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DC power source for DIY preamp
Old 28th February 2014
  #1
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DC power source for DIY preamp

I can't find a power supply for a portable preamp I'm building.

I'm using 4 Eden preamps that need 15V bipolar power; each drawing about 50mA.

I would like to power it with 12V, but my portable battery has other voltages so it doesn't have to be 12V.

I'm hoping to find a completed module or a DIY kit. (And if it also has 48V output, that's a bonus)

I've tried a DIY forum, but not getting too many reads. Anyone have any suggestions? This is the last piece to my preamp puzzle.
Old 28th February 2014
  #2
Old 28th February 2014
  #3
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Thanks. That one is AC input though. But I haven't looked at their product line. Looks like they might have something workable.
Old 1st March 2014
  #4
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Did some Googling.

FabModules Shop

Seems the FAB1215 is 12v to 2x15v.
And you can order it with an optional FAB1248 (12v to 48v) module.
Leo..
Old 1st March 2014
  #5
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The Fab1215 isn't for sale. I emailed about it last week and was told he's not yet happy with the design, so won't be releasing it yet.

This has been the luck I've had so far.
Old 1st March 2014
  #6
Have you looked into the VICOR "Bricks". they make a wide range of DC/DC converters and do have units with 12 volt input. (PDF attached)

Another alternative, which may be a simpler and more reliable solution in the long run might be to just use (2) DC inverter LiI batteries like the PowerStream.
The Powerstream can be set for 15 volts (use two, one for the positive supply and one for the negative) and has a capacity of 60w/Hrs.

Your (4) preamps will draw 3 watts total from each 15 volt supply, so a pair of PowerStreams should run the preamps for around 20 hours on a full charge.

I have an Anker Astro 3, 10,000mAH battery that will produce 5, 12 or 15 volts (at up to 2 Amps), but it appears to not be in production any longer. I use it to power a SD 788T. The current version, the Astro 3E seems to only produce 5 volts. You might want to contact Anker to check if they have any 15 volt battery/converters like to original Astro3 available. It produces very clean (low ripple) DC and is exceptionally well regulated.
Attached Files
File Type: pdf VICOR BRICK Converters.pdf (746.3 KB, 462 views)
Old 1st March 2014
  #7
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Thank you. Yeah, I was looking at those bricks. They're all single channel, so I'd need two. The ones i see in stock are over $100 a pop.That's a bit more tham i would like to spend.

If I go that route I was looking at this one from Murata:

Murata

I'm told I'll may need an LC filter as well.

That's all doable, but I was really hoping to find a "plug n play" type of solution that covered all the bases (including 48V). Doesn't look like there is such a beast.
Old 1st March 2014
  #8
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Quote:
Originally Posted by Lotus 7 View Post
Another alternative, which may be a simpler and more reliable solution in the long run might be to just use (2) DC inverter LiI batteries like the PowerStream.
The Powerstream can be set for 15 volts (use two, one for the positive supply and one for the negative) and has a capacity of 60w/Hrs.
Going this route, do you mean like have two DC jacks (one POS, one NEG) that would go straight to the preamps? Is that ok to do? (Ok, prob a fuse in there for protection)

It does sound simple, but worries me a bit. Could you explain that a little more?
Old 1st March 2014
  #9
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You have put several limitations on the specifications while hinting that other options are available, and then you want "low cost" as well.
What you seek may not be possible with the limitations you have posted here. Reveal all your options.
Being vague and generic will limit our ability to help you find creative solutions.

You said " my portable battery has other voltages so it doesn't have to be 12V". What does that mean exactly?
Is one of the options 15V? If you already have +15V, it is easy enough to make -15V

That Murata BEI15-150-Q12P-C seems like an ideal solution. In fact, I think I will use that for a couple projects I am working on. Thanks for finding it.
Putting some additional filtering on the output (if necessary?) seems pretty trivial, especially filtering for a high frequency (which doesn't need giant capacitors).

Is the the preamp you are asking about? Eden Microphone Preamplifier | expataudio

Finding something that puts out ±15V AND +48V is pretty unlikely on a budget. It is easy enough to use a separate module for the +48V, especially those nice little Murata things.
Old 1st March 2014
  #10
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Yes, that's the Eden. I really like that Lucid pre you recommended, but the dimensions just didn't work for my design. This Eden is pretty tiny. Should be arriving soon.

For the other battery voltages I have to work with...well, my thought is to first exhaust my options with 12V before moving to that. The phantom power module I'm looking at is tiny, looks like it'll do a great job and priced nicely.

FAB1248 - 12V to 48V DC/DC Converter Module

And it takes 12V

But if there was something out there giving 15V & 48V, then I'd be happy to switch to whatever voltage it needs.

