Aleph L PSU and 50V secondaries

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I just wonder - original AL has trannie with 60V secondaries - that gives around 85V after CRC filtering and before stack of 9V1 zeners - but I have a 50V trannie at hand - so I'll have "only" around 65-70V after CRC ...
But that should be still enough for desired 60V or is there some other catch and I'll have to recalculate some more values???
 
so I'll have "only" around 65-70V after CRC ...
Thats a bit too close to the regulated voltage, as your main supply (The 220v) will drift at least +/- 10%. Just swap out one 9,1v zener with a, say 4v or there about, and you should be fine.
A starving Zenerstring is not supposed to sound pretty:)

Steen:)

BTW. To be sure you dont starve the Zener value, you could just jumper one of them. That would net you some 50V supplies.
 
55V idea sounds great :D

Thanks to both for tips!

Probably I'll do as steenoe sugested - I'll replace one 9V1 zener with 4V one and so get 55V - and then see what will I get out and if there are any major corrections needed in preamp circuitry ...

THANKS again!
 
Well, I'll see what will be put together in this chassis afterall - original idea was the MiniA + BoZ - so that's why 50V secondaries ....

But in last days I'm thinking of making p2p AL instead ...

Btw - which solution should be better - more simple is to put trannie at the back, than PSU caps and preamp on the front panel - so pot is mounted directly to front plate, etc .... But then again - if trannie at the back - it's probably too close to RCA connectors, etc??? BUT OK, the trannie itself has a shield!

Any ideas or even better - experiences with possible troubles when trannie is mounted at the back ???
 

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The finnal look will be - heatsinks silver (I've got them as 2nd hand and were allready eloxated in sliver ...) and the rest black ...

Not so OK considering heat dissipation - but for MiniA I think more than enough ...

Btw - I plan to have +/-15 to 16V (trannie is 12V) and around 1,4A bias - I need highest power at 5R - and those are the numbers that suits me fine ...
 

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Reducing PSU for AL

Hi,

I just wonder - the PSU for AL - "the bottom half" in the schematic - that is one irf 610 and irf 9610, relay and some resistors is there only because of that relay? I don't intend to use delay - so I can easilly left the whole thing out.

Btw - would AL make any thumps during powering ON or why was that relay implemented??
 
Hint: Use a bipolar transistor as the pass device in the regulator.
That way you'll only lose .65V instead of 4V. Adjust the Zener stack to use ten 6V Zeners instead of the 9V ones in the original product. This will make up the difference between the MOSFET Vgs and the bipolar Vbe and you'll end up with the target 60V rail.
Nuthin' to it!

Grey
 
mbr3045

Me again ...

Looking for some nice small heatsinks I've dissassembled some old PSUs - and found inside interesting diodes - MBR3045 by Motorola - I gues since they are 30A/45V - and fast shottky ones - they could be a good choice for my MiniA rectification!

It's the version with 2 diodes inside one chassis - e.g.:
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9100806&N=401
 
Re: mbr3045

Stabist said:
Me again ...

Looking for some nice small heatsinks I've dissassembled some old PSUs - and found inside interesting diodes - MBR3045 by Motorola - I gues since they are 30A/45V - and fast shottky ones - they could be a good choice for my MiniA rectification!

It's the version with 2 diodes inside one chassis - e.g.:
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9100806&N=401

Forget it ... After carefull look - I've discovered I have only one type available - and with only it it's not possible to make gretz ... :(
 
Magura - in this case I can use MUR1560 that were primary meant for this job - the thing I liked about those MBR was that I hoped I can use 4 for double bridge ...

But than again - I should check - are MBR3045 maybe a better choice than MUR - in that case - your sugesstion might be worth of consideration ... :D
 
(1 x bipolar pass device) + (3 x 20V Zeners) = Perfect
The reason that most people use small values and stack them is that it's simpler and more versatile to buy small values in bulk (read: cheaper) than to try to stock smaller quantities of each of a half-dozen 'exact' Zeners that would be used in only one design. They make 60V Zeners, for instance, but it's easier for Nelson to buy a great, whonkin' box full of 9V ones and use one for the Vref in the Aleph amp front end, six in the L preamp regulator...etc. Imagine ending the production run of the L preamp and having a couple hundred 60V Zeners left over. What are you going to do with the beggars? Give 'em to the local orphanage? Easier to select one value that can be used in series to handle anything and everything you're likely to want to do. Take CJ as an example. They used to use rows of 33V Zeners in everything (may still, for all I know). There's not a rule to this, it's just what works for any particular manufacturer.
A bit of trivia. Zeners are not as quiet as we might like. For various subtle quantum mechanical, mumbo-jumbo reasons Zeners in the 5 to 6 volt range are slightly quieter than voltages above or below that. If you're doing something where you're striving for the utmost in quietude, try to arrange things so that you can use Zeners in that range. For this application your 20V Zeners will be great--you're not building a NASA deep space probe. It's just a preamp and you're doing this to have fun. If you want to guild the lily later and use quieter Zeners, have at it, but the majority of the noise you hear through the preamp will likely be from the gain device, not the power supply regulation.
Quieter gain devices?
That's another thread.

Grey
 
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