DIY-Central.com - Go Create something! - PCB Design, Electronics - Power Supply

DC-DC Converter How-To

DIY-Central.com Administrator — Sat, 19 Dec 2009 20:10:27 GMT

Maxim offers a great explanation of DC-DC converters.

DC-DC Converter Tutorial

Abstract: Switching power supplies offer higher efficiency than traditional linear power supplies. They can step-up, step-down, and invert. Some designs can isolate output voltage from the input. This article outlines the different types of switching regulators used in DC-DC conversion. It also reviews and compares the various control techniques for these converters.

http://www.maxim-ic.com/app-notes/index.mvp/id/2031

Portable Preamp TS-2 Redesign

DIY-Central.com Administrator — Thu, 17 Dec 2009 14:16:09 GMT

The TS-2 has been getting some traction recently... and I'm thinking maybe it's time to revisit this product again and do a Revision B.

The first TS-2 design was very good, and I love the sound of it! (Of course, it's based on the SC-1mk500 and SC-1mk2 preamps, but in a smaller form factor.)

But assembling a single TS-2 unit takes up a lot of time/manpower and with the small profit I have on each unit, it's a losing proposition. I'd come out ahead if I DON'T build a TS-2!

So to fix this problem, I'd need to raise TS-2 prices, or reduce my production cost, or a little bit of both. For now, I'm going to concentrate on reducing production cost. With today's economy, it may not be smart to raise prices (unless that price increase brings with it additional features that the original TS-2 didn't have.)

Question: So what can I do to reduce production cost?
Answer: Reduce the time/manpower to build a TS-2 unit.

Question: How can I reduce time to build a TS-2 unit?
Answer: Good question...

I'm thinking of several possibilities.
1. Through automation. Using SMD parts and pick and place machines. Ask a manufacturer to build the boards for me.

Cons: A little on the expensive side, and requires a lot of capital. I think 100 boards is the minimum. Assuming it will cost $50 per board assembly fee, 100pcs is a staggering $5000!

And I doubt it will cost only $50 per board... maybe closer to $100. And that's just the labor. The cost of parts for 100 boards is not included yet.

2. Minimize "wiring". Yes, soldering wires to the PCB board and connectors, and jacks take a lot of time. So if we can get rid of "flying wires", then that will reduce a lot of time and labor. So as much as possible, use PCB mounted jacks, switches, LEDs, etc... everything should be soldered to the PCB. No more hookup wires, if I can avoid it!

3. Reduce the number of PCBs. Right now, the original TS-2 preamp has 4 PCBs. A motherboard and a switchboard, and 2 VU meter PCBs.
That's a lot! And of course, there are hookup wires to connect all 4 PCBs to each other (see #2 above). So I need to reduce the number of boards required to build a TS-2.

I've upgraded my PCB design software last year, to allow me to make the bigger boards. Unfortunately, the TS-2 board design was prior to my software upgrade.

Now, with the ability to make bigger boards, I think I'll be able to combine more functions in a single board.

We've got plenty of real estate space FREE!

What else...

Revision B will also give the user the option to have INPUT TRANSFORMERS! So that will be cool! Maybe even add a switch to bypass Input Transformer. Hmmm... I'm getting too far ahead here.

So that's my goal.... redesign the TS-2 preamp to minimize wiring, combine more functionality in a single board, and add some new features.

X-12 Preamps in a 1u rack case.

DIY-Central.com Administrator — Fri, 02 Oct 2009 03:49:22 GMT

Lunchbox pres racked in a 1u case

Just a test.... checking clearances, and how the whole thing will look.

The real deal will be a setup for (2) X-12 pres.

update:

Finished X-12 preamp, 2 channel in a 1u rack.

check it out... We now have audio samples of the X-12 Mic Preamp.

http://fivefishstudios.com/index.php/Audio-Samples.html

Special thanks to Farview Recording (Jay Walsh) and Jason Mallow. You guys ROCK! Also thanks to Madison Rhoades for the vocal clips.

Check out the Servant song... all tracks recorded through an X-12 Mic Preamp.

SC-1mk2 with Cinemag Input Transformers, 1u 4-channel

DIY-Central.com Administrator — Tue, 24 Feb 2009 15:32:26 GMT

Just finished this unit for a customer... 4 channels of transformer goodness!

SC-1 Solo Preamp (Prototype) powered by 12VDC wall wart (or battery)

DIY-Central.com Administrator — Wed, 02 Apr 2008 19:22:20 GMT

I'm making CAD measurements of trying to fit an SC-1 preamp plus a Mini-IO module in my extruded aluminum "brick case"... hmmm.. its a tight fit, the TRS jack is almost hitting the top of the case, and the soldered terminals touching the blue trim potentiometer of the SC-1.

