marce
Thank you asking again good questions.
In early 30's single ended amps could not strive against the push pull amps ,because no any measurement method was possible to show the fresher sound they provide to justify much higher cost per watt.Similarly you can not ask to have the measurements of freshness for a tomato, or a frozen pizza.
After all, I can ask you. "Hey fellow ,don't you have 20£ and few hours to built it and hear it by yourself". Absolutely not. Don't wast your time and money for this.I discourage everyone to built this amplifier.The BASIC3886 is not an audio amplifier. It is, what the bread is for the sandwich.
In next posts ,If I will explain how to make a sandwich,I can not start by explaining everytime how to cook the bread .It will be refered to this thread as reference .
The next post that will in few, on a different forum ,I advise you to consider it as a "may be". Even if you find it very interesting ,deal with it later.
Because, the highlight is in two months .I assure everyone ,it is extraordinary.
I am sorry not to deal with audio subject all year long,but from time to time.
KOKORIANTZ
Thank you asking again good questions.
In early 30's single ended amps could not strive against the push pull amps ,because no any measurement method was possible to show the fresher sound they provide to justify much higher cost per watt.Similarly you can not ask to have the measurements of freshness for a tomato, or a frozen pizza.
After all, I can ask you. "Hey fellow ,don't you have 20£ and few hours to built it and hear it by yourself". Absolutely not. Don't wast your time and money for this.I discourage everyone to built this amplifier.The BASIC3886 is not an audio amplifier. It is, what the bread is for the sandwich.
In next posts ,If I will explain how to make a sandwich,I can not start by explaining everytime how to cook the bread .It will be refered to this thread as reference .
The next post that will in few, on a different forum ,I advise you to consider it as a "may be". Even if you find it very interesting ,deal with it later.
Because, the highlight is in two months .I assure everyone ,it is extraordinary.
I am sorry not to deal with audio subject all year long,but from time to time.
KOKORIANTZ
If you like the sound of high amounts of THD from an amplifier that's fine but you're going to have to expect to catch some $hit around here if you call that way better. I would say that accurate reproduction of the source material is way better, ya know what I mean?
kokoriantz,
You have ignited the fires underneath those who protect folks from ... just what is it they are protecting us from? But they have taken on the mantle of protecting their unknown children of trying something that doesn't suit them or their textbooks.
All of the typical nonsense from people who have no intention of trying what you suggest and I suspect further have never used a chip amp. I have not kept up with the chip amps forum in the last few years so I could be completely wrong about that but the tone is all too familiar. One wonders where mankind would be if EVERYONE was like the majority of respondents to your posts. Would we have even progressed to the wheel? They would have found something scary/dangerous about the wheel; it could roll down a hill and you would never ever find it again or you can go so fast with that thing under your cart you might escape the binds of earth and never be heard from again!!! I get nervous just thinking about it! It would have to have a very dire ending.
The heating of a chip amp harming nearby components? Like the two resistors that are close in? Doubt that heat is going to bother them that much. One could make a resistor selection that would minimize that potential problem, anyway.
I am glad you are not the least bit hesitant to make your case with all of these naysaying do-nothing types around here.
Still amazed that they cannot figure out this scenario is part of a commercial product that is not known for failure. I guess they would never let a fact like that get in way of self-righteous indignation.
I am looking forward to hearing how you configure a heat sink that will allow such a temperature rise to that lofty height and then keep it under control.
I am tempted to pull out all of my old chipamp pieces. I assume you are not saying "modern 300B" with irony? But then I doubt I heard my chipamps at their best.
Good sense like the fellow who pointed out (swooosh, it went right over their heads) how inexpensive these chips are compared to vacuum tubes which HAVE to be replaced eventually ... Well, other than marce I have no idea what the others use. marce has mentioned he is a valve enthusiast.
I do not doubt marce is an excellent engineer but I wonder if he uses DIYAudio as a means to entertain himself. He posts on boards he has no demonstrable interest in in the capacity of the bully's advocate all too often wanting to engage in circuitous games of "gotcha". To what purpose I have no idea. Part of the landscape here ...
