I need to know if this is OK.
I drew this schematic And I want to know if it's good
so it should have a 12.5gain right?
and 8ohm as a speaker should be good?
I will need something like a 3 or 5 W res for R4, sould I use another res value?
maybe I need to put a capicitor between ground and R2
tell me want you think about it
thanks
simon
I drew this schematic And I want to know if it's good
so it should have a 12.5gain right?
and 8ohm as a speaker should be good?
I will need something like a 3 or 5 W res for R4, sould I use another res value?
maybe I need to put a capicitor between ground and R2
tell me want you think about it
thanks
simon
Attachments
Your resistor valvues are too high and it is best to keep the maximum gain to 10! And you are missing the connection from pin 8 to the output! 
Below is what I used and it works very well.
Below is what I used and it works very well.
An externally hosted image should be here but it was not working when we last tested it.
Nuuk said:Your resistor valvues are too high and it is best to keep the maximum gain to 10! And you are missing the connection from pin 8 to the output!
Below is what I used and it works very well.
An externally hosted image should be here but it was not working when we last tested it.
Agreed with Nuuk's on the max gain ( Sawaddee Nuuk!)
However, Be remind that the using 22K/680 (shown in the picture) have x33 gain which heavily degrade the mid & high. To get max gain 10, I personally try 10K/1K on feedback, and change Ri to 10K --> directly feed by CD player via 50K pot. it run beautifully.
now working on the power supply
So I am done with the amplificator circuit, i've made two of them and tried them on a computer power supply +12V/-12V it worked fine, but im not sure is it for an 8ohms spk?
anyway now i'm working on the power supply I just figured out how to obtain a negative tension out of a transformator.
now my questions are is this power supply a +28V 0V -28V? here is the link :http://cgi.ebay.ca/28-28V-500VA-Tor...15QQihZ017QQcategoryZ4660QQrdZ1QQcmdZViewItem
then is 500 VA mean 500Watts?
then is that going to be too much power, should i go with less powerful, if yes then what is the minimum i can use
thanks your time
I will post some pics of my work later on
simon
So I am done with the amplificator circuit, i've made two of them and tried them on a computer power supply +12V/-12V it worked fine, but im not sure is it for an 8ohms spk?
anyway now i'm working on the power supply I just figured out how to obtain a negative tension out of a transformator.
now my questions are is this power supply a +28V 0V -28V? here is the link :http://cgi.ebay.ca/28-28V-500VA-Tor...15QQihZ017QQcategoryZ4660QQrdZ1QQcmdZViewItem
then is 500 VA mean 500Watts?
then is that going to be too much power, should i go with less powerful, if yes then what is the minimum i can use
thanks your time
I will post some pics of my work later on
simon
nuuk not sure I understand your gain factor
If your input was 1 volt and your amps gain was 1*10 that would net generally about 11 volts rms out. Now 1 volt input is not outrages but you'll usually find .6 to.8 volt levels in home audio equipment.
The opa541 is quite capable of more than 100 watts into a 4 ohm load which you will not get close to at this gain level.
I agree the high value resistors used in the original schematic are too high in value but not in relationship for feedback.
feedback needs revision
If your input was 1 volt and your amps gain was 1*10 that would net generally about 11 volts rms out. Now 1 volt input is not outrages but you'll usually find .6 to.8 volt levels in home audio equipment.
The opa541 is quite capable of more than 100 watts into a 4 ohm load which you will not get close to at this gain level.
I agree the high value resistors used in the original schematic are too high in value but not in relationship for feedback.
feedback needs revision
No, the Va rateing is different than watts...I believe they get the VA Rateing by multiplying the Voltage with the Amps to get the Va rateing....
Also that isn"t a Power supply that is just a Transformer you will still need a bridge rectifier or a Diode Bridge and about 10,000uF of Caps (Per Rail?) and some resistors to make a workable Power supply.....
also a 2x28v Transformer will give you about 40v+ after rectification which might be a bit high for a chipamp, Maybe 2x24v would be better to give you closer to 35v.....
