[jamont]

I'd like to put a META42 and AC power supply in one of the larger Hammond 1455 cases, preferably using an IEC power inlet. Can anyone suggest a suitable power supply? I suppose it would have to be a switcher, all the open frame linears I know of are way too big.

 

[Voodoochile]

Like this?

I'd build a linear yourself, rather than going with a switcher that will probably cost the same.

Hi John, BTW!

 

[jamont]

Looks good to me!

What case and trafo are you using? Thanks, Mark!

 

[fiddler]

I'm working on a similar project.

Does anybody know if this type of transformer is suitable for a +/- ~12V PS??

http://www.hammondmanufacturing.com/162.htm

I don't think I can afford a toroidal this time...

 

[10SNE1]

>>Does anybody know if this type of transformer is suitable for a +/- ~12V PS??<<

Depends on the PS design especially the degree of regulation you want to achieve.

Also depends on the form factor (physical size) constraints of your enclosure.

You're probably going to need a 12 - 20 VA, 24 - 28V CT model.

 

[fiddler]

I want to keep it as small enough to fit in a Hammond 1455 case. I want it to be linear regulated, but nothing exotic.

 

[jamont]

You could try the Hammond 164G56 (or 162G56), which is 28V @ .44A (12VA). Allowing for dropout, this should give you +-12V or so. The Hammond 1455N1601 case has 1.906" clearance inside the case, the 164G56 trafo is 1.5" high, but this does not include the pins. So it looks tight, but may well be doable.

This is a split-bobbin transformer, should work pretty well in a LM317/337 regulated supply.

 

[Voodoochile]

The two toroids I often use are TE62032 (12v .584a) and TE62043 (15v .666a), depending whether it will be a dual 12v or dual 15v.

The case is the ~2x4x8.5" Hammond, and is roomy. If you get creative with mounting things, it fits in the ~2x4x6" box as well, but it's pretty snug. I'd rather not crowd things too much, although I do like to see amps in small places if done well.

 

[guzzler]

thats a neat little PSU voodoochile, just wondering what kinda temps those little heatsinks produce ??

g

 

[Voodoochile]

They just warm up a bit... you could likely do fine without them, but I like to have at least a little one on the regs.

Even running for several days enclosed, they don't really get more than lukewarm.

 

[fiddler]

My PS n00bness requires your input:

Questions:

Is the input-output voltage differential on regulators too high? It's 6.8V according to my calculation.

In a META42 with C2-C4 populated, is there much sense in putting caps after the regulator?

Are there fixed-voltage versions of the above regulators that I should use instead?

 

[jeffreyj]

Quote:

Originally posted by fiddler I'm working on a similar project. Does anybody know if this type of transformer is suitable for a +/- ~12V PS?? http://www.hammondmanufacturing.com/162.htm I don't think I can afford a toroidal this time...

On that page the 162E24 would be more than enough transformer for a circuit like this (yes, that would be a piddling 2.4VA). The dual 12v secondary is perfect, as it will give plenty of overhead for any 3 terminal regulator to do it's job well but not so much that it will sweat from even this light a load.

You only need to use one bridge rectifier, btw. You connect the two secondaries in series and that connection becomes the ground for the supply rails. The output capacitor stabilizes it against high-frequency oscillation and is very much a good idea. 1-10uF tantalum is usually sufficient. for the job and should be placed very near the output terminal of the regulator.

Don't sweat not using a toroid if you can put at least a couple of inches between the transformer and the op-amps.

edited to add a reference to the ps drawing

 

[fiddler]

Would this be a better choice of tranny?

http://rocky.digikey.com/scripts/Pro...&V=196&M=70022

Seems to be cheaper and shorter, which would be perfect..

I guess I'd use the 12V dual secondary, 5.0VA?

Okay, I'll put a small tantalum for C3/4 then...

What about the caps bypassing R1 and R2? In this little RadioShack book tangent sent me it says that it increases ripple rejection from 65dB to 80dB. Would a tantalum work there, too?

 

[MERTON]

are you talking about my amp? just curious..(80

 

[guzzler]

i think you'll want more than a tantalum for your C3/4, more like some more electrolytics with smaller tantalums in parallel, and then a film cap, just to remove some more noise from the regulators...

tantalums are fine for C5/6

and your input differential isn't too high, 36V is the max input voltage, just remember at 1A output (which is way above anything a headamp delivers, more like 50-100mA max for an amp), the regs will be dumping over 7W of power, so a small heatsink might be a good idea!

g