Using the JLM PSU to power a 312 clone...

Is there any reason I can't use the JLM AC/DC PSU to power a 312 clone?

The description reads:

"JLM AC/DC PCB below is a Linear based universal power supply with can generate 3 voltage rails from a single or dual 24 to 30vac. It has one pump charge rail for 48vdc, 1 +/- Rails that can be set from +/-2v to 37v by a 25turn trim pot. All regulators are on one edge for easy heatsink or case mounting. "

Has anyone tried building this one?

Kato

It's a great power supply should be no problem for the 312 the only difficulty is the caps as they have to be a certain diameter or they don't fit I would use the 1000 uf caps.

Yes the AC/DC will run about 10 x 312 cards with a good heatsink or bolted to the side of a metal case.

For transformers use a 20 to 24v wall wart or 40 to 48v vac centre tapped toroid transformer which will give you a unregulated voltage of 28v to 34v so the 8 x 470uF or 1000uF caps can be 35v ones. The largest diameter caps the PCB takes are 13mm. Our kits come with 1000uF 50v low ESR caps that are 13mm. The caps on the +/- rails are in parallel so 470uF give you about 1000uF each rail or 1000uF give you 2000uF per rail.

Joe

www.jlmaudio.com

[quote author="JLM Audio"]... or 40 to 48v vac centre tapped toroid transformer which will give you a unregulated voltage of 28v to 34v ...[/quote]

Thanks for the info Joe!
In my preliminary searching (digikey, parts-express) it looks pretty hard to find a 40-48v vac toroid.

Does anyone know an american supplier of such a part?

(I'm a total beginner.)
My understanding of "VA" is load, not voltage so I assume by 40-48v VAC that's what you're referring to. So I could probably get away with a lower value if I'm only powering 1 or 2 channels.

Is there a chart somewhere that shows what unregulated voltage you should start with for a range of expected unregulated outcomes?

The 312 schematics I have call for +-15v although I know most people here are building in the +-18 to 20 range.

Should I be looking for something like this:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-670
Or more like this:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-605

Here is the toroids that digikey offer www.amveco.com/
the TE62075-ND will get you up past 24V +- using Jlm's board
or the TE62063 is good for the 15 V +- both are about 20 bucks a pop and
very quiet in the circuit. Jlm's power supply is very adjustable but I recomend a heat sink on the 317's, 337 I got one from a computer psu that worked perfectly including holes and insulating pads. Almost finished my JLM 99v
so I will post pics soon.

The TE62063 will give you +/-15v but will not be enough if you want a regulated 48v rail. Neither of the above two parts express transformers are any use. The TE62075-ND is perfect.

This transformer is overkill but is a bargain and fully sheilded for $7USD but it will only just fit in a 2 rack high case.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=129-088

This toriod can have its 2 x 12v wired in series but the TE62075-ND 44v digikey one would be better than this one and cheaper.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-600
http://dkc3.digikey.com/PDF/T051/1378.pdf

It is also worth concidering the wall mount or wall wart type external transformers as no mains wiring needs to be done and the problem of hum due to the power transformer being in the same case as the audio transformers is solved. MT7132-ND or MT7128-ND will work fine. Or if you need a metal case ground wire use MT7116-ND.
http://dkc3.digikey.com/PDF/T051/1377.pdf

Joe

www.jlmaudio.com

Very nice kit. That was the easiest to stuff board I've done. (With tinned pads and solder mask.) Very impressive. And you have to love the smiley face; it inspires confidence in newbie builders.



Only one dumb mistake. After soldering all the resistors and diodes, I turned the board over to find one resistor soldered a full 1 & 1/2 inch off the board. It slipped and somehow I soldered it in place without noticing.

I almost left it that way knowing it would really make no difference to the final circuit. But the nagging voice telling me to do it right won out. I spent more time desoldering and resoldering that one resistor than I did with the rest of the board combined.

Toroid on order...

Can't wait to get my order!!!!! I bought a PSU from Joe last year and it was fantastic. The new updated one should be even better and I'm anxious to try his Go Between circuit.

:thumb:

Thanks Guys for the kind words :grin:

Joe

www.jlmaudio.com

Joe,

Let me start by saying that your kit was of absurdly high quality, came crazy fast considering the distance it traveled, and went together like a charm. Cheers!

I understand why you suggest a 20-22 V secondary in order for the 48V doubler circuit to work correctly. However, I?m gonna run this supply at +/- 15V for eight Green Pres, which should draw 1-1.2 A total from the power rails. Even with an 18V toroid, which I have installed right now, the phantom can?t quite reach its goal, and the 15 V regulators are tossing out way too much in heat. They really want a 15V secondary at the current I intend to draw. 18 V secondaries, when running in an ideal world, would still give off over 11W of heat at 1.2 A for each regulator. I would rather not push them that much.

So I guess my long-winded question is, if the bi-polar portion of the supply would work best with 15 V secondaries, how can I get the 48 V working? Is there a way to insert an additional stage of voltage doubling, or is another small transformer needed to power the 48V section?

Thanks much,
Andrew

So it seems that there are conflicting requrements for this PSU. There are many solutions. One of them:
If you have a second PCB from JLM you could build a second PSU and run four channels off each PSU at 18V rails.

