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Old 3rd March 2006, 07:13 PM   #1
Khron is offline Khron  Romania
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Default GC "hybrid" supply

I intend on using a "hybrid" PSU for my RevC's, as follows:


An SMPS (with a hefty tranny, ~6 cu.in) (link's on my dad's comp, i'll attach it ASAP)

Two two-stage LM338s, first stage being a conventional reg, and the second being a "super-reg" (as in http://www.neilmcbride.co.uk/preamp.html), followed by the snubber that CarlosFM recommended.


I just received my 5-sample order of LM3886s from NatSemicon, so i hope to start work ASAP

I hope that this "frankenstein" of a PSU will sound near perfection (considering the good reviews that SMPS's). Has anyone else tried anything similar???
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Old 3rd March 2006, 10:13 PM   #2
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Yes, I have tried several variations on various themes of PSUs for "My Ref" RevC, but never a SMPS. It should be an interesting experiment. Just out of curiosity, have you tried it as designed? The PSU is actually very purpose designed for the interaction with the opamps configured as they are (think PSSR). You may not feel the need to do anything else, but curiosity says "hey it would be fun to try". Certianly it is fun to fiddle. So go for it.



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Old 4th March 2006, 08:04 AM   #3
Khron is offline Khron  Romania
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By "have you tried it as designed" do you mean the PSU on the RevC PCB? If you do, then i haven't tried that yet.

It's just that my dad had the great idea of modding some PC PSUs that we had lying around. After we redid the windings on the power tranny, results looked promising, so we're gonna build an SMPS according to the schematic/PCB from a site i'll have to ask dad about.

I think a first reason would be costs, then weight.
A several hundred watt tranny / toroid is, to say the least, huge, not to mention sort of expensive compared to what i'm willing to spend
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Old 4th March 2006, 02:16 PM   #4
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The link to the SMPS, only mine will have two separate 35Vdc secondaries.


http://www.qrp4u.de/docs/en/smps_new/
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Old 4th March 2006, 03:07 PM   #5
Bazukaz is offline Bazukaz  Lithuania
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LM3886 has a typical supply rejection ratio of ~100db or more.What is the reason to do a regulated supply ?
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Old 4th March 2006, 04:39 PM   #6
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Because it sounds better.
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Old 4th March 2006, 05:18 PM   #7
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Quote:
LM3886 has a typical supply rejection ratio of ~100db or more.


And at what typical frequency does this happen?
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Old 4th March 2006, 07:17 PM   #8
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Originally posted by analog_sa
And at what typical frequency does this happen?
On the negative rail, up to ~100Hz.
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Old 4th March 2006, 07:47 PM   #9
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So, should i consider that i've received the blessing of CarlosFM?
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Old 4th March 2006, 07:54 PM   #10
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Quote:
So, should i consider that i've received the blessing of CarlosFM?
Mmm. Probably not. Those PC SMPSs will be noisy as hell and the effort to reduce the noise will negate any cost advantage of using them. Still, your aim might not necessarily be absolute sound quality.
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