"To build, Or not to build" API 500 PSU

[tubetastic]

Greetings fellow gearheads and geeks.

I'm the proud new owner of my first api500 series unit. It's an OSA MP-1c "the vintage." I'm quite excited about it, however I'm still hashing out my stance on a PSU. You must remember, I'm still quite new to this whole world of modding out vintage pres and retrofitting your own outboard circuitry. SO I was hoping someone could help me find some answers to help extinguish my naivety.

After doing my research on PSUs and Rack units for these 500 series units I've decided paying someone else $600 for a fancy AC/DC converter with some line filters in it rather disgusts me. I guess my question is, "Should it?" Really that's my artsy way of asking, is there anything wrong with making one myself? I know that there is some huge tonal differences in the components and circuitry in these preamp modules, but is there in the power supply?

DO I need any special vintage or New/Old stock transformers or caps? Or should I just focus on good sterile, consistent power of the right voltage and amperage, and let the pre module do the rest? Or maybe it's just a terrible Idea and I should bone up and throw down the cash on a manufactured PSU?

I'm no Brent Averill, but I've always been a DIY-er. So soldering, and circuitry aren't an issue (i've even been known to wind my own inductors (geek!!)), and where my knowhow fails me, there's always my genius, neighbor who has his masters in electronics =)
But like I said, I'm a green horn (and my neighbor doesn't know squat about tone or vintage pres). So Let the wisdom roll in...

Thanks brothers .

[tubetastic]

Actually, I may have found my answer. Tell me what yall think of this. I just discovered FiveFishStudios.com. He sells kits for 18V PSUs. Now according to the specs on the the api website the 500 units are designed for +-12/18 volts. So would this work?

[TAVD]

Just go buy a International Power IHAA15 -0.8 or -1.5 depending on how many modules you need to power. Power supplies are probably the least exciting thing in the world to DIY, at least they are for me.

[rotation]

I would just buy that kit and make it myself. PSU for this kind of things is very simple to make. But, test it first well before connecting it to your new preamp.

Good luck!

[owel]

The three rails on my PSU are adjustable via the on-board trimmers.

Switching* PSUs are noisier than Linear PSUs. So not unless you really, really need it to be a switching type, Linear PSUs are preferable.


* If you need boost/buck/buck-boost functionality in your PSU, or very high wattage and efficiency, then switching PSUs are the only solutions. But EMI/RFI from the Switching PSU inductors can find it's way to your mic input circuitry and can be heard as "hashing", "white noise", "whining" sound.

Note that line regulation and ripple of switching PSUs can match that of Linear PSUs, but Linear PSUs are generally quieter because they don't have any switching transients that can generate RFI/EMI.

[tubetastic]

Great. Thanks boys. Lots of great info. My next step is, how to connect it all. I planned on mounting it in my own custom wood frame instead of a manufactured one. Is that heard of? Can I find one of those 15 pin sockets, or is there another clever way? Help?!?!

I embarked on the research a bit already and found my best resource to be the spec sheet on the api512c. It gives a layout and description of all the pins in the socket. Of course this is for the api512c and I have an OSA MP-1c, but if they are universally interchangeable it should be the same layout... right? The diagram doesn't totally make sense to me. The power stuff (pin 12, 13, 14) is pretty obvious. Remaining mysteries.

Pin 1: Chassie of module?

Pin 2: + audio out (+4 db) ?
Pin 3: + audio out (-2 db) ?
*so I'm guessing I pick weather I want to run at +4 db and -2 db And wire my + XLR in pin to that? (assuming I don't install a switch)


Pin 4: "Out put Low"? What is that? Is that my out - ?

or is...

Pin 5: "Audio Ground" My out - ?

Or do the In and the out share pin 5 Audio Ground for their - ?

This is where it all gets lost on me. Can anyone just explain Where my +, -, and GND for my XLR in and XLR out go?

Finally. I understand I'll need a separate power supply for the +48v (pin 15) Where does my - for that power supply go? PWR GND (pin 13) with the main power?


Peace.

[TAVD]

I embarked on the research a bit already and found my best resource to be the spec sheet on the api512c. It gives a layout and description of all the pins in the socket. Of course this is for the api512c and I have an OSA MP-1c, but if they are universally interchangeable it should be the same layout... right? The diagram doesn't totally make sense to me. The power stuff (pin 12, 13, 14) is pretty obvious. Remaining mysteries.

I think the pinout for the 525 is a little clearer.

Pin 1: Chassie of module?

Pin 2: + audio out (+4 db) ?
Pin 3: + audio out (-2 db) ?
*so I'm guessing I pick weather I want to run at +4 db and -2 db And wire my + XLR in pin to that? (assuming I don't install a switch)


Pin 4: "Out put Low"? What is that? Is that my out - ?

or is...

Pin 5: "Audio Ground" My out - ?

Or do the In and the out share pin 5 Audio Ground for their - ?

This is where it all gets lost on me. Can anyone just explain Where my +, -, and GND for my XLR in and XLR out go?

+4 = pin 2, low = pin 3, ground = pin 1 of the XLR

Finally. I understand I'll need a separate power supply for the +48v (pin 15) Where does my - for that power supply go? PWR GND (pin 13) with the main power?

Yes.

[tubetastic]

Thanks Tom. It's beginning to come together in my head. I'm still wondering about the input XLR pins. In my opinion, it gets more complex here. I'm gonna guess:

8, 9, & 10 all look like healthy candidates for Pin 2 of the XLR in. So which would it be?

7 (low) = pin 3 of my input XLR??

5 (Audio Gnd) = Pin 1 input XLR (again)?

Also, is the chassis connection (pin a1) necessary?
Aside from the power, the IN the OUT what else is necessary?

