Can anyone help with this opamp circuit?

lt cdr data · 19th May 2005, 08:38 PM

I posted this off to Erno Borbely who was a real gentleman, but hadn't seen it before.

I can't upload it, no scanner, I will try to describe as best I can, perhaps someone could try to draw it?

its the 2nd stage of an IC phonostage.

ne5532 positive input comes from the riaa.

output goes out to the preamp.

in the feedback loop coming off this is the other half of the 5532 with a :

5k series resistor and a 1k to ground, at the positive input,

this is where it gets tricky...

a 5 k feedback resistor and 1k to ground goes to both the negative of the feedback opamp, AND the negative terminal of the original half of the first opamp.

That's as clear as I can make it, any ideas on what the feedback opamps function is, desperate to find out.

thanks.

jcx · 20th May 2005, 02:24 AM

at linear.com you can download the free Lt SwCAD III spice tool, its easy to draw with, just use any standard op amp to show us the circuit - capture a screen shot with paint, crop and save as .gif (not jpg!)

xplod1236 · 20th May 2005, 02:59 AM

Something like this? I ran a simulation on it, and it shows a gain of 6.

lt cdr data · 20th May 2005, 07:45 AM

spot on xplod....that's it

anyone know what the feedback opamp does?

if no-one replies, I shall try a post in the opamp section, or a new one here.

brilliant, thanks guys, IM

BobEllis · 20th May 2005, 10:12 AM

Funny, this very topic was discussed here yesterday. http://www.diyaudio.com/forums/showt...411#post642411

19th May 2005, 08:38 PM	#1
lt cdr data diyAudio Member Join Date: Dec 2003 Location: earth	Can anyone help with this opamp circuit? I posted this off to Erno Borbely who was a real gentleman, but hadn't seen it before. I can't upload it, no scanner, I will try to describe as best I can, perhaps someone could try to draw it? its the 2nd stage of an IC phonostage. ne5532 positive input comes from the riaa. output goes out to the preamp. in the feedback loop coming off this is the other half of the 5532 with a : 5k series resistor and a 1k to ground, at the positive input, this is where it gets tricky... a 5 k feedback resistor and 1k to ground goes to both the negative of the feedback opamp, AND the negative terminal of the original half of the first opamp. That's as clear as I can make it, any ideas on what the feedback opamps function is, desperate to find out. thanks.

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20th May 2005, 02:24 AM	#2
jcx diyAudio Member Join Date: Feb 2003 Location: ..	at linear.com you can download the free Lt SwCAD III spice tool, its easy to draw with, just use any standard op amp to show us the circuit - capture a screen shot with paint, crop and save as .gif (not jpg!)

20th May 2005, 07:45 AM	#4
lt cdr data diyAudio Member Join Date: Dec 2003 Location: earth	spot on xplod....that's it anyone know what the feedback opamp does? if no-one replies, I shall try a post in the opamp section, or a new one here. brilliant, thanks guys, IM

20th May 2005, 10:12 AM	#5
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	Funny, this very topic was discussed here yesterday. http://www.diyaudio.com/forums/showt...411#post642411

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