Double Bass My AI Focus 2 Gets Very Hot...

[bolo]

A yacht gig huh? That's pretty cool! We don't get too many of those in Central North Carolina.

Yup, got me one of them thar little yellow volt meters too. I keep it in my gig bag, and I try to remember to use it to check out the wall outlets whenever I play in a new room.

Or a new boat in your case!

 

[Bob Gollihur]

what about this;
and I am no techie.

was it at a place you play at a lot? can you check the output from the outlet with a volt meter like this

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I seem to remember doing a gig on a yacht and the harp player (string) was using an AI amp that got pretty hot. It was attributed to extreme power fluctuations from the boats generator. Every other (dry dock) gig I've done with him the amp has been just warm

I did a dockside gig with a classic rock band a few years ago, at the time my big rig (Kern IP777/QSC2402) had a Furman power unit with the voltage readout in my rack. I could watch the voltage sag dramatically every time I played a note.

 

[Randy Ward]

A yacht gig huh? That's pretty cool! We don't get too many of those in Central North Carolina.

Yeah bolo, but the gigs you're doing are probably more fun and easier on your bass. (salt air anyone)

Just a side note: these 'yachts' are about 4 to 6 times the size of my house! You guys may know that Palm Beach is a VERY exclusive island, home to more millionaires per square inch than anywhere else in the world. These 'boat' gigs are basically cruises to nowhere, where they just go up and down the inter coastal waterway, the strip of water between the mainland and Palm Beach.

Anyway the way I've solved the fluctuation power thing was by buying the smallest APC uninterruptible Power supply.

http://www.apcc.com/tools/ups_selector/index.cfm

One of the battery backup home office units for a computer. Which was about 40 bucks on sale at CompUSA. I think the Furman Power Regulator that Bob uses is probably better idea but this thing is fine for 'boat gigs' or outdoor wedding jobs where the power might be funky. not only does it spit out the correct power (some amps have a hard time with 'brown' power) but if the power goes off you can still get a couple of notes in. The bad thing about having it is that the guitar player always wants to plug in.

 

[hensonbass]

I've found that my focus head runs cooler with a 4-ohm load rather than a 8-ohm load. I thought it would be the other way around myself.

I also find that the high pass filter really helps the speaker operate more efficiently. Great feature to have with a bass amp!

 

[KJung]

Just played a gig with the Focus 1 into a 5.3 ohm Epifani310UL using a 5 string electric bass. Very loud gig... I felt like I had the Focus up pretty much full blast..... 3 hours of solid, aggressive funk.... the amp stayed totally, completely cool. It does sound like the heat generated in these amps has nothing to do with power output, how hard they are driven, etc. In my case... very impressive unit to take that kind of abuse and stay absolutely cool.

 

[drurb]

PWM/Class-D amps don't work the same as conventional amps. They don't generate heat in the same way as conventional amps. Just because the amp feels hot when you're barely cranking it, doesn't mean it's going to get hotter with more signal through it. It's a different paradigm.

http://en.wikipedia.org/wiki/PWM_amplifier

Well, with real-world physical systems you never get something for nothing. When the class-D amplifier is being driven, as opposed to idle, more current is flowing through the final stage of the output circuitry. That will generate more heat. Now, class-A designs are very different because their output transistors are always drawing full current. Still, I believe it is correct that you are not likely to notice the increase in heat in a class-D design like you will with class-B or class-AB.

 

[Tim__x]

...Just because the amp feels hot when you're barely cranking it, doesn't mean it's going to get hotter with more signal through it....

Class D amps have two main losses, switching losses which are pretty well constant for a given design and switching frequency, and conduction losses which vary as the square of load current. A higher output power will increase total losses.

The more likely cause of your amp's heating is low line voltage, a low line voltage makes a regulated SMPS much less efficient.

 

[robgrow]

The more likely cause of your amp's heating is low line voltage, a low line voltage makes a regulated SMPS much less efficient.

I'm not sure if I missed a reference to this elsewhere in this thread, but I would also suspect the switching-mode power supply as being the most likely source of the Focus amp getting hot.

 

[seamonkey]

I'm not sure if I missed a reference to this elsewhere in this thread, but I would also suspect the switching-mode power supply as being the most likely source of the Focus amp getting hot.

This is probably key here. The iAMP 800 is also a class-d but it weights much more. It probably has a linear power supply, with a big transformer.

For the amp part itself - you'll find that pwm amps reach a high percentage of their heat disapation they're going to produce at a lower point in their wattage output than linear amps. They don't get much warmer at higher outputs. Linear amps continue to get warmer and warmer as you raise the output.

PWM Efficiencies are maybe 90% or higher. Class-A is maybe 20% efficient, Class-AB maybe 50%. PWM saves energy at the plug, and are lighter so they save energy getting them to the gig. Only PWM amps for me. Now if only they all had SMPS'.