I thought I had a perfect solution with the FAB1215 & FAB1248. All together in one little package. It's really a nice little piece. All of his are pretty nice actually. So I figured if one guy was making those, there might be someone else doing something similar that I missed.
Old 1st March 2014
  #11
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You could breadboard the module that is used on the FAB 1215.
And maybe add some filtering.

EC4A05H Cincon | Mouser

If you really want things small, and you can get and solder SMD parts, I can supply you with a bare circuit board for four of those Eden-style preamps on a single 3"x4" board.
I hope to get them in next week.

Leo..
Attached Thumbnails
DC power source for DIY preamp-mic-pre.jpg  
Old 1st March 2014
  #12
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glenn_jr said he had four preamps that need 50mA each = total 200mA. The Cincon is only rated for 190mA.
That is cutting it way too close for my comfort level even if the preamps don't need the full 50mA each.
Old 1st March 2014
  #13
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Hi Richard.
Those Eden preamps use three chips that draw according to the datasheets worst case 22.5mA together. x4 boards = 90mA
Add some for the passive parts, and some for driving the cable and load.
Leo..

edit: Just measured the +15 rail for my four preamps. No load, 57mA..
Old 1st March 2014
  #14
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The manufacturer says "Each Eden board consumes about 50mA on the ±15V Rails."
http://expataudio.com/diy/edenmicpre...Dec%202013.pdf
Perhaps you should notify them of their error.
Old 1st March 2014
  #15
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Maybe they play it on the safe side.
Driving a long cable (capacitance) can also add to the current use.
Maybe a safety margin for adding LEDs, relais etc.
Leo..
Old 1st March 2014
  #16
Quote:
Originally Posted by glenn_jr View Post
Going this route, do you mean like have two DC jacks (one POS, one NEG) that would go straight to the preamps? Is that ok to do? (Ok, prob a fuse in there for protection)

It does sound simple, but worries me a bit. Could you explain that a little more?
I mean use two of the battery/DC-DC converters, one connected with it's negative terminal grounded for the +15 supply an the other with it's positive terminal grounded for the -15 supply.

Because of the high output current capacity, a couple of fuses certainly wouldn't hurt just in-case something shorts. Those battery DC-DC converters typically operate at high frequencies (the Anker I have runs at 200kHz and the ripple is typically pretty low (the Anker only produces about 100mV P-P @ 2 Amps and it drops proportionally at lower currents. A small filter cap alone should be enough if the preamps have proper bypass caps on their decoupled power buses, or a small LC filter if you want to be extra careful.

The "5 volt DC" output from the typical "5 volt USB batteries" usually has some HF ripple because those "5 Volt Batteries are actually a 3.7 Volt cell powering a DC/DC converter. If you add a couple of DC/DC converters to raise that to +/- 15 V. you will also have some ripple and will need a little filtering.

I only mentioned the PowerStream because it's easily available and has nice ratings. I believe it's overpriced and personally, I'd check with Anker to see if they have anything that can currently provide 15 volts. A pair of the original Astro3s would be perfect for your application, but not the current Astro 3E.

I think I paid less than $60 for my original Astro3. It's a great power supply and will run a SD 788T (at 12 volts) for almost two hours. or 4.5 hours when used with an internal 7200 mAh cell when using (8) phantom-powered recording channels.

There are plenty of other battery/DC-DC inverter devices around designed as portable external power sources for laptops. Those come in various voltages up to 19 volts.

Building your own DC-DC converter is fine, but you still need a battery. IMHO, it's simpler to just find (2) mass-produced 15 volt battery/inverters (most actually use 3.7 Volt LiI cells) and be done with it.
Old 23rd May 2014
  #17
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Rochey's Avatar
 

Good morning Gents,
I'm normally over at groupdiy for answers on the Edens, but a good search popped this one up. I thought I'd show my working for the power calculations

The ina163's each require 10mA, The drv135's require 5mA each. led's are a total of 15mA and the opa134 is another 5mA... Giving a total of 45mA.

If you want to save power consumptions, remove the LED's from the board. They are only there to show that you have your ±15V hooked up correctly. That should drop around 15mA per Eden.

Cheers

Rochey (@ expat audio)
Old 23rd May 2014
  #18
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dc dc charge pump to voltage splitter seems straight forward to me the dc dc modules can be had on ebay for a about 10 bucks

Old 24th May 2014
  #19
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Have these.
LC XL6009 DC to DC Adapter Non-Isolated Booster Circuit Board Module - Blue + Black - Free Shipping - DealExtreme
3 for <$10
Planning to mod for P48 with higher voltage output cap and new feedback resistor.

