diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Solid State (http://www.diyaudio.com/forums/solid-state/)
-   -   AF filter using opamps - substitution of opamps (http://www.diyaudio.com/forums/solid-state/197926-af-filter-using-opamps-substitution-opamps.html)

neazoi 5th October 2011 07:00 AM

AF filter using opamps - substitution of opamps
 
hello I consider this filter
http://www.hanssummers.com/images/st...es/article.pdf
I guess I could I use another opamp with the same values of external components without affecting it's frequency response?

I think I am going to try the single opamp versions, since it will be easier to align the components and also it will be easier to add more stages or less, to achieve variable bandwidth. Will something like the cheap ne5534 prove better opamp?
Which opamp would you recommend for very low noise?

abraxalito 5th October 2011 07:07 AM

Changing to the 5534 would probably be noisier, as the allpass stages are working at 100k impedance. To get lower noise you'd need to scale down this resistor value and multiply up the capacitors accordingly. Or you could use (much more expensive) low noise JFET opamps like OPA827. Definitely ditch the differencing 741 if you want it to sound half-way decent.

neazoi 5th October 2011 07:10 AM

Quote:

Originally Posted by abraxalito (Post 2735187)
Changing to the 5534 would probably be noisier, as the allpass stages are working at 100k impedance. To get lower noise you'd need to scale down this resistor value and multiply up the capacitors accordingly. Or you could use (much more expensive) low noise JFET opamps like OPA827. Definitely ditch the differencing 741 if you want it to sound half-way decent.

So the OPA827 could be proved better without any changes in the circuit? (except from pinout maybe, I have not checked)

any equivalent DIP version?

abraxalito 5th October 2011 07:13 AM

Well I think the TL074 is probably low noise enough for something acting as a filter for radio signals - those signals are already far noisier than the opamps here. The difference when switching to OPA827 would probably only be heard on hi resolution audio formats with better than 16bit noise floors.

neazoi 5th October 2011 07:14 AM

Thank you. That make sense

Mooly 5th October 2011 07:17 AM

For single (or dual, or quad) opamps I would go with the TL071 (or TL072 dual, TL074 quad).

The 5534 is power hungry and you would need to ensure stability. The TL0's would drop right in place with no problems.

tbh for it's intended use a 741 (or LM324) isn't going to worsen the overall snr of what comes out all that much.

abraxalito 5th October 2011 07:20 AM

SNR - no, but I bet the THD suffers owing to 741's very restricted bandwidth. No reason to use that device these days with the price of 5532s :)

neazoi 5th October 2011 07:26 AM

Could you give me a review about the AD847 or the ad825 in use in this circuit as well please?

If it is ok, could ththese be used with single supply as well in the circuit? (I see a balanced supply in the datasheet)

Mooly 5th October 2011 07:32 AM

neazoi... the signal you are dealing with is extremely limited.

Anything better than a TL071/2/4 is overkill... you gain nothing performance wise and may lose out in terms of cost, stability and power consumption.

If power consumption is an issue then the low power TL061 and TL062 would be fine.

On the random swapping of opamps see this,
http://www.diyaudio.com/forums/analo...avent-you.html

neazoi 5th October 2011 07:35 AM

Thanks, that makes sense!


All times are GMT. The time now is 10:53 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2