Looking (and hearing) forward to your posts. Keep up you investigations, kokoriantz.
You have ignited the fires underneath those who protect folks from ... just what is it they are protecting us from? But they have taken on the mantle of protecting their unknown children of trying something that doesn't suit them or their textbooks.
All of the typical nonsense from people who have no intention of trying what you suggest and I suspect further have never used a chip amp. I have not kept up with the chip amps forum in the last few years so I could be completely wrong about that but the tone is all too familiar. One wonders where mankind would be if EVERYONE was like the majority of respondents to your posts. Would we have even progressed to the wheel? They would have found something scary/dangerous about the wheel; it could roll down a hill and you would never ever find it again or you can go so fast with that thing under your cart you might escape the binds of earth and never be heard from again!!! I get nervous just thinking about it! It would have to have a very dire ending.
The heating of a chip amp harming nearby components? Like the two resistors that are close in? Doubt that heat is going to bother them that much. One could make a resistor selection that would minimize that potential problem, anyway.
I am glad you are not the least bit hesitant to make your case with all of these naysaying do-nothing types around here.
Still amazed that they cannot figure out this scenario is part of a commercial product that is not known for failure. I guess they would never let a fact like that get in way of self-righteous indignation.
I am looking forward to hearing how you configure a heat sink that will allow such a temperature rise to that lofty height and then keep it under control.
I am tempted to pull out all of my old chipamp pieces. I assume you are not saying "modern 300B" with irony? But then I doubt I heard my chipamps at their best.
Good sense like the fellow who pointed out (swooosh, it went right over their heads) how inexpensive these chips are compared to vacuum tubes which HAVE to be replaced eventually ... Well, other than marce I have no idea what the others use. marce has mentioned he is a valve enthusiast.
I do not doubt marce is an excellent engineer but I wonder if he uses DIYAudio as a means to entertain himself. He posts on boards he has no demonstrable interest in in the capacity of the bully's advocate all too often wanting to engage in circuitous games of "gotcha". To what purpose I have no idea. Part of the landscape here ...
Looking (and hearing) forward to your posts. Keep up you investigations, kokoriantz.
Shredhead...
You probably know that thd is important on whole audio chain...also on speakers...and thd for your speaker is??? Maybe 10 times higher than mine...maybe at the end my sistem has much lower total thd than yours.
What is thd for the best Tube amplifier in the world? (one of the best Ongaku-Gakuon max 5% THD )
Last month i had possibility to hear a lot of Audio Note gear and enjoy very much, and thd
... talking about music and emotions that is important to me not just thd.
Like with woman...someone like today skiny anorexic model look pushed by todays media other not... I don"t... I prefer fuller SOUND that thrills me.
You probably know that thd is important on whole audio chain...also on speakers...and thd for your speaker is??? Maybe 10 times higher than mine...maybe at the end my sistem has much lower total thd than yours.
What is thd for the best Tube amplifier in the world? (one of the best Ongaku-Gakuon max 5% THD )
Last month i had possibility to hear a lot of Audio Note gear and enjoy very much, and thd
... talking about music and emotions that is important to me not just thd.Like with woman...someone like today skiny anorexic model look pushed by todays media other not... I don"t... I prefer fuller SOUND
that thrills me.I prefer my baquettes in the fridge and not storing them in the owen.
"Further more, Why no one looks at the table shown ,which calculates the heatsink size.The minimum heatsink temperature preconized by the manufacturer at which it can still deploy it's maximum output power,does not start at 50°C nor 60°C( std. max.) but 90°C MIN"
Nope.
And look at the total power supply voltage TI recomends at high temps. At the highest temps it is tot 30 volts. That is +- 15 volts.
And that is with a small heatsink at 25 degr ambient temp or a big(ich) heatsink at 90 degrees ambient.
The table also says 90 degr ambient and biggest possible heatsink for the package 1.2. The total dissipated power from the amp is MAX 25 watts. That is 25 x 1.5 watts max to the speakers before spike hits in. And before that the thd will rise to higher than spec levels.