I'm concerned about the terminals touching the blue potentiometer. It's plastic so it's non conductive so maybe it's not even an issue. If the case has an extra 0.1" height, it would have been fine. But given this TRS jack is the hi-Z input, I'm afraid it might have side effects.

For sure a VU-meter will fit inside without problems.

Unless I can find a slightly taller case, the SC-1 Solo will probably consist of the SC-1 and a VU meter, plus the PSU board. (at least, for this 1st prototype I'm making.)

My eventual goal is to find a case that will be tall enough to fit an SC-1 plus the IO-module (with input/output transformers)/Mini-IO, and maybe even the VU meter. Now, that would be some hot SC-1 Solo product!

Okay...did the CAD drawings, created the CNC programming then tested it on some .125" scrap aluminum. Looks good.

Loaded the "real" panel and let the program run... X fingers!

Yes... everything fits like a glove! No more manual drilling with a drill press or filing around to make everything fit.

Of course, it takes hours of prep work on the CAD/CAM, testing and final setup... and only about 3 minutes of actual CNC time on the router.

Some photos:

Did the rear panel CAD/CAM/CNC today... I goofed up making measurements on where the DCJack holes should be... so had to do some fudging with a manual file. It's okay... this is just a prototype. But I fixed the CAD drawings to reflect the proper dimensions.

Some photos:

The DC-DC Power Supply installed on the rear panel.

XLR jacks installed

I do have one concern here and that is... with the XLR jacks so near to the DC-DC PSU, will it affect the preamp's performance? From my limited bench testing, it doesn't seem to be... but the proof is in the pudding... so we'll see how this prototype performs.

I have seen one preamp though (and I'm not naming names) and they have a DC-DC PSU, and a microprocessor, and it's associated crystal clock, and 2 preamps crammed into one small case.

By comparsion, what I have is "roomy" compared to what's inside this other preamp.

And finally... a preview of things to come. Rear View of the SC-1 Solo case.

Arghhh... those XLR bolts are too shiny! Will have to replace them in the final prototype with stainless steel bolts to cut down the bling factor.

I'm also using a flat head stainless steel screws to attach the plate to the main case... but I can't properly chamfer the hole openings because the plate is only .036". If it was thicker, I can get away with it. So the (4) corner screws will have to be replaced with pan head screws (also stainless steel)

All these "minor" fixes will be done as the very last step.

SC-1 Solo Preamp

Features:
- Low-Noise, transformerless, High-Quality Mic Preamp
- All solid-state design, using chipsets from THAT Corp and Burr-Brown
- Soft-start, slow ramp-on +48V phantom power
- Crystal clear Red LED indicator for phantom power
- Electronically balanced input and output stages
- 12-position Grayhill gain selector switch
- Gain range from +6 to +72dB, in 6dB increments
- Input RFI protection
- Input clamping protection
- Output surge protection circuit
- Output RFI protection
- Powered by a linear, regulated 18-0-18 Volts supply, with +48VDC for clean power delivery
- Reduced clicking and popping when changing gains
- High quality Bourns, sealed, conductive plastic potentiometer for volume control
- High quality C&K PCB Mounted switch
- Gold-plated, machined, low-profile IC sockets
- Use of high quality 1% Metal Film resistors, and high-quality ceramic and electrolytic capacitors
- With 5-LED VU Meter
- Neutrik XLR input and output jacks
- Powered by 12VDC wall wart

DC to DC Switching PSU (12Volts to +/- 18V & 48V)

DIY-Central.com Administrator — Wed, 26 Mar 2008 06:31:57 GMT

It's done :) My switching DC-to-DC PSU.

I've been working on this design on and off since October 2007. Several prototypes later, and many $$$, I'm happy with it. All output voltages are regulated and adjustable via multiturn trimmers, +18, -18 and it's a true +48V phantom power... all derived from a single 12Volt input. Outputs are short circuit protected. Just a big spark, but keeps on ticking. Nothing gets blown.

Powering my preamp and my I/O module (input and output trafo, pad, polarity) with Active DI, via 12V wall wart. No hashing sound, no RF leak, no noise. (Well, okay... when you're at 66-72dB gain... but could be caused by everything not in a metal enclosure.)

Output on all 3 rails are typical like below:

Switching spikes on the DC output of about 0.06Vpeak-to-peak, and interval of 33.333Khz. I can set switching freq. to about 60Khz but the spikes get larger.

So I compromised for smaller spikes at a lower switching frequency... i.e. smaller spike/transients, less RFI energy emitted, less chance that it will interfere with sensitive mic pre circuitry.

