New preamp with LME49710 - Page 3

sgrossklass · 5th January 2012, 07:40 PM

What exactly is this preamp supposed to do? How much voltage gain and how little noise do you need? (I can tell you right away that feedback Rs in the hundreds of kOhms make a good noise and distortion generator. A 10k resistor has 12.6 nV/sqrt(Hz) of voltage noise, scaled to other values via sqrt(R/10k).) What kind of input signals and loads would it have to handle?
Jumping into building the thing is kinda pointless if you haven't thought of the specs first. I suggest you read this so you get an idea of how the pros do it.

I dunno what's supposed to be wrong with a LM317/337 setup. (The above example got away with bog standard 78xx/79xx jobs, albeit lower-noise ones, and still noise and power supply rejection performance of the finished unit is very good.) A "low-noise" config (electrolytic at the adjust pin and all) gives perfectly acceptable noise levels and regulation for anything that has ever heard of PSRR (and audio opamps tend to have at least 30 dB across the audio band at 20 dB gain, more at lower frequencies). Just make sure you use a good grounding layout, as not having one may reduce regulator performance to very modest levels.

AndrewT · 5th January 2012, 07:42 PM

Quote:

Originally Posted by sgrossklass

........... may reduce regulator performance to very modest levels.

Or would it be more accurate to say "very immodest levels"?

dtses · 12th January 2012, 10:19 AM

hi,

if I use LME49710HA for each channel, would it make any improvement building two +- shunt regs? or one for both opams would be enough?

dtses · 13th January 2012, 12:06 PM

thanks!

gmphadte · 17th January 2012, 04:17 AM

If u make dual mono instead of stereo, it is always better.

Gajanan Phadte

dtses · 17th January 2012, 09:56 PM

thanks!
I think I would stay with two LME49710HA and single +-12v PS.

dtses · 18th January 2012, 09:01 PM

again another question regarding power supply

it appears that 100nf of fkp-2 is huge value, 10nf could be easily found, while 100 is smth rare...

Should I stay with other fkp-2 value or use some other cap in PS equal to 100nf besides 1uf mks and 100uf elko?

gmphadte · 19th January 2012, 04:43 AM

The values shown in the design r a result of spice simulation and best sound, if I am not wrong. U should try them but u can always alter the values for convenience but it will be a compromise.

Gajanan Phadte

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Looking for some NS LME49710 Single DIP Opamp	dtm1962	Swap Meet	0	4th September 2008 12:06 AM
LME49710 missing data in datasheet	peranders	Parts	19	15th May 2008 05:27 AM
LME49710 -- new passive RIAA Circuit	jackinnj	Solid State	7	18th July 2007 09:19 AM
WTB:LME49710 and LME49740	Ryssen	Swap Meet	5	4th June 2007 08:38 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

5th January 2012, 07:40 PM	#21
sgrossklass diyAudio Member Join Date: Nov 2004 Location: Germany	What exactly is this preamp supposed to do? How much voltage gain and how little noise do you need? (I can tell you right away that feedback Rs in the hundreds of kOhms make a good noise and distortion generator. A 10k resistor has 12.6 nV/sqrt(Hz) of voltage noise, scaled to other values via sqrt(R/10k).) What kind of input signals and loads would it have to handle? Jumping into building the thing is kinda pointless if you haven't thought of the specs first. I suggest you read this so you get an idea of how the pros do it. I dunno what's supposed to be wrong with a LM317/337 setup. (The above example got away with bog standard 78xx/79xx jobs, albeit lower-noise ones, and still noise and power supply rejection performance of the finished unit is very good.) A "low-noise" config (electrolytic at the adjust pin and all) gives perfectly acceptable noise levels and regulation for anything that has ever heard of PSRR (and audio opamps tend to have at least 30 dB across the audio band at 20 dB gain, more at lower frequencies). Just make sure you use a good grounding layout, as not having one may reduce regulator performance to very modest levels.

12th January 2012, 10:19 AM	#23
dtses diyAudio Member Join Date: Nov 2009 Location: UK, Manchester	hi, if I use LME49710HA for each channel, would it make any improvement building two +- shunt regs? or one for both opams would be enough?

13th January 2012, 12:06 PM	#24
dtses diyAudio Member Join Date: Nov 2009 Location: UK, Manchester	thanks!

17th January 2012, 04:17 AM	#25
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	If u make dual mono instead of stereo, it is always better. Gajanan Phadte

17th January 2012, 09:56 PM	#26
dtses diyAudio Member Join Date: Nov 2009 Location: UK, Manchester	thanks! I think I would stay with two LME49710HA and single +-12v PS.

18th January 2012, 09:01 PM	#27
dtses diyAudio Member Join Date: Nov 2009 Location: UK, Manchester	again another question regarding power supply it appears that 100nf of fkp-2 is huge value, 10nf could be easily found, while 100 is smth rare... Should I stay with other fkp-2 value or use some other cap in PS equal to 100nf besides 1uf mks and 100uf elko?

19th January 2012, 04:43 AM	#28
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	The values shown in the design r a result of spice simulation and best sound, if I am not wrong. U should try them but u can always alter the values for convenience but it will be a compromise. Gajanan Phadte

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)