"Further more, Why no one looks at the table shown ,which calculates the heatsink size.The minimum heatsink temperature preconized by the manufacturer at which it can still deploy it's maximum output power,does not start at 50°C nor 60°C( std. max.) but 90°C MIN"
Nope.
And look at the total power supply voltage TI recomends at high temps. At the highest temps it is tot 30 volts. That is +- 15 volts.
And that is with a small heatsink at 25 degr ambient temp or a big(ich) heatsink at 90 degrees ambient.
The table also says 90 degr ambient and biggest possible heatsink for the package 1.2. The total dissipated power from the amp is MAX 25 watts. That is 25 x 1.5 watts max to the speakers before spike hits in. And before that the thd will rise to higher than spec levels.
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And of courceDMAX = (TJmax − TAmb)/θJA
TJmax is 150 degr
So PDMAX goes down with rising TAmb
PDMAX goes down with smaller heatsink as θJA gets larger
So maybe rising TAmb to more than 150 degrees will make it absorb heat? Don't argue against it please because is will interfere with my creativity
DMAX = (TJmax − TAmb)/θJATJmax is 150 degr
So PDMAX goes down with rising TAmb
PDMAX goes down with smaller heatsink as θJA gets larger
So maybe rising TAmb to more than 150 degrees will make it absorb heat? Don't argue against it please because is will interfere with my creativity
Shredhead...
You probably know that thd is important on whole audio chain...also on speakers...and thd for your speaker is??? Maybe 10 times higher than mine...maybe at the end my sistem has much lower total thd than yours.
What is thd for the best Tube amplifier in the world? (one of the best Ongaku-Gakuon max 5% THD )
Last month i had possibility to hear a lot of Audio Note gear and enjoy very much, and thd
Like with woman...someone like today skiny anorexic model look pushed by todays media other not... I don"t... I prefer fuller SOUND
I am well aware that for most systems speakers will cause the most distortion first. I think you are ignoring the fact that the OP is running the chip so hot that it noticeably changes the sound. This is probably due to the chip reaching it's power limits faster than it would normally. This not only increases the THD but compresses the output of the amp reducing the dynamic range. Perhaps comparing the best tube amp in the world's sound to a stressed out LM3886 chipamp isn't the most fair comparison.
Everyone here is free to like what they like. Hell, put a limiter on your signal chain and squash the dynamic range further if you like but to say this weird stuff about it sounding noticeably different but it's impossible to measure what's causing that difference in sound because it's a peanut butter sandwich or whatever is nonsense.
Bob Carver proved this in the 80's by matching the sound of a cheap amp against the most expensive in the industry at the time. Amp Modelling: Bob Carver & Transfer Function Amps
nothing wrog with ingenuity, and findling with things other people did not think of.
somehow america was found you know.
really no problem with something like that.
but this is a different case. the effects are known, and avoiving them is a goal set.
going face off against it is not quite the way to find out new things.
take it like fresh food vs something that is on the edge of being consumable by a human.
running a hipamp intentionally overheat is the food that is close to be unedible by humans.
and there is a good reason to keep the food fresh.
or tkae a pizza. while its fresh, and when its allready cold and sevaeral days old.
you can argue that it had more time to have a better mix of flavours, but its not heresy to say that a fresh pizza might be the better option...
somehow america was found you know.
really no problem with something like that.
but this is a different case. the effects are known, and avoiving them is a goal set.
going face off against it is not quite the way to find out new things.
take it like fresh food vs something that is on the edge of being consumable by a human.
running a hipamp intentionally overheat is the food that is close to be unedible by humans.
and there is a good reason to keep the food fresh.
or tkae a pizza. while its fresh, and when its allready cold and sevaeral days old.
you can argue that it had more time to have a better mix of flavours, but its not heresy to say that a fresh pizza might be the better option...
I'm guessing you're talking about the channel resistance (RDS(ON)) of a MOSFET. Yeah. That has little relevance for the LM3886 which is all BJT....
