Advice on CCS_TL431_PNP shunt reg + op amps - diyAudio
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Old 6th December 2012, 01:54 AM   #1
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Default Advice on CCS_TL431_PNP shunt reg + op amps

Hi,

I've made a simple shunt reg for an AMB Mini3 headphone amp, to replace the 78**. Like this :

Click the image to open in full size.
image from http://www.a-ling.net/alweb/hifi/tl4.../tl431_reg.htm

I'd like to improve it with a PNP shunt, BC560C, like this, (I already replaced R8 with a 20mA ccs) :

Click the image to open in full size.
image from Werner Ogier's page http://www.tnt-audio.com/clinica/reg..._noise3_e.html

My question is - in Werner's circuit, can I replace R12 with a constant current diode / jfet cascode ? Like this :

Click the image to open in full size.

The op amps I'm using are LM7321/LM7322 (very similar to the LMH6642 / LMH6643 but higher voltage and lower slew, sound v similar). The amp uses 9.5mA @18V. An LM317L + 62R resistor gives a constant current source of 20mA to the TL431. The circuit is currently this :

Click the image to open in full size.

So I think 2mA CCD, E-202, instead of R12 should work well ?

Thanks for any advice !

Last edited by KlipschKid; 27th December 2012 at 12:43 AM.
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Old 15th December 2012, 12:56 AM   #2
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Does no-one know if this CCD into TL431 is a good or bad idea ?

I haven't tried - I'm very pleased with it as it is, so it's just a mental exercise.... if you do know if it's a bad idea, please say....

Thank you.

Show and tell time. The caps are Panasonic AM, which sound too "fat and slow" with speakers but sound "gentle and rounded" in this use. They balance well with the LM7322/21 and HD650. The daddy bears are 2200uF 35V, mummy bears are 220uF 35V, and baby bears are 100uF 16V (after the rail splitter). The bent caps leads are not a good thing but I don't think it has created any problem. D2 and D3 are shorted (it's hard to see...) and I left a space and protruding lead to add a bypass cap for the TL431, but I don't think it needs it - I can't hear any noise in my headphones. Input voltage is from a full-wave rectified 1VA 24VAC transformer so that creates a 30.5V input with the 20mA CCS constant load. The TL431 is set to 3V below that to give the LM317L enough headroom.

Click the image to open in full size.
Click the image to open in full size.

Last edited by KlipschKid; 15th December 2012 at 01:12 AM.
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