DC to DC Switching PSU (12Volts to +/- 18V & 48V)

DIY-Central.com Administrator — Sat, 02 Feb 2008 22:12:25 GMT

Well, this DCC psu is giving me the headaches. One day, I thought I licked out the problem and it's as quiet as can be... next day, I turn it on, and the fyring noise is back again coming out of the speakers.

I've tested and used my oscilloscope to look for possible problems in the DC-to-DC converter, (though I did found some oscillations that I eventually fixed), there doesn't seem to be any improvement in the crackling sound coming out of my test preamp.

This PSU ripple has never been better, the "frying bacon" sound coming from the inductors is almost negligible, the waveform looks good... but still! There's that crackling sound coming out of the preamp.

In situations like this (i.e. when I become desperate)... I do weird things to my projects. I mean, what more can I lose?

And this time, I decided to remove jumper J1 on the SC-1 preamp, and run using AC coupling. That's strange... the crackling sound STOPPED!

So I went to my shelf, grab a new OPA134 chip, swapped out the old IC2 chip on the pre with the new one, and VOILA! The stupid crackling noise STOPPED! IT's as clean as can be... running on the DC-DC PSU.

I'm going to leave the DC-DC PSU running the whole day, and the preamp... and see if the noise comes back. Otherwise, I think a marginally defective IC2 on the SC-1 PCB was the cause of the noise problem, and not my DC-DC PSU.

I'm happy to report though that using an AC Adapter with my DC-DC PSU powering the preamp and the Mini-IO module, the AC Adapter doesn't even get WARM!

PSU-4448 Kit Assembly Instructions

DIY-Central.com Administrator — Mon, 30 Apr 2007 23:06:31 GMT

Assembly Instructions

Disclaimer:
Working with high voltages (110V/220V) can be lethal. Work at your own risk. Soldering irons are hot. Use caution.

Tools Required:

1. Cutter Pliers
2. Long Nose Pliers
3. Soldering iron (adjustable temperature preferred), or 25-30W soldering iron. (Do not use 100W soldering iron.)
4. Solder lead (60/40 or equivalent)

Step-by-Step Assembly Instructions:

If you bought the kit, all the onboard PCB parts are already included, sorted, and labeled for your convenience. Click here to order the PSU-4448 KIT.

ORDER THE PSU-4448 KIT or PCB.

TIP:

1. Solder components from the smallest/shortest to the biggest/tallest component in that order. This makes assembly easier.

2. Do not use too much solder lead. Use just enough to make a good connection. The PCB is plated-through hole, and molten solder lead will flow into the hole to ensure a good connection. You don't need globs of solder to make a good connection.

3. Work slowly and carefully, especially if this is your first time. Double-check parts before soldering them. It's easier to solder something in, that to desolder them out (if you make a mistake).

4. If you make a mistake solder a part in the PCB (example, wrong location, or wrong orientation/placement), you will need a desoldering tool to suck the solder out from the board. Even then, the part may not easily get out. The easiest thing to do is to "sacrifice" the part, cut the leads, use a long nose pliers to hold the lead, heat the pad while pulling the leads out. Then use a desoldering tool to open the hole. So as I said, double check parts before committing to solder them.

Step 1:

Solder all resistors, and diodes to the board.

(2pcs) 220 ohms - RED-RED-BROWN

(1pc) 8.2K (8K2) - GRY-RED-RED

(1pc) 7.5K (7K5) - VIOLET-GRN-RED = this is marked on the PCB as 7.68K

Note the orientation of the (4) diodes on the board. The white band should all be on top.

Step 2:

Next, solder the 0.1uf capacitor. You may need to open up the legs of the capacitors a bit to fit in the holes.

They'll go into the PCB looking like this.

Step 3:

Next, solder the bridge rectifier W02G. Note the orientation of the component and where the flat side is pointing.

Step 4:

Next, solder the (4) electrolytic capacitors. (2pcs) of 10uf and (2pcs) of 1uf. You will need to open up the legs of the 1uf a little bit to go into the hole.

This is what your PCB board should look like at this point of the assembly. Note the capacitors.

Step 5:

Next, solder the (2) LM317 regulators to the board. For aesthetics, make sure they're the same height when you solder them. Also, note the orientation. The flat side (heatsink mounting part) should be facing towards the outside of the PCB.

Step 6:

The only thing remaining to do now is solder the (2) big electrolytic capacitors.

TIP: The capacitors are snap-in type. So when you put place them on the PCB, do a twisting motion. When you solder the capacitor, the (-) leg of the capacitor is tied to the ground plane of the PCB. The PCB copper can suck the heat out of your soldering iron. So make sure to bump up the temperature of your soldering iron up.

