Inverted GainClone's gain question?

5150ed · 6th July 2006, 12:22 PM

I just finished my inverted gainclone using OPA541AP, 16V-0-16V 5A tran and 100K TKD step. The sound is really impressive.

But I wondering I have to turn on the step around 1.00-3.00 o'clock to get the same loundness as 9.00-11.00 o'clock from my other int'amp. Is there anything wrong? [ I normally found gainclone with step is enough gain for int' amp]

My amp is truely humless, even connected to my 97db isophon fullrange. I measured DC at my bidingpost around .4 and .5 mV. And voltage +- 24V after diod.

Any suggestion

???

Nuuk · 6th July 2006, 12:31 PM

If you have followed the spec sheets then you will have set a much lower gain for your OPA541 GC than for a GC using one of the LM chips. I expect that's why you find you have lower volume levels.

5150ed · 6th July 2006, 05:20 PM

I use R1=10K, R2 and R3 = 220K.

Should I adjust anything?

Nuuk · 6th July 2006, 06:04 PM

I'm not sure what R1, R2 and R3 refer to but it looks like you have set the gain to around 22. This is too high for the OPA541 and you should reduce it to around 10!

5150ed · 6th July 2006, 07:48 PM

Hmmmm....... You mean that I have to adjusted R2 adn R3 to 100K? And the gain will be much lower

.

What should I do to keep to raise the gain ??? Do I need preamp???

Nuuk · 6th July 2006, 08:17 PM

Yes, if you need more gain then you will need a pre-amp with some gain. How about a valve pre? I tried one with my OPA541 GC and the combination was excellent!

5150ed · 7th July 2006, 07:05 AM

Ho in fact my chip is OPA541AM not AP. Is there anything difference?

Do u got schematic of ur tube pre amp?

Anyway, thank u so much

Nuuk · 7th July 2006, 08:23 AM

No it doesn't matter which version of the OPA541 that you use, the gain should be kept to around a maximum of 10.

Details of my preamp can be found

here and some 'simpler' (but very good) preamps can be found here .

theChris · 7th July 2006, 04:54 PM

the opa541 is built to work. it has an excellent "phase margin" and is stable at any gain. but its gain-bandwidth product is low. basically, that term is just as you would expect: gain*bandwidth = GBP. high gains mean low bandwidth.

the lm chips have a high GBP, but are not unconditionally stable, and require a gain around 10 to function.

as for the low volume, i can't tell for sure, but maybe you have something wrong on the current limiting feature of the opa541.

5150ed · 7th July 2006, 04:54 PM

Thank u so much Nuuk, but i still can not see the picture

.

Do u have the schematic for inverted OPA541 with 10X gain?

6th July 2006, 12:22 PM	#1
5150ed diyAudio Member Join Date: Jul 2005 Location: BKK	Inverted GainClone's gain question? I just finished my inverted gainclone using OPA541AP, 16V-0-16V 5A tran and 100K TKD step. The sound is really impressive. But I wondering I have to turn on the step around 1.00-3.00 o'clock to get the same loundness as 9.00-11.00 o'clock from my other int'amp. Is there anything wrong? [ I normally found gainclone with step is enough gain for int' amp] My amp is truely humless, even connected to my 97db isophon fullrange. I measured DC at my bidingpost around .4 and .5 mV. And voltage +- 24V after diod. Any suggestion ???

6th July 2006, 12:31 PM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	If you have followed the spec sheets then you will have set a much lower gain for your OPA541 GC than for a GC using one of the LM chips. I expect that's why you find you have lower volume levels. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

6th July 2006, 06:04 PM	#4
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	I'm not sure what R1, R2 and R3 refer to but it looks like you have set the gain to around 22. This is too high for the OPA541 and you should reduce it to around 10! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

6th July 2006, 08:17 PM	#6
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Yes, if you need more gain then you will need a pre-amp with some gain. How about a valve pre? I tried one with my OPA541 GC and the combination was excellent! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

7th July 2006, 08:23 AM	#8
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	No it doesn't matter which version of the OPA541 that you use, the gain should be kept to around a maximum of 10. Details of my preamp can be found here and some 'simpler' (but very good) preamps can be found here . __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.


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6th July 2006, 05:20 PM	#3
5150ed diyAudio Member Join Date: Jul 2005 Location: BKK	I use R1=10K, R2 and R3 = 220K. Should I adjust anything?

6th July 2006, 07:48 PM	#5
5150ed diyAudio Member Join Date: Jul 2005 Location: BKK	Hmmmm....... You mean that I have to adjusted R2 adn R3 to 100K? And the gain will be much lower . What should I do to keep to raise the gain ??? Do I need preamp???

7th July 2006, 07:05 AM	#7
5150ed diyAudio Member Join Date: Jul 2005 Location: BKK	Ho in fact my chip is OPA541AM not AP. Is there anything difference? Do u got schematic of ur tube pre amp? Anyway, thank u so much

7th July 2006, 04:54 PM	#9
theChris diyAudio Member Join Date: Dec 2001 Location: SIUE, Illinois, USA	the opa541 is built to work. it has an excellent "phase margin" and is stable at any gain. but its gain-bandwidth product is low. basically, that term is just as you would expect: gain*bandwidth = GBP. high gains mean low bandwidth. the lm chips have a high GBP, but are not unconditionally stable, and require a gain around 10 to function. as for the low volume, i can't tell for sure, but maybe you have something wrong on the current limiting feature of the opa541. __________________ if only it could be used for good, not evil...

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