[tubetastic]

P.S. Any word on where to get the female end of those 15 pin sockets, or a healthy alternative?

[ulysses]

You need more than a power supply. A major part of the expense is the big piece of metal that holds your module(s), the edge connector, input and output connectors, and power supply in positions that are reliably consistent relative to one another.

You get what you pay for, whether you pay in dollars or in sweat and blood. There are some good racks out there for 500-series modules, and there's some crap. Both are available in a wide range of prices. When you're trying to decide what this sort of product is worth, remember that it's not so much a matter of subtle tonal differences. It's a matter of build quality, reliability, and usability. Is the power supply going to keep working for years without damage from heat stress? Will it be able to power a rack full of varied modules from varied manufacturers, some of which use more current than others? Is the box wired intelligently? Are the connectors any good? Is the box shaped correctly to accommodate your modules easily without making you swear or cut your thumb? Does the price of the rack/PSU make sense relative to the number of modules it holds? These are all real issues that have come up with various manufacturers' offerings.

If you build something yourself, you have to ask yourself whether you can build something that will actually meet your needs, without spending more of your time and money than an existing product will cost. (Hint: The answer is no.) Saving money is a silly reason to start building your own gear. Those who build their own gear generally learn a lot and have some fun along with their frustration, but they also generally come to appreciate the value of the gear you can buy.

If you just need something to hold your module and don't want to spend a lot of money, you should consider the 2-slot rack from A-Designs and/or Avedis (same product, two brands). I think you can get one for about three bills. I'm told it's done right. I think that makes it a pretty good deal. If you need a lot more space, consider the Purple Audio 10-space rack. It's $800, which in my opinion is a fantastic bargain. Unfortunately, since I run a company that sells audio gear, I don't feel comfortable stating explicitly on this forum exactly which manufacturers I think make overpriced garbage. Come and talk to me at Tape Op, I mean Pot Luck Con, and I'll tell you with a beer in my hand.

[tubetastic]

Thanks Justin. I appreciate the insight. And I'd LOVE to get to discuss the mice and men at TapeOpCon (I'd just love to be there). Unfortunately I wont be going this year. But enjoy it twice at much for me. However, I'd still be interested to hear your insight on the quality builds of the different brands, as I'll probably be purchasing one in the future. Shoot me a message?

Ulysses:
You get what you pay for, whether you pay in dollars or in sweat and blood.

I couldn't agree with you more. Few things could be more true, a hard lesson I learned growing up. (roasted a piece or two in my day)

How ever at this point, I think I am still interested in at least trying. I figure the worst that could happen is in 2 months I could get pissed at my creation, scrap it and buy a Purple Audio 10-500 (Drooling) And once I get a few more modules, I probably will anyway. But I really think this sounds like a fun project (especially if it works ). Not to mention, I've already got most of the materials I need to do it.

So today I found a KILLER deal on discrete linear dual power supplies. 20 bucks a pop!! However they are rated at +-15v (but they give a woppin 1.5amps!!) Is this alright? I know most units do 16v, but the spec sheet on the api site says 12/18v. So I'd think 15 would be acceptable?? Like I said, I'm a newbie at this.

Big progress today though, I've finally figured out my last few questions about the pinout setup.

XLR IN .... EDAC pin#
pin 2 ....=.... 10
pin 3 ....=..... 8
pin 1 ....=..... 5
I think... Anyone want to confirm that?

And I answered my own question about the 15 pin sockets. It's an EDAC 306-015-520-102 in case any future readers are interested. They're pretty cheep. About $5.

[TAVD]

So today I found a KILLER deal on discrete linear dual power supplies. 20 bucks a pop!! However they are rated at +-15v (but they give a woppin 1.5amps!!) Is this alright? I know most units do 16v, but the spec sheet on the api site says 12/18v. So I'd think 15 would be acceptable?? Like I said, I'm a newbie at this.

Yes. If it has trimmers, you can easily ramp it up to 16v. If not, I doubt you'll hear a difference, even if you do lose a few 1/10ths of a db of headroom.

XLR IN .... EDAC pin#
pin 2 ....=.... 10
pin 3 ....=..... 8
pin 1 ....=..... 5
I think... Anyone want to confirm that?

Sounds right.

[Mushy]

I pondered this very question two months ago. Then I found a BA 6 space rack on Gearslutz for $350 shipped and decided that it was a no brainer. I am a DIYer (I just built my first 4 channel preamp!) but there are certain things that it ain't worth messing with.

Power, case and connectors (and transformers) are the main expenses in producing audio gear. The rest is just nickel and dime parts. You are paying for precision machining. What you are talking about doing is going to cost you about 150 in parts and two to three days of time. If you feel that two to three days of time isn't worth $200 then I say go for it. Personally, I feel that my time is more valuable than that so I went ahead and bought one.

The other thing to keep in mind when buying 500 series pres is that this is an expense you only need to pay out once. The reason you can get such great pres at between 450 and 1000 per channel is that you AREN'T paying for power, case and connectors on a per channel basis. It's the biggest bargain in the music business and that is why it caught on so much. In other words, after you've aquired more than two channels, the case has paid for itself.

I'm all for DIY but there is DIY that is worth it and there are boxes that are meant for utility that are worth just going out and buying. This, to me, falls into the latter catagory.

Also, as with all DIY, odds are you aren't the first one to have thought of this idea. Do some research and learn from the mistakes and successes of those who came before you. Here's a good place to get started: Prodigy Pro 500 rack.

Whatever you ultimately decide, good luck...

[tubetastic]

There's the link to that KILLER PSU deal on ebay. I think he's got about 40 more. But it's only got about 18 hours left.

Gotta go eat. I'll write more later.