Cheers
Also that isn"t a Power supply that is just a Transformer you will still need a bridge rectifier or a Diode Bridge and about 10,000uF of Caps (Per Rail?) and some resistors to make a workable Power supply.....
also a 2x28v Transformer will give you about 40v+ after rectification which might be a bit high for a chipamp, Maybe 2x24v would be better to give you closer to 35v.....
Cheers
No, That transformer is a 2x28v Transformer so it has two 28v AC windings which when converted to DC will be in the neighbourhood of 2x40v DC.....
If the Transformer was a 28v Center Tapped Transformer then it could be interperated as 14v ,0v ,14v Transformer but that is not they type of transformer you posted in your Link.....
You want a Transformer with Dual secondaries or Center tapped but at 28v AC the Voltage will be a Bit high unless you regulate it down a Bit.....
Cheers
If the Transformer was a 28v Center Tapped Transformer then it could be interperated as 14v ,0v ,14v Transformer but that is not they type of transformer you posted in your Link.....
You want a Transformer with Dual secondaries or Center tapped but at 28v AC the Voltage will be a Bit high unless you regulate it down a Bit.....
Cheers
It's not only a question of how much you amplify the signal but whether the amplifier remains stable at a given level of gain!
This has been discussed many times on these forums so some searching may help you further. There are also some questions in this thread that could be answered on my GC FAQ page .
My feedback statement was not a lack of understanding it is only to point out that to use this device with a gain of 10 would not be using it to its potential.
If your input device is capable of 1 volt peak to peak output which is fairly standard then you'd be getting .707v rms input this times 10 is 7 volts rms out and if you were driving an 8 ohm speaker this would get you about 6 watts. Even into 4 ohms a mere 12 watts. I will admit however using a device with a gbp as low as this one you will encounter problems near the upper bandwidth but not until you get above gains of 20.
You would be better served by an lm1875, not to mention your wallet. The lm1875 has a lower distortion figure anyway.
If your input device is capable of 1 volt peak to peak output which is fairly standard then you'd be getting .707v rms input this times 10 is 7 volts rms out and if you were driving an 8 ohm speaker this would get you about 6 watts. Even into 4 ohms a mere 12 watts. I will admit however using a device with a gbp as low as this one you will encounter problems near the upper bandwidth but not until you get above gains of 20.
You would be better served by an lm1875, not to mention your wallet. The lm1875 has a lower distortion figure anyway.
Easyamp,
Your point is well made.
With a one volt input... a 10X gain would be quite dissappointing.
Common opinion in these forums seems to say that the OPA54x is more stable, and "sounds" better with a gain limited to about 10x... rather than using it at higher gains like you could with Overature series chipamps.
The solution is that most guys are adding an extra gain stage in the form of a buffer/preamp to make up the difference.
1v input->3X buffer/preamp->10X main amp = a gain of ~30.
In other words, let your preamp do half the work.
Your point is well made.
With a one volt input... a 10X gain would be quite dissappointing.
Common opinion in these forums seems to say that the OPA54x is more stable, and "sounds" better with a gain limited to about 10x... rather than using it at higher gains like you could with Overature series chipamps.
The solution is that most guys are adding an extra gain stage in the form of a buffer/preamp to make up the difference.
1v input->3X buffer/preamp->10X main amp = a gain of ~30.
In other words, let your preamp do half the work.
There is no 'best gain' as so much depends on other equipment like pre amp and speakers.
Using a Burson Buffer with a gain of 6db, and 96db efficiency speakers, my OPA541 with a gain of 8 has more than enough PRAT.
So as ever, always consider your own system before taking general advise on such issues!
Using a Burson Buffer with a gain of 6db, and 96db efficiency speakers, my OPA541 with a gain of 8 has more than enough PRAT.
So as ever, always consider your own system before taking general advise on such issues!
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