Wrong guess. A heatsink Rth-a goes down with increasing temperature. That is, the heatsink temperature increases slower than Rth*Pd where Rth is the thermal resistance @ 25 degrees. Check the data sheet of a large heatsink.
Reason is, you probably guessed, at high temperatures the radiation component increases significantly, it is proportional to the 4th power of the absolute temperature, following Stefan-Boltzman. At lower temperatures, it is the convection only that matters.
Same for all components of the thermal circuit. Unfortunately the Rth decrease with temperature is usually of little practical interest in audio, where the power is rather low, and so is the allowed temperature. Much more significant e.g. for SiC devices (@200 degrees or even more).
I cant see torturing the chip but I do agree that my chipamp sounds better after warming up. Maybe its something else going on, but I always assumed it was the fact that it got warmer that made it sound better after 15 minutes or so. I cant think of any amp I have had in my house that didnt sound better after letting it warm up. I have a good size heatsink on my chipamp. I've built them with larger heatsinks and very small heatsinks. The warming up stage (sounding better after playing a while) happens with small or large heatsinks.
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rickmcinnis
Desperatly I was waiting someone would talk about the inovative power supply :such as
"Sagging power supply delivers only muddy sound"
Strange, why nobody thought about it.When first I branched this amp. I used a very low efficiency speaker 5" without enclosure so that I can run the amp at max power for several hours ,but low sound level.The first thing I noticed with great obviousness ,extraordinary headroom of much higher power amp .The reservoir capacitors are charged at 40V ,so the amp can deliver short bursts of near 90W.
While listening, strange phenomena occurred,regularly I hear objects falling in the room.Before I start thinking about pranormal activities ,I rewind the music,Louis Armestrong and his jazz band.At particular circumstances of double C and the drums played simultaniously ,was giving such phenomena.To say how such freshness associated with dynamics results so realistic sound.
KOKORIANTZ
Desperatly I was waiting someone would talk about the inovative power supply :such as
"Sagging power supply delivers only muddy sound"
Strange, why nobody thought about it.When first I branched this amp. I used a very low efficiency speaker 5" without enclosure so that I can run the amp at max power for several hours ,but low sound level.The first thing I noticed with great obviousness ,extraordinary headroom of much higher power amp .The reservoir capacitors are charged at 40V ,so the amp can deliver short bursts of near 90W.
While listening, strange phenomena occurred,regularly I hear objects falling in the room.Before I start thinking about pranormal activities ,I rewind the music,Louis Armestrong and his jazz band.At particular circumstances of double C and the drums played simultaniously ,was giving such phenomena.To say how such freshness associated with dynamics results so realistic sound.
KOKORIANTZ
[URL=http://www.sherv.net/]
[/URL]
paranormal and Louis Armstrong? reminds me of this ending> Midnight, the Stars and YOU
[/URL]paranormal and Louis Armstrong? reminds me of this ending> Midnight, the Stars and YOU
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That is true. I actually write about that on my Taming the LM3886 - Thermal Design page. Conveniently, Aavid has done the math and calculated the temperature compensation factors for us.
It's also worth noting that most heat sinks - at least those available at common sources, such as Mouser, Digikey, et al. - have their thermal resistance specified for a temperature difference between ambient and heat sink of 70 ºC.
Tom
kokoriantz,
I pointed nige2000 to this discussion.
He is dedicated to the LM3875. He is making a battery power supply using the A123 26650s (though he may be using clones) and I was surprised he did not jump right in. He has his hands full with sorting out this power supply. That could explain his lack of enthusiasm.
He did mention something that he might have said in jest but, in fact , may be the way to get the chip to the best sounding temperature and keep it there.
Use an oven, like you would with precision oscillators.
Instead of intricate heat sink configuration just heat the thing up to the desired temperature and have some kind of servo to maintain that.
Certainly would be simpler.
Have you tried something like this?
Came back to link to this: http://www.romanblack.com/xoven.htm
Take care,
I pointed nige2000 to this discussion.
