hi,
I got basic question.
When people say their amp does 100 watts in 8 ohms, what does that mean?.
is it 100 watts at peak time?. what is average watts? can you do average wattage of amp based on sound signal?
What is the input voltage (maximum) for an amplifier? is it the sensitivity?.
Is it around 1.5 volts or in 200 mv?.
I am designing amp with 10 mv, not getting enough power for that low input. (225ma,8 ohm load).
Let me know.
Thanks
Alexk
I got basic question.
When people say their amp does 100 watts in 8 ohms, what does that mean?.
is it 100 watts at peak time?. what is average watts? can you do average wattage of amp based on sound signal?
What is the input voltage (maximum) for an amplifier? is it the sensitivity?.
Is it around 1.5 volts or in 200 mv?.
I am designing amp with 10 mv, not getting enough power for that low input. (225ma,8 ohm load).
Let me know.
Thanks
Alexk
input sensitity is the max input signal voltage that drives the amp at max output
power it depends on the internal circuitry and gain of the amp, most amp are
designed to work with sensitivities in the range of o.7v to 2v higher sensitivites
mean lower levels of input signal the voltage levels and power are most often
rms values, higher sensitivies mean that the amp can be driven from sources with lower level
hope this help
happy days mate
power it depends on the internal circuitry and gain of the amp, most amp are
designed to work with sensitivities in the range of o.7v to 2v higher sensitivites
mean lower levels of input signal the voltage levels and power are most often
rms values, higher sensitivies mean that the amp can be driven from sources with lower level
hope this help
happy days mate
Sorry to bug you ,
Is the amplification is same at low voltage?. Is it linear? Like 30 times input signal voltage?. If the amp is not linear what is the use of Output power?.
I simulated my first am design with 10 HZ 10 mv and 1000HZ 10 mv , 20000 HZ 10 mv.
What is the output of common Mp3 player at max sound volume?.
Because my amp clips after 1V input signal. Hahhaaha.
Its all in simulation though, so i have n't lost any money.
How do you measure THD?. How do you measure input impedence of an amp and output impedence?. Will it vary with input frequency?.
More questions follow.
Thanks
Alexk
Is the amplification is same at low voltage?. Is it linear? Like 30 times input signal voltage?. If the amp is not linear what is the use of Output power?.
I simulated my first am design with 10 HZ 10 mv and 1000HZ 10 mv , 20000 HZ 10 mv.
What is the output of common Mp3 player at max sound volume?.
Because my amp clips after 1V input signal. Hahhaaha.
Its all in simulation though, so i have n't lost any money.
How do you measure THD?. How do you measure input impedence of an amp and output impedence?. Will it vary with input frequency?.
More questions follow.
Thanks
Alexk
1 Yes, the amp is linear and amplifies voltage and normal gain is 20-30 times.boxedin said:Sorry to bug you ,
1 Is the amplification is same at low voltage?. Is it linear? Like 30 times input signal voltage?. If the amp is not linear what is the use of Output power?.
I simulated my first am design with 10 HZ 10 mv and 1000HZ 10 mv , 20000 HZ 10 mv.
2 What is the output of common Mp3 player at max sound volume?.
Because my amp clips after 1V input signal. Hahhaaha.
Its all in simulation though, so i have n't lost any money.
3 How do you measure THD?. How do you measure input impedence of an amp and output impedence?. Will it vary with input frequency?.
2 Don't know but no fantasy voltages. I'll guess 0.5-1 volts.
3 You can use an ordinary soundcard and a freeware from http://audio.rightmark.org The output from the program look like this Input and output impedance are normally rather uninteresting as long as they are "normal" and not to extreme.
Normal input signal is 0.1-1 volt and a good power amp can take several volts at the input without break down.boxedin said:
Thanks P-A.
I did the simulation with 500 mv.
http://www.diyaudio.com/forums/showthread.php?s=&postid=798935#post798935
You can comment on it.
All i see i sine wave both side without distortion. So it is working. I think.
How do you reduce noise in single ended class A amp without adding Feedeback or using too many capacitors.
Thanks
Alexk
I did the simulation with 500 mv.
http://www.diyaudio.com/forums/showthread.php?s=&postid=798935#post798935
You can comment on it.
All i see i sine wave both side without distortion. So it is working. I think.
How do you reduce noise in single ended class A amp without adding Feedeback or using too many capacitors.
Thanks
Alexk
Hi,
it is normal to quote sensitivity in either of two alternative forms.
1. the input voltage to produce maximum rated output power.
2. the input voltage to produce a standard output voltage.
The manufacturer can sometimes also specify the amplifier gain.
