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Old 22nd March 2010, 01:22 PM   #1
tommy_o is offline tommy_o  United States
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Default Preamp Power Supply Question

Hello everyone,

I'm making my first attempt at building a device without a kit and am having trouble getting the BOM straight. I'm trying to put together a preamp that uses the ESP Audio/Rod Elliot Preamp Power Supply, Project 05. Unfortunately I'm having trouble picking diodes and rectifiers. Can anyone make some suggestions? I'm ordering from Digikey because of their low shipping costs to my area, so any links or information from there would help. The catalog is just a bit, well, daunting.

Thanks!
Tommy O
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Old 22nd March 2010, 01:32 PM   #2
AndrewT is offline AndrewT  Scotland
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the diodes are generally available 1A devices. They come in different voltage versions, denoted by the last numeral.
2 or higher will do i.e. 1n4002, or 1n4004, or 1n4007, etc.
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Old 23rd March 2010, 01:54 AM   #3
tommy_o is offline tommy_o  United States
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Here's my bill of materials. If anyone notices that something won't work then I'd love to hear about it before I order. I'm planning on using a wall wart that outputs 16v at 4.5A.

100v 1A 1n4002 (1N4002DICT-ND)
Panasonic FC 4700uF caps 25v (P10289-ND)
Panasonic .1uF metal film caps 50v (P4525-ND)
Panasonic FC 100uF caps 35v (P10294-ND)
Nat'l Semi Positive TO-220 Regulator (LM340T-15-ND)
Nat'l Semi Negative TO-220 Regulator (LM7915CT-ND)

Those positive and negative regulators don't match up exactly in amp specs, but I'm assuming they'll work. I couldn't find anything more suitable. Do the caps have high enough voltage ratings?

Thanks everyone.
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Old 23rd March 2010, 02:02 AM   #4
just another
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Rod's design uses LM317/LM337 regs. I'd be very wary about changing to a different reg unless you are 100% certain about what you are doing. What might work well for LM317/337 may not work well (or at all) for another reg combo.

I have read that for standard LM317/337 to avoid all but the natsemi ones. I'm personally planning on using some Linear Technology LT317AT's in my own design, but that is a different spec regulator to the standard LM317.

Tony.
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Old 23rd March 2010, 02:23 AM   #5
tommy_o is offline tommy_o  United States
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I may be mistaken, but I believe the Project 05 Rev-B uses the LM317 regulator while the original Project 05 uses 7815/7915.

I couldn't, however, find a strict '7815' positive regulator from Natsemi, although the one I listed does have 'LM7815' as a different name. The negative regulator, on the other hand, does go by LM7915. Go figure.
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Old 23rd March 2010, 02:28 AM   #6
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Hi Tommy, sorry you are correct the original P05 does use 7815/7915 I had recently been looking at the P05A and P05B which both use the LM317/337.

cheers,

Tony.
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Old 23rd March 2010, 03:36 AM   #7
godfrey is offline godfrey  South Africa
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Quote:
Originally Posted by tommy_o View Post
I'm planning on using a wall wart that outputs 16v at 4.5A.
Panasonic FC 4700uF caps 25v (P10289-ND)
Do the caps have high enough voltage ratings?
I'd go for a higher voltage rating for the 4700uF caps.

If the wall-wart gives 16V rms, those caps will have about 22V across them, which is cutting it a bit fine.

With a light load (like your pre-amp), the wall-wart voltage will likely be higher. Then there's variations in the voltage from the wall socket...

35V rating would be safer. Digikey has several for around $2 to $3.

Quote:
Originally Posted by tommy_o View Post
Those positive and negative regulators don't match up exactly in amp specs, but I'm assuming they'll work. I couldn't find anything more suitable.

I found plenty, searching for "7815" and "7915".
e.g. These look OK: LM7815CTFS-ND and LM7915CTFS-ND
They're rated for up to 35V input too (and 1A output).

btw - Hot tip: Get all the components before finalizing the PCB layout. That way, you won't have grief with "wrong" size parts not fitting on the board.

Cheers - Godfrey

edit: d'oh - should have read a bit more carefully above about the regs...

Last edited by godfrey; 23rd March 2010 at 03:43 AM.
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