Passinwind
I know nothing.
- Dec 3, 2003
- 23,093
- 46,079
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- Designer/Toaster Tech @ Passinwind Electronics
More or less true for a continous sine wave, but for bass guitar in often minimalistic playing situations, not so much.
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Why So Few Affordable Battery Powered Bass Amps?
- Thread starter selowitch
- Start date
I may be off or wrong but according to my understanding of how bias voltages work, a typical amp actually consumes quite a bit of power even with no input signal at all. Oregon Jim's math looks pretty generous to me, as the bass is a high dynamic signal.
D
Deleted member 165050
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Battery technology is still well behind the curve and bass amps need a lot of power. At the moment batteries are horrible toxic things with environmental implications from manufacture and disposal that are not even vaguely green, but sooner or later someone will come up with a good portable way of storing power. Potato, anyone?
Btw I played a festival through a solar-powered PA a few years back, that was cool.
Btw I played a festival through a solar-powered PA a few years back, that was cool.
I definitely don't want to get a generator that requires fuel because that's a level of noise, hassle, odor, mess, weight, and safety considerations with which I would prefer not to engage.
So you're saying he is working on it and getting close? Excellent
Noise, bulk, odor, weight, inflammability, need for fuel, etc. Too many disadvantages to be a viable solution for me.Just saw your reject based on noise comment
Passinwind
I know nothing.
- Dec 3, 2003
- 23,093
- 46,079
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
The 100 watt ICEpower Class D 100AS1 module has a 6.5 watt idle power consumption rating, it's not like a Class A amp where idle is more or less the worst case.
You can measure crest factor of your own bass playing in a DAW and infer duty cycle to get a leg up on spec'ing your power needs, in the cases I've measured derating by a factor of 3-4 is in the ballpark. If you look at current ratings on the back of musical instrument amps you'll see derating factors of 3-8 commonly stated, with 1/8th power being the default regulatory standard for general program music applications. As a thought exercise, look at how much PA power we can get by running off a single 15A service.
The inverter will consume some battery power as well. This is why he said 80% efficiency. He's assuming 20% is lost in converting from DC to AC.
I did a more extensive work up here: Choosing a Battery and Inverter
The problem is the answer has many unknown variables and results depend on how hard you run the amp.
AFAIK, the peak power is less relevant than the average power. So you need an inverter that can meet peak demand, but then you base your calculations off the average power drawn by the amp and the aH (amp hour) or wH (watt hour) ratings of the battery. See the example in the link above.
In another thread, someone is talking about using the Quilter Interbass as a head under battery power with any old cabinet. The claim is that even though it's only rated at 45 watts @4 ohms, it's quite a bit louder than expected and can even be used on small gigs. Intriguing.
D
Deleted member 165050
Guest
Has no-one mentioned the Phil Jones Briefcase yet? Very loud for 100w and can run off a leisure battery... not sure what the playing time between charges is though, or if you can plug it into a Tesla outlet.
I have read that the original Briefcase had a run time of about 1 hr on the (optional) built-in battery. The BG-200 manual specifically mentions a class-D amp. I don't know if the original was AB or class-D. AFAIK class-D has a higher efficiency.
The way to get the most out of a Briefcase IMHO is bypass the built-in speakers and use a cab that is much more efficient. Then you can run the amp at a lower volume and get a longer run time.
I have played the original Briefcase. I thought it sounded decent, but it was not very loud and did not handle low notes well at volume. IMHO, the built-in speakers are adequate for bedroom practice, and that's about it.
D
Deleted member 165050
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I heard a guy using one at a local blues jam night and it seemed to hold up pretty well against the other gear in the room. Latest version is claiming 150w just on internal speakers so should theoretically be louder than my 100w Bass Cub, which itself is way way beyond bedroom practice levels.
[Edit] Class D is theoretically greater than 95% efficiency.
The 100 watt ICEpower Class D 100AS1 module has a 6.5 watt idle power consumption rating, it's not like a Class A amp where idle is more or less the worst case.
You can measure crest factor of your own bass playing in a DAW and infer duty cycle to get a leg up on spec'ing your power needs, in the cases I've measured derating by a factor of 3-4 is in the ballpark. If you look at current ratings on the back of musical instrument amps you'll see derating factors of 3-8 commonly stated, with 1/8th power being the default regulatory standard for general program music applications. As a thought exercise, look at how much PA power we can get by running off a single 15A service.
Gotchya, thank you, yes I guess I was thinking of Class A systems.
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The BG-200 claims 150W on the internal speaker and 200W with an extension speaker. Supposedly it is 2dB louder than the original.
As far as how loud it can play and where it would be useful. These are IMHO and YMMV type answers. I was personally surprised and disappointed by the volume limits of the original; so IMHO it would be useful only for bedroom practice, but YMMV.
However, when it came time for me to deploy to the Middle-East I seriously considered a Briefcase...but my intent was to use it with an efficient extension speaker like a Bag End S15D. Ultimately I was not allowed to buy a battery-powered amp, but a Crate TX50D Limo was provided and it worked great.
Unfortunately Crate is no longer with us. The TX50D was rated for 50W and had a 10" woofer that was way more efficient than the little drivers in the Phil Jones or current Roland battery powered amps. We used it with a drummer outdoors. We had a pair of Anchor Liberty PA cabs and the guitarists used little Roland Amps; they may have been Micro Cube GX, but I remember them being even smaller. The guitar amps limited our volume and the guitarists kept whining to use the TX50D
.
How do you determine if one cab is "more efficient" than another and how much more efficiency is needed for a given application? Also, how do you know what "class" (A, B, C, D) an amp is?
In most instances companies tell you the efficiency of their cabs. It's usually expressed as how load a cab plays with 1 watt applied at a distance of 1 meter. For example the rating would look something like this: 97dB 1W/1m
Sometimes sensitivity rating are expressed in terms of 2.83V with the impedance specified. So you might see something like 99dB 2.83V/1m at 4 ohms.
The tricky part of this is 2.83V at 4 ohms = 2W and 2.83V at 8 ohms = 1W. To get the 1W/1m rating for the 4 ohm cab, subtract 3dB. So in this case 99dB 2.83V/1m at 4 ohms is the same as 96dB 1W/1m.
My feeling is the 2.83V rating is often a way to try and hide the fact that the 4 ohm variant of a driver is slightly less efficient than the 8 ohm variant.
When comparing I suggest using the 1W/1m rating.
If you know the 1W/1m sensitivity rating and how much power the amp is rated for, you can estimate the max SPL. This is because we know that SPL increases by approximately 3dB every time you double the power.
Let's assume a 100W amp and count the doublings of power from 1 to 100.
1,2,4,8,16,32,64,128.
As you see, the power doubles 6 times (count the numbers in bold).
Now multiply by 3dB for each complete doubling. 3x6=18dB. This is the decibel change from 1 to 64W.
Add this to the 97dB 1W/1m sensitivity rating. 18X97=115dB.
I suggest you also consider how close the available power is to the next doubling. 100W is closer to 128dB than 64dB, so let's add 2dB.
115+2=117dB. This is our estimated max SPL