He is dedicated to the LM3875. He is making a battery power supply using the A123 26650s (though he may be using clones) and I was surprised he did not jump right in. He has his hands full with sorting out this power supply. That could explain his lack of enthusiasm.
He did mention something that he might have said in jest but, in fact , may be the way to get the chip to the best sounding temperature and keep it there.
Use an oven, like you would with precision oscillators.
Instead of intricate heat sink configuration just heat the thing up to the desired temperature and have some kind of servo to maintain that.
Certainly would be simpler.
Have you tried something like this?
Came back to link to this: http://www.romanblack.com/xoven.htm
Take care,
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Let's see what happens at +/- 40Volts.
At steady state sinusodial signal:
At 8 ohm minimum 40 watts are dissipated from 20 watts electrical output and up.
With heatsink at max size we get max ambient temp at 60 degr C at 20 watts electrical output.
Then lets look at a case with 5 watts electrical output:
Disipated power is 30 watts and case temp of chip is 114 degrees C, assuming adequate heatsink and ambient temperature according to table.
At 114 (125) degrees C, the pulsewith must be less than 1 ms to get under 90 thermal watts. Longer pulsewith will melt the chip. We also see that higher start temp gives lover potential pulse voltage, so lesser dynamics.
Also note that at these case temperatures, 250 degrees C, the spike protection will shut down the chip in an audible way.
Attachments
koko - Tom has more than a passing familiarity with the LM3886, and a rather extensive CV in the semi-conductor industry - I'd be inclined to follow his recommendations.
IIRC, his LM3886DR (done right) runs on 120W continuous 24VDC supply. A quicky prototype of that build I heard about a month ago sounded excellent, and ran barely detectably warm to the touch.
IIRC, his LM3886DR (done right) runs on 120W continuous 24VDC supply. A quicky prototype of that build I heard about a month ago sounded excellent, and ran barely detectably warm to the touch.
For descrete circuits, uniform temperature can be important. It depends on temperature coefficient of the components. One of the advantages of ic power amps is relativ uniform temperature of all transistors and biasing circuits. So ic amps do not need the same warm up as amps made with descrete components.
A minute or two should be enough for lm3886. Then the operating temperature is achived.
A minute or two should be enough for lm3886. Then the operating temperature is achived.
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Competently designed ICs are designed such that the (few) temperature sensitive areas are kept away from the heat-generating devices. In addition, the circuits are laid out such that any temperature gradient affects all components equally. IC design relies on the matching between components as this can be tightly controlled in the fabrication process. In discrete design, you rely more on the absolute tolerance of parts as the absolute tolerance is typically much tighter than part-to-part matching.
Depends on the size of the heat sink. On the 0.4 K/W heat sinks I use for testing, the thermal time constant is on the order of 15 minutes. It takes a good hour before the steady state temperature is reached. Unless you know of a way to circumnavigate the laws of thermodynamics, that means it takes a good hour before the LM3886 reaches thermal equilibrium.
Even with a tiny heat sink, it still takes about 15 minutes to reach equilibrium.
Tom
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Best way to improve an LM3886 based amplfier is to retouch all PCB soldering with a Macho Man soldering tool, not the wimpy wave soodering all Factories use.
,_cuts_carbon_steel_with_an_oxyacetylene_torch.jpg)
And for the widest Sound Stage, blacker noise, improved granularity and spacial tri-phasic bio coherence, add 1 foot long extensions to the LM3886 legs so you can play it submerged in:
Mahler´s Seventh never sounded so good, here I played it through n LM3886 held at exact 149.99 C :
https://www.youtube.com/watch?v=PZdLbBFmXCI
And for the widest Sound Stage, blacker noise, improved granularity and spacial tri-phasic bio coherence, add 1 foot long extensions to the LM3886 legs so you can play it submerged in:
Mahler´s Seventh never sounded so good, here I played it through n LM3886 held at exact 149.99 C :
https://www.youtube.com/watch?v=PZdLbBFmXCI
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