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The Art of Analog Design
Old

Force/sense shunt

Posted 24th April 2013 at 08:35 AM by abraxalito
Updated 24th May 2013 at 03:59 AM by abraxalito (Added pics of prototype fs-shunt. Added noise update.)

I'm a recent convert of the lowest possible impedance of power supply based on my experience of adding caps to my chipamp. So I figure the signal stages can't be harmed by reducing their supply impedance either, particularly at LF.

I note there are a few aftermarket regulators around - I had a look at Paul Hynes and Belleson in the past few days. They're a bit pricey for my tastes, given the cost of the components they're using can't be over single digit $ so I've had a look at "doing it at home, only cheaper".

First off, a simple TL431 is about the best bang for the buck achievable, as the part here is 0.2rmb. But the dynamic impedance is typically 0.2ohms and I was hoping and aiming to go a bit lower than this - perhaps an order of magnitude lower, to around 10mohms. Lower than this and the resistance of the PCB tracks come into play and its also very hard to maintain such a low impedance beyond the audio band as cap ESRs (for the best ones) are of...
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Old

What's in a datasheet?

Posted 7th October 2011 at 05:38 AM by abraxalito
Updated 14th November 2012 at 01:47 AM by abraxalito (Updated with link to new article 14th Nov 2012)

Yesterday I had this very interesting exchange with RocketScientist about his open source design for a headphone amp, the O2.

http://www.diyaudio.com/forums/headp...ml#post2736266

The nub of the issue raised here is - should designers stick only to what datasheets tell them about parts or to what extent use what's 'common knowledge' about parts to eek out better performance?

I was surprised to learn from RS that offsets within dual opamps are so closely matched in practice - its a really new discovery for me. So why don't semiconductor manufacturers tout this feature? Or perhaps RS just 'got lucky' with the relatively few samples he tested?

My experience of reading opamp datasheets is that the specs for offsets (both the typicals and the max) degrade in going from single to dual devices, where the devices are all on one die. Let's have a look at a relevant opamp from...
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Old

An engineer's engineer passes on...

Posted 14th June 2011 at 02:35 AM by abraxalito
Updated 8th September 2011 at 03:13 AM by abraxalito

Analog guru Jim Williams dies after stroke - 2011-06-13 15:26:32 | EDN
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More transparency in active speakers - part II

Posted 15th November 2010 at 12:59 PM by abraxalito
Updated 5th March 2012 at 02:58 AM by abraxalito

Its not something I claim originality for, this use of Cat6 cable for running to speakers. What though I believe is original is combining the function of speaker cable with the sharing resistors - I've seen that nowhere else. Remember guys, you saw it here first

Not only does this save on having low value fairly high power resistors but it comes with another benefit which suits diyers. That's the fact that the amps can be easily tested separately - they're not going to be in parallel until the drive unit is connected to the output, since the cables join together only at the far end, at the terminals of the driver. I've certainly found this an advantage in development - the individual gains I've checked with a multimeter between the outputs when playing a 400Hz sinewave. This frequency was chosen because I'm too lazy to check the frequency response of my multimeter and I wanted a mid-range test.

The gains of the individual chip amps do need matching very...
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Old

More transparency in active speakers

Posted 13th November 2010 at 03:23 AM by abraxalito
Updated 5th March 2012 at 03:05 AM by abraxalito

Those of you who read my earlier posts about improving my Fayou actives might have realised by now I'm a bit fanatical about grounding and its effect on sound quality. I had an idea - could a system be put together without any ground at all, and might this solve many of the sound quality issues I've found in my setup? I could only find out by trying it. So, the idea was born - 'Goundless Sound'.

First up, a groundless amplifier is just another name for a balanced, or bridged design, at least in respect of the output being balanced. A truly balanced amp would also need a balanced input - that's not really ground-breaking (pardon the pun, could not resist) either. Putting the two together is hardly rocket science. But I decided on a few twists - more about those in just a moment.

Convention is a useful thing. Ponder a world without convention in respect of computer keyboards - Asus and Toshiba having one layout of the keys on their notebooks, Dell and Lenovo...
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