DIY Mic Pre Kits, Lunchbox Mic Preamp Kits, Power Supply Kits

I been looking at different ways of powering the SC-1 it seems that Owel is working on a battery powered PCB I thought why couldn’t we use an external desktop or wall wart supply in place of the battery?

I want to build a compact 2 channel pre for remote recording and powering the SC-1's using the standard Transformer Kit makes using a compact size an issue. I read through the "battery powering" thread and I figuring if you can get the SC-1 working on battery power then why not use say a 15v DC table top or wall wart

For simplicity and some cost savings I was looking at 48v DC desktop power supplies this will proved a full 48V for the phantom power and you can use a simple 2 resistor center ground voltage divider for + - 24v or a 1/3 divider for + - 16v to supply the SC-1 and eliminate the regulator circuit all together.

If using batteries or maybe a lower voltage readily available low cost wall wart to boost the DC voltage have a look at the LM2577 adjustable DC -DC booster http://www.national.com/mpf/LM/LM2577.h ... on%20Notes

Tell me what you think

Hey John, thanks for participating.

My attempt #1 requires (2) 9V batteries and is more like a proof-of-concept.



That's exactly what I'm doing. See this thread...
http://fivefishstudios.com/forum/viewtopic.php?t=164
http://fivefishstudios.com/forum/viewtopic.php?t=165

This is my DCC-1848 psu. This is attempt #2 that will be powered by a single battery or wall wart AC/DC.





I tried the voltage divider trick to get a virtual GND to power the SC-1 and it didn't work.

For one, the 48V phantom power's GND will be different from the split/voltage divider's ground. There's probably some way to do it but would probably involve some modifications on the PCB/circuit. I just didn't pursue it, and instead went to working on the DCC-1848 PSU design.



You're on the right track. But they have other parts than the 2577 that have higher switching frequencies. That's what I'm using for my 48V section.

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OK you're way ahead of me very cool!!!!!!!!!

Getting the +48v is the PITA part of the problem but it looks like you have it licked put me down for a few when the PCB's come it

I want to take advantage of your December sale is there a ETA for the DC power supply solution?

My prototype PCB are shipping out tomorrow from the PCB fab house, I'll probably receive them towards the end of this week, then maybe this month I'll be able to do testing and refinement/debugging.. I usually do 2 to 3 prototypes before I start finalizing everything. Then about 3-4 weeks for production runs of the PCB.

So assuming no problems or delays... the earliest will be end of January, or even February. But there are no guarantees. We're just in the R&D prototyping stage.

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That sounds good !!!!

I came across a company that looks like it has some interesting solutions for DC to DC converters, what do you think of these ?

http://www.v-infinity.com/pdffiles/VWRA ... Series.pdf

http://www.v-infinity.com/srchresults_param.asp
just put in parameters at the top

I think they're okay. There is no difficulty generating +/-15V or +/-24V. Plus, ready-to-use solutions like this in my research cost about $50-70... and you still don't have the +48V required for phantom power.

Finding a ready-to-use converter that does exactly +/-18 and +48 is the difficult part. So I had to design my own from scratch. That also allows me to sell it at a reasonable price and still make a little profit. Otherwise, if what I'm selling the PSU is the same price as the cost of parts I buy (like those ready-to-use DC-DC packages), what's the point?

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I was really looking at the single chip +- 24v solution as an add on to the PS. I'm no expert in this area but if we grounded the -24v output wouldn’t the ground to +24v now be 48V? sounds like it’s a perfect solution for around 4 bucks in theory at least

Not trying to be a PITA I really admire guys like you who make the DIY audio world much easier for guys like me. If I could give something back that helps all this along then I'm a happy man.

Using the negaive as a ground and the full difference from -24 to + 24 (=48) (or with 9V batteries for phantom power 18V) is possible, however you need to prevent a direct path from the 0V reference and the -24V. I used internally the 0V ground on the pcb (not a sc1, though), then isolated it from all input and output ground with capacitors, and connected the -24V to the "outer" ground. You have to do this step both on the output and between the phantom power resisitors/Capacitors and the 1510/1512.

Basically you need to make sure that you have 2 ground circuits connectet to each other only through capacitors. Additionally, the user may NOT hav access to both ground circuits, otherwise he can short the system out, and that might not be pretty, depending on your powersource. So for example, connecting the input ground with the ouptu ground may not create a short circuit. You can check that by measuring the Voltage between these 2 ground connectors.

So, it allows you to use just 2 batteries to generate +9V, 0V - 9V and 18V for a THAT1510/1512. (or any other voltages you might have on your PSU).

DISCLAIMER: This is a hack, and may result in a short circuit, the consequences of a short will be whatever shorting your PSU is, or worse. I take no responsobility for doing this, although it's working for me.

The original thread is almost a year ago... Much has happened this year.

I've created this since then, thanks to the work/experience/learned from making the DCC-1848 PSU.

This is basically the PSU section and the SC-1 preamp in one board.



The nice thing about this, you can connect a second SC-1 preamp kit to the above unit (via the through-hole connection pads on the PCB) and basically power 2 channels of preamp from a single 12VDC power source (AC adapter or battery). From my testing... the preamp would still work even with a 3V input though I did not test phantom power at that low voltage. 9-12V will work.

Note: I have (2) SC-1 stock preamps left, and about (5) of the above SC-1/PSU boards.

Note: The above board is sold as a half-kit, i.e. the PSU section is already built. Normal SC-1 build instructions apply.

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How about a USB bus powered SC-1? [even 2 ports if one isn't enough]

Current exceeds the USB spec.



It says the device can ask for 500mA from the computer via a software request. Well.... that aint possible with an analog pre.

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Unless.....


Just kidding.