Nelson Pass, a recent interview.

[anthonyTD]

Its not difficult to understand why so many of us find Nelson Pass' and his ideas and designs inspiring, However, for those who havent read this recent interview, I thought it very apt' since there are often threads started here relating to the sonic diffrences in power amp designs etc.
Read the whole article, and also' I am sure you will find some of the comments at the end quite interesting! :)

https://www.stereophile.com/content/nelson-pass-circuit-topology-and-end-science

[DSJR]

Thanks so much. Interesting comments afterwards by some who took everything literally and didn't try to understand what NP was actually saying.

Interesting his views on what I knew as V-FETs. Sony did lovely things with these, but surviving ones will need great service care as dry joints can kill the amp as well as the speakers connected to it - I speak from experience of a previously utterly reliable and lovely sounding Sony 5650 which committed suicide one day and with no warning, taking some precious and seemingly un-repairable speakers with it :(

[anthonyTD]

:)
Thanks so much. Interesting comments afterwards by some who took everything literally and didn't try to understand what NP was actually saying.

Interesting his views on what I knew as V-FETs. Sony did lovely things with these, but surviving ones will need great service care as dry joints can kill the amp as well as the speakers connected to it - I speak from experience of a previously utterly reliable and lovely sounding Sony 5650 which committed suicide one day and with no warning, taking some precious and seemingly un-repairable speakers with it :(

[Barry]

I found the article of great interest, and greatly admire Pass's minimalist circuit topology ideas. But I found the discussion following the interview to be even more fascinating and a perfect example of what divides the objectivists from the subjectivists. Both sides put forward some interesting thoughts, despite the analogy of viewing a painting being somewhat bogus.

It gave me food for thought, and only bolstered my opinion that there never can be ultimate fidelity to the original performance - it is simply impossible. The best one can hope for is to (paraphrasing Peter Walker's by-line) aim for the "closest approach to the original sound".

Note the difference between 'performance' and 'sound'. It is not simply a matter of semantics.

[Arkless Electronics]

Interesting stuff but I strongly disagree with the "never has there been such a range of devices available for audio". In terms of just output devices it may well be true, but for devices for other uses it is quite the opposite. Many of the best devices for audio have been obsoleted by their manufacturers and not replaced with any newer or improved devices. I refer here to things like low noise parts for phono stages etc. Every home once had a TT but since digital has took over, vinyl is a niche product and there is just not enough demand to make it worthwhile for semiconductor manufacturers to keep making them...

[Starterman]

NP is a very good writer and his articles and interviews are interesting. Some of his earlier articles give more insight that this particular one.
He does sometimes seem to reinvent the wheel and claim it as his own invention though.
I have build a few of his designs but invariably been disappointed with the sound.
He seems to have got a lot of publicity out of sharing shuff with the DIY community.

[Light Dependant Resistor]

Interesting stuff but I strongly disagree with the "never has there been such a range of devices available for audio". In terms of just output devices it may well be true, but for devices for other uses it is quite the opposite. Many of the best devices for audio have been obsoleted by their manufacturers and not replaced with any newer or improved devices. I refer here to things like low noise parts for phono stages etc. Every home once had a TT but since digital has took over, vinyl is a niche product and there is just not enough demand to make it worthwhile for semiconductor manufacturers to keep making them...

I agree with Nelson, parts availability for audio purpose is just staggering. Obsolete parts are just that, obsolete.

[Marco]

Excellent interview and article, Anthony, from IMO one of the most talented audio engineers of modern times. A *true* artisan and innovator [unlike some clueless jokers, who deludedly award themselves that honour, but aren't fit to switch on his soldering iron]!

You know who I mean... ;)

Anyway, most of the techy stuff went over my head, but these snippets from the subsequent discussion (as Barry alluded to), particularly the highlighted parts, struck the most chord with me:


Fundamentally, what interests me most about amplifiers are the differences in sound created by different topologies and the characteristics of the active gain devices. There are few things I enjoy so much as to contemplate the specific (and complex) characteristics of the many transistors (or tubes) and how they might fit into an amplifier to deliver a sound which has a particular signature. Toward that end, I like simple circuits, partly because well-designed, simple amplifiers tend to sound better, and also because they bring the part's personality into sharper relief.

This relates nicely to tubes, in that the economics of tube circuits enforces a discipline of simplicity, where it is not convenient to achieve quality by throwing lots [of] parts and feedback at the problem. You will not see 50 tubes and 80dB of negative feedback under the hood of any tube amplifier.



Measurements and listening go hand in hand. There is a correlation between objective and subjective, but they're not strictly causal relationships. Clearly, there are some amplifiers that measure great with "standard" measurements but don't sound so good, and there are examples of good-sounding/bad-measuring as well. The discrepancies are interesting because they point to either things that have not been measured—more likely, misinterpreted—or aspects of perception and taste that don't correlate to measured flaws. Or both.

In the end, the subjective experience is what our customer is looking for. Our taste in sound may not appeal to everyone, but it's what we have to work with, and we only need a small segment of the market to be successful. I don't neglect the measurements; I put them to work.


He's clearly someone who cares as much about what his ears hear, as his test equipment measures, which is just as it should be! The most talented audio engineers, in my experience, are always those most in tune with that aspect of equipment design, as ultimately whatever is produced has to accurately reproduce MUSIC, not test tones, which is rather more complex.

The last bit above (in bold) especially has sentiments close to my heart, i.e. not everything that *needs* measuring is always measured, and that some of that is crucial in order to correlate measured data with listening experiences. Furthermore, as Pass points out, some measured data perhaps is misinterpreted by being adversely biased by the designer's [often entrenched] belief system, or as he puts it more mildly and less controversially, "perception and taste".

I've been saying the same for a long time, during obv/subj debates, that some conclusions reached, especially by objectivists, might not be quite as 'conclusive' as they think, for reasons above. That's why the discussion/debate of certain contentious subjects (cables, for example) never extends beyond the limitations of their belief system, impaired by the effects of confirmation bias...

Anyway, great article and one of the most interesting things I've read on Stereophile for a long time, so thanks for sharing! :cool:

Marco.

[Arkless Electronics]

I agree with Nelson, parts availability for audio purpose is just staggering. Obsolete parts are just that, obsolete.

I was going to post something about your obvious lack of knowledge but I won't bother.... All those low noise FETs are still available where? the dual matched ones etc? and the super low noise transistors? and the matched mosfet arrays?