Update:
This module (with a 50v cap) was adjustable to about 46volt.
I removed the 10k trim pot, and replaced it with a fixed resistor.
10k/1% gave me 47.1v, so I added another 200ohm to give me exactly 48V.
Output ripple/spikes were removed with a coil (from a broken low energy lightbulb) in series with the output, and a 100n MKT cap to ground.
Runs perfectly on 12v (29mA idle)
48v/50mA is not a problem, even down to 5.5volt input.
I should replace the 50v cap for a 63v one.
And the 40v schottky diode for a 60v type.
Some other day..
Leo..
Attached Thumbnails
DC power source for DIY preamp-p48-dc-dc.jpg  
Old 19th June 2014
  #20
Gear Head
Re XL6009

@LeeYoo

Inneresting! Could you power 2 of these from a single 12V battery and split the outputs for a +/- supply? (I think, unless you used two separate batteries, the input and output ground/(-)'s on the PCB would have to be isolated.)

cheers
Dave
Old 19th June 2014
  #21

You can't change the ground reference on a "non-isolated" VR.

So, voltage inversion is not possible...



-tINY

Old 19th June 2014
  #22
Gear Head
Is there a similar type (and as cheap) charge pump designed for dual output(?)

Or I'll just run a pair of these off two separate batteries (small 12V gel cells).

Dave
Old 19th June 2014
  #23
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Unfortunately there are no small circuit boards like this for a negative rail listed on sites like DealExtreme.com
It would require exactly the same parts, but connected differently.
Two batteries would solve the problem.
Take care that some loads (preamp) want the two rails on and off at the same time.
I am currently working on a homebrew push-pull converter that does [email protected] and [email protected] from a 12v source.
Just winding the toroid transformer for that.
Might take a while, but I'll report back.
Leo..
Old 19th June 2014
  #25
Gear Head
Thanks. Yeah, I know these exist... but they're a mite too expensive to 'experiment' with, which is the great blessing of the chinese cheapie PCBs

Dave
Old 19th June 2014
  #26
Gear Head
Unfortunately there are no small circuit boards like this for a negative rail listed on sites like DealExtreme.com

Too bad 8>/

Two batteries would solve the problem.

Yes.

Take care that some loads (preamp) want the two rails on and off at the same time.

Of course.

I am currently working on a homebrew push-pull converter that does [email protected] and [email protected] from a 12v source.
Just winding the toroid transformer for that.
Might take a while, but I'll report back.
Leo


Will look forward to hearing how it goes 8>]

Dave
Old 19th June 2014
  #27
TPS84259EVM-001 - TEXAS INSTRUMENTS TPS84259EVM-001 - EVAL MODULE, TPS84259 15W NON SYNC BUCK/BOOST CONV | Newark element14 US

Found this ___/

There seems to be a dearth of simple SMPS and charge pumps that can invert more than 5.5v. Makes me think that a pad and pre-amp that can run on +/-5v would make sense....



-tINY

Old 27th August 2014
  #28
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Quote:
Originally Posted by tINY View Post

You can't change the ground reference on a "non-isolated" VR.

So, voltage inversion is not possible...

-tINY


That's what I thought...
But after some reading and experimenting, I found out that it's rather easy to make a dual supply from one of those cheap modules.
I even made a triple output, +15/-15/+48v, with one module.
Got a lot of the info from the "Lineair Technology" datasheets.
They have a whole range of DC/DC converters. Even dual, triple and quad in one chip.
Unfortunately most of them are out of reach for DIY.
What I did...
All you need to add to an original module (as the one in post #19) is two caps and two diodes.
First set the module for 15volt or so.
Solder a short wire to the anode of the rectifier diode on the board. That point has the main switching waveform.
That wire goes to a 1uF (ceramic smd) cap.
Other side of the cap goes to anode of a schottky diode (I used 1N5819). That one's cathode to ground.
Cap/anode junction to the cathode of the second schottky diode.
That one's anode to a second cap. Cap can be electrolytic, 10-100uF. Other leg of the cap (positive) to ground.
On the cap you now have a mirrored negative voltage, minus one diode junction of 0.5v.
(If you put another diode in series with the positive out, you can have equal voltages).
If you build a positive tripler from that same switch point, you can make 48v phantom.
Line and load regulations are not perfect, but quite acceptable.
e.g P48 varies 0.5volt between 5 and 20 mA current draw.
Pictures might follow. Too embarrassed with the dead-bug style build right now.
Leo..
Old 27th August 2014
  #29
Gear Head
Thanks, I'll have to try that!

Dave
Old 27th August 2014
  #30

Ahh.... Now we're rectifying from a high frequency...

Seems like a reasonable approach for a low-cost, high volume product. How much HF hash is left on the outputs to filter out?



-tINY

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