The gain should be constant for all input voltages between noise only and maximum power output and for all frequencies from a low limit of between DC and 20Hz upto an upper limit from 20kHz to 150kHz.
Since you are designing this amp you choose your limits.
I suggest you aim for a high sensitivity to make it compatible to a wider range of sources. Try a gain between 30 (+29.5db) and 60 (+35.5db) times.
For type 1. and 20W output (single ended amp) the minimum input to produce maximum power is 12.6Vac/30 = 420mVac. This may sound a bit quiet and require a preamp from low level sources. That's why I suggest a higher gain. If it's too loud you can either reduce the source signal or add an analogue volume control to attenuate the signal.
For type 2. and 1Vac output the input would be 1Vac/30 = 33mVac. This is more like the average level coming from sources with normal music content. Since the 1V is well below maximum compared to 20W you have a headroom for loud peaks. The headroom is 12.6/1 = 12.6 times and converted to decibels = +22db.
Hope this helps.
I have included a range of concepts here and if you need clarification please ask.
it is normal to quote sensitivity in either of two alternative forms.
1. the input voltage to produce maximum rated output power.
2. the input voltage to produce a standard output voltage.
The manufacturer can sometimes also specify the amplifier gain.
The gain should be constant for all input voltages between noise only and maximum power output and for all frequencies from a low limit of between DC and 20Hz upto an upper limit from 20kHz to 150kHz.
Since you are designing this amp you choose your limits.
I suggest you aim for a high sensitivity to make it compatible to a wider range of sources. Try a gain between 30 (+29.5db) and 60 (+35.5db) times.
For type 1. and 20W output (single ended amp) the minimum input to produce maximum power is 12.6Vac/30 = 420mVac. This may sound a bit quiet and require a preamp from low level sources. That's why I suggest a higher gain. If it's too loud you can either reduce the source signal or add an analogue volume control to attenuate the signal.
For type 2. and 1Vac output the input would be 1Vac/30 = 33mVac. This is more like the average level coming from sources with normal music content. Since the 1V is well below maximum compared to 20W you have a headroom for loud peaks. The headroom is 12.6/1 = 12.6 times and converted to decibels = +22db.
Hope this helps.
I have included a range of concepts here and if you need clarification please ask.
I still don't understand it. But i think i find which particular resistor changes of sensitivity of the amplifier. Input gainstage. Mainly Ac Current path. If i can vary the Resistor it vary the gain of AC current(amplified). By making it low i can increase the sensitivity by increasing the gain of amplifier but it will clip after some stage. To be wide band sensitivity , i had to increase the resistance for ac current path and decrease the gain of Amplifier first stage.
My simulation works good as i do not get my Input do not distort with 0-1 V input. I can get same output with 0-100 mv also by increasing the sensitivity.
Sensitivity do not affect overall performance of amplifier except with higher sensitivity noises also get amplified.
I will work on noise part later.
Now back to my power stage. I don't see anyone uses darlington pair for Current gain stage? why? There is no good darlighton pair transistor suitable for audio?
Thanks
Alexk
My simulation works good as i do not get my Input do not distort with 0-1 V input. I can get same output with 0-100 mv also by increasing the sensitivity.
Sensitivity do not affect overall performance of amplifier except with higher sensitivity noises also get amplified.
I will work on noise part later.
Now back to my power stage. I don't see anyone uses darlington pair for Current gain stage? why? There is no good darlighton pair transistor suitable for audio?
Thanks
Alexk
Hi Boxedin,
in general the lack of flexibility due to only 3 legs being available for circuit connections may put off some designers.
I think the main reason is that many designers choose their components to suit the duty. Inside the darlington the two transistors and resistor (if fitted) are preselected and you're stuck with that.
Further, most higher power darlingtons are based on quite slow devices and many designers have moved on.
in general the lack of flexibility due to only 3 legs being available for circuit connections may put off some designers.
I think the main reason is that many designers choose their components to suit the duty. Inside the darlington the two transistors and resistor (if fitted) are preselected and you're stuck with that.
Further, most higher power darlingtons are based on quite slow devices and many designers have moved on.
Lemme give it a shot...
Your input source signal will have x voltage level.
Your amp, according to its power rateing will be able to produce Y amount of volt after amplifying signal x.
Chips according to their intended use do not have unlimited gain settings, some chips you can't get to low gain levels, some you can't go high, also the more gain you expect to have, the less bandwidth you will be able to produce it over...
Now even amps have specific jobs (if you are smart)
consider that you might want to drive the signal from an exensive turntable cartridge comming in at a whopping 2mv, but you want to drive your 100W speakers for a party... as you can deduce, you will need to ampify that signal many many times before it gets to the minimum voltage your amp will need to deliver its maximum signal....
