OPA549 on single supply

bostjancek · 20th June 2005, 06:38 AM

Hello !

Can anybody comment if the schematic for connecting the OPA549 on the single supply is correct ? If it is not please give me some advice how to make it right.

Cheers

SSassen · 20th June 2005, 08:00 AM

There's a few errors, look at your power supply connections. But more importantly why would you want to run with a single rail? You now have to use a coupling cap at both the input and output which isn't what I'd recommend for anything related to hifi. If you only have a 30-volts single rail you can also split it to 2x15 and settle on that.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

bostjancek · 20th June 2005, 09:01 AM

I have to put this amp in an guitar amp where I have only +30V DC. Can you tell me where are the errors at the power suply connection ?

Cheers

mod_evil · 9th August 2005, 09:56 PM

When do you not have a negative supply. The V- conector go to GROUND.

carlosfm · 9th August 2005, 10:16 PM

Hi bostjancek,

Yes, there are a few errors on your shematic.
The 4,700uf + 100nf caps are in series with the positive voltage rail (?!), they should be parallel from V+ to ground.
The input 2.2uf cap should be before the 47k cap.
And a suggestion: use a 4,700uf cap on the output, although not so important for a guitar amp.

mod_evil · 9th August 2005, 11:52 PM

Quote:

Originally posted by carlosfm
Hi bostjancek,

Yes, there are a few errors on your shematic.
The 4,700uf + 100nf caps are in series with the positive voltage rail (?!), they should be parallel from V+ to ground.
The input 2.2uf cap should be before the 47k cap.
And a suggestion: use a 4,700uf cap on the output, although not so important for a guitar amp.

And... use a snuberized PSU

... I like the snubber that sound is more beautiful than the others schematics! I love your idea.

Thanks

carlosfm · 10th August 2005, 12:18 AM

Quote:

Originally posted by mod_evil
And... use a snuberized PSU

You said that, not me.

carlmart · 10th August 2005, 11:58 PM

Quote:

Originally posted by bostjancek

Can anybody comment if the schematic for connecting the OPA549 on the single supply is correct ? If it is not please give me some advice how to make it right.

One suggestion:

Try a different way for your virtual ground input connection. Increase the value of those resistors to something like 47K each, and don't connect that point directly to the + input, but through another 47K resistor. Then use a a 1uF capacitor from that middle resistor point to the V- rail. That should lower your ripple noise. Or use the parts used in the LM3886 datasheet for single supply application.

A single supply design has several flaws, the large output capacitor being the main one. So I don't think it will help much using a snubberized supply with it.

Carlos

bostjancek · 12th September 2005, 02:05 PM

Thanks for your comments. I realy don't know where my head was when I drown the given schematic.

Cheers !

20th June 2005, 09:01 AM	#3
bostjancek diyAudio Member Join Date: Aug 2003 Location: Koper	I have to put this amp in an guitar amp where I have only +30V DC. Can you tell me where are the errors at the power suply connection ? Cheers __________________ Some are born with more and some born with less so don't take for granted the life we've been blessed it's hard to understand thet we're only a guest and each one of us shall be put to life's test.

9th August 2005, 09:56 PM	#4
mod_evil diyAudio Member Join Date: Dec 2004 Location: Rio	When do you not have a negative supply. The V- conector go to GROUND. __________________ My blog! www.felipenavarro.net

12th September 2005, 02:05 PM	#9
bostjancek diyAudio Member Join Date: Aug 2003 Location: Koper	Thanks for your comments. I realy don't know where my head was when I drown the given schematic. Cheers ! __________________ Some are born with more and some born with less so don't take for granted the life we've been blessed it's hard to understand thet we're only a guest and each one of us shall be put to life's test.

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20th June 2005, 08:00 AM	#2
SSassen diyAudio Member Join Date: Mar 2005 Location: Edam, The Netherlands	There's a few errors, look at your power supply connections. But more importantly why would you want to run with a single rail? You now have to use a coupling cap at both the input and output which isn't what I'd recommend for anything related to hifi. If you only have a 30-volts single rail you can also split it to 2x15 and settle on that. Best regards, Sander Sassen http://www.hardwareanalysis.com

9th August 2005, 10:16 PM	#5
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	Hi bostjancek, Yes, there are a few errors on your shematic. The 4,700uf + 100nf caps are in series with the positive voltage rail (?!), they should be parallel from V+ to ground. The input 2.2uf cap should be before the 47k cap. And a suggestion: use a 4,700uf cap on the output, although not so important for a guitar amp.

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