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Old 5th May 2011, 09:39 PM   #21
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Well, Marchand uses dual LM317's and Elliott Sound uses LM317/LM337 combo, so they can't be all that bad.
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Old 5th May 2011, 09:56 PM   #22
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The TO220 LT3080 with 1.35V drop, 500mA, and a small heatsink should be OK even with a worst-case safety margin. Just wanted to avoid any nasty surprises for Uncle Paul.
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Old 5th May 2011, 09:58 PM   #23
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I quite fond of LM317s myself. They perform well and you need a grenade to destroy one.
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Old 5th May 2011, 11:56 PM   #24
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This is a little old, but interesting for comparison of noise.

LM317:
Simple Voltage Regulators Part 1: Noise - [English]

Basic shunt reg:
Simple Voltage Regulators Part 1: Noise


Here the 337 also shows up worse than the 317, giving a nod to the dual 317 arrangement.
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Old 6th May 2011, 10:55 PM   #25
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I'm currently leaning towards the LT3080 due to it's lower noise. I found this circuit (http://www.awdiy.com/uploads/pdf/LT3080-PSU-DIY-1.0.pdf) which is pretty much the standard configuration with a soft start. I'd also planned to use a pot to fine tune voltage, but just by a couple of volts. Per the data sheet, the noise in Rset is the biggest factor in controlling output noise, so I'll use high quality metal films and cermet pots, and keep the pot around 300 to 400 k (3-4V).

It even uses my LED trick to provide a small load and visual indicator.

One thing I don't fully understand (remember, I'm still a bit rusty) is why the diodes in the bridge are bypassed with caps. I figure it's to snub spikes during the switching while only passing frequencies too high to worry about in rectification.

Still have love for the LM3X7's, and those links are great reads.
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Old 7th May 2011, 01:18 AM   #26
agdr is offline agdr  United States
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Hey that is great that you found a schematic with the part! I see they have 0.1uF bypass caps on both the input filter cap and a load filter cap. I've seen that done quite a bit and is probably a good idea.

You are right, the 47nF caps are snubbers.
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Old 7th May 2011, 07:08 AM   #27
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Quote:
Originally Posted by Uncle Paul View Post
I'm currently leaning towards the LT3080 due to it's lower noise. I found this circuit (http://www.awdiy.com/uploads/pdf/LT3080-PSU-DIY-1.0.pdf) which is pretty much the standard configuration with a soft start. I'd also planned to use a pot to fine tune voltage, but just by a couple of volts. Per the data sheet, the noise in Rset is the biggest factor in controlling output noise, so I'll use high quality metal films and cermet pots, and keep the pot around 300 to 400 k (3-4V).

It even uses my LED trick to provide a small load and visual indicator.

One thing I don't fully understand (remember, I'm still a bit rusty) is why the diodes in the bridge are bypassed with caps. I figure it's to snub spikes during the switching while only passing frequencies too high to worry about in rectification.

Still have love for the LM3X7's, and those links are great reads.
I do have a TO-3 Package LM317K but i only managed to get one
But yeah , the hermetically sealed TO-3 and P packages are and is extremely tough , you'll need a tank to smash it .
I find it useless now tough , is there a negative version of LM317 ?
Or something similar to LM7809 but much more powerful in terms of current .
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Old 22nd May 2011, 03:10 PM   #28
djp150 is offline djp150  United Kingdom
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Default Hi guys ...can you help a non technical guy

I have 2 power capacitors each 2200uf 100v in my power supply . The guy who built the amp has put discharge resistors across them . My question is will these affect either the sound of the amp or performance of the power supply . Thanks and sorry for intrusion Dave
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