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-   -   opa541 schematic (http://www.diyaudio.com/forums/chip-amps/90675-opa541-schematic.html)

s_pics 20th November 2006 06:32 AM

opa541 schematic
 
2 Attachment(s)
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

Nuuk 20th November 2006 08:09 AM

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! :att'n:

Below is what I used and it works very well. ;)

http://nickw.worldonline.co.uk/etc/opa541.jpg

pwan 21st November 2006 04:07 AM

Quote:

Originally posted by Nuuk
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! :att'n:

Below is what I used and it works very well. ;)

http://nickw.worldonline.co.uk/etc/opa541.jpg

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.

Nuuk 21st November 2006 08:28 AM

Sawaddee Pwan,

Quite right about the resistor values! I forgot to add that I am using 10K and 1K3. :)

s_pics 21st November 2006 05:07 PM

thanks guy,

what about C1/R3 is that some kind of filter?
is the value of C2 and C3 1000uF?

Nuuk 21st November 2006 05:47 PM

C1 is the DC blocking cap and R3 a resitor to ground (in case you use the amp without the volume control).

The big caps can be anything really but I found 1000uF worked very well. I have always used Panasonic FCs but now like the Panasonic for Audio types! :)

pwan 21st November 2006 06:28 PM

Quote:

Originally posted by Nuuk

The big caps can be anything really but I found 1000uF worked very well. I have always used Panasonic FCs but now like the Panasonic for Audio types! :)

Nuuk,

Have you ever tried Nichicon "UPW" from mouser? It looks even better than FCs on paper esp. life time.

Nuuk 21st November 2006 08:51 PM

Quote:

Have you ever tried Nichicon "UPW" from mouser? It looks even better than FCs on paper esp. life time.
No, ordering from Mouser isn't really practical from the UK. But I'll keep an eye out for them over here. ;)

s_pics 29th November 2006 12:20 AM

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-Toro...QQcmdZViewItem


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

Easyamp 29th November 2006 12:47 AM

nuuk not sure I understand your gain factor
Quote:

Your resistor values are too high and it is best to keep the maximum gain to 10!
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


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