Trace Elliot ELF bass head

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Trace Elliot ELF bass head

Post by Molotov »

Hi everybody.

Trace Elliot says their ELF bass head has:

30W power consumption
200W continuous into 4 ohms / 130W continuous into 8 ohms??

It also says 4Ω minimum and 28.3 V RMS

subjectively, the amplifier is pretty loud, but I don't understand the calculation from 30W to 200W
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Re: Trace Elliot ELF bass head

Post by Sam Spoons »

Massively oversimplified explanation but typically modern solid state audio amplifiers consume roughly 1/8th of their rated output because the peaks/transients in the music which require the 200 watts are brief and can be supplied by the energy stored in the PSU.
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Re: Trace Elliot ELF bass head

Post by Wonks »

It's basically an average power consumption figure. Over time you can't get more power out than you put in. Note they don't say "30W continuous".

You can use power supply capacitors to store power and then (for a very short period) produce a lot of output power in response to playing a single note, then in-between playing notes the capacitors recharge ready for the next note. But play a lot of notes, or input say a constant sine wave generated from a synth pedal, and the capacitors don't have time to recharge. So the amp either runs out of grunt, or else it has to draw more mains power.

So at 200W continuous, it will probably draw at least 220W-230W, but with normal dynamic playing, gaps between notes and a standard bass note amplitude curve, it will probably average 30W at maximum volume over time. It's rather misleading I know, and that figure entirely depends on how you play, and what you put through the amp.

You could view it a bit like a cold water storage tank that is normally trickle charged from the water mains. All the time it's got water in it, you can draw off a lot more water than the incoming flow rate allows, but once the tank is empty, the tank is of no help. You'd then need a mechanism to switch to drawing directly off the water mains with a much greater flow rate capacity. You are unlikely to have this on a water system but an amp can be designed to do this.

The amp's average 30W power draw is akin to the normal tank make-up flow rate, with the 300W akin to the maximum water flow rate you get get from the tank if say running a bath. The analogy falls down a bit once you start hitting the amp with less dynamic or loud distorted signals, as the amp should be able to draw more current/power if needed, providing up to 200W if you feed in a steady sine-wave.

An amplifier will always consume more power than it outputs if you look at consumption over a decent time period, but for a few milliseconds (which is the length of the initial note transient of a loud note), the output power can be many more times that of the input power. But it can't do that for ever.
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Re: Trace Elliot ELF bass head

Post by forumuser831747 »

Hi Guys,

The mains power consumption may indeed be 30W, but power is expressed as "P=IV", hence "Power = Current x voltage", so the 300W at the speaker output is after the output tubes/transistors and at a much lower voltage than the mains, but at a higher current rate, so 300W represents the output and cannot be correlated to the input power consumption, which is at a much higher voltage. I hope this helps.

Stan
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Re: Trace Elliot ELF bass head

Post by Random Guitarist »

No Stan, it doesn't help because it's wrong. (no offense intended) The input power and output power are comparable because power is defined as energy transferred per unit time. That relationship only breaks down over a short time if you are storing some energy in the PSU, over any decent period of time average input power is always greater than average output power. How it is scaled and modulated by the amp circuitry to feed a speaker is irrelevant, it's still a measure of energy. You can't have 30W in and 200w out because you'd be creating energy from nowhere. You can't even have 200W in and 200W out, because the circuitry will have power losses as heat etc.

The trick here is that the amp power consumption of 30w is quoted as 'typical' in the literature, and so is completely meaningless. Do you typically play in a bedroom with someone telling you to keep it down, or with an aggressive drummer telling you to turn it up?

As far as the other quoted figures go, 28.3Vrms into 4ohms calculates out as 200.2225W, and as described elsewhere, to produce that power continuously the amp will be taking in more power than that.

Thanks,

Grant.
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Re: Trace Elliot ELF bass head

Post by Wonks »

forumuser831747 wrote: Thu Oct 21, 2021 11:13 pm Hi Guys,

The mains power consumption may indeed be 30W, but power is expressed as "P=IV", hence "Power = Current x voltage", so the 300W at the speaker output is after the output tubes/transistors and at a much lower voltage than the mains, but at a higher current rate, so 300W represents the output and cannot be correlated to the input power consumption, which is at a much higher voltage. I hope this helps.

Stan

Hi Stan, welcome to the forum and thanks for chipping in.

As Random Guitarist has said, the power output can be roughly correlated to the input power used. The input power will always be greater than the output power based on the efficiency of the amp's design. A solid-state class D amp design (which is not 'digital') like the TA ELF is one of the most efficient amp designs, and means a lot of amplification can be packed into a small and light package, but it still consumes more power than it puts out on the speaker connection, with the excess power converted to heat. Efficiency varies slightly with the volume used, so you can't definitively say something like "it will always be 1.09 x the output power", but the typical efficiency figure will give you a rough idea of the input power used without measuring the voltage an current.

As you have said, the input voltage (constant) and amps drawn (variable) will be very different to the output voltages and amps drawn (both variable dependent upon volume settings and the audio input signal), but the power drawn will correlate fairly well if you allow for the amp's efficiency. And if you know that and the output power, then you can work back to a rough estimate of the amp's maximum current draw if you need to.

I don't know if we've explained it well enough for you to get the general idea and a better understanding of what's going on, but hopefully we've helped. Please don't feel put off from contributing again as we all have a less than perfect understanding of things at times, and I'm always getting something wrong. But I find stating something that's not right and then being corrected is a good way of learning.
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Re: Trace Elliot ELF bass head

Post by Sam Spoons »

Wonks wrote: Fri Oct 22, 2021 8:03 am
forumuser831747 wrote: Thu Oct 21, 2021 11:13 pm Hi Guys,

The mains power consumption may indeed be 30W, but power is expressed as "P=IV", hence "Power = Current x voltage", so the 300W at the speaker output is after the output tubes/transistors and at a much lower voltage than the mains, but at a higher current rate, so 300W represents the output and cannot be correlated to the input power consumption, which is at a much higher voltage. I hope this helps.

Stan

Hi Stan, welcome to the forum and thanks for chipping in.....

..... Please don't feel put off from contributing again as we all have a less than perfect understanding of things at times, and I'm always getting something wrong. But I find stating something that's not right and then being corrected is a good way of learning.

:thumbup::thumbup::thumbup: Well said that Wonks.
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Re: Trace Elliot ELF bass head

Post by Random Guitarist »

Stan,

Sincere apologies for the tone of my previous post, it wasn't helpful. My short sighted desire for scientific accuracy overtook common courtesy, for which I apologise.

I didn't notice it was a first post, and didn't welcome you to the forum. I do hope you will stick around and post again. There are lots of very smart people here (I'm not one of them) that you can get a lot of great info and help from.

Best Wishes,

Grant.
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