While I had it apart, it really admired the construction techniques used. Even though this amp was built in China, the attention to detail and a few little tricks to make the amp road worthy really stood out.
People talk about why one piece of gear is better than the other. Sure, electrical specs are a big part of it, and we'll talk about how to actually read those in another installment. But the bottom line is that if you're a working band and moving your gear from gig to gig, it's got to be able to stand up to that. I've seen some equipment (designed for home use) that sounded fabulous, but wouldn't survive 10 miles in a U-Haul...even in a road case.
So this week I thought I would point out just what makes a piece of equipment "nice". And even though we're just looking at a power amp, a lot of these points apply to any piece of electronic gear you're going to haul around. And this is not an exclusive endorsement for Crown...there are a lot of other companies today building some very good gear at reasonable prices for the average working musician. But on the other hand...there are a lot of 'em that are building some really bad stuff.
OK students...what is the #1 enemy of electronics? What? Who said heat? That's right...proper system cooling goes a long way toward extending the life of the gear. So that's usually the first thing I look at. On that note, starting at the front panel notice the large vent for air flow:
Moving around to the back panel, check out the speaker connections:
This amp can output up to 800 watts per channel...far more than a 1/4" connector can safely carry. Crown was one of the first companies to move to Speakon connections which are far more secure and can carry a whole lot of power. Binding posts also give you the option of using banana plugs or wire lugs. This is all standard on high power amps now, but this was cutting edge in 2006.
Moving across the back panel, Crown used two cooling fans for this amp:
Two fans give coverage to the entire heat sink field in the amp. Electrically, they're two speed and thermostatically controlled. They run at half speed (which makes 'em pretty quiet) until things get hot and heavy, and then they cut over to full speed. And in the event that the amp still overheats due to a fan failure or extremely high ambient temperatures, the control system will shut everything down before any major damage can occur. You're not going to find that on a cheap Pyle amp!
Inputs are pretty straight forward, a pair of balanced XLRs. This is one place I've got to pick on this amp...it would have been really nice to have a switch that parallels the inputs. In other words, let me plug into one channel, but feed both of them (useful if you're using the amp for subs). I'm not crazy about the plastic housings on the XLRs, as those 4 screws you see (that go into the plastic) are what are holding that panel in place. A couple of them were stripping out, so I used a filler on the holes to give the screws some new meat to bite into.
But you know what makes up for my gripes with the XLRs? Look under the AC power connection. That's not a fuse, it's a circuit breaker!!!! That's right, if something happens and you pull too much power, this trips. No fumbling around to find a replacement fuse...just clear the fault condition, reset the breaker, and you're back up and running. In bulk, these really don't cost that much more than a fuse and fuse holder...and I really wish more manufacturers would go this route.
Now, there's a few things I want to show you on the inside of the amp. If you remember from article I did a few weeks ago about rebuilding a bass amp, I talked about how the power supply is critical to the proper operation of the amp. Check this out:
There are two things to point out here. First, on the left, are the bulk storage filter capacitors. There's about twice an many as theoretically required. And that white stuff between them...industrial adhesive. Components that are tall have a tendency to physically "rock" (not in a good way), and that can result in lead breakage and failed solder joints. Gluing them all together helps prevent that.
To the right, that round thing...it's a toroidal transformer. This is what steps the line voltage down from 120 to the various voltages the amp needs. Toroidals, because of their construction, have a very small magnetic field around them when compared to a standard rectangular transformer. So why is that a big deal? Easy, magnetic fields can induce hum into nearby audio circuits. A transformer like this makes for an amp with very low background noise.
There's one other construction note on this photo. Right below the capacitors, you'll see a row of white rectangular objects. Those are power resistors (we'll look at some different ones next). These essentially balance the loads going to the output transistors, and they can get hot. By selecting this style of resistor (which is relatively expensive), the heat is not going back into the circuit board and deteriorating it. And notice a bead of silicone across the top of them...again to stabilize them and keep them from moving more than they should.
Finally, there's some construction points that the designers really got right on the circuit board.
There are three things I want you to notice here. In the upper left, there are two power resistors (the grey cylinders with the stripes). These are electrically the same kind of thing as the white rectangular ones above, but in what we call an axial package. They're going to get hot as well, but if you look closely they're not sitting down on the circuit board (which would eventually scorch it). They're set up off the board where they won't do damage and will radiate heat better. That's a small thing that a lot of manufacturers miss.
In the top center is a ribbon cable that connects the front panel (pots and LED indicators) to the main board. Remember last week when we had trouble with a ribbon cable because of the connector? You won't see that here...the ribbon is soldered in! It's more expensive because it increases your manufacturing build time, but you won't have a connector problem.
And finally, this is something I've only seen super high end touring amps. See the red and black wires that are going into the board? Those connections are stiffened with adhesive. Otherwise, those wires would eventually break at those points (I've repaired plenty of them). This cost a fraction of cent to do, but improves the reliability immensely.
This amp has a lot of other things going for it electrically that you can't see. Things like a soft start turn-on (it reduces the inrush current when you power up), and a 3 second delay after turn-on before the speakers are connected...so you don't get that loud "THUMP" when you're bringing your system up. And sonically it's just plain good, but that's all in the specs.
So how about next week we talk about amp specs...what is THD, sensitivity, and damping factor? How do these specs impact what the amp sounds like? And probably most importantly, I'm going to show you how to spot a bogus wattage rating from a mile away. You won't need a calculator, but if you're planning on drinking heavily next Friday night you might want to wait to read this one until Saturday afternoon.
Until then, keep the meters (or LEDs) 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
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