Hello!
I'm new here and I hope you can help me with some questions.
Because I have already built several hifi electronic projects I decided to build an aleph-x-clone. Losing the plot in the Aleph-X-High-Power-Thread
I don't know which power configuration I should choose for my Aleph-X.
I'm using diy-loudspeaker: Odin. You can see it here: www. seas.no by using the link "kits" or here: www.intertechnik.de. But I don't use the shown configuration, instead of the tweeter my Odin has an airmotion-transformer (Eton ER4).
So, would it be a good idee to built an Aleph-X with a power output of 90W into 4Ohm nominal impedanz to drive my Odins?
Increasing the power up to 150W or something like that I'm taken fright at the produced heat by the amp. I don't want to be in a sauna every time I'm listening to music.
G.
AudioAngel
P.S. Sorry for my bad English it is not my first language so I make very often some mistakes.
I'm new here and I hope you can help me with some questions.
Because I have already built several hifi electronic projects I decided to build an aleph-x-clone. Losing the plot in the Aleph-X-High-Power-Thread
I don't know which power configuration I should choose for my Aleph-X.I'm using diy-loudspeaker: Odin. You can see it here: www. seas.no by using the link "kits" or here: www.intertechnik.de. But I don't use the shown configuration, instead of the tweeter my Odin has an airmotion-transformer (Eton ER4).
So, would it be a good idee to built an Aleph-X with a power output of 90W into 4Ohm nominal impedanz to drive my Odins?
Increasing the power up to 150W or something like that I'm taken fright at the produced heat by the amp. I don't want to be in a sauna every time I'm listening to music.
G.
AudioAngel
P.S. Sorry for my bad English it is not my first language so I make very often some mistakes.
There's no way around it--an Aleph or Aleph-X will dissipate roughly three times its RMS output in heat.
As for how much power you'll need, that's not a question anyone can answer for you. It depends on what kind of music you listen to, and how loud. 'Live' levels for chamber music aren't going to be as demanding as 'live' levels for a full symphony orchestra. Rock doesn't (barring synthesizers) go very low, but people typically listen to it loud, etc. You'll have to estimate your power requirements on your end.
As a practical matter, speakers usually blow from the amp clipping, not from too much power.
To put the heat output from a class A amplifier into perspective, think in terms of a hair dryer. They're usually in the range of 1200-1500W. Ever tried to heat a room with one? Doesn't work too well. Yes, eventually the room will warm up, but it's not the kind of thing that will happen in thirty minutes.
Grey
As for how much power you'll need, that's not a question anyone can answer for you. It depends on what kind of music you listen to, and how loud. 'Live' levels for chamber music aren't going to be as demanding as 'live' levels for a full symphony orchestra. Rock doesn't (barring synthesizers) go very low, but people typically listen to it loud, etc. You'll have to estimate your power requirements on your end.
As a practical matter, speakers usually blow from the amp clipping, not from too much power.
To put the heat output from a class A amplifier into perspective, think in terms of a hair dryer. They're usually in the range of 1200-1500W. Ever tried to heat a room with one? Doesn't work too well. Yes, eventually the room will warm up, but it's not the kind of thing that will happen in thirty minutes.
Grey
Perhaps I'm mistaken but I thought the Aleph-X was about 33% efficient, meaning it would dissipate about twice its rated power as heat, not three times. At least, I've worked out the numbers on my 49W-into-8Ω monoblocks, and they dissipate 89W heat continuously, which is actually a bit better at 36%.
Ok,
at first thanks for your replies. My preferred kind of music is classical (baroque) music (Bach, Händel etc) especially orgen music. Therefore I thought 90W into 4ohm would be a good compromise concerning produced heat, dimension of heatsink and avialable amplifier power, isn't it?
G.
AudioAngel
at first thanks for your replies. My preferred kind of music is classical (baroque) music (Bach, Händel etc) especially orgen music. Therefore I thought 90W into 4ohm would be a good compromise concerning produced heat, dimension of heatsink and avialable amplifier power, isn't it?
G.
AudioAngel
jwb,
this is a question of how you define efficiency. An Aleph normally has a bit below 50% (with 50% ac-current-gain), meaning that for an output of 50W max your amp will idle at 100 watts. So maximum efficiency is defined at full power!
At 1 watt output, efficiency is only 1%.
The 33% could come from defining efficiency as max power @ 8 ohms / idling power consumption with an amp that has it´s power max around 6-7 ohms.
william
this is a question of how you define efficiency. An Aleph normally has a bit below 50% (with 50% ac-current-gain), meaning that for an output of 50W max your amp will idle at 100 watts. So maximum efficiency is defined at full power!
At 1 watt output, efficiency is only 1%.
The 33% could come from defining efficiency as max power @ 8 ohms / idling power consumption with an amp that has it´s power max around 6-7 ohms.
william
yes,
90 watts would be a good choise if you have 87dB and no less than 4 Ohms.
Dont overestimate the difference between power outputs! I think that it is difficult to tell if an amp has 60 or 90 watts max. This is only 1.8dB louder before clipping.
