I'm waiting on some parts to complete the s22 and I'll have some b22 boards sitting here doing nothing

I'm wondering, in the meantime, if I can get a clean 1amp or so per 24v rail and I simply connect one + to one - to form a middle ground, and I also manually trim the voltages so that both are exactly equal, can that get me by? or even suffice on its own as a mid-end solution?

how important is it that the + and - track each other? the dual TREAD approach is just pure lm317 linear. or I could even use the 317/337 combo for a more textbook +/- supply.

has anyone tried it? any reason why it wouldn't work? I'm assuming it will have worse noise specs than the s22 but for initial use (or budget use), any objection to it?

well, they'll be here soon. I guess I can do that.

the current draw, from your website, says about 200ma per board. if I ran 2 board (only) and was not going to drive speakers, it did sound like I'd be under 500ma, let alone 1A. can't the lm317 take 1 amp with aavid style heatsinks (similar to the b22 variety)?

has no one really tried other PSUs other than the sigma22? I do plan to use my s22 but was curious if anyone had success with others. or even if anyone ever TRIED any others.

If your unregulated voltage going into the LM317 is higher than my example, then it gets worse.

[Edited by amb on 03-02-2009 at 06:55 PM.]

Also, for wire routing is it ok to run the output wires along side the input wires or is that a bad idea? The reason I ask is that the input wires would run along the opposite side of the enclosure where the transformer would be if I decide to run one box in order to mitigate the risk of humming and following that same logic, I thought I would run the output wires there as well.

if I can get it as close as possible to the 24v point (plus the overhead of the reg chip) then it sounds like it could be do-able.

I think the lm317 drops 1.2v, right? so if I need 24v out I'd need at least (24+1.2) ? that's about 25v and if we assume .0707 as a factor for going thru the fullwave bridge, I'd need 17.8v AC to 'jut make it' with minimal heat loss. that would be my ideal trafo, if they made such a thing. (is my math right so far?)

since I can't get a 17.8v trafo, anything close to that would work, with the farther away I go the more heat I have to dissipate in the reg.

the 24vac trafo would yield that 32v that you used in your example, and so that's the upper limit (I guess) in what this scheme could deal with, heat wise.

maybe I should seek out a 20vac trafo, if one could be found?

I'm just looking for alternatives before I finally setting on things. I have the recommended avel trafo but I just want to consider all the possibilities before cutting into my metal cabinets

Choosing transformers is not as straightforward as you might think, if you want to minimize the drop across the voltage regulator and have sufficient headroom under load. This is because despite a transformer's nominal specifications, its output voltage changes with load. Use a really big, efficient transformer, and its voltage won't sag much but it would be quite a bit higher than its spec says. Use a small transformer and you might get close to your "sweet spot" in terms of voltage under a light load, but increasing its load may cause the voltage regulator to drop out of regulation. Add to this the complication that ordinary transformers are not adjustable, so you get stuck with having to use what's available...

All of this is why σ22 is equipped with two paralleled high current MOSFETs per rail, each with a large-ish heatsink. This gives you the thermal dissipation capability needed to support not only the current load for up to four β22 boards, but also a fair amount of voltage drop without self-destructing.

[Edited by amb on 03-03-2009 at 12:48 AM.]

Due to low output impedance, it's not much of a problem running the output wires near the DC power rail wiring, but definitely keep the power and output wires away from the input wires.

Btw, judging from your Mini³ questions, I suggest that you get someone who's more experienced with electronics to help you with the β22 and σ22. If you don't know what you're doing, it could become an expensive and frustrating failure. Also, you'll be working with potentially lethal AC line voltages...

[Edited by amb on 03-04-2009 at 12:26 AM.]

I'll be the first to admit that I'm still a newbie at the DIY scene. I took my time with the CMoy, gamma 1, and mini millet max and didn't have any problems so I thought I was ready for the Beta22 knowing you and other folks would be a resource for me. Perhaps I was overconfident! Unfortunately, I don't have anyone to help out personally, so if it's ok with you, I may be bugging you and the rest of the community with my "noob" questions.

Then again, I live pretty close to you (San Francisco) so I'd be happy to accept any first hand help from you if you're free!

As to my original question, I'm running a 100V toroid but you got the rest right (single sigma, three beta boards). Is 2A slow blow still a good place to start or should I up it a bit?

So I replaced my fuse and everything with the sigma checked out fine so I started running the initial checks on the beta boards. The ground board and one of the channels are both good. The third board, however, has some issues with the R9-R12 checks.

R9 = 4.5
R10 = 0.41
R11 = 4.9
R12 = 0.0

Any thoughts on what might be wrong? I checked the resistor values and they are correct.

-J

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[Quoting dk123]

question: Can i use a 1w 12v zener diode instead of the 500mw 12v diode.

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[Quoting dk123]

ok thanks, unfortunately its really hard to get it from around here, and shipping from overseas, will cost me quite a bit.

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