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Old 25th January 2005, 03:26 AM   #601
Prune is offline Prune  Canada
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It's exactly because it looked simple that I posted it. I'm not sure how I would go about regulating this kind of high power supply.

Halcro amplifiers supposedly have double regulation.
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Old 25th January 2005, 03:33 AM   #602
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Regulation need not be complex. A resistor/Zener pair to set the reference voltage and a pass device will get you started. Even softer is a resistive divider, but that won't lock the voltage.
The next step is to use a differential to compare the reference voltage to the output voltage. Still not much of a problem. Add a cap or two to smooth the reference further. Still not too bad.
It's when you start massaging the references with current sources and such that the regulator starts looking more like sphagetti. Slow start add-ons and short circuit protection come sneaking in the back door and suddenly you have a dedicated amp on your hands--one designed to current-amplify a high-purity DC signal generated within the amplifier circuitry itself. It's kinda neat, really. I mean, you think you're a hardware nut? Not until you've got a separate chassis for the power supply and regulation.
Man, I'm starting to breathe heavy just thinking about it. Someone start dragging out the heavy iron. I need a fix.
There's no question that regulators can get complex, but they can also improve the sound greatly.
The problem, at least for power amplifiers, is that they will need their own heat sinks and create a decent amount of heat. That, in turn, makes the circuit heavier and more expensive.
Fortunately, you don't have to go to those extremes in order to begin seeing some benefit.

Grey
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Old 25th January 2005, 03:37 AM   #603
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I frequently use double regulation on smaller circuits like the line stage I'm building.
Think of sanding wood. First you use 100 grit, then 220...

Grey
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Old 25th January 2005, 05:36 AM   #604
Prune is offline Prune  Canada
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Quote:
I mean, you think you're a hardware nut? Not until you've got a separate chassis for the power supply and regulation.
Not quite, but close. I like to use separate subchassis for PSU and the rest, and then put them in one big chassis, star grounding all chassis. But I've not built a power amp yet, so I'm talking about smaller equipment. For a power amp I'll probably omit the overall enclosure. One thing that's a problem is the thickness of the power interconnect (unless I have a large capacitance on the amp side, so then it acts like another RC filter section, but then the regulator has to be on the amp side).

So what would be a good approach if I wanted to go a bit beyond just pi filters on the PSU for an Aleph-X? If I go to the trouble of regulating, would I need to use a complex regulator to make a difference, or would a simple one work good too?


One time I used an old power amp through a step-up transformer to generate the AC power for a DAC and headphone amp. I think the setup sounded better when the frequency was around 100 Hz rather than 60...
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Old 26th January 2005, 05:17 PM   #605
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Actually, using a higher line frequency to get better sound is not so surprising. Given that it pushes the ripple higher in frequency, the power supply filter would be more efficient in removing it. That said, there are limits to how far you can push the frequency without taking a look at the power supply design itself.
Two other points are involved:
--The amplifier serves as a filter for bad things coming in.
--The amplifier serves as a filter for bad things going out. Anything that spews as much RF as a digital circuit can easily influence how the rest of the system sounds. Keeping the RF out of the main AC is a huge benefit. Even something as an isolation transformer can work wonders in this case.

Grey
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Old 26th January 2005, 06:54 PM   #606
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Grey,

Your post on how far you can take a regulator reminds me of another downside to modelling/simulation software, the fact that you can test whatever you want without spending a single cent. I started a little design project a few months ago to create a high current regulation circuit for a power amp. The development path you describe is exactly what I did in spice, started with a voltage follower, changed it to a differential, started adding CCS's, then darlingtoned the pass transistors, then realized that it would work fine as long it never had to turn on, etc. In the end, I had wasted literally weeks of time refining a regulator design that became more costly and complex than the amp it was to power. One day I finally recognized my lunacy and realized that it was far too expensive and complex to justify in reality, and scrapped it. If I would have had to build and test the thing, it never would have got that far out of hand.

Cheers, Terry

EDIT: Oh yeah, I was going to mention that I 100% agree with you on the big wad of capacitance after the regulators. In the development of my Zen headphone amp the biggest improvement that resulted from a single parts change was when I added a big whopping cap after the regulation stage.
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Old 27th January 2005, 02:31 AM   #607
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Precisely. I just go build the silly things instead of spinning in circles trying to argue all sides of the issue.
Now, I will confess a curious thing...while I adore simple audio circuits, I am not all that bothered by the idea of complicated power supplies. I frequently regulate each and every stage of a circuit separately. Doesn't bother me a bit to have all kinds of different voltages going on; after all, once you're using separate regulators, there's no reason not to set them to different voltages if it works out in the circuit. As a concrete example, the line stage I'm doing right now (the solid state one) uses +30 and -10V rails. The CCS under the differential didn't need to be dissipating any more heat than necessary, so I let the power supply drop the heat. They're more robust devices, anyway.

Grey
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Old 6th March 2005, 10:29 AM   #608
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Default X vs Aleph complication

Evening All,

Until Christmas I was just about to order all my parts for 2 Aleph 30's, or a 30 and a 60, after I had consulted this venerable board for final advice on some fine points of power supply, and how to set up PSUD II to help me out.

But Christmas got in the way and I decided I needed to buy an ultralight(!), but wife, quite reasonably said "NO" and now I am back living in reality, or as near as I can so judge my current mental state to be.

I have read, but not necessarily understood, the first 400 posts of this thread thinking I might cast my attentions to the Aleph X rather than a straight Aleph. But, at around post 400, Kilowattski, quite a bright chappie it seems, was having lots of trouble setting up his Aleph X.

The impression I have picked up is that the parts selection and setting up of an Aleph X is much more difficult than for an Aleph, and that small errors and modifications are much more unpredictable or difficult to predict than the standard amp.

1. Is this correct?

I had planned to "supe" up the Aleph with some inductors in the power supply, low value bypass all the large capacitors and buy the "best" caps for the signal path I could find.

2. Bearing this in mind, has anyone compared the X with a "suped up" version of a standard Aleph? Is the "extra work" worth it? (I believe in asking purely quantitative, objective questions as you can see!)

I am concerned, because I don't want to have another unfinished project lying around if I start on something too complicated. (e.g. re-plumbing the waste pipe for the bedroom airconditioner, re-finishing the front verandah's wood grain protection, re-aligning the settling stumps under the front sliding doors which have moved over 5 or 6 wet seasons, filling in my tax returns, learning to carve a gybe on my windsurfer, and repairing the hole its nose, etc. etc.) ... although a lot of those look like work rather than "projects".

Regards,
George.
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Old 6th March 2005, 01:47 PM   #609
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I'd build an amp that best suits your needs and skill level.

I wouldn't build an Aleph-X as my first amp. It is a little bit more
complicated than building an Aleph.

If this is your first amp, i'd build something from the ZEN series.
Construction articles are a big help! You are more likely to have
a finished, working amp if you do so.



Also, an Aleph (or ZEN) will sound wonderful without a bunch of fancy
expensive parts. Saves you money (a good thing), Allows for
"upgrades" later (when you get the bug to do some mods!)


Good luck!
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Old 6th March 2005, 04:20 PM   #610
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George,

building an X isnīt that much more complicated than an Aleph. For sound comparisons and a bit of information you can look at this thread:
One Aleph-X working, One to go

William
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