External Power Supplies and Hi-Output designs

[OddHarmonic]

Greetings!

I want to start by thanking those responsible for both maintaining this forum as well as filling if with such an amazing amount of knowledge. I was an avid reader of Tech Talk, and enjoy countless hours of just reading about what folks are doing here. Not to waste too much space in my first thread, but I will take a moment to introduce myself. Only get one change, right?

My name?s Andrew, and I work for the National Center for Voice and Speech in Denver, CO. I also help run a small non-profit that produces/promotes experimental music in Colorado. I like to record music more then most things, but economy spreads my time to many other activities? At the NCVS, most of my work is spent on a project that uses a modified Pocket PC with custom audio inputs and software to analyze in real time a signal from a small vibration accelerometer. A bit of DIY.

Throughout the years I have put together a fair amount of knowledge about basic circuits, etc.. I have done tons of soldering on very tiny things. (Like inside PPCs?.yikes) I own a Neotek Series III console that I brought back to life in a few ways, and have learned quite a bit about how it works and how to fix problems. With all of that said, I am still quite a novice, but I plan on diving into this hobby with no hesitation. First, a power supply or two, followed by some of the more common projects discussed on this board.

Ahhhh, now to my question, or two as it is:

When speaking with some mastering engineers, I was informed that a common practice in mastering facilities was to modify all equipment for external DC power supplies, which would be located in a machine room. So there would be multiple lines of 48V, +- 24V, etc? available for all equipment. Reasons I think are obvious, as EMI issues with internal supplies are surmountable, but not without their problems. Also, it seems that one hefty 24V supply could be built for less cost/effort than many, many small supplies. Is this concept something anyone considers for their own studios filled with DIY equipment? Obviously a variety of voltages would be necessary, but having a good bi-polar 24V supple with plenty of juice, and specially made power cables would clean thing up a bit I imagine. Comments?

My second question is regarding hi-amp power supplies. When I first got my Neotek, I didn?t know much about power supplies, but I knew enough to be sure my supplies needed replacement or total repair. Through the ever-helpful Neotek users group I was advised to buy linear power supplies from a company such as Power-One that would suit my needs. Rack them up and I would be ready to go. In fact, I was told that even NEW Amek 9098i desks come with fancy cases built around Power-One linear modules! I did just that for the logic voltages, and planned on eventually replacing the bi-polar 18V supplies the same way. My question is now that I have spent a lot of time here, I have heard, buried within other discussions, that commercial linear supplies are not as effective for audio as the many custom supplies suggested here, which are simple circuits and not very intimidating even from my small DIY experience. What is the difference between these types of supplies? Are the benefits great from one to the other? Would it make sense to build custom supplies for my Neotek after I have learned the ropes with some smaller supplies? Are there resources available for taking a supply design such as SSLtech?s bi-polar 18V and modifying it to have 6 Amps or so output?

I apologize for both the length and the multitude of questions bundled together. I look forward to some discussion on the topic, and I hope that I will be able to input into the forums from now on instead of just reading with fascination.

Andrew

P.S. And to my fellow Americans out there, I leave you with this:

?I am looking forward to an orderly election tomorrow, which will eliminate the need for a violent blood bath.? ? Kodos

no really, I pray for fairness, nothing else?.

 

[jrmintz]

Hi Andrew,

You raise some interesting questions. I have no empirical evidence to base a reply on, but I do have some experiences that might help. Firstly, I know some people have been unhappy with Power One supplies. I think one poster didn't like Power One supplies for Neve gear, that it made no audible difference for other gear. My experience is that I have used Power One supplies for various gear includng console audio rails and I've been perfectly happy, they're extremely reliable and the gear sounds great to me.

My biggest hesitation about using large DC supplies to power many boxes is that if it's not an improvement when it's rigged up you've gone to a great deal of expense and trouble for no benefit. If you have a general noise problem, I'd try a balanced power transformer first. I did that in my studio and electronic noise is nil - all the fans are killing me. If you have a specific unit that's noisy, I'd try to correct that by itself. I'd also be a bit concerned about the resale value of the gear after you've modified it to accept external supplies.

Hope that helps,

:thumb:

 

[OddHarmonic]

Seth,

Thanks for the response, good to hear that others have had positive experiences with the Power-One modules. I also found them to be incredibly reliable and well priced. I suppose I will continue using them when the task calls for many amps....

I hear you on the hesistation about external gear. I myself would never modify commercially available gear for external supplies, I mentioned that becuase I had heard of mastering engineers doing just that. However, with custom DIY gear, it seems like it could avoid some problems, although I may be overly paranoid about EMI, when folks use torroids, everything seems to work out well. Perhaps I'll build myself a dedicated power supply box to test the concept. A good first project I would guess.

If specs on a power supply are not present, how does one determine the available current? Is the amperage rating on the regulator the final rule on what kind of power is to be had? For example: Looking at the Seventh Circle supply (PS02)., the transformer is rated @ 1.59 A, the Rectifier @ 4 A, the regulators @ 1.5 A, and the various other diodes @ 1 A. Tim lists the supply as "conservatively rated at 600mA at +/-27VDC" How does one compute such a number?

Thanks again for the insight!

Andrew

 

[Guest]

[quote author="OddHarmonic"]mastering facilities was to modify all equipment for external DC power supplies [/quote]
There is problem with power - related ground loops.
If you have something with simple input and simple output
(say a BOX), and this box will have transformer floating power supply,
you need only one (output) transformer to have no ground loop.
Output transformer is cheaper than input. It may not have shield.

If you will have good bus DC power input (+- 48 V) ,
you will must have input and output transformer to not have ground loop.

And input transformer must be mumetal, shielded and is more
costly than good power toroidal.

And the other unbenefit of DC bus power:
The large power line is ideal to make ground loop with itself.
If you have filtering capacitor in the PSU and filtering capacitor in
the unit, these capacitors are shorts for noise. And this form noise
loop. If you want to break it, use good series stabilizer (as LM7812)
with electrolytic capacitor only at the output (at the input use small
ceramic).

Meanings of your "mastering engineer" are some out of time.
To have battery powered studio ?
And what about surroundings, everywhere is electricity.
To DIY studio at Alasca, or Antarctic ? To record pinguin choirs ?

xvlk