TESTING:

Solder AC1 and AC2 terminals of the board to the SECONDARY windings of your power transformer. Apply power to your power transformer, and measure that you're getting 44V and 48V DC at the output of the PSU board.

Note: You may not measure EXACTLY get 44 and 48V due to component tolerances. But if it's of by a few millivolts, you'd be fine. If you're measuring something like 0V or 60V or higher, something is wrong and most probably you have a short somewhere.

If everything checks out, then attach a heatsink to each voltage regulator. I recommend you use TO-220 insulators/spacers so there is no electrical connection between the heatsink and the regulator. You can also use TWO SEPARATE heatsinks, one for each regulator. Just make sure the two heatsinks DO NOT touch each other.

	BUY the Power Supply KIT or PCB
	Order PSU-4448 PCB. Only $20.00 per PCB Plus $3.00 for shipping to US addresses (except HI,PR)
	KITS ARE NOW AVAILABLE! Order PSU-4448 PCB+KIT. Only $30.00 per KIT Plus $5.00 for shipping to US addresses (except HI,PR)

PM1000 PSU PCB

DIY-Central.com Administrator — Sat, 17 Mar 2007 01:41:29 GMT

Okay, I received the PCBs from the fab. It's pretty. Measuring a tiny 2-1/2" by 2-1/8".

I'm selling a few extra PCBs as I ordered a few more than what I needed. Cost is $20 per board.

I test-built one of the PCBs to test that it's working properly. Here's my completed prototype PSU (+44V) and (+48V) for phantom power, suited for those racking their Yamaha PM1000 channel strips.

And here's a shot of the bare PCB.

I have a few extra PSU boards so if you're interested, the cost of the PCB is $20 each, +cost of shipping fees. I'll include a Bill of Materials with Digikey part numbers along with your PCB so you can order the parts direct from Digikey or Mouser or wherever.

Email me if you're interested to buy. Thanks!

Sony MXP-3036 Preamp + EQ

DIY-Central.com Administrator — Sun, 11 Feb 2007 00:46:24 GMT

It's done... some pictures. Using my custom PCB for the power supply, and an MCI output transformer on the outputs to convert it to balanced outs.

It works... sounds nice and clean! The EQ lets you sculpt the sound nicely. No hum, no noise. It's great!

DIY: PSU for Yamaha PM1000 preamp

DIY-Central.com Administrator — Thu, 01 Feb 2007 01:55:59 GMT

I designed a new PSU for people who'd like to rack those Yamaha PM1000 channel strips.

The Yamaha PM1000 are usually called Japanese "Neves" because of a similar approach in design. Just like the Neves, this is all discrete transistor and uses an input transformer and output transformer.

The EQ section is especially sweet because there is not a single IC on this preamp. The EQ section uses inductors and capacitors... totally analog manipulation and shaping of your frequency. (circa 1974)

I've tested them on drums and vocals and they really make the sound FAT. The EQ section shapes your sound anywhere from slight barely noticeable to extreme gain/reduction. Bass frequencies are solid. Of course, being an analog EQ, it is not as precise in shaping the sound as IC chip Equalizers. But the curve is smoother I would think.

So if you're racking a PM1000 strip you bought from eBay, this PSU will be perfect for you. Output is +44VDC and +48VDC for the Phantom Power.

I'm having prototypes built. If you're interested, email me.

Screenshot:

PCB Rev.2.00

The new PCB designs will be smaller and double-sided measuring 2.25" x 2.25"

I don't have this mass-manufactured, so I'm selling it at a low price just to recover some of my costs. $20 each. Email me first before ordering. Thanks.

DIY: PSU PCB

DIY-Central.com Administrator — Fri, 26 Jan 2007 02:48:53 GMT

This is a continuation from this article.
http://www.diy-central.com/DIYSplitPowerSupplyWith48VPhantomPower.aspx

Well, I received the PCBs today but it seems there was a manufacturing error. Everything is flipped/mirrored... Here's how the top layer looks like... the bottom layer is also flipped/mirrored.

BUMMER!

I sent this picture to the manufacturer along with what the Eagle board is supposed to look like. I emailed them... and within a couple of hours, I got a call from them on the phone apologizing for the mistake and they found out where in their process they had the mistake... they're going to remanufacture my boards and resend them to me at no charge! Talk about great service! The quality of the boards and it's workmanship do look very nice too, and their prices are great.

This is my first order from them, and even if they did screwed this up, I think I'll use them in the future. I like how they handled the problem very well and took steps to correct it.

I'll keep you guys updated about the progress.