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Old 4th October 2006, 01:38 AM   #1
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Default Regulated DC power supply

Although the psu I made using LM317T audio grade components and toroidal transformer ''sounds'' good with my phono preamp I would like to build a more sophisticated one mainly to improve sound. Can anybody help?
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Old 4th October 2006, 08:52 AM   #2
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How does it look know?

One way to improve is to insert small resistors in the rectifier bridge so you will attentuate 200, 300, 400 Hz (50 Hz country) components coming from the rectification.

You could also add or switch to a low noise regulator.
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Old 4th October 2006, 11:55 AM   #3
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Thanks P-A. Is there any direct replacement for LM317T?
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Old 4th October 2006, 12:16 PM   #4
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www.linear.com has slightly better types but if you want substantially better you must "go discrete".

What are you looking for in terms of performance?
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Old 4th October 2006, 01:32 PM   #5
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To be honest Im quite happy with LM317T especially after i used the toroidal transformer.It is very quiet but Im just wondering if a better psu-whatever this might mean-can improve sound further.A more delicate and higher resolution sound would definitely be welcomed.So its not so much a matter of noise or is it?
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Old 4th October 2006, 02:35 PM   #6
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Quote:
Originally posted by Panicos K
To be honest Im quite happy with LM317T especially after i used the toroidal transformer.It is very quiet but Im just wondering if a better psu-whatever this might mean-can improve sound further.A more delicate and higher resolution sound would definitely be welcomed.So its not so much a matter of noise or is it?

We can make you even happier with the LM317T -- search for an article entitled "Finesse Voltage Regulator Noise" -- it's a simple way of outboarding some further noise reduction and very easy to implement.
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Old 4th October 2006, 02:42 PM   #7
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Thanks jackinnj I'll search for it.
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Old 20th October 2006, 05:40 PM   #8
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peranders and jacjinnj,a couple of weeks ago you helped with a question on dc supplies.Although I tried several things with mine I just couldnt get rid of some compression in sound of my phono pre that led to a prominant midrange and impared harmonics.Somehow I new it was the psu as with batteries things were simply great.I have decided to read again what National had to say about the LM317 and what I finally experienced might be of interrest to some who use LM317.I have been using a 24vac transformer to the circuit and I needed 24vdc to the preamp and I could get it right.I noticed however that LM317 run very very hot.The higher the input to output differential the LM317 sees the hotter it gets.Some of the trafos I tried had up to 32vac(off load)rather than 24 so the dc fed to the LM317 after the rectifier could be higher than 44vdc not really necessary for the 24vdc required.So I have thought to lower the dc to the LM317 by using a 18vac transformer.I measued around 31vdc after rectifier,enough for 24vdc output.The results are interresting as now even after hours of use the 317 runs just slightly warm(it could burn fingers before)but more importantly the sound became much smoother,gained the lost harmonics,it is clearer and faster without being in any way forward,hard or annoying.Soundstage is now larger and deeper and overall sound is more neutral and sooooo easy on the ear with excellent dynamic range and power,while at very low sond levels you can hear all details clearly.Any comments would be welcomed.
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Old 20th October 2006, 07:12 PM   #9
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Yes, the current rateing falls very sharply after 10V diffirential... I think ending with as little as 10mA at 40V...
Click the image to open in full size.

LM350 and LM338 are rated at 3A and 5A, and are pin compatible as far as I can see.
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Old 20th October 2006, 07:57 PM   #10
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Nordic,actually National suggest tha maximum current with LM317 is achieved at around 15v differential.In my case it was not so much a matter of current as the phono preamp draws little current.I suspect that LM317 can handle 40v differential but sems it doesn't really like to reach it's limits.
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