Tech Notes
DSP Presets and Power Amplifier Voltage Gain
by Marty McCann
on Nov 01 2025
In order for electronic crossovers, and especially DSP based crossover presets to workproperly, all power amplifiers in the system MUST have the same amount of fixed gain. Specifically, that is matched voltage gain and NOT matched input sensitivities. All Peavey amplifiers have a fixed voltage gain of times Forty (X's 40 or 40X) which is +32 dB of gain on the decibel scale. The voltage gain in some models of CREST power amplifiers are 40X's, while some are 20X's (+26 dB), and some have switchable gain settings that include a common input sensitivity of 0.775 Volts.
Digitool Application for a Small Church
by Marty McCann
on Sep 09 2025
There are numerous churches whose method or style of worship includes the use of a full Praise and Worship Ensemble or Praise Band. Of course, the successful performance of these Praise Ensembles requires a quality sound system along with an experienced and skilled system operator. However, there are also many churches such as some Baptist, Catholic, Episcopal, Methodist, Presbyterian, and others that simply will not have a sound system operator.
by Marty McCann
on Aug 01 2025
Sooner or later every sound person encounters a ground loop hum' in their sound system. Most people think that adding a Peavey PL2 transformer module to the power amplifier rack will eliminate the problem, but this is not always the case.
In professional audio, the sound audio signal path should only be grounded at a single point. This single point grounding is circumvented when we place the mixing console remotely or away from the power amplifiers. Our USA National Electrical Code (NEC) specifies that all electrical equipment that draws potentially harmful amounts of current from the AC Mains must have its metal chassis grounded to the electrical systems earth' ground.
Talk About Balanced vs Unbalanced Systems
by Jack Sondermeyer
on Aug 01 2025
The idea of a balanced system is one that has confused even the most experienced audiophile. The actual application of balanced systems are further confused by relating them to the characteristics of low vs. high impedance. A balanced system is unique in that it possesses an electrical characteristic called common mode rejection.
Side Fills or True Cross Fade Monitors? Do You Know the Difference?
by Marty McCann
on Jun 06 2025
Here is my take on so called Side Fills. Now this is a qualified opinion, and is shared by many of us. First of all, when I hear the phrase "Side Fills," my first inclination is this guy, may not be doing it right. It is commonly thought that Side Fills are there to duplicate the FOH mix. This is not what I would have, as this just contributes to more bleed into open mics, and will only result in the band playing even louder. Oh, so you want to ruin the FOH mix, just crank EVERYTHING UP in the "Side Fills." On the other hand (you have five fingers) when I hear Cross Stage Monitor Mix, then I think that someone may indeed have more than a clue. Here is a little more of a Clue: Spell it X-Stage, or better yet it should be REV X-Stage Mix for Reverse Stereo Cross Stage Mix.
Long Cable Runs Waste Power and Reduce Performance
by Marty McCann
on Apr 02 2025
Recently I had a customer who had an application where he had to run a loudspeaker line 1500Ft. I suggested that he run a 70-volt distributed line instead. Since he didn't understand 70-volt lines he opted to do it his way, so I did a little math regarding speaker line losses, here are the facts:
Power in Watts equals the voltage squared, divided by the resistance of the load (V x V / R):
40 x 40 = 1600 1600 / 4 ohms = 400 Watts 1600 / 8 ohms = 200 Watts
Power in Watts also equals voltage times the current (W = V x I). It is more difficult to measure the current flowing through a device; however voltage and resistance can be determined or measured with a simple inexpensive multimeter. So, if you want to know the current that is present in the circuit, you can simply measure the voltage and resistance and calculate the power from the first formula, and then use the second formula to calculate the current present in the circuit by dividing the power in watts by the voltage to find the current (I = W / V). 400 Watts divided by 40 volts equals 10 Amperes of current flow (400 / 40 = 10).
Constant Directivity Horn Equalization
by Marty McCann
on Mar 01 2025
Every so often I encounter floor salespersons and sound people that do not have an understanding of why compression drivers that are mounted on Constant Directivity high frequency horns require a special form of equalization that permits them to exhibit proper high frequency response. In this article we will explain the need for the high frequency compensation know as CD EQ.
The Peavey 22, 22A, 22T, 22TI, 22XT, RX-22, 44T, and 44XT compression drivers require this form of high frequency equalization when used on our constant directivity high frequency horns, or for that matter, any manufacturers constant directivity high frequency horn.
by Marty McCann
on Feb 01 2025
I am aware of a lot of church music directors that want to do this, and they insist that the guitar player plug direct into the console. Some folks are real naive when it comes to this. First of all the guitar pickup is very very high impedance and can not be run through a snake with out a Balanced D.I. But that is still a very small part of this issue. Those of you that are guitar players, have you ever tried to play an electric guitar through your stereo? The sound is short of disgusting. When you play any chord on the guitar that is taken direct thru the console, it is like playing through that stereo. The fundamentals are so intense that they step on or mask the harmonics. Leo Fender recognized this many many years ago, and that is why his amplifiers have a mid-range notch at about 250 Hz (near Middle "C"). Most other conventional guitar amplifiers have a similar notch, sometime a little higher in frequency, but never the less they are notching out the mid's.
Power Shading and More for Loudspeaker Systems
by Marty McCann
on Jan 30 2025
Power shading is something that many of us have been doing for years. It involves reducing the sensitivity controls of some of the power amplifiers driving the loudspeaker components, and is usually done top to bottom and/or outside to inside.
Power Shading Outside to InsideFor many years I did the sound at the International Steel Guitar Convention, a music event that is held in a nice size hotel ballroom in St. Louis, Missouri. The stage was set up on a long wall, and the distance to the back wall was about 1/3 shorter than the needed left to right coverage. Before I began to shade the levels to the power amps, I would receive complaints that the lead instruments could not be heard nearly as well in the seats that were off-axis to the stage (and of course we had speaker enclosures pointed at those seats).
by Marty McCann
on Dec 03 2009
When you are specifying equipment for a large installation such as a church, nightclub, or recording studio, you should also include recommendations for a proper electrical power distribution system for that installation. If you ignore the electrical system, it is very likely you will be spending more time in the future trying to solve ground loop and EMI interference problems. More often the time spent running down these gremlins is beyond that which you estimated as labor time for the installation. If everything is taken care of up front, then everyone benefits.
Boundary Cancellation - How to Eliminate Low Frequency Cancellation with Proper Woofer Placement
by Marty McCann
on Oct 21 2009
How to eliminate low frequency bass cancellation with proper woofer placement
Many local bands and sound companies are unknowingly victims of a type of low frequency cancellation known as boundary cancellation. This phenomenon occurs when a loudspeaker is 1/4 of a wavelength away from a boundary. Assuming that the boundary (like most walls or floors) absorbs little or no energy, the reflection off of the boundary plays against the energy still coming from the speaker source.
Why Large Sound Systems Need to Go Vertical
by Peavey Electronics
on Sep 18 2009
In this article I will address the issue of vertically arrayed sound systems, explaining why arraying the larger sound system vertically can immensely improve upon the performance of the same number of components spread out in the horizontal plane. I have been both a student and practitioner of concert-level sound-reinforcement applications for more than twenty years now. I have closely observed major-sound company systems and conducted numerous experiments of my own. One problem, as I see it, is that many smaller sound companies don't array their loudspeakers in a tall-enough vertical array. They tend to spread the system out in the horizontal plane, which increases the overlap of the constant-directivity horns and results in less-than-ideal polar patterns.
