent in a long time. 

 

The program also supports Bluetooth pedals that will scroll the page and advance to the next song hands free. 





 

 

Mic Stand Drink Holder

'Cause you know you're gonna drink something. Saves you from spilling your beverage into your amp or knocking it over on the floor. Plus, you don't have to bend down or turn your back to the audience (unless that's part of your stage persona). There's lot's of 'em out there for $10 to $20.

 

 

 

Hope this gives you a few ideas.

 

Next week, we'll talk about something a little different.  This is the time of year a lot of bands are getting out of the clubs and into private parties.  They're two very different gigs, and we'll discuss how you should be approaching each one.

 

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

 

OK...Let Me Hear The Kick

PA in place...everything tested and working...monitors set.  Now, it's time to build the mix that you'll be presenting to the audience this evening.

If you've got 3 vocal mics, this is going to be real quick.  If you're fully mic'd up with all the instruments going through the PA, this is going to take a bit.  

Before you start mixing, you need to have some idea what you're going for.  It's no different than if you sit down to draw something.  If you just start, there's no telling what you're going to wind up with or even when you're done.  If you're a band member that running sound, you should have some idea what you want to sound like.  

If you're working with a sound man, take a moment to convey some idea of what you would like in the house mix.  If you're a country band, you don't want a death metal or funk kick drum dominating the mix.  Likewise if you're a rock band, you don't want the vocals 12dB in front of everything else.  Try to put it in general terms, such as a well known band.  One of the best examples I've heard was from Pat DiNizio of The Smithereens when he told the house sound man "make it sound like The Beatles...just louder".  That gave the sound man an instant point of reference to start his mix.

For vocals only, get things balanced and intelligible, add a dash of reverb and away you go.  Don't get really hung up on a lot of effects on the vocals unless you have a way to turn them on and off.  Otherwise, if you're talking to the crowd between songs with a lot of echo on your voice, it's just silly.

And don't forget to use the low-cut on your inputs if you have it.  I pretty much use it on everything except kick, bass guitar, and keys.  Your voice has no useful information below 100Hz...the only thing down there in a vocal mic is rumble and bleed from other instruments.

If you're running instruments through the PA, there are entire books written on various mixing techniques.  How you set this up, again, depends on the band, the style of music, and the room.  

Just remember that unless you're in a huge room, you're not trying to displace the stage sound completely with the PA...you just want to build on it.  The idea is just help the instruments project into the venue.

Somewhere down the road, we'll go a little more in depth on different ideologies of building a mix.  For now, just keep these bullet points in mind:

• Make sure the vocals are present and intelligible.  People like to hear the words to the song so they can sing along.
• If you're a Cookie Monster-vocals death metal band, you can forget about the above
• Fortunate enough to have a stereo PA?  Keep the vocals, bass, kick, and snare in the middle and pan guitars to the side.  If you have keyboards and enough channels, run 'em in stereo and pan 'em 9:00-3:00.
• If you're playing to a dance crowd, then a solid kick drum in the mix is very advantageous. But keep in mind that the kick you hear on a lot of recordings is either electronically generated or is a result of a complicated chain of multiple mics / EQs / Compressors.   It's more important that you make it work well with the bass guitar than it is to have this huge monster sound all by itself.
• In reference to the above, don't burn 50 minutes of your 1 hour sound check on the kick drum...nobody has ever left a show humming the kick drum part from a song.
• If you notice you're cutting the same frequency on every channel, then you've got an issue with the house EQ.  Make your system adjustments there...not on the individual channels.
• The idea is to make the instruments fit together like a sonic puzzle.  If you have both the kick drum and the bass guitar trying to dominate the low end, it's not "heavy"...it's just mud.
• Likewise, if you have 2 guitar players with similar tones then you just wind up with a bunch of white noise.  EQ them slightly differently and pan them if you have the option.
• You can always cut what you don't want, but you can't add back what isn't there.  Guitarists who insist on scooping all of their mids out are guaranteed to be totally covered up by the drums in the PA.  The midrange is where the majority of a guitar's sonic information is...don't throw it away before your sound man has a crack at it.
• Once sound check is done...don't touch the input levels on the channels!!!  If you do you've not only jacked up the main mix but the monitors as well (unless you're using a separate monitor board...and if you are you don't need these articles).

Having a sound man is a luxury, that you can't always afford.  Heck, there are some rooms I play that there wouldn't even be a place to set up a front of house console without knocking out 15% of the seating.  And running back and forth between a mixer on stage and listening out front is a pain as well.  

But there are a lot of technologies out there now that let you drive your console by remote control.  Behringer (those guys again) just introduced their X32 digital console that lets you set the fader levels through an iPad wirelessly.  Presonus steps that up a notch with their Studio Live consoles by giving you access to every channel function via iPad remote.  I just built a new PA around the Studio Live 24.4.2...it's an amazing piece of gear that not only sounds good, it replaced the equivalent of a 24 space rack of compressors and EQs.

Granted, those solutions will set you back from $2000 up to over $15,000.  Mackie, however, has broken the $1000 barrier with a 16 channel host frame that uses an iPad as it's user interface and mixing engine.  The DL1608 is a game changer...it's the first digital mixing system I know of at that price range and in a small console format.  If you're looking to upgrade or replace your mixer anytime soon, you at least owe it to yourself to look at some of the digital solutions.

That's enough for today.  I gigged last night and still have to clean my instruments and gear.  

Next week, we'll take a step away from the heavy duty tech stuff.  A few weeks ago in the "What's In Your Tool Box" post I talked about a few of my go-to gizmos that I have to have in my tool box.  I'll share a few more of my "gotta have" things next week...still in time for you to drop hints for the holidays!

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