Voltage reference in JSR03 regulator

[jamont]

I have built the JSR03 using the LM431 and P-A's recommended parts values, and it works fine, the board is very nice.

I am interested in trying the LM329, which presumably is a quieter reference.  Looking at the schematic for the JSR03, it looks like the effective reference voltage using the LM431 is

Vref = 2.5V * (R4/(R5||R6) = 7.41V

using R4 = 10K, R5 = 5.6K and R6 =56K as shown in the schematic.

So if I replace the LM431 with the LM329 and remove R4-R6, the reference voltage will be now 6.95V and I will get a slightly different output voltage unless I replace R8 and R9.

Is this correct?

It also looks like if R6 is omitted when using the LM431, the effective reference voltage will then be 6.96V (from the formula above), almost the same as the LM329.  Is there any reason not to build it this way, leaving out R6?  Then you could get essentially the same output voltage using either LM431, with R4 and R5, or LM329 and omit R4-R6.  Does R6 serve any other purpose?

Thanks for any replies!

[peranders]

First: The LM329 hasn't got the same pinning as LM431

Check the picture:
http://home5.swipnet.se/~w-50674/hifi_pics/hifi_100pr/jsr03r0_lm329.jpg

Secondly: Check the datasheet of LM329

You will get 13.5-13.8 V with a LM329 and gain of 2. If you want 15 volts out you must increase the gain a bit.

If you only let a few mA's through the LM329 it will work fine.

You should only use R3 and none of the R4-R6.

As it is a LM431 plus AD825 gives me approx. 5 uF noise and I'll gather this is more than sufficient for you, even for a MC preamp so changing to a LM329 probably give you only better temperature stability, hardly any lower noise but this is a recomendable tweak because some parameters will get better but the question is if you will notice the difference.

R6 is for trimming the voltage.

[Sigurd Ruschkowski]

There is one voltage ref that according to my research
beats any other voltage reference:
OnSemi's TL431 BI/BV has extraordinary "audio" performance.

Check these data out and let me know if anyone found an other voltage ref that can beat the TL431 BI/BV.







Datasheet can be found at
http://coset.se/tmp/Audio/PerAnders/TL431B/TL431-D.pdf


Sigurd

[peranders]

Which parameters are good when it comes to audio? What is good is very much dependent where you put the 431.

[Sigurd Ruschkowski]

Maybe I am thinking of an application where a TL431 is used as
a normal Zener diode and that this zener is supplying some kind of amp.

For such an applicaton I think that

* low noise over the audio bad

* low output impedande over the audio band

are the most important factors.



Sigurd

[Khron]

If an LM329 is used, there's no way to increase its reference voltage, am i right? So the output is "stuck" at 2x (LM329 reference voltage). The only "adjustable" reference we're left with is the xx431 series, i guess...

[peranders]

Indeed, if you'll use a fixed voltage reference you are stuck with that but you can change the gain instead without any big sacrifice.

[Khron]

Let me guess.. by soldering a resistor where the (optional) 100p compensation cap would be? 

[peranders]

No! I'll recommend that you read what I have written about the JSR01 and JSR03. Have you done that?

[Khron]

Whoops.. silly me.. i got it now.. Many thanks..