Good point, but I'm pretty sure one board will have enough juice to cover all eight channels of the Green Pre. I'd like to have only one board to save space, this box is gonna be crazy crowded as it is. Also, I need +- 15, not 18 V. The real problem is, 15 V wants a toroid that won't be enough for phantom, and phantom wants a toroid that will overheat the 15 V regs. I'd rather not have two transformers in the box, but if that is the only way to go, I'll make it happen!

Andrew

I do confirm, that joe's PSU is a great tool, I get 6 from him this year :thumb:
Mik.

Another solution:
Build a separate voltage tripler and a simple regulator. There are schematics all over this forum that will work. They require little more than a few capacitors, four to five diodes, a zener and a transistor.

Thanks everyone for the great comments on the power supply kits. :grin:

The green pre from looking at its circuit should draw between 20mA to 35mA at idle as each NE5532 draw between 6mA to 16mA plus a couple of mA for the transistor input stage. To work out maximum current a NE5532 into a short circuit can only drive 38mA per opamp and this only applies to the output opamp. So the maximum total per green channel should be about 90mA. If all 8 channels are driving full voltage swing into a dead short maximum current draw should be 700mA. Driving all 8 outputs into 600ohm about a 600mA. Driving all 8 outputs into modern 10k loads the maximum current will be about 250mA. This is all roughly calculated but should be int he ball park.

Also when laying out a circuit like the green pre an improvement in output performance when using NE5532 can be gained by not making one NE5532 drive the output but make each NE5532 have one input and one output stage each. So the 1.1watt maximum for the DIP package is not reached before full output current is. To increase the DIP package maximum wattage stick on the copper heatsinks used to cool memory chips.

http://www.fairchildsemi.com/ds/NE/NE5532.pdf

So to minimise regulator heat you can run a 15v or 30v centre tapped transformer into the normal AC inputs on either the AC/DC or Power Station PCB's to get the +/-15vdc rails and leave out the two caps marked below and wire a 22vac to 25vac between AC 0v and one of the pads that went to the + of either cap or 44 to 50vac centre tapped to AC 0v and both pads that went to + on the caps left out. Removing the two caps separates the 48v pump charge from the +/- rails on either the AC/DC or Power Station PCB. The 48v rails transformer could be as small as 7va.

You could also use a 30vac centre tapped transformer and put one winding to AC 0v and the centre tap to AC in and the other winding end to one of the + cap pads. This would give 15vac to the +/-rails and 30vac to the 48v pump charge. The 30vac is a bit high for the pump charge but you could try changing the zener to a 1n4002 and try the LM317 or better still change the 48v rail LM317 to a TL783 and 1n4002 instead of the zener and make sure there is at least 15mA load on the TL783 all the time by adding a 8.2k output load resistor to keep it regulating.



Just some quick thoughts :grin:

Joe

www.jlmaudio.com

Nice! It's great to have a couple options to work with. I appreaciate the help, I'm gonna mull over the two methods and decide which route to take.

thanks Joe
Andrew

[quote author="OddHarmonic"]18 V secondaries, when running in an ideal world, would still give off over 11W of heat at 1.2 A for each regulator. I would rather not push them that much.
[/quote]
[quote author="OddHarmonic"]Good point, but I'm pretty sure one board will have enough juice to cover all eight channels of the Green Pre. I'd like to have only one board to save space, this box is gonna be crazy crowded as it is. Also, I need +- 15, not 18 V.[/quote]

Your statments contradict above. Can you measure the current consumption of a channel?

Also, you should be able to run the Green Pre on 18V without a problem.

Sorry 'bout that. In the first statement I was talking about having the regulators set to 15V, but feeding them with 18 V secondaries from the power transformer. 18 VAC = 25.5 VDC - .6 V (rect.) = 24.9 V. the regulators would be tossing out 9.9 V, or almost 12 W of heat if I was pulling 1.2 A into the pres.

The second statement I was just mentioning the power rails I intended to run, being 15 V not 18V. Although, now that you mention it, 18 V would work fine for all the componants involved. I just have always planned on running them at 15V since that seems to be what everyone is doing with this particular card.

I can't measure the consumption yet, as the pres aren't built, jsut the supply. However, over a wide variety of posts, PRR, PeterC, and now JLM have all made similar estimates/measurements as to the consumption. JLM in this thread said a peak of 700mA for eight channels. I am holding to the assumption that it would be just over an amp, jsut to be on the safe side!

Running these at 18V might be nice, I wouldn't need to pick up a 15V toroid, although the phantom problem would still need to be solved, as the 18 V secondaries still aren't enough for the present voltage doubling circuit.

Hope that all made sense, the day has become long!

word,
andrew

With the 18vac transformer you will get about 50vdc unreg on the 48v regulator input. So you could set about 45v to 46v regulated which would be fine for any 48v phantom powered mic to run off. Even down to 40v you should not notice any difference in mic preformance.

Joe

www.jlmaudio.com

I agree, Joe's kits couldn't get any better! I bought 4 "go betweens" and a DI kit about a month ago... If only everything else went together so easily!

:thumb: