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Superregs for your line-level projects

Posted 9th December 2013 at 07:52 AM by jan.didden
Updated 10th December 2013 at 06:02 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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Heretical 834p mods

Posted 9th December 2013 at 12:00 AM by hbc
Updated 14th December 2013 at 05:23 PM by hbc

The EAR 834p, is a marvellous and clever circuit, in its various optimisations and design features that are often not really understood... I acquired my second one a while ago, my first one was tweaked quite successfully to make very acceptable sound by adjusting the 10pf to 5pf and changing output CF to ECC81, and removing some surplus output potential dividers, and careful valve selection. Lowest noise first, and highest gain second.

However, it went away...

The problem I have seen with these is that they sometimes suffer muddy woolly sound in the bass which tends to spoil the over all effect. The new phono box I recently got suffers this way. Now I am suspicious of feedback loops, and how they work. I suspected that the 834p was maybe running a little short of gain in the lower registers. As I enjoy heresy, and after much consideration, I decided that bootstrapping the second stage ought to give me some more gain for the feedback loop to work. See circuit...
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