Optimum gain for Inverted OPA-541 AP

100db · 26th July 2006, 02:58 AM

Hi,

I read through several threads talking about OPA-541 will give best sound quality at gain less than 10, I don't know if this is for Non inverting configulation only or for Inverting also ?

I did try running this chip using inverted 3875 circuit, gain ~22 and face a lot of distortion at high fequency.

Now I reduce gain to ~9. With out any pre / buffer I need to turn the volume up to 3pm. No more distortion, but look like I'm lossing dynamic.

Shall I try to increase gain up to~15 by using Ri 10k and Rf 150k ?
Or it's better to run this amp with pre-amp ?
( I've OPA627 and AD797 in hand )

Thanks

mike.m216 · 26th July 2006, 04:37 AM

Run it with a preamp.

100db · 26th July 2006, 05:02 AM

Many thanks for your suggestion mike.m216 .

One more question

I'm using 25-0-25 Trasformer that give +/- 35.x volt.
Chip is not hot at all, but since I see the datasheet mention that max voltage supply is +/- 35v, I'm not sure that this slightly over voltage will harm the chip or not ?

mike.m216 · 27th July 2006, 12:05 AM

It shouldn't be too bad.. but if you push it hard, it will get warm. Be sure to have a good sized heatink!

100db · 27th July 2006, 02:46 AM

Again, thanks for your answer.

I loss one of 541 by connect ground to heat sink that's already isolated from the chip.... Don't understand why

Mrpong · 27th July 2006, 04:17 AM

Don't worry Ball. Let's try LM4780 in parallel mode. Hopefully this little giant (parallel 4780) could shake your room.

100db · 27th July 2006, 11:35 AM

Waiting for 0.1 Ohm resistor from Mundorf to build my BPA200
( or 300 )

But honestly this opa-541 give some interesting sound when use with 12au7 line pre-amp, would like to try with opa-627 buffer but my 541 already death. This chip is quite sensitive... this is the second time that I blew it off

26th July 2006, 02:58 AM	#1
100db diyAudio Member Join Date: Dec 2005 Location: Bangkok, Thailand	Optimum gain for Inverted OPA-541 AP Hi, I read through several threads talking about OPA-541 will give best sound quality at gain less than 10, I don't know if this is for Non inverting configulation only or for Inverting also ? I did try running this chip using inverted 3875 circuit, gain ~22 and face a lot of distortion at high fequency. Now I reduce gain to ~9. With out any pre / buffer I need to turn the volume up to 3pm. No more distortion, but look like I'm lossing dynamic. Shall I try to increase gain up to~15 by using Ri 10k and Rf 150k ? Or it's better to run this amp with pre-amp ? ( I've OPA627 and AD797 in hand ) Thanks

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26th July 2006, 04:37 AM	#2
mike.m216 diyAudio Member Join Date: Jun 2006	Run it with a preamp.

26th July 2006, 05:02 AM	#3
100db diyAudio Member Join Date: Dec 2005 Location: Bangkok, Thailand	Many thanks for your suggestion mike.m216 . One more question I'm using 25-0-25 Trasformer that give +/- 35.x volt. Chip is not hot at all, but since I see the datasheet mention that max voltage supply is +/- 35v, I'm not sure that this slightly over voltage will harm the chip or not ?

27th July 2006, 12:05 AM	#4
mike.m216 diyAudio Member Join Date: Jun 2006	It shouldn't be too bad.. but if you push it hard, it will get warm. Be sure to have a good sized heatink!

27th July 2006, 02:46 AM	#5
100db diyAudio Member Join Date: Dec 2005 Location: Bangkok, Thailand	Again, thanks for your answer. I loss one of 541 by connect ground to heat sink that's already isolated from the chip.... Don't understand why

27th July 2006, 04:17 AM	#6
Mrpong diyAudio Member Join Date: Aug 2004 Location: Bangkok	Don't worry Ball. Let's try LM4780 in parallel mode. Hopefully this little giant (parallel 4780) could shake your room.

27th July 2006, 11:35 AM	#7
100db diyAudio Member Join Date: Dec 2005 Location: Bangkok, Thailand	Waiting for 0.1 Ohm resistor from Mundorf to build my BPA200 ( or 300 ) But honestly this opa-541 give some interesting sound when use with 12au7 line pre-amp, would like to try with opa-627 buffer but my 541 already death. This chip is quite sensitive... this is the second time that I blew it off

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