I think it´s more important that you design the the amp to have it´s power maximum at 4 ohms be it 90 or 60 or 45 watts.
william
90 watts would be a good choise if you have 87dB and no less than 4 Ohms.
Dont overestimate the difference between power outputs! I think that it is difficult to tell if an amp has 60 or 90 watts max. This is only 1.8dB louder before clipping.
I think it´s more important that you design the the amp to have it´s power maximum at 4 ohms be it 90 or 60 or 45 watts.
william
I'm assuming that your speakers are similar to these:
http://www.madisound.com/odinmk3.html
(I know there are slightly different versions of these around the world.) These have a sensitivity of 89db/Wm which is good. 90Watts should be fine as William indicated in the last post.
http://www.madisound.com/odinmk3.html
(I know there are slightly different versions of these around the world.) These have a sensitivity of 89db/Wm which is good. 90Watts should be fine as William indicated in the last post.
Hi Wuffwaff:
In your post, you said: "I think it´s more important that you design the the amp to have it´s power maximum at 4 ohms be it 90 or 60 or 45 watts." How does one go about this?
On my old Leach amp, or similar AB designs, I expect to see more power into 4 than 8 ohms--one reason my Magnaplanars really open up with that amp (even if the sound quality and finesse really ain't so hot). But with my Zen this doesn't hold, and with the Aleph- [fill in the blank] I plan to build I am not sure whether I will invariably have less oomph at 4 ohms than 8 ohms. One of the spreadsheets I looked at seemed to suggest that some permutations of the Aleph would put out more into 4 ohms, before dropping off at lower impedances. Other evidence seems to contradict this. Head hurt....please explain.
Is there a simple way to think of this relation?
Larry Wright
In your post, you said: "I think it´s more important that you design the the amp to have it´s power maximum at 4 ohms be it 90 or 60 or 45 watts." How does one go about this?
On my old Leach amp, or similar AB designs, I expect to see more power into 4 than 8 ohms--one reason my Magnaplanars really open up with that amp (even if the sound quality and finesse really ain't so hot). But with my Zen this doesn't hold, and with the Aleph- [fill in the blank] I plan to build I am not sure whether I will invariably have less oomph at 4 ohms than 8 ohms. One of the spreadsheets I looked at seemed to suggest that some permutations of the Aleph would put out more into 4 ohms, before dropping off at lower impedances. Other evidence seems to contradict this. Head hurt....please explain.
Is there a simple way to think of this relation?
Larry Wright
The short explanation is this: the amplifier's power is limited by two curves: Irms^2*R and Vrms^2/R. If you plot these two curves, the amplifier must be operating in the area under the curves. Where the curves intersect is the maximum power.
Here is the plot for my Aleph-X amps with 14V rails and 1.54A idle current per side. The blue line is the current limit, the red line is the voltage limit. If you can replicate this plot, you will have a good understanding of amplifier power and load impedance.
PS: I consider this a 40W amplifier.
Here is the plot for my Aleph-X amps with 14V rails and 1.54A idle current per side. The blue line is the current limit, the red line is the voltage limit. If you can replicate this plot, you will have a good understanding of amplifier power and load impedance.
PS: I consider this a 40W amplifier.
Attachments
Thanks to panelhead and to jwb for the explanations. It is a tough row to hoe, but some of this stuff is beginning to make sense to me! As Harry Connick, Jr. (and maybe Bobby Darin before him) sang: "I'm beginning to see the light". From jwb's graph I infer that any given amp/setting has a well defined operating area, if that's what you call it. Panelheads arithmetic leads me to conclude that amps designed to stay tough into low impedances must have prodigious bias current (current capability?). I am reminded of a statement that Nelson made in the A-75 article, something like: 'we know that about a hundred of you will write in and ask how to bias the amplifier for class A in 1 ohm'.
Larry Wright
Seattle area
Larry Wright
Seattle area
Zapped said:Thanks to panelhead and to jwb for the explanations. It is a tough row to hoe, but some of this stuff is beginning to make sense to me! As Harry Connick, Jr. (and maybe Bobby Darin before him) sang: "I'm beginning to see the light". From jwb's graph I infer that any given amp/setting has a well defined operating area, if that's what you call it. Panelheads arithmetic leads me to conclude that amps designed to stay tough into low impedances must have prodigious bias current (current capability?). I am reminded of a statement that Nelson made in the A-75 article, something like: 'we know that about a hundred of you will write in and ask how to bias the amplifier for class A in 1 ohm'.
Larry Wright
Seattle area
There is an even bigger issue here also. A 4 ohm rated speaker usually has the impedance vary from 2.8 ohms to 20 ohms or so across the audio spectrum.
Plugging all those real impedances into the equations make the math worse than my confusing examples.
George
For me, its easier. I have one set of Maggie MG II-A's with 6 ohm purely resistive impedance, and one set of Maggie MG-12's, with 4 ohm purely resistive impedance. So your equations have made things much easier for me to figure out which way to go. ( Both systems are bi-amped with a subwoofer, so power in the deep base regions is not a big issue either. )
Larry Wright
Seattle area
Larry Wright
Seattle area
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