Lets just say the amp does 30V on the rail and had a gain of 30, it would mean it needs 1V (times 30) on the input before it will produce 30V on the output. THESE ARE JUST FIGURES I SUCKED OUT OF THE AIR.
Does this make it a bad amp? No. It is simply keeping the amp within its specified parameters for best performance over the audiable spectrum. What may be needed is another stage or 2, thats why people use preamps... (2mv x15 = 30mv, 30mv x30 = 0.9V, getting close to driving maximum power).
My integrated amp's inputs (except phono) are on average 250mv sensitivity, for reference... modern DVD players etc. tends to drive a more powerfull signal though.
P.S.
Output values are probably of little meaning, what (and I thank PA for teaching me it with his PDF attachments) is important, is the max power the amp can handle when driven by a sinosoidal wave, before Spike protection kicks in... obviously the amp will be able to play normal music sources at even higer power...
Your input source signal will have x voltage level.
Your amp, according to its power rateing will be able to produce Y amount of volt after amplifying signal x.
Chips according to their intended use do not have unlimited gain settings, some chips you can't get to low gain levels, some you can't go high, also the more gain you expect to have, the less bandwidth you will be able to produce it over...
Now even amps have specific jobs (if you are smart)
consider that you might want to drive the signal from an exensive turntable cartridge comming in at a whopping 2mv, but you want to drive your 100W speakers for a party... as you can deduce, you will need to ampify that signal many many times before it gets to the minimum voltage your amp will need to deliver its maximum signal....
Lets just say the amp does 30V on the rail and had a gain of 30, it would mean it needs 1V (times 30) on the input before it will produce 30V on the output. THESE ARE JUST FIGURES I SUCKED OUT OF THE AIR.
Does this make it a bad amp? No. It is simply keeping the amp within its specified parameters for best performance over the audiable spectrum. What may be needed is another stage or 2, thats why people use preamps... (2mv x15 = 30mv, 30mv x30 = 0.9V, getting close to driving maximum power).
My integrated amp's inputs (except phono) are on average 250mv sensitivity, for reference... modern DVD players etc. tends to drive a more powerfull signal though.
P.S.
Output values are probably of little meaning, what (and I thank PA for teaching me it with his PDF attachments) is important, is the max power the amp can handle when driven by a sinosoidal wave, before Spike protection kicks in... obviously the amp will be able to play normal music sources at even higer power...
Input : 0-100 mv Output 11 V (p-p) , 1.5 A (p-p) with 30 V+ Only
Input : 0-1V Output 11V (p-p) , 1.5A(p-p) with 30 V+ Only
at my 8 ohm load (Speaker).
If i get this is my amplifier has wide band ? Actually i can get both that by adjusting sensitivity pot of my amp without distoring my sin signal input for 20-20000hz.
My only problem is i still need more power than what it is giving now without any more distortion. I am still working on power part of it.
After power i have to do input protection and noise removal with open input.
Thanks
Alexk
Input : 0-1V Output 11V (p-p) , 1.5A(p-p) with 30 V+ Only
at my 8 ohm load (Speaker).
If i get this is my amplifier has wide band ? Actually i can get both that by adjusting sensitivity pot of my amp without distoring my sin signal input for 20-20000hz.
My only problem is i still need more power than what it is giving now without any more distortion. I am still working on power part of it.
After power i have to do input protection and noise removal with open input.
Thanks
Alexk
Hi Boxed,
11Vp-p =5.5Vpk=1.9W into 8R P=Vpk*Vpk/2/R
A 30Vdc single ended amp should get about 20Vp-p to 26Vp-p depending on your design.
By the time you get above a couple of kHz the distortion will rise. Start by doing your testing on 1kHz sine to sort things out, checking occasionally at 10kHz to see if all is OK.
11Vp-p =5.5Vpk=1.9W into 8R P=Vpk*Vpk/2/R
A 30Vdc single ended amp should get about 20Vp-p to 26Vp-p depending on your design.
By the time you get above a couple of kHz the distortion will rise. Start by doing your testing on 1kHz sine to sort things out, checking occasionally at 10kHz to see if all is OK.
The ncore 1200 data specifies:
input sensitivy: 2V
max output in 8 Ohm: 400 W
gain: 26 db
2V * 26db = 39.9V
39.9V/8Ohm = 4.99 Amp
4.99 Amp * 39.9V = 199 Watt
but 2v rms = 2.8284 peak
2.8284 *26db = 56.435 V
56.435 V/ 8 Ohm = 7.05 Amp
7.05 Amp * 56.435 = 398 Watt
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