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

jar240

jar240

Aug 30, 2004
543
15
Ottawa, Ontario, CANADA
www.chrisbreitner.com
#1
I was playing guitar of all things for a gig, and I loaned the bassist for that gig my AI Focus 2 head. It was driving a single SWR 8-ohm 2/x10 cab. He was working it as the volume was pretty loud.

During set break, I went over to check things out, and noticed that the head was very hot. I probably couldn't leave my hand on top for more than 5 seconds without discomfort.

Is this normal? ...or at least, is it something to worry about?

As a contrast, I've driven my iAMP 800 HARD with 3 8-ohm cabinets and there was no heat whatsoever.

Makes me want to keep my iAMP and return the Focus 2.

Chris
 
#2
I've just had this same issue with my Focus. Sometimes it
runs very cool, other times very hot. I sent it back to the
guys at Acoustic Image. My amp is fine. Rick said that its
fine. They can run hot sometimes. My amp is a real workhorse.
 
#3
Mine has always been just warm so far. I've been a little concerned because I have it in the compartment in my LDS cab and took the rubber feet off to fit it in there. I was a little concerned that if it really did get seriously hot underneath that it might start a fire in the carpet compartment. Paranoid I know but it wouldn't be funny if it did happen. What you're describing is pretty damn hot.
 
#4
B String said:
I've just had this same issue with my Focus. Sometimes it
runs very cool, other times very hot. I sent it back to the
guys at Acoustic Image. My amp is fine. Rick said that its
fine. They can run hot sometimes. My amp is a real workhorse.
Click to expand...
I've played a couple gigs with it myself, but haven't driven it hard as it was driven at Sunday's gig (electric bass).

I'll see how it fares in the future.

I'm surprised it generates any heat at all considering the amp contains nothing but magic air...judging by the weight... :D

Chris
 
#7
jar240 said:
I've played a couple gigs with it myself, but haven't driven it hard as it was driven at Sunday's gig (electric bass).

I'll see how it fares in the future.

I'm surprised it generates any heat at all considering the amp contains nothing but magic air...judging by the weight... :D

Chris
Click to expand...

Didn't you know that magic works by convection?
 
#10
Adrian Cho said:
It's never really occurred to me before but I guess electric is going to drive an amp a lot more than upright will just because of the nature of the sound. Not being an electric player myself...
Click to expand...
In terms of looking at the signals on an oscilloscope, they are comparable. What I think happens is that we simply tend to play the electric louder.
 
#14
There's probably a lot more sustain (depending on how your guitarist plays) in a guitar waveform. The bass has a big attack and then average sustain, so the overall energy is probably less than with a guitar where the attack could be similar in level to the sustain.

If an amp runs with a continuous signal as it might with guitar then it's got less chance to dissipate energy and so will get hotter.
 
#15
Doug Ring said:
...

If an amp runs with a continuous signal as it might with guitar then it's got less chance to dissipate energy and so will get hotter.
Click to expand...

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
 
#16
seamonkey said:
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.
]
Click to expand...

What he said. It doesn't get hotter the louder I push it.
Sometimes it just runs hotter than other times. Again, Rick
says this is typical in these amps. No worries.
 
#17
Adrian Cho said:
It's never really occurred to me before but I guess electric is going to drive an amp a lot more than upright will just because of the nature of the sound. Not being an electric player myself...
Click to expand...
I think I understand Adrian's point, in theory anyway. Granted, I'm not an engineer or a techie, but just for kicks here is something else to consider.

I think a double bass actually produces more low low freqs than slab, or sub-sonics as I call them, regardless of where you are in the bass register (except for the really high thumb position stuff probably).

Here's why I say that. I was doubling on upright and electric during a rehearsal once, and because of the room lighting and where I was standing, I was able to watch the excursion on my speaker really clearly.

Even though the slab and my upright were producing the same perceived volume to my ears, the upright was making the driver jump and wobble quite noticably, but with the electric, you could barely see it move.

I emailed EA since I was concerned about the wild speaker excursion I witnessed with the upright. John Dong's reply was that basically the double bass generates a LOT of low freqs, unless I misinterpreted what he was saying. (Wish I'd saved the email.) John's suggestion was to use the EQ to cut the bass around the 40 Hz range. I tried it, but didn't like what it did to my sound, so I went back to my flat EQ, and just tried to limit the overall volume.

So ... you would almost think given this example that the upright would drive the amp hotter than an electric bass. I say this (again admitting my lack of techie expertise) since I thought the low freqs require more juice to produce, i.e. would "drive" the amp harder, and thus generate more heat.

FWIW
 
#19
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

[Invalid or Expired Link Removed]

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
 

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