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Superregs for your line-level projects

Posted 9th December 2013 at 08:52 AM by jan.didden
Updated 10th December 2013 at 07:02 PM by jan.didden

It’s a recurrent issue: you want to build a preamp, a DAC, a phono stage, anything that needs a nominal supply voltage between 3.3 and 15VDC, positive and/or negative polarity. Sometimes you want several supplies to isolate stages from mutual interference via the power supply. So you want a power supply regulator that approaches an ideal DC voltage source as best as possible within reasonable cost. In your search, you inevitably run into the term ‘superreg’ – so where does the name come from and what is it?

The history of very high performance low-voltage regulators is well documented on Walt Jung’s website (www.waltjung.org – look under Library|Regulators & References). An early design that attracted attention was Mike Sulzer’s, published in 1980 and 1981 in Audio Amateur. I added something to that in 1987, and then I was invited by Walt Jung to work on a further improved version. This was published in a series of four articles in Audio Amateur in 1995 by Walt (part...
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The F-word - or, why there is no such thing as too much feedback

Posted 8th September 2011 at 03:55 PM by jan.didden
Updated 8th September 2011 at 03:59 PM by jan.didden

Well, I did already a blog on feedback, it's uses, misuses and misconceptions. But there is someone who can explain it much better than I can, someone who has proven that he really understands what's going on in a feedback amplifier. Someone who knows what the terms 'fast amplifier' and 'slow amplifier' really mean (and what not). Enter Bruno Putzeys, who wrote the article with the subject name in my bookzine Linear Audio, Volume 1. I feel that this is such an important matter for audio that I decided to place it online for free download. You'll find it at Linear Audio | your tech audio resource under the tab Online resources.
Enjoy the ride, and do let me know what you think about these issues.

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Feedback, or how to be late and be on time the same time, all the time.

Posted 3rd November 2010 at 06:19 AM by jan.didden
Updated 3rd November 2010 at 11:20 AM by jan.didden

Just a couple of days ago I posted something to try to debunk that tired old myth that 'feedback always comes too late and therefor can't work'. Apart from the fact that obviously it does work, which makes the first statement pretty stupid to begin with, here's my take on it.

The myth may result from an often repeated misconception that feedback comes 'after the fact' and therefore always comes too late.
This has been shown to not be the case over and over again but if you have no engineering background it may be difficult to grasp the concept. Let me try to help.

Obviously, there is a signal delay in an amp from input to output and back to the input through the feedback loop. Since the feedback loop is generally a pair of resistors, the bulk of the delay is in the amp. That is the case both in non-feedback as well as in feedback amps. Such delays are very small, often fractions of a microsecond, and in this context can be ignored.

What...
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Don't be such a scientist!

Posted 15th June 2010 at 05:21 PM by jan.didden
Updated 15th June 2010 at 05:25 PM by jan.didden

I didn't get it. There are gifted design engineers on this forum. They get involved in threads. BUT, in most cases, eventually an 'issue' develops and the engineering guy gets binned or banned or asks to be banned. Why why why? Happened to me a few times. Not that I got banned, thank Ohm, but I got close to leaving because I too got enough of it.
Of what?
Let me explain. Most engineering types like to explain things, to tell others with less experience and knowledge what they are doing wrong and how they can do it better. They inundate you with facts, figures, links to engineering papers etc, and expect that the other guy flows over with gratitude. But, funny enough, it doesn't happen that way. The 'other guy' gets pissed off from being corrected all the time. Hell, he didn't come here for that, he came to have fun, discuss his hobby and his latest creation.

[flashback] At the time Al Gore's An inconvenient Truth came out, the same director (!) also made Too...
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Nelson Pass Interview

Posted 23rd February 2010 at 07:05 PM by jan.didden
Updated 3rd November 2010 at 10:38 PM by jan.didden (fixed broken link)

My interview with our own Nelson Pass appeared in MultimediaManufacturer.
Read it here: http://www.linearaudio.nl/interviews/np.pdf
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Tech note: Balanced lines-1

Posted 13th January 2010 at 06:54 PM by jan.didden
Updated 13th January 2010 at 06:57 PM by jan.didden

Why would one use balanced interconnects, and how can we make them work well?

Balanced lines came about at a time where very long signal lines were coming in use for telephone and later for large audio performance venues. If you use a single screened line for your signal, and the line is long, the ground current through the screen causes a voltage between the ground points of the cable ends. Since the signal send out (and received) is the difference between the voltage on the signal wire and the ground wire, the unwanted signal (noise, hum) is effectively added to the wanted (music) signal. We don’t want that.

The trick is to use TWO signal lines in parallel. You send the signal over the two lines in such a way that the signal you want to transmit is the difference between the signals on these two wires, and then at the receiving end you have an amp that reacts to the difference between the two lines, so your signal at the far end is the difference between...
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Tech note: voltage regulators-1

Posted 7th January 2010 at 06:10 PM by jan.didden
Updated 11th February 2010 at 04:31 AM by Jason

There are lots of types of voltage regulators, but in this installment I’ll talk about series regulators.

What’s a regulator? It’s all in the name: it REGULATES the voltage to the circuit to be powered to keep it constant and as free of noise and ripple as practical. The ‘regulation’ means that there is some circuitry that compares a reference voltage, like from a zener diode, to the regulated output voltage, and then uses the difference between the two to adjust another element to null that difference. The ‘compare-and-correct’ is crucial for a regulator, and is done by negative feedback….

Look at Fig 1: is there a regulator in there? No, they are all circuits that try to give a constant, ripple free voltage, but if you start to draw varying currents from them, the output will vary with that current and there is no mechanism that somehow tries to null out that variation. Fig 1c is better than 1b, because Q1 buffers the voltage from the zener reference, so...
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